Nutrients in Foods are Best, with Supplements Filling Narrow Niche

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Nutrients in Foods are Best, with Supplements Filling Narrow Niche

By Neil Osterweil, Senior Associate Editor, MedPage Today

Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of

Pennsylvania School of Medicine.

July 20, 2005

Review

BOSTON, July 20-Essential nutrients that come from foods are better

than pills from bottles, concluded nutrition researchers. Indications

for supplements, they added, occupy a narrow niche.

So file it under mom was right again, with her mantra about drinking

your milk and eating your vegetables.

Taking massive or even moderate quantities of pills containing single

nutrients may in some instances do more harm than good, cautioned

nutrition experts Alice H. Lichtenstein, D.Sc., and M. ,

M.D., of the Mayer USDA Human Nutrition Research Center on Aging

at Tufts here.

" The identification, isolation, and purification of nutrients in the

early 20th century raised the possibility that optimal health outcomes

could be realized through nutrient supplementation, " they wrote in the

July 20 issue of the Journal of the American Medical Association.

Recent attempts using this approach for cardiovascular disease and lung

cancer have been disappointing, as demonstrated with vitamin E and beta

carotene.

Vitamin E supplementation, once touted for its cardiovascular benefits

based on epidemiologic evidence and results of a few small intervention

studies, does not appear to reduce the risk of heart disease, agreed

the American College of Cardiology, American Heart Association

Nutrition Committee, and the U.S. Preventive Services Task Force.

Even more notoriously, beta carotene, an antioxidant thought to protect

against the risk of lung cancer (particularly among smokers), was

associated in two large-scale intervention studies with an increased

risk of lung cancer among smokers and asbestos-exposed workers, the

authors noted.

The authors conceded that for some people, supplements can play an

important role in maintaining health, such as the use of calcium and

vitamin D in people at risk for osteoporosis, fluoride to prevent

cavities in children, and omega-3 fatty acids to reduce the risk of a

major event in patients with coronary heart disease (the latter

recommended by the American Heart Association).

In addition, people with genetic mutations that affect nutrient

absorption and metabolism may benefit from individualized

supplementation, but such people are the exceptions rather than the

rule.

Sometimes with supplements it's a case of no harm, no foul when a

promising dietary intervention fails to live up to its potential. But

even seemingly benign dietary interventions may have unforeseen

consequences, Drs. Lichtenstein and noted.

Also, large quantities of supplemental nutrients may cancel out the

benefits of others.

" For example, calcium inhibits heme and nonheme iron absorption. Other

nutrient interferences are as follows: iron inhibits zinc absorption,

zinc inhibits copper absorption, and vitamin E antagonizes vitamin K

action, " the nutritionists wrote.

Then there is evidence from studies looking at more comprehensive

approaches, such as the Dietary Approaches to Stop Hypertension, or

DASH diet, which is rich in fruits and vegetables and low-fat dairy

products, and which reduced blood pressure significantly even when

there was not a concerted effort to restrict salt intake.

" There are insufficient data to justify an alteration in public health

policy from one that emphasizes a food-based diet to fulfill nutrient

requirements and promote optimal health outcomes to one that emphasizes

dietary supplementation. Our conclusion is based on the lack of a

complete understanding of nutrient requirements and interactions,

disappointing results of intervention studies with single nutrients or

nutrient cocktails, and limited understanding of how the message would

be interpreted with respect to dietary and lifestyle behaviors, " Drs.

Lichtenstein and concluded.

http://www.medpagetoday.com/PrimaryCare/DietNutrition/tb1/1394