Do you need to take a dietary supplement?

Do you need to take a dietary supplement?

On Nutrition

I’m often asked if vitamin and mineral supplements are good nutritional insurance, or if they just produce expensive urine. The answer is … it depends. (You knew that was coming, didn’t you?) The dietary-supplement industry brings in billions of dollars each year, and certainly some of the supplements flying off the shelves are useless to the person buying them. That said, some people benefit greatly from supplementing their diet. Let’s break it down.


More than 1 in 3 Americans take a multivitamin, according to the National Institutes of Health, even though there’s no evidence supporting use of multivitamins for people who are eating a healthy diet (prenatal vitamins are an exception). However, some people have diets that fall short on many essential nutrients — including people who are on low-calorie diets, have a poor appetite or avoid certain food groups — and a multivitamin can fill in the blanks. I advise avoiding gummy multivitamin/mineral supplements, as they contain fewer nutrients and degrade much faster than “regular” multis.

Vitamin D

An estimated 4 in 10 Americans are deficient in vitamin D because their bodies aren’t manufacturing enough vitamin D on their own. Older adults are at higher risk of deficiency, as are people who have dark skin or seldom expose their skin to the sun. If you’ve had gastric bypass surgery or have a condition that interferes with absorption of dietary fat — such as celiac disease, Crohn’s disease and ulcerative colitis — you may need to ingest more vitamin D than other people just to make sure you absorb enough.

Vitamin B12

Vitamin B12 is naturally found in animal-based foods. Some nutritional yeasts, breakfast cereals and other food products are B12-fortified. You might not be getting enough vitamin B12 from food — or might have trouble absorbing it — if you are age 50 or older, avoid animal foods, have health conditions or previous surgeries that affect the stomach or intestines, or regularly take certain medications. Most people in that boat do fine with oral supplements. However, people whose stomachs don’t secrete enough intrinsic factor may need B12 injections.

Folate/Folic Acid

Folate is a B vitamin found naturally in many foods, especially dark-green leafy vegetables. Many breads and other grain products are fortified with folic acid, the synthetic form of folate. Most people in the U.S. get enough of both, but women who are pregnant or might become pregnant have increased need for folic acid — 400 micrograms per day of folic acid from supplements or fortified foods in addition to whatever folate they get naturally from food — to help prevent neural tube birth defects.


Most people in the U.S. get enough iron because it’s found in so many foods in natural or fortified forms. Because too much iron is harmful, don’t take supplements unless you’re deficient or at risk of deficiency. Women and girls who have heavy menstrual periods, and anyone who donates blood frequently, may need iron supplements. Supplemental iron is also important during pregnancy to support the growing baby and a major increase in red blood cell formation.


Calcium is important for healthy bones and other body functions. Postmenopausal women and anyone who doesn’t consume dairy products will likely need calcium-fortified foods or a calcium supplement to bridge the gap between their actual intake and the recommended intake.

Note: Because recommended nutrient intakes vary by age and gender, I suggest visiting the NIH’s Office of Dietary Supplements website at for fact sheets on these and other nutrients.