You Could Be Taking the Wrong Vitamin D Supplement, Scientists Say

There's a good chance that, in the past couple of years, you've started thinking more about what you can be doing to take care of your immune system. Maybe you've added more fruits and vegetables to your diet, or maybe you've been exercising more. Beyond that, however, it can sometimes be difficult to figure out which changes will actually be helpful.

When it comes to vitamin supplementation, new research finds that, especially for people of white European descent, taking vitamin D3 may help your body fight off viruses and bacteria, while vitamin D2 could play an actively harmful role.

In the study, published in the journal Frontiers in Immunology, researchers from the University of Surrey and the University of Brighton examined the results of 12 weeks of vitamin D supplementation on nearly a hundred of women of South Asian and white European descent, comparing the results of participants given foods fortified with vitamin D2 to those of participants whose foods were fortified with vitamin D3.

They found that D3 appeared to play a role in stimulating your immune system's helpful interferons, part of your body's defense against viruses, while D2 appeared to do the opposite for white European women in the study. Notably, researchers flagged the "possibility of ethnic differences," suggesting that these results may differ for people of other ethnic backgrounds.

"Taking vitamin D2 supplements may not be beneficial to your health. In fact, they may be harmful by counteracting the roles of vitamin D3," the study's lead author Colin Smith, Professor of Functional Genomics at the University of Surrey, told Eat This, Not That! in an interview. "[My advice is to] take a vitamin D3 supplement. You are not going to get enough from your diet, or from the sun between October and March if you live in northern Europe or other northern [areas]."

Additionally, he recommended that those with darker skin "take a vitamin D3 supplement all year round."

Of course, no single supplement is going to be the difference between an immune-system-friendly diet and one that leaves you at increased risk of illnesses. If you're concerned, it's worth taking a look at your diet overall, making sure you're eating a wide range of nutritious foods.

"Focus on nutrient-rich fruits and vegetables, as well as proteins that provide amino acids such as legumes and fish—these proteins are needed to support a functioning immune system," Jerlyn Jones, MS, MPA, RDN, LD, CLT, registered dietitian nutritionist and media spokesperson for the Academy of Nutrition and Dietetics, suggested in an interview with Eat This, Not That!. "A variety of nutrients such as vitamin A, C, D, and zinc alter immune responses to support, enhance, and fight off invading bacteria and viruses."

She added that probiotics can also play a beneficial role, while sugary beverages and other refined carbohydrates could have a negative impact on your body's ability to protect you from diseases.

For more on the subject, find out about the Best Eating Habits to Strengthen Your Immune System, Says Dietitian.