& Alan Titchenal Tuesday ,April 19, 2011
Common nutrition beliefs are merely urban myths
Today’s technology is amazing. Information can be spread in minutes throughout the world via the Internet and broadcast media. But advances in communication technology also have opened a Pandora’s box of misinformation. Correcting that misinformation is a never-ending, impossible task. The following are examples of this misinformation.
Urban myth from a recent news report: Inadequate Vitamin D is correlated with age-related macular degeneration, and therefore people are urged to eat more vitamin D-rich foods “such as fish, dairy, eggs and leafy vegetables.”
Facts: Inadequate vitamin D is correlated with age-related macular degeneration. In addition, a 4-ounce portion of fatty fish like salmon and sardines meets about half of the recommended daily intake, and a cup of milk provides about one-sixth of daily needs. But, it takes 15 eggs to meet the current adult recommendation for this fat-soluble vitamin, and leafy greens contain no vitamin D at all.
Urban myth: Protein in vegetable foods is more easily digested than protein in animal foods.
Facts: Although this is a common claim, it has been known for more than 100 years that animal food proteins are more digestible than plant food proteins. For example, the human intestine digests more than 95 percent of the protein in eggs, milk, meat and fish. In contrast, the digestibility of protein in nuts and beans is less than 80 percent.
Urban myth: All of the protein in eggs is contained in the egg white.
Facts: A large egg contains on an average 6.3 grams of protein. However, only 60 percent, or 3.6 grams of protein, is in the egg white, with 2.7 grams of protein in the yolk (along with many other essential nutrients).
Urban myth: Eating eggs is a major cause of high blood cholesterol levels.
Facts: Since eggs are high in cholesterol, this would seem to be logical. However, for most people, cholesterol in the diet has a very minor impact on blood cholesterol level. Because the body produces cholesterol, it is possible to have high blood cholesterol with zero cholesterol in the diet. When cholesterol is consumed, the body responds by producing less, and blood levels remain relatively constant. Of course, there are limits to everything, but the cholesterol in a couple of eggs is unlikely to have a measurable impact on blood cholesterol levels of most people.
Urban myth: Good food sources of iron include almonds, broccoli, dried apricots, eggplant and kale.
Facts: For a woman to consume the recommended 18 milligrams of iron per day from these plant-based foods, it would require almost 3,000 calories of almonds (more than a pound), 35 cups of broccoli, more than 1,600 calories of dried apricots, 72 cups of eggplant or more than 15 cups of cooked kale. Compared with beef and other meats containing heme iron (the nonprotein pigment that is part of hemoglobin), the iron in most plant foods is only about one-tenth as readily absorbed due to the chemical forms of iron in these foods. Additionally, the recommended iron intake for vegetarians is greater, at 33 milligrams of iron a day for women and 14 milligrams of iron a day for men.
Although it can be challenging, it is possible to weed out most of the myths from the scientific facts. But it is not an easy process. It requires a healthy dose of skepticism and remaining a lifelong learner.
Joannie Dobbs, PhD, CNS and Alan Titchenal, PhD, CNS
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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