What’s the Deal with Vitamin D?

This nutrient plays an important role in keeping our bodies healthy

Photo: Smiling woman with bright sun behind her

Vitamin D should be everybody's favorite vitamin. For starters, the main source of vitamin D is the sun. Who doesn't love a prescription that requires spending time outside basking in the warm sun? 

As it turns out, vitamin D as we know it is not actually a vitamin. It's a hormone our body produces as a result of exposing the skin to sunlight. After the body absorbs it through sunlight, food, or supplements, it is converted into its active steroid hormone form known as calcitriol, which is what the body then uses. So what does vitamin D do and why do we need it?

Why Your Body Needs the Sun Vitamin
Vitamin D is important for a variety of different reasons, like supporting healthy, strong bones and a robust immune system. "Vitamin D plays a crucial role in maintaining optimum health,” says Fahd Al Qureshah, Ph.D., lead author of a study on the effects of vitamin D inadequacy in women during the winter months. "Several studies have shown an association between low levels of vitamin D and increased risk of diabetes, cancer, osteoporosis, heart attack, and other conditions." 

Rickets, a disease characterized by dry brittle bones, is the result of a vitamin D deficiency. A deficiency can also cause dormant T cells, which are bad for healthy immune function. When T cells are inactive they don't go out into the body and attack viruses and bacteria, so for those whose immune systems are already compromised—diabetics, cancer patients, and multiple sclerosis patients—vitamin D is incredibly important.
One group that's at risk for low vitamin D: women with health risks like anxiety, insomnia, and low energy, Al Qureshah’s study revealed. To check your vitamin D levels, consult your doctor and take a blood test.

How to Get It
Although the easiest and safest way to get vitamin D is through sun exposure (your skin will never absorb too much), you can also fulfill your vitamin D requirements through diet and supplements. The daily recommended amount of vitamin D for adult males and females is 600 International Units (IU). If you are concerned about sun exposure and cancer risks, stick with food or supplements, which The Skin Cancer Foundation recommends. If you're still not sure, talk to your healthcare professional. 

In the Sun
Ten minutes of sun exposure in the bright midday sun in a bathing suit produces about 10,000 IU for the fairest-skinned among us. As with any form of vitamin absorption, your body doesn't take in 100% of all the nutrients to which it is exposed. While latitude, season, skin color, and clothing make vitamin D absorption variable, twice-weekly 30-minute sessions in short sleeves and shorts are generally considered to be sufficient.  The best months for sun exposure are during the warmer months, or May through September. 

The best part? Your body can't overdose on vitamin D from the sun. Processes like sweating release heat from your skin, prevent overproduction of calcitriol. Getting more than the daily recommend amount of vitamin D may not be a bad thing—it may reduce the risk of developing multiple sclerosis. However, spending excessive time outside, especially if you have fair skin, can lead to other health risks like sunburn and skin cancer. 

There has been some controversy about excess vitamin D, but in today's indoor-centric society it is hard to oversaturate your blood stream based on time spent outside. Overdosing is more likely to come from diet, taking too many supplements or falling victim to a malfunctioning digestive system that is holding stores of the nutrient. Oversaturation levels measure at about 4,000 IU, although the body has been known to tolerate those levels for short periods of time. Consult your physician to check your vitamin D levels if you are worried, and ask for advice before taking supplements. 

Through Food
Al Qureshah recommends getting vitamin D through foods like:

  • Milk: Choose the fat percentage you prefer, the vitamin D levels are typically the same from non-fat to whole.

  • Fish: Per ounce, cooked rainbow trout has the most vitamin D out of any other type of food. Get your fill with two 3-oz portions a week.  Also try sockeye, pink, and Chinook salmon; swordfish, tuna, halibut, and sardines.

  • Mushrooms: Try fresh shiitakes, white button, and brown Portobello  varieties. Fun fact: mushrooms function like we do in terms of vitamin D production: They get it from the sun!

Via Supplements
Vitamin D is also available in supplement forms, commonly D2 and D3, which come from vegetarian and animal sources, respectively. Talk to your doctor to find the supplement right for you.

Sunblock and clothing will block UV light. So try to spend an hour a week outside with minimal sunscreen to get your fill of vitamin D. Otherwise, lather up!