Swan song for antioxidant supplements?
For the past few years, antioxidant supplements have been experiencing
a steady fall from grace. Once hailed as a cheap and easy way to ward
off chronic diseases, antioxidants such as vitamin C, beta carotene,
and vitamin E haven't panned out as a way to prevent heart disease
In 2003, the federal Agency for Healthcare Research and Quality looked
at the most rigorous studies of three antioxidants — vitamin C,
vitamin E, and coenzyme Q10 — and heart disease. Perhaps a little
smoke, but no fire, the agency concluded.
The American Heart Association's Nutrition Committee set itself much
the same task. It evaluated 15 large trials in which more than 100,000
volunteers didn't know whether they were taking an antioxidant pill or
a placebo. The result of this analysis? No evidence that antioxidant
supplements affect heart disease. The committee's report, published in
the August 3, 2004, issue of Circulation , warns against using
antioxidant pills or potions to ward off heart attacks or heart disease.
These two assessments seem to slam the door on antioxidant supplements.
Yet optimistic presentations made at a three-day symposium on vitamin
E held this May in Boston could represent the proverbial foot in the
What's the real story on antioxidant supplements? The first
question that needs answering is: Where did people first get the delightful
idea that you could take a simple vitamin pill to prevent or treat heart
disease? Let's look at the case of vitamin E.
Over the years, study after study after study has shown that people
who eat plenty of fruits and vegetables are less likely to have heart
disease than people who shy away from these foods. Eager to understand
how fruits and vegetables protect the heart and blood vessels (and other
systems, too), scientists looked for likely suspects. They turned first
to compounds that were abundant in food and easy to identify and extract.
The early list included antioxidants such as vitamin C, beta carotene,
and vitamin E.
The discovery that a chemical reaction akin to rusting, called oxidation,
activated LDL (bad) cholesterol in the body and kicked off the artery-clogging
process of atherosclerosis heightened interest in these vitamins. By
protecting LDL from oxidation, so the thinking went, vitamin E could
block an early event leading to heart disease. Studies in which people
were asked about their dietary habits backed this up, showing that people
who took vitamin E supplements or got plenty of vitamin E from food were
less likely to develop heart disease.
Yet studies testing vitamin E against placebo have been disappointing,
to say the least. In five trials, rates of heart disease and death were
the same for vitamin E and placebo. In three others, vitamin E reduced
nonfatal heart attacks but not deaths. In another, it seemed to counteract
the beneficial effects of a cholesterol-lowering statin.
Why do the results from clinical trials seem to contradict the positive
picture for vitamin E and other antioxidants? There are several reasons.
People who choose to take vitamin E or eat foods rich in it could also
do other healthy things, like maintain a healthy weight or get more exercise,
and it may be that these other factors offer protection against heart
disease. It is also possible that randomized trials are too short, and
that it takes more than a few years to see what antioxidants can do.
Plus, many of the vitamin E trials included people who already had heart
disease, and it could be that antioxidants have no effect once arteries
are already pocked with cholesterol-filled plaque, but may work earlier
in life. Or maybe single antioxidants, or even combinations of them,
aren't what we really need.
We tend to think of antioxidants as interchangeable. That's misleading.
Each antioxidant has a unique set of chemical behaviors and biological
properties. They work together as parts of an elaborate network, with
each different substance (or family of substances) playing a slightly
different role. No single antioxidant can do the work of the whole crowd.
And it may be that taking too much of any one could throw the network
At the vitamin E symposium in Boston, researchers described what this
vitamin can do in laboratory studies: It acts as an anti-inflammatory
agent and prevents platelets from clumping, much as aspirin does; it
boosts production of nitric oxide, a substance that keeps blood vessels
healthy and relaxed; it affects the activity of some genes; and it influences
the production of cell-signaling molecules. But no one knows just what
it does in our bodies, how much we really need, or in what form we should
Natural vitamin E is an amalgamation of eight different substances:
four tocopherols (alpha, beta, gamma, and delta) and four tocotrienols
(also alpha, beta, gamma, and delta). Vitamin supplements contain all
or mostly alpha tocopherol, yet research on gamma tocopherol suggests
it — and the other six components — might also be important
for fighting disease.
We'll keep you posted on that. In the meantime, it's best to get your vitamin
E and other antioxidants the old-fashioned way, from fruits, vegetables,
whole grains, nuts, and oils made from corn, soybeans, or peanuts.
December 2004 Update
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