Your questions on vitamin D (and other supplements), answered

On Nutrition

I received some excellent questions following my recent column on recent vitamin D research, so this week I’m answering a few of them, along with two additional questions I received about dietary supplements.

Do infants and children still need vitamin D supplements?

Recent research has eroded the idea that most adults should take vitamin D supplements — with exceptions for those with actual deficiencies or certain health conditions — but infants and young children still benefit from supplemental vitamin D. In children, vitamin D deficiency leads to rickets, a disease in which the bones become soft, weak, deformed and painful. Severe rickets can cause failure to thrive, developmental delay and other serious health issues.

Breast milk alone does not provide infants with an adequate amount of vitamin D, so prolonged exclusive breastfeeding without vitamin D supplementation can cause rickets. Formula is fortified with vitamin D — but doesn’t provide enough unless the infant is drinking 32 ounces each day. The American Academy of Pediatrics recommends that all infants who are at least partially breastfed, or who consume less than 32 ounces of vitamin D-fortified formula daily, receive 400 IU of supplemental vitamin D per day. After the first birthday, the recommended amount increases to 600 IU per day.

Although sunlight can be a vitamin D source, the AAP strongly recommends that all children be kept out of direct sunlight as much as possible. They also recommend using shade and clothing as protection for infants — especially for those less than 6 months of age — instead of sunscreen whenever possible.

The main reason I take vitamin D is for immune health. What does the research say about that?

Vitamin D does play a role in immune system function, but it’s still unclear if taking vitamin D supplements can “boost” immune health. Some research has focused on whether vitamin D can reduce risk of developing an autoimmune disease — in which the body’s immune system attacks its own organs and tissues — while other research has looked at whether taking vitamin D supplements can help the body fight off infectious diseases such as colds, seasonal flu and COVID-19.

The Vitamin D and Omega 3 Trial, which I wrote about last month, found that taking 2,000 IU of vitamin D daily for five years reduced the incidence of autoimmune diseases by about 22%, compared with a placebo. For context, 123 participants in the vitamin D group were diagnosed with an autoimmune disease during the study, compared with 155 participants in the placebo group. Autoimmune conditions observed in the study included rheumatoid arthritis, psoriasis and autoimmune thyroid diseases (Hashimoto’s thyroiditis, Graves’ disease). Other examples are multiple sclerosis, Type 1 diabetes, lupus and inflammatory bowel disease. Note that someone’s risk of developing an autoimmune disease is partially genetic.

Results of a randomized controlled trial published earlier this month in the British Medical Journal found that participants who were not taking vitamin D supplements, then took 800 or 3,200 IU of vitamin D daily for six months, were no less likely to contract the COVID virus than participants who did not take vitamin D. The authors of this study pointed out that their findings were consistent with other recent randomized controlled trials that reported no effect of vitamin D supplementation on risk of upper respiratory infections.

Are gummy multivitamins as good as brands that come in tablets or capsules?

Multivitamin and mineral supplements come in a variety of formulations — tablets, capsules, softgels/gelcaps, powders, liquids, chewables and gummies. For most people, the “right” vitamin formulation is the one that you prefer. If the product is manufactured properly so it can deliver the nutrients to your digestive system and dissolve once it gets there, the formulation doesn’t matter. Gummy vitamin supplements are an exception.

Gummy vitamin and mineral supplements contain fewer nutrients than their “regular” counterparts, because some vitamins and minerals aren’t easily incorporated into gummies, and others aren’t included due to poor taste. Compare a gummy multivitamin to a standard multivitamin, and you’ll find that gummies contain fewer nutrients, have smaller amounts of the nutrients they do contain, and tend to be higher priced. They also expire sooner, as the moist, gel-like consistency of gummy supplements can cause some of the nutrients to degrade faster.

The Center for Science in the Public Interest tested 37 brands of gummy multivitamin/mineral supplements, and none came close to being a good substitute for an ordinary multivitamin tablet. Independent testing by ConsumerLab found that some gummy supplements — especially gummy multivitamins — don’t contain the amounts of vitamins or minerals listed on the label or contain impurities.

Are dietary supplements regulated or not?

The dietary supplement industry brings in billions of dollars each year, with an estimated 90,000 products on the market, including vitamins, minerals, herbs or other botanicals, amino acids, probiotics, or other substances. A 2015 Consumer Reports survey found that most people think that dietary supplements are vetted for safety by the U.S. Food and Drug Administration. Unfortunately, this isn’t true.

Unlike prescription or over-the-counter drugs, which must be approved by the FDA before they can be marketed, the FDA is not authorized to review dietary supplements for safety and effectiveness before they are sold. The FDA can take action through warnings or recalls — often voluntary — if they receive reports that a supplement already on the market is causing harm, but this can take several years, if it happens at all, and may not be effective.

One of the biggest concerns about supplement safety is adulteration with ingredients that aren’t listed on the label. Several independent organizations — notably U.S. Pharmacopeia, ConsumerLab and NSF International — offer quality testing. Their seals of approval mean that the supplement was properly manufactured, contains the ingredients listed on the label, and doesn’t contain harmful levels of contaminants. That can give you confidence that the product isn’t adulterated, but it doesn’t guarantee that a product is safe or effective.