The NY Times article Go With Your Gut recommends that we enjoy our foods because allegedly "when you eat something you like, your body makes more efficient use of its nutrients." The caveat is to begin with food with nutritions.
Harriet Brown concludes in the article that "call it Slow Food, conscious eating, or eating the French way, the point's the same: eating well and with pleasure is more than hedonism — it's good nutritional policy and practice." Thumbs up for that statement. Now, what's for dinner?
Monday, February 20, 2006
Friday, February 17, 2006
Decision
This is an interesting study on the process of decision making and the satisfaction on its outcome. The study by Dutch scientists showed that "simple choices (such as between different towels or different sets of oven mitts) indeed produce better results after conscious thought, but that choices in complex matters (such as between different houses or different cars) should be left to unconscious thought". Now this new finding makes me want to read the nonfiction book Blink: The Power of Thinking Without Thinking by Malcolm Gladwell, author of The Tipping Point.
Read more about the study in Science journal: Don't think too much; On Making the Right Choice: The Deliberation-Without-Attention Effect; Psychology: Tough Decision? Don't Sweat It.
Read more about the study in Science journal: Don't think too much; On Making the Right Choice: The Deliberation-Without-Attention Effect; Psychology: Tough Decision? Don't Sweat It.
Wednesday, November 16, 2005
Turkey for Thanksgiving
In The Pilgrims Didn't Brine, Kim Severson set out to find a simple way to prepare the turkey. After much consultations with various experts, she "settled on a roasting temperature of 425 degrees... started with a room-temperature turkey... the breast tented with foil", and "no flipping, no basting." It's important to have a meat thermometer because when the thigh hit 165 degrees [Fahrenheit], we ought to let the turkey "rest for a half-hour, covered with foil and a slightly damp kitchen towel, to allow the juices to settle back into the meat." It takes about two hours to roast a 12 to 14 pound turkey by using Kim's method. Maybe sometime down the road, I'll need to refer back to this simple recipe. By the way, a fresh bird from the local butcher seemed to be the key to success in roasting for Thanksgiving.
Tuesday, October 18, 2005
In Quotation
"In this world, there is a kind of painful progress: longing for what we left behind and dreaming ahead," Harper Pitt from Tony Kushner's Angels in America.
"Leaving things open... so gaps remain... so that one has time to look to others who in some cases need time to get to know themselves," Julie Lopes-Curval director of Seaside.
"And it's not a matter of whether the war is not real or if it is. Victory is not possible. The war is not meant to be won, it is meant to be continuous. Hierarchical society is only possible on the basis of poverty and ignorance. This new version is the past and no different past can ever have existed. In principle the war effort is always planned to keep society on the brink of starvation. The war is waged by the ruling group against its own subjects and its object is not the victory over either Eurasia or East Asia but to keep the very structure of society intact," Michael Moore in Fahrenheit 9/11 paraphrasing George Orwell's 1984.
"Leaving things open... so gaps remain... so that one has time to look to others who in some cases need time to get to know themselves," Julie Lopes-Curval director of Seaside.
"And it's not a matter of whether the war is not real or if it is. Victory is not possible. The war is not meant to be won, it is meant to be continuous. Hierarchical society is only possible on the basis of poverty and ignorance. This new version is the past and no different past can ever have existed. In principle the war effort is always planned to keep society on the brink of starvation. The war is waged by the ruling group against its own subjects and its object is not the victory over either Eurasia or East Asia but to keep the very structure of society intact," Michael Moore in Fahrenheit 9/11 paraphrasing George Orwell's 1984.
Friday, June 18, 2004
Magnesium
Introduction
From a biological perspective, an adequate dietary intake of magnesium is essential to maintain a good health. Excess of magnesium may cause diarrhea, whereas deficient of magnesium may affect severe muscular and neurological functions. There had been reports suggesting a linkage between magnesium and heart diseases. By singling out magnesium as the risk factor of heart diseases, we can save thousands of lives and millions of health care costs through supplementation programs. However, after the hypothesis was initially published, researchers had found conflicting results, which set off a controversy of whether magnesium is the panacea of heart diseases. In this paper, the efficacy of magnesium in preventing and treating hypertension and heart attack will be discussed. Evidences will be drawn from the results of research trials published in journals as well as those cited in online sources. Each of the evidences will be evaluated critically as an attempt to determine the current state of this issue.
Background Information
Biological Functions of Magnesium
The survival of an organism is highly dependant on its ability to detect, process, and respond to stimuli from the surrounding environment. Signal transduction pathways that allow us to react to environmental changes are complex in their natures. Magnesium ion is important in cell signaling; it is required for the formation of cyclic adenosine monophosphate, which is a second messenger that can trigger responses such as enzyme activation. Being a component of active ion transporters, magnesium is related to the regulation of intracellular concentration of calcium and potassium ions. It helps to elicit actions to avoid harmful conditions by contributing to an increase of the intracellular calcium concentration that causes muscle contractions.
Magnesium is an essential mineral that contributes to a good health. It is involves in many biological functions. One of the apparent functions of magnesium is to maintain the ionic strength of body fluids. Magnesium may not be commonly associated with bones, but it is a composite of the skeleton, where majority of magnesium in our body can be found; it supports the structure of human body. Production of high-energy molecule, adenosine triphosphate (ATP), by ATPase in mitochondria requires magnesium. Magnesium-dependent reactions had been identified as the metabolic intermediates of carbohydrates and lipids. Besides involved in metabolism, magnesium has its role in synthesis of nucleic acids; it is required by deoxyribonucleic acid (DNA) polymerase that catalyzes the formation of DNA.
