Safely Getting Vitamin D From The Sun & How Much You Need

Nov 11, 2020
Oct 21, 2021
18 minutes
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E. P. Diamandis, MD, Ph.D
E. P. Diamandis, MD, Ph.D
Medical Biochemistry Professor
Dr. Diamandis is the division head of clinical biochemistry in the department of pathology and laboratory medicine at Mount Sinai Hospital. Dr Diamandis has published more than 250 research papers, review articles, and book chapters.
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One of the four major fat-soluble vitamins, vitamin D is an all-important micronutrient that your body needs for healthy bones and to perform optimally. It’s an interesting vitamin because it doubles up as a steroid hormone that can be made naturally by our skin from sunlight, which is why it is often called the sunshine vitamin. Here in North America, we get the biggest chunk of our recommended daily intake of vitamin D from the sun from early spring to around September.

Vitamin D helps your body absorb phosphorus and calcium, two vital minerals that keep your muscles, teeth, and bones healthy and strong. It may promote brain health, boost the immune system, regulate cell growth, and reduce the risk of chronic inflammation. According to recent research, it seems like vitamin D may also be helpful for those looking to lose weight or beat depression. Additionally, it has been found that vitamin d deficiency might affect your risk of COVID-19 infection.

Yet, most of us can’t get enough of this micronutrient from our diets. Surprisingly vitamin D deficiency is quite rampant in the US, affecting roughly 40 percent of the entire population, according to a 2018 study published in the journal Cereus. That’s why doctors and dietitians recommend that you get enough vitamin D from the sun to maintain optimum levels in your body.

Unfortunately, exposure to too much sunlight can put you at risk of developing skin cancer, causes heat exhaustion, skin damage, and even immune suppression, losing the body’s ability to fight skin tumors. So, there should be a balance between appropriate and inappropriate amounts of sun exposure. Here we’re diving into how to safely and effectively get enough vitamin D from the sun.

How does vitamin D work?

Vitamin D was discovered in the early 1920s by scientists researching malnutrition diseases, most notably rickets. This is a weak-bone disease that affects predominantly children, causing pain, motion problems, and bowed legs. It has since been curbed with vitamin D-fortified foods, and cases of rickets are now rare in the United States.

Like all vitamins, D is essential for good health and is needed only in trace amounts. It can also be obtained from a very few natural foods, such as egg yolks, beef liver, tuna, cod liver oil, salmon, and sardines. These natural foods listed above can’t come close to fulfilling your recommended daily intake (RDI) of vitamin D of at least 15mcg (600 IU) for an adult, and you would have to eat them nearly every day.

Unlike other vitamins that must be obtained solely from dietary sources, vitamin D can be synthesized naturally by the body from sunlight. Getting vitamin D from the sun is perhaps your best shot at making a significant dent in your RDI needs.

Here’s the interesting part

Whether you get vitamin D from sunlight, natural foods, or dietary supplements, it must first be converted by the kidney and liver into an active form before it can be beneficial for your body.

You see, vitamin D is available in multiple chemical forms, of which vitamin D2 (ergocalciferol) and D3 (cholecalciferol) are the two major types.

Vitamin D2 is typically obtained from dietary sources. It’s what you take as a dietary supplement, usually made in labs by illuminating a range of plant sterols with ultraviolet rays. On the other hand, cholecalciferol (D3) is the natural form and what people have in mind when they talk about vitamin D from the sun. Both forms of vitamin D are almost similar and inactive, so the kidney and liver must do their magic before the vitamin D can do any good for either form. Learn more about the difference between vitamin d2 vs d3.

Vitamin D deficiency

It’s easy to overlook the importance of vitamin D until you are diagnosed with a deficiency. When you have normal vitamin D levels, you can expect your intestines to absorb between 30 and 40 percent of dietary calcium. If you’re vitamin D deficient, on the other hand, your intestinal absorption of dietary calcium drops to the 10-15 percent range. That’s a substantial drop.

Vitamin D deficiency, which affects around 40 percent of Americans, has been linked to osteomalacia in adults, a debilitating condition in which bones become abnormally weak and soft. It also causes rickets in kids. Although both bone conditions are rare in the US today, cases of osteoporosis are on the upward trend. This is a bone-thinning condition that elevates your risk for arthritis, spinal deformities, and movement problems.

Medical studies have shown that low bone calcium reserves correlate to low vitamin D levels, elevating the risk of skeletal deformities and fractures. Nonetheless, this vitamin does much more than protect your bones.

Recently, scientists have unearthed evidence that seems to show that vitamin D does much more for your body than maintain bone health. More specifically, they’ve discovered that vitamin D receptors — which are proteins that interact or bind to vitamin D — are found in tissues throughout the body. Ongoing research has noted that several health benefits result when these receptors bind to vitamin D.

