If dieting omits a nutrient, its effects take time to show

When people are feeling and functioning well, it is common for them to assume that their diet is good and meeting their nutrient needs. However, once health starts to decline, and problems such as easy fatigue become common, people often start searching for nutritional solutions. There are, of course, thousands of health gurus or special products that promise to fix whatever ails you.

At the very least, programs that promise to return youthful vigor, decrease pain, improve memory naturally, etc., can be seductive. Frequently, adopting a new way of eating does, in fact, make you feel better — at least initially and even for some time. But when health problems start to return, it is human nature to assume that the dietary changes that made you feel better initially are the answer and that you need to follow the diet more carefully.

Often, when someone has attempted to eat healthfully, a lot of thought, time and effort has gone into that. Frequently these hard-earned dietary beliefs become ingrained in one’s personal philosophy and take on a religious fervor. As a consequence, it can be difficult to make changes even if the eating style starts to cause nutrient deficiencies and result in health problems.

Question: How can a person be unaware of an essential nutrient deficiency?

Answer: It generally takes time for inadequate intake of an essential nutrient to significantly affect the body’s level of the nutrient. When supply of a nutrient in the diet does not keep up with demand, the body is gradually drained of the nutrient over a period of weeks, months or even years before negative effects become obvious.

For example, a plant-based diet that is free of animal foods contains little or no vitamin B12. If the diet is not supplemented with B12 or with B12-fortified food, it can take several years before body levels of the vitamin are excessively drained. But when levels get critically low for too long, the effects on nerves and blood cells can be severe. The effects of the nerve damage can be subtle initially but can progress and affect many parts of the body, including the brain. If the damage from deficiency goes on too long, the neurological effects can be irreversible. Even serious psychological and severe short-term memory problems have been caused by B12 deficiency.

Q: Can one nutrient deficiency affect other nutrients?

A: Yes. Nutrient deficiencies can have a domino effect. For example, if someone is deficient in iron for too long, it can damage cells in the stomach lining, among other things. Parietal cells are one of the key types of cells affected. These cells secrete a substance that is required for normal vitamin B12 absorption. Consequently, a normally adequate level of vitamin B12 in the diet will not be enough because it is not being absorbed properly. Frequently, someone suffering from vitamin B12 deficiency also might be iron-deficient. The symptoms of these two nutrient deficiencies overlap somewhat, and the impact on health can be severe.

The delayed impact on the body of a deficient nutrient intake is one of many things that make nutrition complex and confusing — especially when it comes to applying alternative approaches to eating. For more than a century, nutrition scientists have stressed the importance of meeting nutrient needs by consuming a variety of food both across and within all of the major food groups — fruits, vegetables, grains, legumes (beans and peas), nuts and seeds; grains; milk and milk products; and eggs, fish, poultry and meat. Each group has nutrient strengths and weaknesses.

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, University of Hawaii-Manoa. Dobbs also works with University Health Services.