Interaction of Magnesium with Other Nutrients
Some of the magnesium functions are complimentary to functions of other nutrients. We would find that these nutrients often cause interference to the uptake of magnesium in human body. Zinc supplement of 142mg each day has been observed to significantly reduce both the absorption and the balance of magnesium in adult males (Spencer et al, 1994). Fiber had been found to lower magnesium utilization, but researchers have not ascertained the degree of this effect. However, not all nutrients have negative effects on magnesium absorption. Researchers have found that increased protein intakes correlate with higher magnesium absorption; meanwhile, decreased protein intakes also correlate with lowered absorption, among teenagers. Among the nutrients that could affect the absorption of magnesium, calcium which is chemically similar to magnesium has not been identified to affect magnesium balance; but there are signs of interference with magnesium absorptions.
Surplus of Magnesium
Among the countries which have established their daily recommended allowances (RDAs) of nutrients, the RDA for magnesium will varies to some extent. Based on the results of balance studies (by comparing the amount consumed versus the amount excreted, hence the amount retained), the Food and Nutrition Board of the Institute of Medicine in the US had recommended the daily magnesium intake of 400mg for male adult through 30 years old, 420mg for male of 30 year-old and above, 310 mg for female adult up to 30 years old, and 320mg for female over 30 years old. Adverse effects from dietary intake of magnesium have not been found, and perhaps illness has not been reported as caused by excess magnesium by itself. The effects of taking supplemental magnesium have been identified. Diarrhea is a widely recognized symptom of excess magnesium since it has been used as a laxative. People with kidney problems are cautioned for taking magnesium-containing drugs because they are more susceptible to its toxicity. Hypotension or a decrease in blood pressure, palpitation or irregular heartbeats, and lethargy, are some of the symptoms of excess magnesium at a toxic level (hypermagnesemia). Severe hypermagnesemia may eventually causes heart attack.
Deficiency of Magnesium
According to a national survey in the US, the population is taking magnesium at a level significantly lower than the RDAs; on average the daily intake is 100mg to 80mg lower than the RDA for men and women. The survey results suggest a general magnesium deficiency among the Americans. However, magnesium deficiency is uncommon if a healthy individual is consuming a balanced diet (not further defined) because our kidneys usually limit the excretion of magnesium when the balances are low.
Elderly people, alcoholics, and people with certain diseases are more susceptible to magnesium deficiency. Elderly people are at a higher risk because magnesium absorption is likely to be less than optimal, and it is compounded by the increased excretion of magnesium. Alcoholics are more susceptible than the average population because of increased likelihood of imbalance dietary intake, gastrointestinal complication, and elevated level of magnesium excretion, which all may add up to a significant deficiency. People with diabetes mellitus, malabsorption syndrome, and other renal or gastrointestinal disorders also have increased risks of deficiency because of abnormal excretion or absorption of magnesium.
In experimentally induced severe deficiency, the initial symptom is lowered concentration of magnesium in blood (hypomagnesemia). Under prolonged deficiency, a reduced calcium concentration in blood (hypocalcemia) is observed, even with enough calcium intakes. Other symptoms of severe deficiency include nausea, loss of appetite, low potassium concentration in blood (hypokalemia), low levels of parathyroid hormone, and muscular, neurological, as well as psychological changes.
The Evidence for Disease Prevention and Treatment
The evidences to be mentioned below are derived from the summative information posted by Linus Pauling Institute at Oregon State University. Two online sources, one is a private website which support of ‘magnesium in water’, another is a governmental website will be discussed. These evidences could be one sided, and might not present both sides of the issues. Each of these evidences will be evaluated.
Preventing Hypertension
There are three prospective studies cited by LPI. A research group at Harvard School of Public Health did the first two studies. The first study published in 1992 was a follow-up on 30,681 mostly white male health professionals, aged 40 to 75 years old, who had no hypertension diagnoses in the beginning. Four years later, 1,248 of them had diagnoses of hypertension. Age, relative weight, and alcohol consumption were the strongest factors that contributed to hypertension. After some statistical adjustments, dietary fiber, potassium, and magnesium were nutritional factors, which lowered the risk of hypertension. However, when these nutritional factors were considered together, dietary fiber stood out as the only factor that significantly reduced hypertension. Furthermore, fruit fiber but not cereal or vegetable fiber was identified as the important kind of fiber that would lower the risk of hypertension.
The researchers concluded, “These results support hypothesis that an increased intake of fiber and magnesium may contribute to the prevention of hypertension (Ascherio et al, 1992.)” We should be doubtful about the conclusion drawn by this study because potassium was excluded from the conclusion, even though similar to magnesium, it was a significant nutritional factor when considered independently. A more appropriate conclusion would be to urge people to think twice about alcohol consumption, to keep an eye on their relative weight, and to encourage people to consume more fruits or to increase their dietary fiber intake, which will significantly decrease the risk of hypertension (that at least will be true for white male in US.)
A similar follow-up study was done among 41,541 mostly white female nurses, aged 38 to 63 years old. This time, after four years, 2,526 women reported hypertension diagnoses. With statistical adjustments (for age, body mass index, alcohol, and energy intake), dietary fiber, potassium, magnesium, and calcium were found not associated with the risk of hypertension; these nutritional factors were identified to reduce systolic and diastolic pressures. When these nutrients were considered together, only fiber and magnesium were found to lower blood pressures. Intakes of fruits and vegetables could lower systolic and diastolic pressures, and intakes cereals and meat were directly associated with systolic pressure. They concluded, “These results could support hypotheses that age, body weight, and alcohol consumption are strong determinants of risk of hypertension in middle-aged women. They are compatible with the possibilities that magnesium and fiber as well as a diet richer in fruits and vegetables may reduce blood pressure levels (Ascherio et al, 1996.)” We could accept these conclusions because they were specific, comprehensive, and relevant to the results of this study.
