A search of all types of media, especially social media, shows that many people are interested in consuming “super foods” or specific nutrients in large amounts to help with whatever ails them. Essential nutrients are vital for health and longevity. Too often, however, it is not understood that many essential nutrients can cause health problems or can be toxic when consumed in excess.

Question: What nutrients can cause problems?

Answer: Virtually any nutrient has the potential to cause problems if consumed at high enough levels. However, some nutrients are known to have much more toxic potential than others.

For example, the Institute of Medicine set the tolerable upper intake level for vitamin A at only twice the recommended daily intake provided on food and supplement labels. Someone who takes a supplement that provides 100 percent of the so-called “daily value” and consumes a fortified breakfast cereal with 100 percent daily value is already at the upper limit for vitamin A without accounting for other sources of the vitamin in a daily diet. Consuming excess vitamin A on an ongoing basis can cause liver damage, bone loss and birth defects when toxic levels of vitamin A are consumed during pregnancy.

Beta-carotene, the compound that makes carrots and other foods orange in color, can be converted into vitamin A in the body. Although the institute did not establish an upper limit for beta-carotene, the Food Standards Agency in the United Kingdom recommends not exceeding 7 milligrams of beta-carotene per day in dietary supplements. Risk of beta-carotene toxicity is greatest in those who smoke and those who have been heavily exposed to asbestos, but anyone may be affected.

Vitamin B6 is another nutrient with known toxicity issues caused primarily by excessive intake from dietary supplements. The institute set the upper limit at 100 milligrams per day (50 times the daily value) and the Food Standards Agency set the safe upper limit from supplements at 10 milligrams per day. Excess B6 is well known to cause neurological problems, especially numbness and pain in the limbs.

Any essential mineral can be toxic when consumed in excess. For example, copper consumed at levels in excess of five times the daily value has the potential to cause intestinal problems and liver damage.

Both iron deficiency and iron excess cause oxidative stress in the body. Excessive iron can cause liver damage and is especially risky for those with the genetic condition hemochromatosis. Over-consumption of manganese can cause neurotoxicity and excess zinc can impair immune function.

Q: Can you consume too much of an essential nutrient from foods?

A: In general, it is uncommon to exceed upper limits for nutrients from foods. Manganese is one exception to this. It can become a neurotoxin and can accumulate when consumed in excess over time. Many otherwise healthful foods have high levels of manganese. Examples include blueberries, garbanzo beans, whole grains, various seeds, hazelnuts and some seaweeds.

Q: What is the safest way to get enough of all the essential nutrients but not too much of any?

A: Like we often recommend, consume foods from all of the key food groups and select a wide variety of foods from within each group. Avoid relying on a small number of foods no matter how much they are hyped to be healthy foods. For a table on the upper limits for nutrients, check www.nutritionatc.hawaii.edu/UL.htm

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.