As temperatures rise, you’ll probably find yourself soaking up sunshine – and producing ample amounts of vitamin D – as you relax by the pool, lounge in a hammock or pull weeds in your garden. But what you might not realize is that you’re actually doing your body a favor: Studies show that moderate amounts of vitamin D lowers the overall risk of certain types of cancers. Research suggests that women with low levels of vitamin D are particularly at risk for breast cancer as vitamin D is theorized to play a role in controlling normal breast cell growth.
Vitamin D – a powerhouse for your body
So, what is vitamin D? Vitamin D is often known as the sunshine vitamin because people produce it when their skin is exposed to sunlight. Interestingly, it’s not really a vitamin at all – it’s actually a hormone that helps maintain levels of calcium and phosphorous in the blood.
Vitamin D plays these crucial roles:
- Absorbs calcium
- Promotes bone health
- Helps with immunity
- Reduces inflammation
- Prevents serious disease (including rickets and osteomalacia)
The link between vitamin D and cancer
A growing number of studies tie vitamin D deficiency to a variety of cancers. In particular, a significant link between breast cancer and vitamin D deficiency has been documented. Although vitamin D and breast cancer may seem like an unlikely pairing, a link between the two makes perfect sense. Vitamin D is a precursor of calcitriol, a steroid hormone that’s involved with multiple actions throughout the body and could have a link with cancer risk and prognosis.
"There appears to be a relationship between vitamin D levels and risk of breast cancer," says Chasse M. Bailey-Dorton, MD, Chief of Integrative Oncology at the LCI Center for Supportive Care and Survivorship at Atrium Health. "Growing evidence has demonstrated its important role in defending against cancer, and studies link a deficiency of vitamin D to as many as 18 different cancers."
According to Dr. Bailey-Dorton, vitamin D levels may additionally vary by race. "The lowest levels I have found are in African-American breast cancer survivors," she says. Supporting studies show that the darker the skin color, the less vitamin D you produce.
Although some experts suggest that vitamin D supplementation could possibly help prevent breast cancer and other forms of cancer, as pointed out by Dr. Bailey-Dorton, this effect is still unclear.
"We don’t know how vitamin D replacement or supplementation has an effect on cancer risk," she says, "and this theory needs to be studied to clearly define any link."
In addition to possibly curbing cancer risk, vitamin D may also decrease the risk of hypertension, psoriasis, autoimmune diseases (such as multiple sclerosis and rheumatoid arthritis), and bone fractures.
How to get enough of the sunshine vitamin
According to the National Institutes of Health (NIH), excellent dietary sources of vitamin D include fortified foods, eggs, salmon, tuna, mackerel and sardines. Sunshine is also very important in vitamin D production.
"I think the best way to obtain vitamin D is through diet and safe sun exposure," says Dr. Bailey-Dorton.
The following factors can inhibit how much vitamin D your body produces in the sun:
- Season
- Time of day and length of day
- Cloud cover and smog
- Skin melanin content (the dark brown to black pigment responsible for tanning sun-exposed skin)
- Sunscreen usage
But while UV radiation is crucial for producing vitamin D, you should use caution when you’re soaking up the sunshine. According to the American Skin Association, the sun’s rays are strongest between 10 a.m. and 4 p.m. To prevent against skin damage, you should limit your exposure to direct sunlight during those hours. Fortunately, even brief exposure during the day is generally ample for vitamin D production.
"Exposing the face and hands to roughly 10 minutes of direct sunlight daily is quite safe and a good way to boost vitamin D," says Dr. Bailey-Dorton.
Factors that limit vitamin D production
What about cloudy or smoggy conditions? Rest assured you’re still boosting your vitamin D production if you’re outdoors on those dreary days. Total cloud cover decreases UV energy by only around 50 percent, while shade (including from pollution) decreases it by 60 percent.
Most people know the importance of applying sunscreen to protect against skin damage. But how does that tube of sunblock affect the amount of vitamin D you produce? Yes, sunscreen with a sun protection factor (SPF) of 8 does appear to block the UV rays that produce vitamin D. However, if you’re like most people, you’ll probably still get your vitamin D if you wear sunscreen. That’s because it is difficult to make sure you use enough of it, cover every inch of your sun-exposed skin, and remember to reapply it regularly.
One way you won’t get your vitamin D? Soaking up sunshine through your window. The radiation responsible for vitamin D production can’t penetrate glass.
Do you need vitamin D supplements?
You understand sunshine and diet — but what about supplements that come in pill or liquid form? Dr. Bailey-Dorton advises that you should speak with your physician before taking vitamin D supplements. "You should have your vitamin D level checked prior to taking a supplement because you might not need it."
Importantly, in those who don’t need a supplement, excess amounts of vitamin D can cause negative side effects. Vitamin D is fat soluble and thus can quickly build up in your body, unlike water-soluble vitamins that wash out.
"Excess vitamin D has been associated with hypercalcemia and should be used with caution in certain populations," says Dr. Bailey-Dorton. "These include those with chronic kidney disease, granulomatous diseases, including sarcoidosis and certain infections, are at risk of increased hypercalcemia."
If you are vitamin D deficient, you should discuss dietary intake and supplements with your physician. When taking vitamin D supplements, check that they contain vitamin D3 (cholecalciferol) and not vitamin D2 (ergocalciferol). Vitamin D2 is cheaper to produce, but research reveals it is not as effective as vitamin D3 at raising vitamin D blood levels.
