In a review published in April 2014 in the journal Nutrients, researchers found that people who took vitamin D supplements saw an improvement in their symptoms of depression, and that the effect of taking a supplement was comparable to that of taking an antidepressant. Another review published in April 2014, in the journal Psychosomatic Medicine, was less conclusive, but it did indicate that among people with more severe depression, taking extra vitamin D seemed to help ease their symptoms, backing up other research indicating that supplements might be less useful for people whose depression isn’t so severe. “There is some research to show that our levels of vitamin D can impact cognitive function … and also that vitamin D [supplementation] may help improve symptoms of depression in people who already have a deficiency,” says Marisa Moore, RDN, LD, an integrative and culinary dietitian in Atlanta. Trouble is, quite a few of us — about 40 percent — simply aren’t getting enough D, according to a study published in June 2018 in the journal Cureus. “How much you get depends on where you live,” notes Abbie Gellman, RD, CDN, a nutritionist in New York City and the author of The Mediterranean DASH Diet Cookbook. People who live in the northern half of the United States, in or above cities such as San Francisco, Denver, St. Louis, and Richmond, Virginia, are unlikely to soak up enough vitamin D from sunlight, she says. Add to that the fact that vitamin D is found naturally in only a few foods, including fatty fish — salmon and tuna — some mushrooms, and in smaller amounts in egg yolks, cheese, and beef liver. Fortified foods, including cow’s milk, milk alternatives — soy, oat — and many cereals, have much more of the fat-soluble vitamin. Here’s how to tell whether you’re getting too little D and how to up your intake.
Who’s Getting Too Little Vitamin D?
To find out if you’re low in vitamin D, you’ll need to get a blood test. A result of 30 nmol/L (nanomoles per liter) or under is too low, and anything over 125 nmol/L is too high. Aim for 50 nmol/L or slightly above, according to the National Institutes of Health Office of Dietary Supplements (ODS). Some people are at higher risk of vitamin D deficiency, including those with darker skin. Darker skin contains more melanin, the pigment that gives skin its color, and more melanin makes it harder for skin to produce the vitamin from sunlight. People who are lactose intolerant (i.e., those who have trouble consuming lactose, a protein found in milk and milk products), may also be less likely to get enough vitamin D, since fortified milk is an important dietary source of it, according to the National Institute of Diabetes and Digestive and Kidney Diseases. African-Americans, Hispanics/Latinos, American Indians, and Asian Americans are more likely to be lactose intolerant than people of European descent. Other groups at higher risk, according to the ODS:
Older adults (As we age, our skin doesn’t synthesize vitamin D as efficiently.)People who are obese (Greater amounts of subcutaneous fat traps vitamin D, possibly interfering with how much of the vitamin can circulate in the body.)Anyone who has difficulty absorbing fat, such as those with inflammatory bowel disease or celiac disease or who have had gastric bypass surgeryIndividuals who do not spend time outdoors or do not expose their skin
Should You Take a Vitamin D Supplement?
The ODS recommends that adults age 19 to 70 get 15 micrograms (600 International Units, or IU) daily. (You may be getting this amount already if you take a multivitamin.) But before you take anything, be sure to speak with your doctor. “I like for people to get a blood test to see where they are before making a recommendation about supplementation,” notes Moore. If you do need extra vitamin D, either D2 or D3 will work, and you may need 1,500 to 2,000 IU daily. (Vitamin D2 is derived from plants, whereas vitamin D3 is synthesized from animal sources.) In cases of extreme deficiency, your doctor may give you a vitamin D injection of 50,000 IU once a week for eight weeks to bring your levels up. Start by getting more D from sunlight and fortified foods, such as milk alternatives and cereals, if you can. “In order for vitamin D to be well absorbed, it needs to be taken with a source of fat,” Moore notes. When it comes to increasing your time in the sun, the ODS says there’s no clear answer about how to balance exposure with cancer risk but points out that most people don’t need much sunlight exposure to make enough vitamin D. And while sunscreen is essential in helping prevent skin cancer, keep in mind that it also blocks some of the sun’s UVB rays, which your body needs to make vitamin D.
