Vegetarian Journal July/Aug 1998
Scientific Update
By Reed Mangles, Ph.D., R.D.
A Review of Recent Scientific Papers Related to Vegetarianism
Dietary Fat and Risk of Stroke
Back in December of last year, newspaper headlines trumpeted "High-Fat
Diet for Men is Linked to Fewer Strokes." These reports were based
on a study of 832 men aged 45 to 65. Back in the late 1960s, researchers
asked the men what they ate in the previous 24 hours. The men were then
followed for 20 years. Those men who had the highest intakes of fat, saturated
fat, and monounsaturated fat were found to have the lowest risk of having
a stroke. Does this mean we should all change to a high fat, high saturated
fat diet? Not at all.
First of all, this study did not reach any conclusions with regard to
women, so women should not make changes based on this study. Secondly,
diets high in fat and saturated fat have been associated with increased
risk of heart disease and possibly with obesity (high total fat diets).
Do men really have to choose between heart disease and stroke? Probably
not. Perhaps the answer to reducing risk of both conditions lies in a diet
with moderate levels of fat, low levels of saturated fat, and moderate
levels of monounsaturated fats. However, don't rush to change your diet
based on the results of this one study. We must question whether one day's
worth of information on what foods were eaten 20 years ago can reliably
predict health outcomes like stroke. Additionally, subjects whose diets
were lowest in fat were highest in alcohol. Excessive use of alcohol raises
risk of stroke. Other factors which could also have increased risk of stroke
were not examined.
Gillman, M.W., Cupples, A., Millen, B.E., et al. 1997. Inverse
association of dietary fat with development of ischemic stroke in men.
JAMA; 278: 2145-2011.
Sherwin, R., Price, T.R. 1997. Fat chance. Diet and ischemic stroke.
JAMA; 278: 2185-2011.
Zinc and Vegetarian Diets
Do vegetarians get enough zinc? Not only are our diets devoid of meat,
fish, and poultry, which are commonly considered good sources of zinc,
but we also have higher intakes of phytates and fiber, which keep our bodies
from absorbing zinc as well. Researchers from the USDA evaluated zinc status
in 21 women who followed a lacto-ovo-vegetarian diet for 8 weeks. The subjects
did absorb less zinc when they were on the vegetarian diet compared to
when they were on a non-vegetarian diet. Despite the lower absorption of
zinc, the subjects' blood zinc levels remained in the normal range and
they appeared to be getting an adequate amount of zinc from their diet.
The authors recommend that vegetarians eat good sources of zinc--like whole
grains and legumes--regularly.
Hunt, J.R., Matthys, L.A., Johnson, L.K. 1998. Zinc absorption, mineral
balance, and blood lipids in women
consuming controlled lacto-ovo-vegetarian and omnivorous diets for
8 wks. Am J Clin Nutr; 67: 421-430.
Health Canada Approves Fortification of Plant-Based Beverages
Canadian Food and Drug Regulations have not permitted the addition of vitamins
or minerals to beverages such as soymilk and rice milk. Prior to December
of last year, only unfortified plant-based beverages could be sold in Canada.
Fortification of juice is still not permitted.
New recommendations allow for the fortification of plant-based beverages
provided they contain a specified level of protein or are labeled as "not
a source of protein" and if they have no more than a specified level of
fat, saturated fat, and trans fatty acids. Beverages are to be labelled
"fortified [name of plant] beverage. " Fortified plant beverages
may not contain ingredients derived from cow's milk or goat's milk. Fortified
beverages must contain vitamin A, vitamin D, vitamin B-12, riboflavin,
calcium, and zinc at specified levels, and may contain vitamin B-6, vitamin
C, thiamine, niacin, folacin, pantothenic acid, phosphorus, potassium,
and magnesium, again at specified levels.
New Recommendations to Reduce Risk of Cancer
The American Institute for Cancer Research and the World Cancer Research
Fund commissioned a review of the literature on diet and cancer and asked
experts to devise recommendations suitable for all societies designed to
reduce the risk of cancer. They concluded that inappropriate diets are
responsible for around one-third of all cancer deaths.
They looked specifically at vegetarian diets and cancer and concluded
that vegetarians have decreased incidence of several kinds of cancer. They
attributed the reduction in risk to both the exclusion of meat and the
increased intake of plant foods.
