March is "Nutrition Month," and we want to share some bits of knowledge that often are underappreciated.

The nutrient that is most commonly deficient in the world and in Hawaii is iron, and this fact is often not fully appreciated. Despite the widespread and serious impact on health, a low intake of iron often is ignored until it causes serious health problems, and even then this deficiency sometimes is taken lightly.

First, however, it is important to acknowledge that consuming adequate amounts of all essential nutrients is critical for optimal physical and mental health. Adequate amounts of nutrients, which are food chemicals, are required for normal development of an embryo into a fetus during pregnancy.

The continued development of an infant into an adult and throughout life continues to require an adequate supply of essential nutrients.

Here are some nutrition facts well worth knowing for your next trivia game:

» Iron is the most common nutrient deficiency, and it plays an essential role in well more than 60 metabolic functions in the body.

» Iron deficiency (even without anemia) can cause fatigue and many other symptoms.

» Iron deficiency is a more common cause of fatigue and tiredness than thyroid problems.

» Iron (along with iodine) is required for thyroid hormone production. A deficiency of iron can aggravate thyroid problems.

» Normal production of blood cells requires an adequate supply of essential nutrients, including iron, vitamin B12, folate, riboflavin and more.

» Some nutrients (and other food components) can inhibit the absorption of other nutrients. For example, consuming iron and a high calcium food or supplement at the same time strongly inhibits the absorption of the iron. To put this into perspective, consuming 300 mg of calcium (a cup of milk or yogurt) can decrease the amount of iron absorbed by 65 percent. This should be considered when taking dietary supplements or, for that matter, choosing a cheeseburger rather than a regular burger.

» Women and children are most likely to be affected by iron deficiency. Older people whose diets become limited also are at high risk.

» Popeye did not consume spinach to get iron. Spinach is a good food for a number of nutrients but not for iron. Spinach contains too much calcium, aluminum and otherwise healthful compounds, called polyphenols, that strongly inhibit iron absorption.

» Iron is found in food in two major forms: heme iron and nonheme iron. Heme iron is found in red meats, and it is much more efficiently absorbed than the nonheme iron found in most other types of food.

» The effects of inadequate iron in a diet can develop slowly over time and cause symptoms that range from thinning hair and misshapen fingernails to challenges in mental function that can include difficulty concentrating and depression.

It also is possible to consume excessive amounts of iron. This is more likely to happen in men because their iron needs are less than half of what women need. So, it is all a balancing act when it comes to nutrients.

This is best summed up by the Goldilocks principle, "Not too much, not too little, but just right."

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.