Individual nutrients are too often overly simplified as having one or two functions in the body. This is even the case in many nutrition and medical textbooks. A lack of awareness of the multiple functions of a nutrient can result in serious health problems that actually have an easy fix.

Even with iron, the most common nutrient deficiency in the world, there is a common lack of awareness of the diverse effects inadequate iron can have on the body. Both too little and too much iron can cause health problems, but the importance of meeting basic needs for this essential nutrient often is underappreciated.

Before iron deficiency is identified by blood tests for anemia, low iron levels can already cause health problems. Fatigue, of course, is the most common symptom of iron deficiency. But many other health problems can occur with inadequate iron. Listed below are a number of iron-related problems that too often can be overlooked by the public and health professionals alike.

Brain problems: It is well known that iron deficiency in a fetus or infant damages brain development. A lesser-known fact is that iron deficiency in the normally developed brain can hamper attention and concentration, and impair intellectual performance, at any age. Even sleep problems and some types of depression can be due to iron deficiency in the brain. Dizziness also occurs in some people with low iron, possibly due to limited oxygen supply to the brain.

Heart problems: The function of heart muscle can be impaired by iron deficiency, causing rapid fatigue with light physical activity such as walking up stairs. This also can trigger the pain called angina and even cause heart-rhythm problems — even without anemia.

Thyroid problems: If the thyroid gland runs low on iron, the chemical reactions that use iodine to form thyroid hormone cannot proceed normally. This iron-thyroid link may be why women have more thyroid problems than men. Men require less iron than women.

Stomach and intestinal problems: Iron deficiency prevents normal stomach acid production and impairs digestion and absorption of many nutrients. The lining of the small intestine also is damaged, hampering normal nutrient absorption and increasing the risk of food proteins triggering new food allergies.

Restless legs syndrome: Although many things can trigger RLS, iron deficiency has been found to be the cause in some cases.

Drug and alcohol problems: The liver plays a major role in the breakdown of toxins in the body. For example, alcohol and many drugs are broken down by the liver and intestinal enzymes that require iron to function.

Hair, fingernails and paleness: Hair can become very thin, and one or more fingernails can become flattened or concave with long-term iron deficiency. Because the skin requires a certain level of iron to produce a chemical called melanin, iron-deficient people often have sun-sensitive skin.

Poor temperature regulation: If you are colder than others, it may be an indication of iron deficiency.

If you have any of these problems: It is important to not self-prescribe iron. Some people have a genetic condition that causes excess iron accumulation in the body. An overload of iron can cause many of the same symptoms as an iron deficiency. So, it is important to get your iron status evaluated.

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.