As someone who loves numbers and details (not to mention sunscreen), I sometimes wonder how much time I need to spend outside every day to get my daily value for vitamin D. Unfortunately, it’s clearly a catch 22: Although the Sunlight provides vitamin D, it is also harmful to your health without adequate protection such as sunscreen, clothing, time in the shade, and general caution about sunburn. according to the Skin Cancer Foundation. Its experts, as well as the Centers for Disease Control and Prevention, agree that some exposure to sunlight can be beneficial to your well-being as long as you take the necessary protective precautions for your age, skin type and health.
related stories
So how are we supposed to get vitamin D safely? “Our bodies are very efficient at making vitamin D in the skin, but the amount varies greatly from person to person due to various factors,” he says. Shengyi Mao, MD, Clinical Assistant Professor of Internal Medicine, The Ohio State University Wexner Medical Center. “This makes it difficult to provide specific recommendations on how much time to spend in the sun. Some people may be prepared to get exactly what they need without extra effort, while others may need to get more in their diet from outside or talk to their doctors.” about supplementation. Here, we ask Dr. Mao to break down exactly what kinds of factors may determine your body’s absorption of vitamin D.
What is vitamin D and why do you need it?
The first is the first. “Vitamin D is a vitamin that all humans need. It helps our bodies absorb calcium and phosphorous, which are critical for bone health,” says Dr. Mao. In children, he explains that it helps build healthy bones; in adults, it helps maintain strong bones and prevents fractures or breaks. “But this nutrient is truly a powerhouse of important benefits that go far beyond strong bonesIn fact, according to Dr. Mao, vitamin D possesses anti-inflammatory, antioxidant, and neuroprotective qualities that support brain health, immune system function, and even prevent things like joint pain, low energy, and mood swings. In turn, low vitamin D levels in the winter are part of the reason some people may experience seasonal affective disorder.
How does your body get vitamin D?
Vitamin D, unlike many other important vitamins, does not occur naturally in many foods, according to Dr. Mao. In fact, the The United States government began fortifying milk with vitamin D in the 1930s as a public health measure against rickets., a musculoskeletal disease caused by vitamin D deficiency. Since then, more foods have been fortified with the nutrient, including alternative milks, cheeses, cereals, flours, orange juice, snack foods, and more. (For those wondering, a major natural source of vitamin D is fish, including tuna, salmon, flounder, herring, sardines, and tilapia—a big win for sushi fans everywhere.)
Is there a specific amount of time that must be spent in the sun to meet vitamin D requirements?
As mentioned, aside from your diet, your body may get the vitamin D it needs from the sun. However, this is a bit more complicated than you might think: the sun doesn’t just trigger vitamin D to land on your skin and do its job. Instead, according to Dr. Mao, UVB rays from sunlight trigger a molecular reaction within the skin and fat cells to create the nutrient we know as vitamin D. This nutrient is fat-soluble, meaning it is created and /or is absorbed and lodged in fat cells until it is sent to the liver to be used. Unfortunately, UVB rays are also the same rays from the sun that cause your skin to burn, so it’s imperative that you wear sunscreen to protect yourself from cancer-causing rays.
All of the above are reasons why Dr. Mao emphasizes that the more you know about what can disrupt your vitamin D absorption, the more informed your diet and supplement decisions can be. This is how you can naturally thwart getting the amount of vitamin D your body needs.
5 Key Factors That Can Affect Your Vitamin D Absorption
1. Sun protection
Sun protection is important and healthy, but it also prevents optimal absorption of vitamin D. According to Dr. Mao, things like clothing coverage, sunscreen, and sunglasses prevent you from getting nutrients from the sun. Even if your commute home from work is sunny or your desk is near a window, UVB rays cannot penetrate glass (although UVA rays can) and therefore do not offer the same type of vitamin D-rich sunlight.
2. The amount of melanin you have in your skin
Melanin is a molecule in the body that determines the pigmentation of a person’s skin.. “Vitamin D absorption decreases as the amount of melanin a person has increases,” says Dr. Mao. Black and brown individuals, according to a 2021 study published in the peer-reviewed clinical journal nutrients, often face a 20- to 25-fold higher prevalence of vitamin D deficiency.
3. Your age, body composition, where you live, and ability to be outdoors
Adding to the list of things that can disrupt vitamin D absorption are factors like location, age, time spent outdoors, body composition, and location. There are many reasons someone may not be able to spend a lot of time outdoors, whether it’s because of the risk of dehydration, a time-consuming job, or living in a climate that doesn’t offer much sunlight. Because the vitamin D you get from the sun is acquired through your skin and lodged in your fat cells, fat stores can sometimes store the nutrient, which means fat and plus-sized people can sometimes use less vitamin D based on sunlight.
“Location, weather conditions, seasons and time of day also make a big difference in the amount of ultraviolet light that reaches a person’s skin and can affect vitamin D levels,” says Dr. Mao. “For example, vitamin D levels often drop in the winter due to less sun exposure.”
4. Certain diseases and conditions
“Certain diseases can impede vitamin D metabolism at numerous stops along its journey to get to where it’s needed in the body, such as kidney and liver disease,” says Dr. Mao. People with type 2 diabetes may have reduced vitamin D absorption, as can gastric bypass patients. Bariatric patients are also sometimes at risk of vitamin D deficiency, since the part of the stomach that is removed is the upper part of the small intestine, which is where the body normally absorbs most of the vitamin D.
5. Follow a specific diet, such as veganism or gluten-free
“A common misconception is that vitamin D can be found easily in food. It’s not found naturally in many foods, so it’s very difficult to get enough vitamin D in our diets,” says Dr. Mao. This is why some people on a gluten-free diet can often miss out on fortified foods like cereals, whole grains, wheat flour, and bread. The same goes for vegans who don’t get fortified vitamins from products like dairy or foods naturally rich in vitamin D like fish or eggs.
Another misconception is that more is better, according to Dr. Mao. “In general, it’s very safe to supplement vitamin D, but extremely high levels can lead to kidney stones, bone pain, confusion, weakness, vomiting, and more,” she says. That’s why talking to a provider about her options is a great way to go.
At the end of the day, there is no single factor or guarantee that you will be vitamin deficient forever. In fact, most people probably experience some barrier to getting the vitamin D they need at some point in their lives. The best thing you can do is stay informed about what your specific obstacles are. This can help inform your decision to order a vitamin D blood test at your annual physical or make a decision to eat more vitamin D-rich foods or take vitamin D supplements with a health care provider’s approval.
