Some Simple Truths about Nutrition
Most Americans who take vitamins don't need them. Could
you be one of these people? Are you afraid that our food supply is lacking in nutrients?
Do you think that vitamin pills can give you extra energy?
That extra vitamins should be taken in times of stress? That vitamin C can prevent colds? That vitamin E has been proven to
prevent heart disease? That large doses of other nutrients can prevent or cure many other ailments? Or that methods labeled
"alternative" offer something special?
Are you afraid there are
"too many chemicals" in our food? Do you believe that foods labeled "natural" or "organic" are safer or more nutritious? Or
that diet plays a major role in behavior? Or that most diseases are caused by improper eating?
Do you think that most nutrition advice in books, magazines,
newsletters, and talk shows is reliable? Or that "alternative" health methods hold great promise? Or that the health marketplace
is tightly regulated by government agencies?
If you have any of these fears or beliefs, you have plenty
of company. But you have been misled!
America is in the midst of a vitamin craze.
Health hustlers who spread false ideas have
developed a huge public following. But nutrition is not a religion. It is a science—composed mainly of human biochemistry
and physiology. What a nutrient can or cannot do in the body is determined by its specific chemical structure and the specific
biochemical reactions in which that structure can become involved.
How can you tell what to believe? The answer to this
question has two parts. First, you should know what is meant by "scientific truth." Then you must determine who is telling
the truth.
How Do We Know What We "Know"?
How are medical facts determined? Humans have always
been curious about disease and what causes it. The more we understand, of course, the better we can control illness. Down
through the centuries, thousands of theories have been formulated to explain the reasons for both health and sickness. During
the past century, however, speculation has been supplanted by reliable knowledge based on experimentation and sound clinical
experience. Armed with this new knowledge, doctors have been able to prevent and cure many diseases in a way that seems almost
miraculous.
As part of the process of scientific development, good
methods have been developed to test whether theories are logical. The sum of these methods is known as the "experimental"
or "scientific" method. This method is used to answer questions like: "If two things happen, one after the other, are they
related?" For example, suppose you take a pill when you have a headache and the headache goes away one hour later. How can
we tell whether the pill relieved you or whether the headache would have gone away by itself anyway? Throughout the world,
hundreds of thousands of scientists are working continuously to determine the boundaries of scientific thought.
As mountains of information are collected, how can we
tell which evidence is valid? "Valid" means honestly collected and properly interpreted— using valid techniques of analysis.
One hallmark of a good experiment is that others can repeat it and get the same results.
This brings us to the question of who can best interpret
experimental findings. Scientists are judging each other all the time. People with equal or superior training look for loopholes
in each others' experimental techniques and design other experiments to test conclusions. Skilled reviewers also gather in
groups whose levels of ability far exceed that of the average scientist. Such experts are not likely to be misled by poorly
designed experiments. Among the reviewers are editors and editorial boards of scientific journals; these people carefully
screen out invalid findings and enable significant ones to be published. (Most reliable journals that cover nutrition topics
are listed in the Index Medicus of the National Library of Medicine.)
As good ideas are put to use, more reports are generated.
When controversies arise, further research can be devised to settle them. Gradually a shared set of beliefs is developed
that is felt to be scientifically accurate. Expert panels convened by government agencies, professional groups, voluntary
health agencies, and other organizations also contribute to this effort. When we speak of the "scientific community," we refer
to this overall process of separating what is truly fact from what is not.
Three basic questions are involved in evaluating whether
a treatment method works:
1. Is it
more effective than doing nothing, or than a placebo?
2. Is it
as safe as doing nothing?
3. If there
is a question about safety, does the potential for benefit exceed the likelihood of harm?
One of the central premises
of science is that no method should be regarded as proven until it is actually proven.
Quacks, of course, operate outside of the scientific
community. They do not use the scientific method to evaluate what they see. In fact, they seldom bother to experiment at all
and ignore the three questions listed above. When scientists point out that they are wrong, quacks try to cover up their inadequacies
by pointing out that the scientific community has made mistakes in the past. This, of course, is true but irrelevant. In recent
years, the odds of major error by the scientific community have decreased greatly. So if you find someone referred to as a
"scientist ahead of his time," he is probably aquack. Quacks may boast of "thousands of cases" in their files. But they won't
tell you that none of these cases separates cause and effect from coincidence, suggestibility, or misdiagnosis. Nor do they
ever keep score and reveal how many failures they have had for each "success."
Interpretation of experimental findings is not always
simple. Consider antioxidants, for example. Certain recent studies have found a lower incidence of death from heart disease
among people who take vitamin E supplements than among similar people who do not. Does this prove that taking high doses of
vitamin E will reduce the risk of a heart attack? Does this prove that taking high doses of vitamin E will do more good than
harm? Does this mean that everyone should take a vitamin E supplement?
The answer to each of these questions is no. The reduction in death rate among the vitamin
E group may have resulted from other lifestyle characteristics of the group such as eating a more healthful diet. Studies
to answer the first question are underway and may be completed within a few years. Even if the results are promising, however,
they may not indicate which people should take a supplement, what dose would be optimal, or whether long-term administration
of vitamin E will turn out to have a detrimental effect. [Subsequent research found a 5% greater risk of dying over a 4-year period—jk.]
Excess vitamin C may damage growing bone, produce diarrhea,
produce "rebound scurvy" in adults and in newborn infants whose mothers took large dosages, caused adverse effects in pregnancy,
produce kidney stones, and cause false urine tests for sugar in diabetics. Vitamin C in large doses can also produce false
negative tests for blood in the stool and thereby prevent early detection of serious gastrointestinal diseases including cancer.
In 1980, the megavitamin world was rocked by a report
of seven cases of unsteady gait and numbness of the feet and hands from taking 2,000 mg or more of vitamin B6 daily
for several months. (The RDA is 2 mg/day.) Although all of them improved greatly within a few months after stopping B6,
their recovery was not complete. Soon afterward, the scientists who made this report heard from at least forty persons with
similar symptoms that had improved after stopping their B6 intake. Some had been misdiagnosed as suffering from
multiple sclerosis! In 1987, a survey at a clinic specializing in the treatment of premenstrual syndrome (PMS) discovered
that 107 patients had developed neurological symptoms as a result of taking vitamin B6. Ninety-two had taken less
than 200 mg (one hundred times the RDA) daily for more than six months, and twenty had taken less than 50 mg/day. The lowest
dosage on which anyone developed symptoms was 20 mg/day for two years; the shortest time was two months of 100 mg/day. Although
all of their symptoms resolved when the B6 was stopped, it is clear that megadoses of B6 pose considerable
risk.
Adverse effects such as those listed above are unlikely
to occur with water-soluble vitamins at intake levels below ten times the RDAs, or with fat-soluble vitamins below five times
the RDAs. But even if lesser dosages don't harm you physically, if you don't need
them, they are a waste of money. The number of reported cases of toxicity is not large, but since there is no evidence
that self-prescribed megadoses are helpful, taking them is senseless.
A recent study by the U.S. Centers for Disease Control and Prevention showed that Americans
who took supplements had exactly the same mortality rate as those who did not. We interpret this to mean that supplements
help some people, harm others, and are a waste of money for most. { The Lancet recently reported that , “9,000 in every million users of such vitamin supplements will
die prematurely as a result of taking something they think is good for them.”--jk}