One plausible explanation for the direct association of cereals with systolic pressure was the high sugar content of cereals; perhaps it is a wishful thinking that it did not apply to unsweetened muesli that some consumers prefer to eat every morning. A surprising feature of this study was the lapse of eight years between the survey from 1984 until 1988, and its publication in 1996. What took it so long to get this study to publish? In fact, this study ought to be finished before the previous study on men was published in 1992. Was it a vigorous peer-review that could have delay the publication? A possible explanation would be due to the demand of computational power to perform a multiple regression on the data collected from these individuals.
Atherosclerosis Risk in Communities Study examined a biracial group of 3541 men and 4190 women, aged 45 to 64 years old in four American communities. The six-year study showed a decreasing trend in the odds of incident hypertension across ascending quartiles of serum magnesium in both gender, but the trend was statistically significant only in women. They concluded that low magnesium might play a modest role in the development of hypertension (Peacock et al, 1999.) The study had a much smaller sample size than the previous two studies. The subjects were from four communities, which could have given us an insight of geography as a potential factor, but it was not mentioned in the report. Perhaps it was clarified in the article, but it was not mentioned in the abstract – what was the range of the lowest quartile of serum magnesium that seemed to have a higher risk?
Treating Hypertension
The results of giving magnesium supplements to treat hypertension were inconsistent according to a number of studies. However, there were two placebo-controlled studies, which had shown significant blood pressure lowering effects. Kawano et al (1998) found that the blood pressures in hypertensive patients lowered during the eight-week period. The subjects were given 20mmol or 485mg magnesium per day in the form of magnesium oxide. They concluded, “These results indicate that magnesium supplementation lowers blood pressures in hypertensive subjects and this effect is greater in subjects with higher blood pressures.” Given the antihypertensive effect might be minor, they suggested the increased intake as a lifestyle modification.
In another study, Witteman et al (1994) also found a modest but significant decrease in systolic and diastolic blood pressures, when hypertensive women were given 485mg magnesium per day in the form of magnesium aspartate HCl. They recommended the usage of oral supplementation among people with mild to moderate hypertension. The scholars at Linus Pauling Institute further suggested that magnesium supplementation might be helpful for hypertensive subjects who have low serum magnesium because of insufficient intake, chronic use of thiazide diurectics, or both. The results of all these studies were mentioned as statistically adjusted for age, relative weight, alcohol consumption, et cetera, but so far none had accentuate regular exercise or sports participation, and smoking, which are also significant choices of lifestyle that could affect the odds.
Preventing Cardiovascular Diseases
Studies have found lower death rate of cardiovascular diseases in populations who consume hard water. However, hard water can be higher in magnesium as well as more calcium and fluoride than soft water. It is difficult to single out magnesium as the element in hard water that contributes to lower the rate of cardiovascular diseases.
Liao et al (1998) carried out a four to seven years follow-up of 13,922 middle-aged adults of which 319 individuals had developed coronary heart disease. Statistically analyses revealed a significant trend of decreasing risk of coronary heart disease ascending the quartiles of serum magnesium in women, but not in men. However, the adjusted relative risk of coronary heart disease in the bottom quartile of dietary magnesium intake was not significantly different from the top quartile in men and women. The researchers at University of Minnesota concluded that low serum magnesium might contribute to the pathogenesis of coronary heart disease.
Treating Cardiovascular Disease
The group of researchers at University of Leicester conducted a placebo-controlled study with 2,316 patients with acute myocardial infraction (heart attack). They reported a significant relative reduction of 24% in mortality; 7.8% in the group given intravenous magnesium sulphate, compared to 10.3% in the control group (Woods et al, 1992). In the short-term study, the group concluded that intravenous magnesium sulphate is safe and its efficacy in decreasing early mortality of myocardial infraction is comparable to, but independent of, that of thrombolytic or antiplatelet therapy. Two years later, the same group published another paper on the long-term effect of intravenous magnesium sulphate, the 2,316 patients with acute myocardial infraction were examined over a one-year to five-and-half year period, 2.7 years on average. Mortality rate from ischeamic heart disease2 was reduced by 21% in the group treated with magnesium (Woods et al, 1994).
However, there was another study of 58,050 individuals entering hospitals up to 24 hours (median is eight hours) after the onset of acute myocardial infarction, were conducted by a collaborative group known as Fourth International Study of Infarct Survival (ISIS-4). Besides 24-hour intravenous magnesium sulphate, the randomized factorial study also examined the efficacy of prescribing captoril and mononitrate supplement to lower mortality among the patients. Results of the placebo-controlled trials did not show significant reduction in five-week mortality. This finding contradicts with the positive results of the two previous studies by Woods et al. Therefore, the usefulness of magnesium in treating heart attacks remains uncertain. On the light side, the results of different preliminary studies by a research group at Cedars-Sinai Medical Center indicated that oral magnesium supplementation might improve endothelia function in people with cardiovascular disease (Shechter, et al, 1999 & 2000).
Opinions from the Magnesium Web Site
Amid the controversy, the scholars at Linus Pauling Institute took the closer-to- middle-ground approach by maintaining that the relationship between dietary magnesium intake and the risk of cardiovascular diseases remains unclear. However, the Magnesium Web Site posted an excerpt from page 440 to 447 of the Report of the Safe Drinking Water Committee of the National Academy of Sciences in 1977 which assumingly claimed, “Studies in the United States and Canada have shown that age-adjusted cardiovascular mortality among populations using very soft water may be as much as 15-20% higher than among populations using hard water; differential reported for the United Kingdom may be as high as 40%.1” Without appropriate references, people may find the statements difficult to believe. The web site should include a list of the publications that could be found in scientific journals to justify statements such as “more than 50 studies have been carried out in nine countries.1” It is possible that the web site had omitted the citation that appeared in the original report. There were some forms of citations in the first two paragraphs. Astonishingly, the references given at the end of this excerpt were on mercury, copper, and other trace metals, which made the report seemed irrelevant to the argument and the element of interest – magnesium.