For example, vitamin D receptors in the intestine are well-documented for capturing the micronutrient, helping facilitate the absorption of dietary calcium. Because such receptors have been found in numerous other organs, including muscles, blood vessels, heart, and hormone-producing glands, it’s clear that vitamin D is a micronutrient important throughout the body and with immense potential. But most people don’t have enough reserves, which underpins the need to get more vitamin D from the sun.

How much vitamin D do you need?

Yes, vitamin D is essential for skeletal health, but it helps the body in a myriad of other ways, too. Immune cells require this micronutrient to fend off viruses, bacteria, and other harmful pathogens; it’s needed by nerves to effectively relay messages between the brain and other body parts, and muscles need it to function properly.

A lack of vitamin D leads to inefficient calcium absorption. This, in turn, causes your bones to become thin, brittle, and fracture-prone, a condition called osteomalacia in adults and rickets in kids. Vitamin D deficiency may also result in a lackluster immune system, weak teeth, and osteoporosis in older adults.

Most recently, researchers at Northern University have established a potential link between low levels of vitamin D and more severe cases of the novel coronavirus (Covid-19). An even more recent study published in the Journal of Infection and Public Health seems to arrive at the same conclusion.

There are numerous factors to keep in mind when determining the right amount of vitamin D your body requires. Your age is usually the most important factor to consider because vitamin D requirements go up as you get older. But skin color is another, as darker skin tones have greater amounts of melanin, which absorbs less sunlight and diminishes the body’s ability to synthesize vitamin D.

Infants under 12 months old

Infants are recommended to take at least 10 mcg (micrograms) or 400 IU (International Units) daily from birth until their first birthday. In the first six months of life, babies should not be exposed to direct sunlight. After then, however, you can slowly expose them to sunlight, so they can get a good dose of vitamin D from the sun.

Formula fed babies do not need additional supplementation, as long as they’re drinking about 32 ounces of formula a day. Formulas are supplemented already with vitamin D.

Does a breastfed infant need vitamin D supplementation? A nursing mom with sufficient vitamin D in her own body ensures that her nursing infant receives enough. One detailed study suggests that nursing moms should consume about 6400 IU per day to ensure adequate vitamin D to their nursing infant. But many moms are deficient in vitamin D. Thus, supplementation may be necessary and breastfed infants aged between 0 and 12 months should take a 10-mcg daily supplement of vitamin D. 

12 months old - Adult

Anyone else, from one-year-olds and tweens to teens and adults up to 70 years of age, should get a daily minimum of 15 mcg (600 IU) of vitamin D. While this figure is the daily recommended intake, some experts suggest that you take more. This is especially important for anyone in the following groups:

  • Older adults, which means anyone older than 65
  • Darker-skinned individuals, most commonly those of South Asian, African-Caribbean, and African descent, as their skin is less able to generate vitamin D from the sun.
  • Overweight and obese individuals, since their higher body fat content often means less vitamin D gets into their bloodstream.
  • Individuals with digestive disorders, such as celiac disease and Crohn’s disease, because their body’s ability to absorb fat is impaired. And since vitamin D is a fat-soluble micronutrient, they may have to supplement to get enough.

As a rule of caution, you might want to avoid exposing your babies, toddlers, and younger kids to direct sunlight. This is particularly the case in hours between 10 am and 4 pm when the sun naturally shines with the greatest intensity.

Do pregnant women need to increase or reduce their vitamin D intake? Pregnant women—unless they stay indoors all day, have been diagnosed with vitamin D deficiency, or wear sunblock at all times outside, should stick to the recommended 15 mcg per day.

Unfortunately, our bodies tend to synthesize less vitamin D from the sun as we age. Also, kidneys of older adults are often less efficient in transforming vitamin D2 and D3 to the active form that the body needs. As a result, seniors aged 71 years and older are recommended to take at least 20 mcg (800 IU) vitamin D per day.

How do you get vitamin D from the sun?

Experts recommend that whenever possible we should get most of our vitamin D from the sun, and with good reason. While diet can help, this all-important nutrient is absent from nearly all natural foods except for some oily fish, beef liver, and egg yolk.

Here are some tips you should use to ensure that you’re getting enough vitamin D from the sun:

1. Pick the right time to bask in the sun

Most people in the US get their sun fix between spring (around late March/early April) and deep into fall. Even so, summer remains the best season to soak up some sunshine, but with great caution.

The time of day does matter, as well. Your skin tends to produce vitamin D at its peak when you go out during the middle of the day. This is a window in which the sunlight shines with the greatest intensity, as the sun is at its zenith in the sky.

The rule of thumb is that you won’t get enough vitamin D if your shadow is taller than your real height. It pays to go out in the sun between 11 a.m. and 3 p.m., which is usually when you’ll achieve optimal vitamin D levels.

