SCIENTIFIC UPDATES
By Reed Mangels, PhD, RD
EATING RIGHT AFTER A HEART ATTACK
If diet can reduce risk of heart disease in a healthy person, could it also reduce
the risk of death after a heart attack? Researchers in India set out to answer this
question. They studied 406 predominantly male patients who were assigned to either a
diet rich in fruits, vegetables, cereals, nuts, and fish or to a standard low
calorie, reduced fat and cholesterol diet. The diets were started within 48 hours
after the subjects had a heart attack. The subjects on the near-vegetarian diet had
higher intakes of fiber, polyunsaturated fat, vitamin C and vitamin E. Their dietary
cholesterol, calories, and saturated fat were lower than the other group's.
After 6 weeks, those on the near-vegetarian diet had a larger decrease in blood cholesterol, LDL-cholesterol and triglycerides and greater weight loss than did sub-jects on the more traditional diet. These differences were accompanied by fewer fatal and non-fatal repeat heart attacks and a lower rate of sudden cardiac death in the 6 weeks after the first heart attack in subjects eating a diet rich in cereals, nuts, fruits and vegetables, and fish.
Both groups got about 28% of calories from fat. Those on the near-vegetarian diet averaged 128 milligrams of dietary cholesterol per day; the others averaged 266 mg per day. Dean Ornish, M.D., has successfully used a diet with close to 10% of calories from fat and almost no cholesterol in treatment of severe heart disease. We can only wonder if a similar diet would have been even more helpful for the 12 subjects of this study on vegetarian diets who died within 6 weeks of their first heart attack with less rigorous dietary changes.
For more information see: Singh RB, Rastogi SS, Verma R, Bolaki L, Singh R: An Indian experiment with nutritional modulation in acute myocardial infarction. Am J Cardiol 69:879-85, 1992.
DIETS HIGH IN CALCIUM, LOW IN ANIMAL PROTEIN REDUCE RISK OF KIDNEY
STONES
In 1986, more than 2 billion dollars was spent on the treatment of kidney stones.
About 10% of men and 3% of women will suffer (and from what I've heard, suffer is a
mild term) from kidney stones at some time.
Since kidney stones are commonly composed of calcium oxalate and calcium phosphate, conventional wisdom says that to prevent the formation of calcium-containing kidney stones, dietary calcium should be reduced. Until recently no studies had been done examining the validity of this advice.
Dr. Gary Curhan and co-investigators at Harvard studied more than 45,000 men for four years. They asked the subjects about their diets at the start of the study and then saw who got kidney stones over the next four years (505 men). Those men who had the highest intake of dietary calcium (over 1050 milligrams daily) had almost half the risk of having a kidney stone compared to men with the lowest dietary calcium (under 600 mg per day). The authors speculate that increased dietary calcium may reduce the absorption of oxalate. Oxalate is also a culprit in kidney stone formation. If less was absorbed, less would be available to form stones.
Readers who want to reduce their risk of kidney stones should not rely on calcium supplements. In the Harvard study, they did not have the same protective effect as did dietary calcium, for unknown reasons. Dairy products are not necessarily the best way to prevent kidney stones. In this study, high animal protein intakes were found to increase risk of kidney stones. Since dairy products are so high in animal protein, it seems sensible to rely mainly on non-dairy sources of calcium to reduce risk of kidney stones.
In addition, those subjects who had high potassium intakes (potassium is found in many fruits and vegetables) and generous fluid intakes also had a lower risk of kidney stones. An editorial in the same issue of New England Journal of Medicine points out that vegetarians have a reduced risk of kidney stones. The editorial also recommends that anyone with calcium oxalate-containing kidney stones drink enough water to keep urine volume above 2 liters per day, limit oxalate rich foods, and limit animal protein.
For further information see: Curran GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones. N Engl J Med 328:833-838, 1993.
Lemann J, Jr. Composition of the diet and calcium kidney stones. New Engl J Med 328: 880-882, 1993.
DIET OF BREAST- FEEDING WOMEN AFFECTS INCIDENCE OF ALLERGIES IN THEIR
CHILDREN
Swedish researchers studied infants to see if their mothers' diets while
breast-feeding affected the infants' incidence of allergy. All infants studied were
from families with a history of allergies (rashes, asthma, runny noses). Half of the
mothers were placed on diets free of eggs, cow's milk, and fish for the first three
months of lactation. The other half had no dietary restrictions. All infants were
started on cow's milk after six months and on eggs and fish after nine months.
At four years, those children whose mothers had avoided cow's milk, eggs, and fish had fewer and less severe allergic-type rashes than the other children. No difference was seen in asthma or other respiratory symptoms. It would have been interesting to see if a longer period of avoiding cow's milk and other foods by mothers and infants would have reduced the incidence of respiratory symptoms and if this would have had an even greater effect on other symptoms.
The researchers state that "we still believe that it is too early to advocate ... avoidance of [foods] during lactation to families with [allergies]". They recommend further studies. While one small study does not prove that this type of diet is effective in reducing allergic symptoms, since a diet free of cow's milk and eggs can be nutritionally adequate, it seems reasonable to recommend such a diet to breast-feeding women with a family history of allergy.
For further information see: Sigurs N, Hattevig G, Kjellman B. Maternal avoidance of eggs, cow's milk, and fish during lactation: Effect on allergic manifestations, skin-prick tests, and specific IgE antibodies in children at age 4 years. Pediatrics 89: 735-739, 1992.