“The credibility of these water-factor studies depend more on the consistent trend of the findings than their plausibility or the size of the correlation coefficients or the actual significance levels, 1” is a rather deceitful statement; it denies the power of statistical analysis. How could a study allegedly funded by Environmental Protection Agency (EPA) and cited by US National Academy of Sciences, urge the public to ignore the logic of scientific experiments? There is a fallacy that ought to be point out – how do we know that there is a consistent trend if we do not consider the statistical values such as correlation coefficient? The P value, confidence interval, and other statistics inform the reader what is the probability that there is a correlation among the sets of data. In a comparable situation, consumers should not be encouraged to buy product X because it simply provides nutrition, and advised them to care less about the amount of carbohydrate, fat, protein, vitamins, minerals, or fiber that the product contains; the numbers on the food labels reflect the nutritional values of the product, which can be helpful for consumers to make decisions. Furthermore, it could be that US National Academy of Sciences and EPA were mentioned as the authorities to make the audience believe what is being told.
Opinions of an Expert
Harold Foster wrote about groundwater resources of British Columbia. His report was presented on the website of the Canadian Ministry of Water, Land and Air Protection. In chapter six, he discussed about the relation of groundwater and human health. The relationships between health and contaminants in water are difficult to evaluate. Deficiencies of minerals are known to have caused severe illnesses. It is important to elucidate the level of balance consumption because excessive intakes of minerals will have adverse effects on health.
It was noted that there is a controversy over the significance of the relative absence of certain inorganic solutes from surface and groundwater supplies. The report by US National Academy of Science in 1977 was cited again by Foster. The report seemed to be crucial for people who believe that water hardness affects mortality rate from cardiovascular disease. What had the National Academy of Science found on the subject since 1977? Have they changed their position regarding the controversy that emerged after their report?
The statement, “Soft water, deficient in calcium and magnesium, has also been linked to elevated rate of Sudden Infant Death Syndrome, diabetes, cerebrovascular disease, and cancer,” was supported by five references; three out of the five publications cited were authored by Foster. In his report, magnesium was mentioned together with calcium as potentially beneficial solutes in hard water. Magnesium did not seem to be a separate entity in his argument; he did not strengthen nor had weakened magnesium as the vital element to reduce the risk and mortality of heart disease.
Conclusion
The evidences are contradicting; we cannot reject the hypothesis of a relation between magnesium and cardiovascular disease. There are certainly hopes that more promising results will be obtained to support the theory. Magnesium had been proven to reduce the risk of hypertension; prevention by increasing the intake of magnesium was more successful in women than men. On the downside, the effect of increasing magnesium intake was suggested to be smaller than the effect of fiber. Magnesium had been identified as an effective treatment of mild hypertension, but not for severe cases.
Studies had shown that magnesium is not a significant factor in reducing the risk of heart disease, but low levels of magnesium in blood may indicate the pathogenesis of coronary heart disease. Intravenous injection of magnesium had also given different results in the attempts to reduce the mortality of individuals with myocardial infarction. In regard to magnesium in drinking water, Marx and Neutra (1997) had summed up precisely, “Future research must provide better answer about low level waterborne magnesium before recommendations to the public can be made.” People should remain sceptical about the information posted on privately funded websites; they should be aware of the agenda behind these websites, in regard to a controversial issue.
Bibliography
Ascherio, A., Hennekens, C., Willett, W.C., Sacks, F., Rosner, B., and Manson, J., Witteman, J., and Stampfer, M.J. “Prospective study of nutritional factors, blood pressure, and hypertension among US women.” Hypertension. May 1996. 27(5): 1065-1072.
Ascherio, A., Rimm, E.B., Giovannucci, E.L., Colditz, G.A., Rosner, B., Willett, W.C., Sacks, F., and Stampfer, M.J. “A prospective study of nutritional factors and hypertension among US men.” Circulation. November 1992. 86(5): 1475-1484.
Marx, A., and Neutra, R.R. “Magnesium in drinking water and ischemic heart disease.” Epidemiology Review. 1997. 19(2): 258-272.
“Exhibit B – Drinking Water and Health.” The Magnesium Web Site. 10 Dec 1998. Accessed on 22 Nov 2002. Online at http://www.mgwater.com/exhibitb.shtml
Foster, H.D. “Chapter 6: Groundwater and Human Health.” Groundwater Resources of British Columbia. Canadian Ministry of Water, Land and Air Protection. Accessed on 22 November 2002, online at http://wlapwww.gov.ba.ca/wat/gws/gwbc/C06_health.html
ISIS-4 Collaborative Group. “ISIS-4: a randomized factorial trial assessing early oral captopril, oral mononitrate, and intravenous magnesium sulphate in 58,050, patients with suspected acute myocardial infarction.” Lancet. 18 March 1995. 345(89051): 669-685.
Kawano, Y., Matsuoka, H., Takishita, S., and Omae, T. “Effects of magnesium supplementation in hypertensive patients: assessment by office, home, and ambulatory blood pressures.” Hypertension. August 1998. 32(2): 260-265.
Liao, F., Folsom, A.R., and Brancati, F.L. “Is low magnesium concentration a risk factor for coronary heart disease? The Atherosclerosis Risk in Community (ARIC) Study.” American Heart Journal. September 1998. 136(3): 480-490.
“Magnesium (reviewed by Rude, R.K).” Linus Pauling Institute. Updated on 5 February 2001. Accessed on 22 November 2002, online at http://www.orst.edu/dept/lpi/infocenter/minerals/magnesium/magnesium/magnesium.html
Peacock, J.M., Folsom, A.R., Arnett, D.K., Eckfeldt, J.H., and Szkio, M. “Relationship of Serum and dietary magnesium to incident hypertension: the Atherosclerosis Risk in Communities (ARIC) Study.” Annals of Epidemiology. April 1999. 9(3): 159-165.
