& Joannie Dobbs Monday,
A diet of only good foods is impossible
Wouldn't it be wonderful if making healthy food choices were as clear as black and white. But, alas, the nutrition world can seem more complex then the colors and shapes of a spinning kaleidoscope. All elements are the same, but somehow the view keeps changing.
The goal of this piece is to show both the good and bad sides of individual foods, to make the point that a healthy diet is all about balance.
Question: Why isn't it possible to simplify nutrition to a list of good foods to eat and bad foods to be avoided?
Answer: There is still too much to learn in the fields of nutrition and medicine to make it that simple. But, that doesn't mean we can't make intelligent and balanced food choices.
Most natural foods contain both healthful properties and properties that in excess can cause harm. For example, the cabbage family contains phytochemicals that help prevent a number of cancers. But cabbage also contains a naturally occurring toxicant which when eaten in excess can cause an enlarged thyroid gland, called a goiter.
Goiters occur when there is an inadequate amount of the mineral iodine in the diet. Consuming iodized salt can counteract the toxin in cabbage and help to prevent a goiter from forming.
Q: Are there other examples where too much of a healthful food can be harmful?
A: Fruits, vegetables, and whole grains have many wonderful properties. But the dietary fiber and other substances in some of these same foods can interfere with the absorption of minerals such as iron and calcium.
For example, spinach contains significant amounts of both iron and calcium, but Popeye was fooling himself, as most of these minerals are bound up in a form that can't be absorbed by the body. Spinach is still a good food to include in a well-rounded diet; it contains other important nutrients and phytochemicals that are absorbed.
Fish is another healthy food appreciated for its content of omega-3 fatty acids that are known to prevent heart disease and possibly other conditions, such as prostate cancer and macular degeneration of the retina. But don't go chugging down fish oils day after day. Consuming excessive amounts on a regular basis could impair immune functions and increase the risk of hemorrhagic stroke due to a blood-thinning effect. People taking anticoagulant drugs should use fish-oil supplements only with proper medical supervision.
Soy products are touted for their beneficial phytochemicals, called isoflavones, which are associated with a reduced risk of breast cancer and may help minimize symptoms of menopause.
But too much of these isoflavones may suppress thyroid function. Certainly, those with thyroid conditions should moderate their use of soy foods. Some health professionals also caution that infants fed only soy formulas should have their thyroid function checked periodically.
Because there is no perfect food, nutrition is a balancing act.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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