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Prevention of Hypertension (High Blood Pressure)

by Hans R. Larsen, MSc ChE

Dietary fiber and magnesium prevent hypertension
Hans Larsen BOSTON, MASSACHUSETTS. Doctors at the Harvard School of Public Health have completed a study to determine the relationship between diet and hypertension (high blood pressure). The study involved over 30,000 male health professionals 40 to 75 years old. The baseline mean systolic blood pressure for the men was 125.5 mm at age 40-44 and 133.7 mm at age 70-75. The diastolic blood pressure at 79.3 to 80.4 mm was relatively unchanged with age. During four years of follow-up 1248 of the men developed hypertension. An analysis showed that participants consuming less than 250 mg per day of magnesium had a 50% greater chance of developing hypertension than had men who consumed 400 mg/day or more. Similarly, an intake of less than 2.4 g/day of potassium increased the risk of hypertension by 50% as compared to an intake of 3.6 g/day or more. The most striking effect was found in the case of dietary fiber where an intake of 24 grams/day or more was found to provide significant protection. A higher intake of dietary fiber, magnesium, and potassium was also found to be associated with lower blood pressure in healthy men. The results of this study confirm the findings of an earlier study involving 58,000 nurses. The authors point out that although diet is important in preventing hypertension, its effect is overshadowed by the risk imposed by obesity and excessive alcohol intake.
Ascherio, Alberto, et al. A prospective study of nutritional factors and hypertension among US men. Circulation, Vol. 86, No. 5, November 1992, pp. 1475-84

Vitamin C lowers blood pressure
AUGUSTA, GEORGIA. Researchers at the Medical College of Georgia have confirmed that people with a high vitamin C concentration in their blood have lower blood pressures than do people with little vitamin C. They tested 168 healthy people, 56 of which were taking supplements containing ascorbic acid. Among their findings: plasma ascorbic acid levels were 11% higher in supplement users than in non-users; both diastolic and systolic blood pressure were about 5 mm lower in people having a high plasma level of vitamin C than in people having a low level. Blood levels of selenium, vitamin A and vitamin E were not found to affect blood pressure, but both obesity and smoking had a significant adverse effect.
Moran, John P., et al. Plasma ascorbic acid concentrations relate inversely to blood pressure in human subjects. American Journal of Clinical Nutrition, Vol. 57, March 1993, pp. 213-17

Calcium combats high blood pressure
PORTLAND, OREGON. Researchers at the Oregon Health Sciences University have just published a major overview on the current knowledge concerning the effect of dietary minerals on high blood pressure. They conclude that the effect of sodium intake on blood pressure is still not clear. It may be that only a subset of people with a genetic defect are sensitive to salt intake. The chloride ion in itself does not seem to increase blood pressure, but when combined with sodium it does cause hypertension in salt-sensitive individuals. A four-year study of 60,000 nurses concluded that women who have a calcium intake of 800 mg/day or more have a 23 per cent lower risk of developing high blood pressure than women with an intake of 400 mg/day or less. The benefits of calcium are even greater among pregnant women. Controlled trials have found that women who consume between 1500 - 2000 mg/day of calcium reduce their risk of developing pregnancy-induced hypertension by as much as 50 per cent. It has also been shown that maternal calcium intake directly affects the infant's blood pressure. Women with a high calcium intake gave birth to babies with higher birth weights and lower blood pressures. This lower pressure persisted throughout at least the first five years of life. The effect of potassium on blood pressure is still being actively investigated. One trial found that a 50 per cent increase in potassium from natural foods lowered blood pressure and dramatically reduced the need for blood pressure-lowering drugs. Another trial found that supplementation with potassium lowered blood pressure by 10 - 14 mm Hg. Several studies suggest that a low magnesium intake is associated with hypertension, stroke, and ischemic heart disease. It has been proposed that supplementation with about 900 mg/day of magnesium, about 2.5 times the RDA, is required in order to effectively lower blood pressure. (71 references)
Reusser, Molly E. and McCarron, David A. Micronutrient effects on blood pressure regulation. Nutrition Reviews, Vol. 52, No. 11, November 1994, pp. 367-75