Shechter, M., Merz, C.N., Paul-Labrador, M., Meisel, S.R., Rude, R.K., Molloy, M.D., Dwye, J.H., Shah, P.K., and Kaul, S. “Oral Magnesium supplementation inhibits platelet-dependent thrombosis in patients with coronary artery disease.” American Journal of Cardiology. 15 July 1999. 84(2): 152-126.
Shechter, M., Sharir, M., Labrador, M.J., Forrester, J., Silver, B., and Bairey Merz, C.N. “Oral magnesium therapy improves endothelial function in patients with coronary artery disease.” Circulation. 7 November 2000. 102(19): 2353-2358.
Spencer, H., Norris, C., and Williams, D. “Inhibitory effects of zinc on magnesium balance and magnesium absorption in man.” Journal of American College Nutrition. 1994. 13: 479-484.
Witteman, J.C., Grobee, D.E., Derkx, F.H., Bouillon, R., de Bruijn, A.M., and Hofman, A. “Reduction of blood pressure with oral magnesium supplementation in women with mild to moderate hypertension.” American Journal of Clinical Nutrition. July 1994. 60(1): 129-135.
Woods, K.L., Flectcher, S., Roffe, C., and Haider, Y. “Intravenous magnesium sulphate in suspected acute myocardial infarction: results of the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).” Lacent. 27 June 1992. 339(8809): 1553-1558.
Woods, K.L., and Flectcher, S. “Long-term outcome after intravenous magnesium sulphate in suspected acute myocardial infarction: the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).” Lancet. 2 April 1994. 343(8901): 816-819.
From a biological perspective, an adequate dietary intake of magnesium is essential to maintain a good health. Excess of magnesium may cause diarrhea, whereas deficient of magnesium may affect severe muscular and neurological functions. There had been reports suggesting a linkage between magnesium and heart diseases. By singling out magnesium as the risk factor of heart diseases, we can save thousands of lives and millions of health care costs through supplementation programs. However, after the hypothesis was initially published, researchers had found conflicting results, which set off a controversy of whether magnesium is the panacea of heart diseases. In this paper, the efficacy of magnesium in preventing and treating hypertension and heart attack will be discussed. Evidences will be drawn from the results of research trials published in journals as well as those cited in online sources. Each of the evidences will be evaluated critically as an attempt to determine the current state of this issue.
Background Information
Biological Functions of Magnesium
The survival of an organism is highly dependant on its ability to detect, process, and respond to stimuli from the surrounding environment. Signal transduction pathways that allow us to react to environmental changes are complex in their natures. Magnesium ion is important in cell signaling; it is required for the formation of cyclic adenosine monophosphate, which is a second messenger that can trigger responses such as enzyme activation. Being a component of active ion transporters, magnesium is related to the regulation of intracellular concentration of calcium and potassium ions. It helps to elicit actions to avoid harmful conditions by contributing to an increase of the intracellular calcium concentration that causes muscle contractions.
Magnesium is an essential mineral that contributes to a good health. It is involves in many biological functions. One of the apparent functions of magnesium is to maintain the ionic strength of body fluids. Magnesium may not be commonly associated with bones, but it is a composite of the skeleton, where majority of magnesium in our body can be found; it supports the structure of human body. Production of high-energy molecule, adenosine triphosphate (ATP), by ATPase in mitochondria requires magnesium. Magnesium-dependent reactions had been identified as the metabolic intermediates of carbohydrates and lipids. Besides involved in metabolism, magnesium has its role in synthesis of nucleic acids; it is required by deoxyribonucleic acid (DNA) polymerase that catalyzes the formation of DNA.
Interaction of Magnesium with Other Nutrients
Some of the magnesium functions are complimentary to functions of other nutrients. We would find that these nutrients often cause interference to the uptake of magnesium in human body. Zinc supplement of 142mg each day has been observed to significantly reduce both the absorption and the balance of magnesium in adult males (Spencer et al, 1994). Fiber had been found to lower magnesium utilization, but researchers have not ascertained the degree of this effect. However, not all nutrients have negative effects on magnesium absorption. Researchers have found that increased protein intakes correlate with higher magnesium absorption; meanwhile, decreased protein intakes also correlate with lowered absorption, among teenagers. Among the nutrients that could affect the absorption of magnesium, calcium which is chemically similar to magnesium has not been identified to affect magnesium balance; but there are signs of interference with magnesium absorptions.
Surplus of Magnesium
Among the countries which have established their daily recommended allowances (RDAs) of nutrients, the RDA for magnesium will varies to some extent. Based on the results of balance studies (by comparing the amount consumed versus the amount excreted, hence the amount retained), the Food and Nutrition Board of the Institute of Medicine in the US had recommended the daily magnesium intake of 400mg for male adult through 30 years old, 420mg for male of 30 year-old and above, 310 mg for female adult up to 30 years old, and 320mg for female over 30 years old. Adverse effects from dietary intake of magnesium have not been found, and perhaps illness has not been reported as caused by excess magnesium by itself. The effects of taking supplemental magnesium have been identified. Diarrhea is a widely recognized symptom of excess magnesium since it has been used as a laxative. People with kidney problems are cautioned for taking magnesium-containing drugs because they are more susceptible to its toxicity. Hypotension or a decrease in blood pressure, palpitation or irregular heartbeats, and lethargy, are some of the symptoms of excess magnesium at a toxic level (hypermagnesemia). Severe hypermagnesemia may eventually causes heart attack.
