You Asked: How do I get enough vitamin D in the winter?

As the days get shorter and colder, our time inside tends to grow longer. Thanks to daylight saving time, it is also dark when we leave our house and get home. Many Americans find it difficult to get enough sunlight during the winter months, and that poses a significant risk to people’s vitamin D levels.

Keri Carpenter, RD, health educator and dietitian for the Diabetes Education Program at the Texas A&M Coastal Bend Health Education Center breaks down why we need vitamin D and how we can make sure we get enough of it.

What is vitamin D?

“Vitamin D regulates the amount of calcium and phosphate we have in our blood, and it also helps calcium to be absorbed,” Carpenter said. Because calcium is crucial to your bone health, Carpenter explains that without vitamin D, the health and strength of your bones may suffer.

Vitamin D is a fat-soluble vitamin that is naturally present in very few foods, added to other foods and available as a dietary supplement, or it can be made in the body when sunlight is absorbed through the skin. As a result, the best way to get enough vitamin D is through the sunlight. “I recommend for people to get out for at least 15–20 minutes in the afternoon, so their bodies can absorb the sunlight.”

What happens when you don’t get enough vitamin D?

Vitamin D insufficiency affects almost 50 percent of the population worldwide, with an estimated 1 billion people worldwide having a vitamin D deficiency. In children, a true vitamin D deficiency can lead to rickets, rare disease that causes bones to become soft and bend. In adults, a serious lack of vitamin D can cause osteomalacia, a disease that causes weak bones, bone pain and muscle weakness.

Now before you run to the store to buy a large amount of vitamin D supplements, Carpenter notes that it is possible to get too much vitamin D. If your vitamin D levels are too high, then you can be at risk for hypercalcemia. This condition can actually weaken your bones, create kidney stones and interfere with how your heart and brain work.

“There is not a toxicity of vitamin D that you can get from the sun,” Carpenter explained, “whereas you can get too much vitamin D by taking too many supplements.”

She highly recommends getting your daily dose of vitamin D through everyday sunlight, but if that is not possible, then she recommends speaking to a health care provider before taking any supplements in addition to a multivitamin.

Influences to vitamin D absorption

Carpenter noted the recommended 15 to 20 minutes of sunlight is an estimation. The rate of vitamin D absorption can be influenced by external factors like the amount of pollution in your city. She also says the closer you are to the equator, then the less time you need in the sun—someone in Canada may absorb vitamin D slower than someone in Mexico. The amount of melanin in your skin can also influence the rate of vitamin D absorption. In other words, the more melanin in your skin—the darker your skin color—then the slower you absorb vitamin D from the sun.

Additionally, the use of sunscreen can prevent the body’s absorption of vitamin D, but this is not an excuse to avoid using sunscreen. Your body really only needs 15 to 20 minutes of sunlight to absorb enough vitamin D, and that is all your body can absorb at one time. So, after that 15 minutes in the sun, your body starts to dispose of the extra vitamin D. More specifically, if you are in the sun for an extended period of time, you absolutely need to wear sunscreen because you will not be absorbing vitamin D the entire time.

Natural ways to get vitamin D

Besides sunlight, you can get vitamin D through your diet. Carpenter says foods like fatty fishes, including salmon and tuna, egg yolk and cod liver oil are high in the vitamin. “Especially in the winter months, it can be difficult to get that daily amount of sunlight, so we need to pay close attention to our diets to make sure we are eating the right kinds of foods.”

For those who do not eat animal products, it may be more difficult to absorb vitamin D through diet, but it is possible. Foods like mushrooms, spinach and soybeans are especially helpful in these circumstances.

Similarly, there are some foods like milk, orange juice, yogurt and even some breakfast cereals that are considered vitamin D-fortified. Keep an eye out at your local grocery store for foods that say they are calcium-fortified, because not all have that label.

If you are concerned that you do not get enough sunlight or vitamin D-rich foods in your diet, then speak with your health care provider. They can give you advice on increasing your vitamin D intake, or even run some diagnostics to test your levels.