Fish oils recommended for diabetes and hypertension
TROMSO, NORWAY. Fish and fish oils help protect against the development of atherosclerosis and heart disease. It is believed that fish oils exert their protective effect by lowering blood pressure and the levels of triglycerides and very-low-density lipoprotein (VLDL). Fish oils are also believed to reduce platelet aggregation and to suppress the growth of smooth-muscle cells in the arterial walls. Many people with hypertension also suffer from diabetes and there has been concern that fish oil supplementation may aggrevate problems with glucose intolerance. Researchers at the University of Tromso now report that fish oil supplementation lowers blood pressure significantly in people with hypertension and has no effect on glucose control even in people with mild diabetes. The study involved 78 obese volunteers with essential hypertension. The participants were randomly assigned to one of two equal-sized groups. The fish oil group received four fish oil capsules a day (containing a total of 3.4 grams of a mixture of eicosapentaenoic acid and docosahexaenoic acid) for a period of 16 weeks. The control group received four corn oil capsules a day. At the end of the test period the average (mean) systolic blood pressure had dropped by 4.4 mm Hg and the diastolic pressure by 3.2 mm Hg in the fish oil group. The average blood pressure in the control group did not change. The researchers also found that plasma triglyceride and VLDL levels in the fish oil group decreased significantly (by about 9 per cent) while they increased significantly (by about 12 per cent) in the control group. There were no changes in total or low-density-lipoprotein levels in either group. Extensive tests (oral glucose tolerance, hyperglycemic and hyperinsulemic clamps) were done to evaluate the effect of fish oil supplementation on glucose control. No adverse effects were found. An editorial accompanying the research report concludes that fish or fish oil is useful in the prevention of vascular disease in diabetics. Patients with diabetes should eat fish two to three times a week or, as an alternative, supplement with two to three one gram capsules of fish oil per day.
Toft, Ingrid, et al. Effects of n-3 polyunsaturated fatty acids on glucose homeostasis and blood pressure in essential hypertension. Annals of Internal Medicine, Vol. 123, No. 12, December 15, 1995, pp. 911-18
Connor, William E. Diabetes, fish oil, and vascular disease. Annals of Internal Medicine, Vol. 123, No. 12, December 15, 1995, pp. 950- 52

Garlic lowers blood pressure and cholesterol
PROVIDENCE, RHODE ISLAND. Researchers at Brown University School of Medicine report that supplementation with aged garlic extract lowers cholesterol levels and blood pressure in men with high cholesterol levels. Their experiment involved 41 men aged 32 to 68 years who had total cholesterol concentrations between 5.7 and 7.5 mmol/L (220-290 mg/dL) at the start of the study. After a four-week baseline period half the men were given nine aged garlic capsules (Wakunaga of America) daily. Each capsule contained 800 mg of aged garlic extract. The capsules were taken three at a time with meals for a six-month period. The other half of the men were given a placebo. At the end of the six- month period the supplementation was changed so that the former garlic group was given the placebo and the placebo group was given the aged garlic extract for an additional period of four months. Cholesterol levels and blood pressure were measured monthly. The researchers conclude that supplementation with aged garlic extract lowers total cholesterol levels by an average of 6-7 per cent. Low-density- lipoprotein cholesterol was lowered by an average of 4.6 per cent. The researchers also noted a 5.5 per cent decrease in systolic blood pressure and a smaller decrease in diastolic pressure. They found no adverse effects of the garlic supplementation in regard to blood count, blood chemistry, or thyroid function and conclude that garlic supplementation for extended periods of time is safe and beneficial.
Steiner, Manfred, et al. A double-blind crossover study in moderately hypercholesterolemic men that compared the effect of aged garlic extract and placebo administration on blood lipids. American Journal of Clinical Nutrition, Vol. 64, December 1996, pp. 866-70

Potassium supplementation lowers blood pressure
BALTIMORE, MARYLAND. Researchers at the Johns Hopkins University School of Medicine have come out in favour of using supplementation with potassium in the treatment and prevention of hypertension (high blood pressure). A group of seven medical researchers reviewed 33 randomized, controlled supplementation trials involving over 2600 participants. They conclude that potassium supplementation is effective in lowering both systolic and diastolic blood pressure. The average observed decrease in hypertensive patients was 4.4 mm Hg and 2.5 mm Hg for systolic and diastolic pressure respectively. In people with normal blood pressure the observed decreases were 1.8 mm and 1.0 mm. The amount of elemental potassium used in the studies varied from 60 mmol (2.5 grams) to 120 mmol (5.0 grams) daily. Sixty mmol of potassium is equivalent to 4.5 grams of potassium chloride, 6 grams of potassium bicarbonate or 20 grams of potassium citrate. Oral potassium supplementation appeared to be well tolerated in all the studies examined. The researchers conclude that potassium supplementation "should be considered as part of recommendations for prevention and treatment of hypertension." Potassium supplementation is particularly important in people who are unable to reduce their intake of sodium.
Whelton, Paul K., et al. Effects of oral potassium on blood pressure. Journal of the American Medical Association, Vol. 277, May 28, 1997, pp. 1624-32

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