Deficiency of Magnesium
According to a national survey in the US, the population is taking magnesium at a level significantly lower than the RDAs; on average the daily intake is 100mg to 80mg lower than the RDA for men and women. The survey results suggest a general magnesium deficiency among the Americans. However, magnesium deficiency is uncommon if a healthy individual is consuming a balanced diet (not further defined) because our kidneys usually limit the excretion of magnesium when the balances are low.
Elderly people, alcoholics, and people with certain diseases are more susceptible to magnesium deficiency. Elderly people are at a higher risk because magnesium absorption is likely to be less than optimal, and it is compounded by the increased excretion of magnesium. Alcoholics are more susceptible than the average population because of increased likelihood of imbalance dietary intake, gastrointestinal complication, and elevated level of magnesium excretion, which all may add up to a significant deficiency. People with diabetes mellitus, malabsorption syndrome, and other renal or gastrointestinal disorders also have increased risks of deficiency because of abnormal excretion or absorption of magnesium.
In experimentally induced severe deficiency, the initial symptom is lowered concentration of magnesium in blood (hypomagnesemia). Under prolonged deficiency, a reduced calcium concentration in blood (hypocalcemia) is observed, even with enough calcium intakes. Other symptoms of severe deficiency include nausea, loss of appetite, low potassium concentration in blood (hypokalemia), low levels of parathyroid hormone, and muscular, neurological, as well as psychological changes.
The Evidence for Disease Prevention and Treatment
The evidences to be mentioned below are derived from the summative information posted by Linus Pauling Institute at Oregon State University. Two online sources, one is a private website which support of ‘magnesium in water’, another is a governmental website will be discussed. These evidences could be one sided, and might not present both sides of the issues. Each of these evidences will be evaluated.
Preventing Hypertension
There are three prospective studies cited by LPI. A research group at Harvard School of Public Health did the first two studies. The first study published in 1992 was a follow-up on 30,681 mostly white male health professionals, aged 40 to 75 years old, who had no hypertension diagnoses in the beginning. Four years later, 1,248 of them had diagnoses of hypertension. Age, relative weight, and alcohol consumption were the strongest factors that contributed to hypertension. After some statistical adjustments, dietary fiber, potassium, and magnesium were nutritional factors, which lowered the risk of hypertension. However, when these nutritional factors were considered together, dietary fiber stood out as the only factor that significantly reduced hypertension. Furthermore, fruit fiber but not cereal or vegetable fiber was identified as the important kind of fiber that would lower the risk of hypertension.
The researchers concluded, “These results support hypothesis that an increased intake of fiber and magnesium may contribute to the prevention of hypertension (Ascherio et al, 1992.)” We should be doubtful about the conclusion drawn by this study because potassium was excluded from the conclusion, even though similar to magnesium, it was a significant nutritional factor when considered independently. A more appropriate conclusion would be to urge people to think twice about alcohol consumption, to keep an eye on their relative weight, and to encourage people to consume more fruits or to increase their dietary fiber intake, which will significantly decrease the risk of hypertension (that at least will be true for white male in US.)
A similar follow-up study was done among 41,541 mostly white female nurses, aged 38 to 63 years old. This time, after four years, 2,526 women reported hypertension diagnoses. With statistical adjustments (for age, body mass index, alcohol, and energy intake), dietary fiber, potassium, magnesium, and calcium were found not associated with the risk of hypertension; these nutritional factors were identified to reduce systolic and diastolic pressures. When these nutrients were considered together, only fiber and magnesium were found to lower blood pressures. Intakes of fruits and vegetables could lower systolic and diastolic pressures, and intakes cereals and meat were directly associated with systolic pressure. They concluded, “These results could support hypotheses that age, body weight, and alcohol consumption are strong determinants of risk of hypertension in middle-aged women. They are compatible with the possibilities that magnesium and fiber as well as a diet richer in fruits and vegetables may reduce blood pressure levels (Ascherio et al, 1996.)” We could accept these conclusions because they were specific, comprehensive, and relevant to the results of this study.
One plausible explanation for the direct association of cereals with systolic pressure was the high sugar content of cereals; perhaps it is a wishful thinking that it did not apply to unsweetened muesli that some consumers prefer to eat every morning. A surprising feature of this study was the lapse of eight years between the survey from 1984 until 1988, and its publication in 1996. What took it so long to get this study to publish? In fact, this study ought to be finished before the previous study on men was published in 1992. Was it a vigorous peer-review that could have delay the publication? A possible explanation would be due to the demand of computational power to perform a multiple regression on the data collected from these individuals.
Atherosclerosis Risk in Communities Study examined a biracial group of 3541 men and 4190 women, aged 45 to 64 years old in four American communities. The six-year study showed a decreasing trend in the odds of incident hypertension across ascending quartiles of serum magnesium in both gender, but the trend was statistically significant only in women. They concluded that low magnesium might play a modest role in the development of hypertension (Peacock et al, 1999.) The study had a much smaller sample size than the previous two studies. The subjects were from four communities, which could have given us an insight of geography as a potential factor, but it was not mentioned in the report. Perhaps it was clarified in the article, but it was not mentioned in the abstract – what was the range of the lowest quartile of serum magnesium that seemed to have a higher risk?
Treating Hypertension
The results of giving magnesium supplements to treat hypertension were inconsistent according to a number of studies. However, there were two placebo-controlled studies, which had shown significant blood pressure lowering effects. Kawano et al (1998) found that the blood pressures in hypertensive patients lowered during the eight-week period. The subjects were given 20mmol or 485mg magnesium per day in the form of magnesium oxide. They concluded, “These results indicate that magnesium supplementation lowers blood pressures in hypertensive subjects and this effect is greater in subjects with higher blood pressures.” Given the antihypertensive effect might be minor, they suggested the increased intake as a lifestyle modification.