This committee found convincing evidence that higher intakes of vegetables
and fruits decrease risk of cancer of the mouth and pharynx, esophagus,
lung, and stomach and that higher intakes of vegetables decrease risk of
cancer of the colon and rectum. Increased meat consumption probably increases
risk of cancer of the colon and rectum and possibly increases risk of cancer
of the pancreas, breast, prostate, and kidney. Increased egg consumption
possibly increases risk of colon and rectal cancer. Increased milk and
dairy product consumption possibly increases risk of prostate and kidney
cancer.
The recommendations of this expert panel include:
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Choose predominantly plant-based diets rich in a variety of vegetables
and fruits, legumes, and minimally processed starchy staple foods.
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Eat 15-30 ounces, or five or more servings a day, of variety of vegetables
and fruits, all year round.
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Eat 20-30 ounces, or more than seven servings a day, of a variety of grains,
legumes, roots, tubers, and plantains.
-
Choose minimally processed foods. Limit consumption of refined sugar.
-
If eaten at all, limit intake of red meat to less than 3 ounces daily.
The report concludes that on a global basis and at current rates, use of
appropriate diets may prevent 3-4 million cases of cancer each year.
World Cancer Research Fund/AICR. Food, Nutrition, and the Prevention
of Cancer: a Global Perspective. Washington, DC: AICR, 1997.
The Effect of Protein Intake on Calcium Lost in the Urine
Several studies have shown that high-protein diets increase urinary
calcium loss, possibly leading to a reduction in bone mass and an increase
in osteoporosis. Japanese researchers (Itoh et al.) confirmed these results
in a study of close to 750 men and women aged 20-79 years. In both older
and younger subjects, a higher intake of protein was associated with greater
calcium loss in the urine. When animal protein and vegetable protein were
examined separately, higher intakes of animal protein were associated with
greater calcium loss, while there was no such association between plant
protein and calcium. All the subjects included animal protein in their
diets.
The subjects in this study all had protein intakes which were higher
than the Japanese RDA for protein. (Average intake for younger men was
89 grams of protein per day; for younger women it was 72 grams.) Does this
suggest that diets which are lower in protein are better for bone health?
Perhaps. However, it may be that a diet which contains moderate levels
of protein is most desirable. One study (Kerstetter et al.) has suggested
that while high protein intakes are not desirable because of their effect
on urinary calcium, very low intakes of protein (around 44 grams a day
for women) also have a negative effect on calcium metabolism. Perhaps the
answer is a diet containing moderate amounts of protein from plant sources.
Vegetarians can hope that this will be a new area of study.
Itoh, R., Nishiyama, N., Suyama, Y. 1998. Dietary protein intake and
urinary excretion of calcium: a cross-sectional study in a healthy Japanese
population. Am J Clin Nutr; 67: 438-444.
Kerstetter, J.E., Caseria, D.M., Mitnick, M.E., et al. 1997. Increased
circulating concentrations of parathyroid hormone in healthy, young women
consuming a protein- restricted diet. Am J Clin Nutr; 66: 1188-2011.
New Statements from the AAP
The American Academy of Pediatrics (AAP), a widely recognized organization
of pediatricians, has developed two statements of interest to vegetarian
parents. The first deals with the level of fat recommended for children.
As they have stated previously, the AAP calls for no restriction of fat
for infants of less than two years, when rapid growth and development call
for plenty of calories. After two years, children should gradually limit
dietary fat so that by around age five, between 20 and 30 percent of calories
comes from fat. This type of diet should be used throughout childhood and
adolescence. Saturated fat should provide less than 10 percent of total
calories and dietary cholesterol should be less than 300 milligrams daily.
The AAP's second statement deals with soy protein-based infant formulas.
These formulas (not soymilk) are safe alternatives to breast milk or cow
milk-based formulas. The AAP lists parents seeking a vegetarian-based diet
for a term infant as one of a number of conditions where soy formulas
should be used.
Committee on Nutrition, American Academy of Pediatrics. 1998. Cholesterol
in childhood. Pediatrics; 101: 141-147.
Committee on Nutrition, American Academy of Pediatrics. 1998. Soy protein-based
formulas: Recommendations for use in infant feeding. Pediatrics;
101: 148-153.
Excerpts from the Jul/Aug Issue:
The Vegetarian Journal published here is not the complete issue,
but these are excerpts from the published magazine. Anyone wanting to see
everything should subscribe to the magazine.
This article was converted to HTML by Jeanie
Freeman
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