Perhaps you’re familiar with the wintertime blues. As days grow shorter and temperatures drop, many people feel their mood and energy level slump. Lower amounts of vitamin D may be to blame.
“We produce vitamin D when sunlight hits our skin, so it is more common to have a vitamin D deficiency in the winter,” says Ronette Lategan-Potgieter, PhD. She’s an assistant professor of health sciences at Stetson University in DeLand, Florida. “Our skin is covered with clothing, and we tend to stay indoors.”
Vitamin D’s most notable role is helping your body absorb calcium and phosphorus. These nutrients help you build strong bones, says Lategan-Potgieter. But vitamin D is also involved in how you feel day to day.
A deficiency can contribute to depression, muscle weakness, fatigue and pain, according to the Cleveland Clinic. A low level of vitamin D is also a risk factor for cardiovascular disease, according to a review published in the journal Clinical Hypertension.
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Of course, you should do your best to keep your vitamin D levels high. Here are 5 ways to do just that.
1. Go outdoors — even when it’s cold
It’s hard to say exactly how much daylight you need each day, says Lategan-Potgieter. Time of day and distance from the equator both affect sunlight in various ways. Plus, there are personal variables, such as age and skin color. Older people and those with darker skin need more sunlight, says Lategan-Potgieter. And even a city’s smog levels can affect how much light shines through.
But one huge variable is the season. In a study from Spain, people met their vitamin D requirements with just 7 minutes of sunlight in July. But in January, they needed more than 2 hours of sun.
That means that as the temperature drops, you should actually make an even bigger effort to get outdoors. And that’s difficult for many people.
“With everyone working from home these days, we are inside more,” says Gigi Rubin. She’s a registered dietitian based in New York City. “Getting outside and getting sunlight every day is important so we can get enough vitamin D.”
But according to the Skin Cancer Foundation, you should still wear sunscreen on exposed skin. An SPF of 15 filters out 93% of UVB rays. That means that 7% of the rays still reach your skin. So you’ll protect yourself from skin cancer while still producing vitamin D.
Recommended reading: How light therapy can help ease symptoms of depression.
2. Include foods that contain vitamin D in your diet
“Very few foods are naturally good sources of vitamin D,” says Lategan-Potgieter. Fatty fish are perhaps the best: A 3-ounce salmon fillet delivers 71% of your daily intake, according to the National Institutes of Health (NIH). Other vitamin D–rich foods to eat in winter include mushrooms and egg yolks.
But the easiest source of dietary vitamin D is often dairy. Milk isn’t a natural source of vitamin D, but food manufacturers began fortifying it with the vitamin in the 1930s. This was to help combat childhood rickets, a weak-bone disease caused by chronically low levels of vitamin D.
That makes yogurt and many cheeses good sources of vitamin D. You can also get vitamin D from many breakfast cereals, which are also fortified.
Some nondairy milks are also fortified with vitamin D, says Rubin. But be sure to check the label.
3. Take a supplement
Unless you’re eating a lot of fish and dairy, it can be hard to get all of your vitamin D through food. That’s why the Harvard T.H. Chan School of Public Health says that supplements are more reliable than diet alone for vitamin D.
In a large review published in the journal The BMJ, researchers linked vitamin D supplements with a 15% lower chance of cancer death.
“People can definitely benefit from taking vitamin D supplements,” says Lategan-Potgieter. “Especially if they do not get enough sun exposure to produce the vitamin.” The U.S. government considers 400 to 800 international units (IU) per day, depending on your age, to be adequate. But many people require more. Talk to your doctor about finding the right amount for you. He or she may take a blood sample to test your vitamin D levels before making a recommendation.
Over-the-counter vitamin D supplements generally contain between 800 and 2,000 IUs. Prescription-strength supplements can be several times stronger. (Click here to search for a discount on prescription-strength vitamin D.)
If your bloodwork reveals low levels of D, or you’re experiencing symptoms of a deficiency — fatigue, muscle aches, cramps and weakness, for instance — it’s important to remember that supplements take time to work, Rubin says. That means it might take a few months to experience a noticeable improvement. “If your doctor recommends a vitamin D supplement, you will probably be told to wait 4 to 6 months before getting your levels checked again,” she says.