In another study, Witteman et al (1994) also found a modest but significant decrease in systolic and diastolic blood pressures, when hypertensive women were given 485mg magnesium per day in the form of magnesium aspartate HCl. They recommended the usage of oral supplementation among people with mild to moderate hypertension. The scholars at Linus Pauling Institute further suggested that magnesium supplementation might be helpful for hypertensive subjects who have low serum magnesium because of insufficient intake, chronic use of thiazide diurectics, or both. The results of all these studies were mentioned as statistically adjusted for age, relative weight, alcohol consumption, et cetera, but so far none had accentuate regular exercise or sports participation, and smoking, which are also significant choices of lifestyle that could affect the odds.
Preventing Cardiovascular Diseases
Studies have found lower death rate of cardiovascular diseases in populations who consume hard water. However, hard water can be higher in magnesium as well as more calcium and fluoride than soft water. It is difficult to single out magnesium as the element in hard water that contributes to lower the rate of cardiovascular diseases.
Liao et al (1998) carried out a four to seven years follow-up of 13,922 middle-aged adults of which 319 individuals had developed coronary heart disease. Statistically analyses revealed a significant trend of decreasing risk of coronary heart disease ascending the quartiles of serum magnesium in women, but not in men. However, the adjusted relative risk of coronary heart disease in the bottom quartile of dietary magnesium intake was not significantly different from the top quartile in men and women. The researchers at University of Minnesota concluded that low serum magnesium might contribute to the pathogenesis of coronary heart disease.
Treating Cardiovascular Disease
The group of researchers at University of Leicester conducted a placebo-controlled study with 2,316 patients with acute myocardial infraction (heart attack). They reported a significant relative reduction of 24% in mortality; 7.8% in the group given intravenous magnesium sulphate, compared to 10.3% in the control group (Woods et al, 1992). In the short-term study, the group concluded that intravenous magnesium sulphate is safe and its efficacy in decreasing early mortality of myocardial infraction is comparable to, but independent of, that of thrombolytic or antiplatelet therapy. Two years later, the same group published another paper on the long-term effect of intravenous magnesium sulphate, the 2,316 patients with acute myocardial infraction were examined over a one-year to five-and-half year period, 2.7 years on average. Mortality rate from ischeamic heart disease2 was reduced by 21% in the group treated with magnesium (Woods et al, 1994).
However, there was another study of 58,050 individuals entering hospitals up to 24 hours (median is eight hours) after the onset of acute myocardial infarction, were conducted by a collaborative group known as Fourth International Study of Infarct Survival (ISIS-4). Besides 24-hour intravenous magnesium sulphate, the randomized factorial study also examined the efficacy of prescribing captoril and mononitrate supplement to lower mortality among the patients. Results of the placebo-controlled trials did not show significant reduction in five-week mortality. This finding contradicts with the positive results of the two previous studies by Woods et al. Therefore, the usefulness of magnesium in treating heart attacks remains uncertain. On the light side, the results of different preliminary studies by a research group at Cedars-Sinai Medical Center indicated that oral magnesium supplementation might improve endothelia function in people with cardiovascular disease (Shechter, et al, 1999 & 2000).
Opinions from the Magnesium Web Site
Amid the controversy, the scholars at Linus Pauling Institute took the closer-to- middle-ground approach by maintaining that the relationship between dietary magnesium intake and the risk of cardiovascular diseases remains unclear. However, the Magnesium Web Site posted an excerpt from page 440 to 447 of the Report of the Safe Drinking Water Committee of the National Academy of Sciences in 1977 which assumingly claimed, “Studies in the United States and Canada have shown that age-adjusted cardiovascular mortality among populations using very soft water may be as much as 15-20% higher than among populations using hard water; differential reported for the United Kingdom may be as high as 40%.1” Without appropriate references, people may find the statements difficult to believe. The web site should include a list of the publications that could be found in scientific journals to justify statements such as “more than 50 studies have been carried out in nine countries.1” It is possible that the web site had omitted the citation that appeared in the original report. There were some forms of citations in the first two paragraphs. Astonishingly, the references given at the end of this excerpt were on mercury, copper, and other trace metals, which made the report seemed irrelevant to the argument and the element of interest – magnesium.
“The credibility of these water-factor studies depend more on the consistent trend of the findings than their plausibility or the size of the correlation coefficients or the actual significance levels, 1” is a rather deceitful statement; it denies the power of statistical analysis. How could a study allegedly funded by Environmental Protection Agency (EPA) and cited by US National Academy of Sciences, urge the public to ignore the logic of scientific experiments? There is a fallacy that ought to be point out – how do we know that there is a consistent trend if we do not consider the statistical values such as correlation coefficient? The P value, confidence interval, and other statistics inform the reader what is the probability that there is a correlation among the sets of data. In a comparable situation, consumers should not be encouraged to buy product X because it simply provides nutrition, and advised them to care less about the amount of carbohydrate, fat, protein, vitamins, minerals, or fiber that the product contains; the numbers on the food labels reflect the nutritional values of the product, which can be helpful for consumers to make decisions. Furthermore, it could be that US National Academy of Sciences and EPA were mentioned as the authorities to make the audience believe what is being told.
Opinions of an Expert
Harold Foster wrote about groundwater resources of British Columbia. His report was presented on the website of the Canadian Ministry of Water, Land and Air Protection. In chapter six, he discussed about the relation of groundwater and human health. The relationships between health and contaminants in water are difficult to evaluate. Deficiencies of minerals are known to have caused severe illnesses. It is important to elucidate the level of balance consumption because excessive intakes of minerals will have adverse effects on health.
It was noted that there is a controversy over the significance of the relative absence of certain inorganic solutes from surface and groundwater supplies. The report by US National Academy of Science in 1977 was cited again by Foster. The report seemed to be crucial for people who believe that water hardness affects mortality rate from cardiovascular disease. What had the National Academy of Science found on the subject since 1977? Have they changed their position regarding the controversy that emerged after their report?
