In February we discussed the importance of variety in food choices to consume safe and adequate amounts of essential nutrients. This column delves into the second fundamental nutrition principle, which is like the Goldilocks rule: not too much, not too little, but just right. In other words, moderation. Meeting all the physiological needs for health requires adequate calories and essential nutrients. Still, it’s important not to get too much.

In general, there’s little risk of consuming too much of any essential nutrient from food. The exceptions are specific vitamins and minerals that are needed in tiny amounts. It’s relatively easy to over-consume them through fortified food and dietary supplements.

Question: Which nutrients are most likely to be over-consumed?

Answer: Fat-soluble ­vitamins.

Vitamins are divided into two categories, water-soluble and fat-soluble, and the body handles each category differently. Vitamins soluble in water (they include B vitamins and vitamin C) are relatively safe because any excess consumed is removed via urine. They are not stored in the body. This also means that these vitamins are required nearly daily in the diet.

On the other hand, fat- soluble vitamins (such as A, D, E and K) are stored in the body and can build up to harmful levels.

As for toxic levels of minerals, toxicity is unlikely for a person whose diet is a typical, nonfortified one that includes a variety of foods within all food groups. Excess mineral absorption is generally restricted to people with a rare genetic predisposition to mineral overload.

But amid the current “superfood” trend, there is one exception: the over- consumption of food containing high levels of manganese. These include berries, whole grains and vegetarian proteins. Excessive amounts of manganese over time can cause symptoms similar to Parkinson’s disease.

Q: How can an excess of an essential nutrient be bad?

A: Each nutrient plays multiple roles in how the body works. As a result, excessive amounts of one nutrient can sometimes interfere with the functioning of another. An excess of folic acid (vitamin B9), for example, can hide a key symptom of vitamin B12 deficiency. And the delay in diagnosing a B12 deficiency can result in irreversible short-term memory loss.

Other examples: Excessive amounts of vitamin A is linked to liver damage and bone and joint pain; excessive vitamin D increases brain and artery calcification; and excessive amounts of vitamins E and K are associated with blood clotting problems and red blood cell damage.

Q: How much is too much?

A: The Food and Nutrition Board of the Institute of Medicine has established safe levels for many essential nutrients. Its limits are called upper limits, or UL. See nutritionatc.hawaii.edu/UL.htm.

Remember, a healthy diet is all about variety and moderation.

Alan Titchenal and Joannie Dobbs are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa.