Scientists Say Sunlight May Not Reliably Raise Vitamin D Levels

In the pubic imagination, vitamin D and sunshine are all but inseparable—you’ve probably heard someone refer to sunbathing as “getting some vitamin D” or call vitamin D the “sunshine vitamin.” But it turns out that the two may not be as closely linked as we thought. In fact, new research reveals that exposure to sunlight may not significantly affect our vitamin D levels.

That’s the takeaway from a recent study published in the European Journal of Clinical Nutrition, which investigated the relationship between sunlight and vitamin D levels among older adults and ethnic minorities with darker skin pigmentation. Of the 299 participants screened for the study, about 55% of the older adults and 72% of the darker-skinned individuals had vitamin D deficiencies or insufficiencies—deficits that weren’t remedied during the summer months, when the participants were theoretically exposed to more sunlight.

So, is vitamin D really the “sunshine vitamin” after all? Below, experts break down what you need to know.

Meet the experts: Melissa Prest, D.C.N., R.D.N., spokesperson for the Academy of Nutrition and Dietetics; Keri Gans, M.S., R.D.N., C.D.N., registered dietitian and author of The Small Change Diet

Why are the findings significant?

We’ve long known that vitamin D is essential for health. “Vitamin D helps the body absorb calcium, making it essential for strong bones and teeth,” says Melissa Prest, D.C.N., R.D.N., spokesperson for the Academy of Nutrition and Dietetics. “It also supports muscle function and plays an important role in immune health.”

Because of vitamin D’s importance, some experts have urged adults to ensure they spend time in the sun regularly—even though unprotected sun exposure can lead to sunburn, certain types of skin cancers, and other skin spots. However, the findings of the study challenge a long-held assumption that increasing our sunlight exposure will increase our vitamin D levels.

“The biggest takeaway is that if someone is already deficient in vitamin D, relying on sunlight alone may not be enough to restore healthy levels,” Prest says.

While we should all strive to get enough vitamin D, the findings are particularly applicable to those at higher risk for vitamin D deficiency, according to Keri Gans, M.S., R.D.N., C.D.N., registered dietitian and author of The Small Change Diet. “This appears especially relevant for older adults and people with darker skin, who may need to rely more on dietary sources, fortified products, or supplementation to meet their needs.”

What does this mean for you?

If you’ve been relying on fun in the sun to get your vitamin D fix, you may need a new strategy. “Don’t assume that spending more time outdoors will correct a vitamin D deficiency,” Prest warns. “If you’re at risk or have been diagnosed with low vitamin D, ask your healthcare provider about having your levels tested and whether a vitamin D supplement is appropriate for you.”

Furthermore, if you do take vitamin D supplements, or make efforts to increase the amount of vitamin D-rich foods in your diet, don’t slack on those efforts when the sun comes out. “The major takeaway is that vitamin D insufficiency can persist year-round among groups already at higher risk,” Gans says. “In this study, more than half of older adults and nearly three-quarters of darker-skinned participants had low vitamin D levels, with little improvement in the summer.”

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It’s also worth noting that not only does unprotected sunlight exposure have little impact on vitamin D levels, but Gans warns not to “rely on additional sun exposure or sacrifice sun protection to improve [your] vitamin D levels. Instead, include vitamin D-rich or fortified foods regularly and discuss supplementation with a healthcare provider, especially if you are older, have darker skin, or have limited sun exposure.”

How to get more vitamin D

First, how much vitamin D should you be getting? According to Prest, “most adults up to 70 years old need 600 IU (15 micrograms) of vitamin D per day, while adults over age 70 need 800 IU (20 micrograms) daily. Some people with a deficiency may require higher doses under medical supervision.” (Gans notes that these dosage recommendations assume minimal sun exposure.)

Both dietitians suggest the following measures to increase your vitamin D absorption.

Eat more vitamin D-rich foods

The best natural way to increase your vitamin D levels is to get as much of it from food as you can. “Fatty fish, such as salmon, trout, tuna, and sardines, are among the best natural sources,” Gans says. “Fortified milk, plant-based beverages, yogurt, cereals, and some orange juices can also help, as can egg yolks and UV-exposed mushrooms.”

Consider a vitamin D supplement

“For many people, food alone isn’t enough to meet vitamin D needs,” Prest explains. “If blood tests show you’re deficient, a vitamin D supplement is often the most effective and reliable way to restore healthy levels, under the guidance of your healthcare provider.”

While vitamin D supplements can be helpful, Gans warns not to overdo it. “Some people may benefit from a supplement. However, more is not necessarily better, and the appropriate amount should be discussed with a healthcare provider,” she explains.

The bottom line

While the study’s findings are intriguing, Prest notes that the researchers are vague about important factors like exactly how much sunlight the participants were exposed to, whether they wore sunscreen or protective clothing, or whether medical conditions affected their ability to produce or metabolize vitamin D. “These factors can all influence vitamin D levels and should be considered when interpreting the results,” she says.

Gans also points out that the study’s population is relatively small and specific, focusing on higher-risk adults in northern Britain, which means the findings may not be widely applicable. “Excluding many people already taking vitamin D3 may also have made insufficiency appear more common than it is in the broader population,” she adds.

Still, if you’re striving to increase your vitamin D levels, a day in the sun probably isn’t going to cut it. “If you’re concerned about your vitamin D status, it’s important to work with your healthcare provider to determine the best approach, which may include diet, supplements, or both,” Prest concludes.