The statement, “Soft water, deficient in calcium and magnesium, has also been linked to elevated rate of Sudden Infant Death Syndrome, diabetes, cerebrovascular disease, and cancer,” was supported by five references; three out of the five publications cited were authored by Foster. In his report, magnesium was mentioned together with calcium as potentially beneficial solutes in hard water. Magnesium did not seem to be a separate entity in his argument; he did not strengthen nor had weakened magnesium as the vital element to reduce the risk and mortality of heart disease.
Conclusion
The evidences are contradicting; we cannot reject the hypothesis of a relation between magnesium and cardiovascular disease. There are certainly hopes that more promising results will be obtained to support the theory. Magnesium had been proven to reduce the risk of hypertension; prevention by increasing the intake of magnesium was more successful in women than men. On the downside, the effect of increasing magnesium intake was suggested to be smaller than the effect of fiber. Magnesium had been identified as an effective treatment of mild hypertension, but not for severe cases.
Studies had shown that magnesium is not a significant factor in reducing the risk of heart disease, but low levels of magnesium in blood may indicate the pathogenesis of coronary heart disease. Intravenous injection of magnesium had also given different results in the attempts to reduce the mortality of individuals with myocardial infarction. In regard to magnesium in drinking water, Marx and Neutra (1997) had summed up precisely, “Future research must provide better answer about low level waterborne magnesium before recommendations to the public can be made.” People should remain sceptical about the information posted on privately funded websites; they should be aware of the agenda behind these websites, in regard to a controversial issue.
Bibliography
Ascherio, A., Hennekens, C., Willett, W.C., Sacks, F., Rosner, B., and Manson, J., Witteman, J., and Stampfer, M.J. “Prospective study of nutritional factors, blood pressure, and hypertension among US women.” Hypertension. May 1996. 27(5): 1065-1072.
Ascherio, A., Rimm, E.B., Giovannucci, E.L., Colditz, G.A., Rosner, B., Willett, W.C., Sacks, F., and Stampfer, M.J. “A prospective study of nutritional factors and hypertension among US men.” Circulation. November 1992. 86(5): 1475-1484.
Marx, A., and Neutra, R.R. “Magnesium in drinking water and ischemic heart disease.” Epidemiology Review. 1997. 19(2): 258-272.
“Exhibit B – Drinking Water and Health.” The Magnesium Web Site. 10 Dec 1998. Accessed on 22 Nov 2002. Online at http://www.mgwater.com/exhibitb.shtml
Foster, H.D. “Chapter 6: Groundwater and Human Health.” Groundwater Resources of British Columbia. Canadian Ministry of Water, Land and Air Protection. Accessed on 22 November 2002, online at http://wlapwww.gov.ba.ca/wat/gws/gwbc/C06_health.html
ISIS-4 Collaborative Group. “ISIS-4: a randomized factorial trial assessing early oral captopril, oral mononitrate, and intravenous magnesium sulphate in 58,050, patients with suspected acute myocardial infarction.” Lancet. 18 March 1995. 345(89051): 669-685.
Kawano, Y., Matsuoka, H., Takishita, S., and Omae, T. “Effects of magnesium supplementation in hypertensive patients: assessment by office, home, and ambulatory blood pressures.” Hypertension. August 1998. 32(2): 260-265.
Liao, F., Folsom, A.R., and Brancati, F.L. “Is low magnesium concentration a risk factor for coronary heart disease? The Atherosclerosis Risk in Community (ARIC) Study.” American Heart Journal. September 1998. 136(3): 480-490.
“Magnesium (reviewed by Rude, R.K).” Linus Pauling Institute. Updated on 5 February 2001. Accessed on 22 November 2002, online at http://www.orst.edu/dept/lpi/infocenter/minerals/magnesium/magnesium/magnesium.html
Peacock, J.M., Folsom, A.R., Arnett, D.K., Eckfeldt, J.H., and Szkio, M. “Relationship of Serum and dietary magnesium to incident hypertension: the Atherosclerosis Risk in Communities (ARIC) Study.” Annals of Epidemiology. April 1999. 9(3): 159-165.
Shechter, M., Merz, C.N., Paul-Labrador, M., Meisel, S.R., Rude, R.K., Molloy, M.D., Dwye, J.H., Shah, P.K., and Kaul, S. “Oral Magnesium supplementation inhibits platelet-dependent thrombosis in patients with coronary artery disease.” American Journal of Cardiology. 15 July 1999. 84(2): 152-126.
Shechter, M., Sharir, M., Labrador, M.J., Forrester, J., Silver, B., and Bairey Merz, C.N. “Oral magnesium therapy improves endothelial function in patients with coronary artery disease.” Circulation. 7 November 2000. 102(19): 2353-2358.
Spencer, H., Norris, C., and Williams, D. “Inhibitory effects of zinc on magnesium balance and magnesium absorption in man.” Journal of American College Nutrition. 1994. 13: 479-484.
Witteman, J.C., Grobee, D.E., Derkx, F.H., Bouillon, R., de Bruijn, A.M., and Hofman, A. “Reduction of blood pressure with oral magnesium supplementation in women with mild to moderate hypertension.” American Journal of Clinical Nutrition. July 1994. 60(1): 129-135.
Woods, K.L., Flectcher, S., Roffe, C., and Haider, Y. “Intravenous magnesium sulphate in suspected acute myocardial infarction: results of the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).” Lacent. 27 June 1992. 339(8809): 1553-1558.
Woods, K.L., and Flectcher, S. “Long-term outcome after intravenous magnesium sulphate in suspected acute myocardial infarction: the second Leicester Intravenous Magnesium Intervention Trial (LIMIT-2).” Lancet. 2 April 1994. 343(8901): 816-819.
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