Extreme devotion to fad diets can sap key nutrients

Nutrient limitations can impair brain development starting in the womb and continue throughout childhood into young adult years. Our last article highlighted the importance of normal iron nutrition for brain development. Here, we focus on some other essential nutrients involved in brain development such as iodine, choline and vitamins B-12 and D.

Iodine: New research indicates that iodine intake has been declining in the United States due to decreased iodized salt intake and to changes in production methods of milk and bread. A variety of emerging health problems may be related.

It is well known that iodine deficiency impairs brain and nerve development. There is suspicion that a marginal iodine intake can contribute to conditions like cerebral palsy, impaired hearing and more subtle conditions like attention deficit hyperactivity disorder and autism.

The American Thyroid Association recommends daily iodine supplementation for all pregnant and lactating women in the United States. Iodine needs increase substantially during pregnancy and lactation due to the need to provide an adequate supply of iodine to the fetus and infant.

Choline: Like iodine, choline is one of those somewhat "off the radar screen" nutrients. It didn’t even have a recommended level of intake until 1998. Eggs and meat are the richest food sources of choline, so the intake of this nutrient declines as people follow recommendations to cut back on eggs and meat. Animal studies of choline deficiency demonstrate that it impairs normal brain development in ways that compromise brain function for the life of the animal. The same is likely true for people.

Vitamin B-12: This vitamin is present only in foods of animal origin. Anyone consuming a strict vegetarian (vegan) diet needs to obtain this vitamin from supplements or fortified foods. Those consuming diets with only milk and egg animal products also may develop a B-12 deficiency, but it can take several years to become symptomatic. Like iodine and choline, B-12 is critically important for fetal and infant brain development.

Vitamin D: The few good dietary sources of vitamin D include fatty fish like salmon and swordfish and vitamin D-fortified versions of milk, soy milk, orange juice, etc. With moderate exposure of the skin to sunlight, a form of cholesterol is converted into vitamin D. So, without these foods and/or sun exposure, vitamin D status can plummet.

Researchers are proposing that vitamin D deficiency might be a major contributor to autism. Vitamin D is one of the few nutrients that is inadequate in human milk. Even the breast milk of a healthy mother is too low in vitamin D to meet a baby’s needs. Consequently, the baby needs some sun exposure or a supplemental source of vitamin D.

Unfortunately, taking some of the currently popular diet and lifestyle recommendations to extremes may lead people into these nutrient deficiencies as they attempt to lead what they think is a healthful life. Cutting back on salt reduces iodine intake. Cutting out eggs and meat removes two of the richest sources of choline from the diet. Similarly, decreasing or cutting out animal foods in the diet can eventually result in a serious vitamin B-12 deficiency. To top this all off, avoiding sun exposure to decrease the risk of skin cancer can lead to vitamin D deficiency unless vitamin D-rich foods and/or supplements are consumed.

There are some standard blood tests for vitamin B-12 and D status, but iodine and choline status are not commonly assessed in usual medical practice. Eating a variety of foods from all the major food groups can greatly increase the odds of meeting these nutrient needs.

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Joannie Dobbs, Ph.D., C.N.S., and Alan Titchenal, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.