Of course, it wouldn't be wise to spend a prolonged time out in the scorching hot summer sun. To prevent sunburns and possibly skin cancer, make sure to limit exposure time (between 5-30 minutes according to the NIH), and always stay hydrated. Studies show that sunscreens with an SPF of 8 or higher appear to block vitamin-producing rays from the sun, but it’s important to balance time spent in the sun without sunscreen and preventing long-term sun damage.


2. Be conscious of your skin type

As noted earlier, lighter-skinned folks are more efficient at making vitamin D from the sun than darker-skinned individuals. It’s no wonder vitamin D deficiency is more common in African American and non-white Hispanic communities. 

Darker-skinned people have more melanin, which acts as a natural sunscreen by absorbing the sun's ultraviolet rays to protect against skin cancers, sunburns, and skin damage. Unfortunately, this creates a barrier for UVB rays which are essential for making vitamin D in the skin. Accordingly, people with darker skin are advised to stay longer out in the sun with proper safety measures in place.

3. Expose more skin to speed up vitamin D production

Cholesterol is converted into vitamin D when your skin is exposed to Ultraviolet B (UVB) rays from the sun. That’s the main reason why you’d be better off exposing as much skin as possible to sunlight to make adequate amounts of vitamin D.

More specifically, experts generally agree that you expose about one-third of your skin surface area to sunlight. For people with pale color skin, going out in the sun during summer in bouts of 10 to 30 minutes thrice per week should be plenty if they wear shorts and a tank top. It's also okay to use sunglasses and a wide-brimmed hat to safeguard your eyes and face when you expose other body parts. 

If your skin is darker — for instance, you have got an Asian, African-Caribbean, or African background -- you might want to stay out a bit longer in the sun.

4. Short unprotected sun exposure can do you good

No one can argue against sunscreen’s importance when it comes to protecting from skin cancer and sunburns. A typical sunscreen comprises a chemical blend that helps absorb, reflect, or diffuse sunlight, preventing harmful ultraviolet rays from reaching your skin cells.

Some research findings have suggested that a strong sunblock like SPF-30 sunscreen can cut vitamin D production in your skin by between 95 and 98 percent.

That would otherwise be all good and dandy except that UVB rays are needed to make vitamin D. But, instead of ditching sunscreen altogether (which is obviously a bad idea), you should consider exposing much of your skin to the sun without sunscreen for around only 10-15 minutes. Thereafter you can slap on a good sunblock.

Staying safe in the sun

Although the sun's ultraviolet rays are essential for making vitamin D, they can, unfortunately, cause sunburns, premature aging, and other forms of skin damage, as well as induce immune suppression. In a worst-case scenario, prolonged exposure can also up your risk of skin melanoma, a malignant form of skin cancer.

So, if you choose to get limited sun exposure for vitamin D’s sake, you should stick to the following safety tips:

  • During particularly hot summer days, stay out of the sun when it’s shining the most, often between noon and 2 p.m.
  • Wear a wide-brimmed hat that will protect at least the top of your ears, eyes, and face since these are very vulnerable to sun damage. It’s also perfectly fine to wear wrap-around sunglasses.
  • Perk up your sunscreen game. Summer wear is usually highly exposing and lightweight, which can fuel skin damage. So, after 10-15 minutes of unprotected exposure, apply sunscreen liberally and frequently.
  • See to it that your sunblock sports a minimum SPF of 15, but lighter-skinned folks should stick to SPF-30 and higher. You should also shoot for a broad-spectrum sunscreen because it has the right blend to keep off both UVA and UVB rays.

If you have any questions or concerns about your time in the sun, consult with a dermatologist for a skin check and to discuss your skincare routine including sunscreen.

What happens if you don’t get enough vitamin D in your body?

Vitamin D deficiency is a shockingly common nutritional problem, affecting nearly 1 billion around the globe. This may be partly fuelled by the fact that some groups of the population are more susceptible to low vitamin D levels.

Once again, the elderly, obese, breastfed infants, dark-skinned people, and those who suffer from celiac disease, Crohn’s disease, and other metabolic disorders may be more prone to vitamin D deficiency. If you don’t go outdoors often, always wear sunblock, or live in an area that rarely receives sunshine or has only weak daytime sun, you may also be at risk of low vitamin D.

The short-term and long-term effects of vitamin D deficiency could be serious. Here are common health complications and symptoms that you will experience if you don’t have enough vitamin D in your blood.

1. Excessive tiredness and fatigue

If you’re overly lethargic, weak, and fatigued, low vitamin D levels in your body could be to blame. In a 2015 study, scientists showed that extreme vitamin D deficiency can cause serious fatigue that can affect one’s quality of life. In another 2010 research published in the Journal of Clinical Sleep Medicine, researchers found that extremely low blood levels of vitamin D can lead to excessive daytime sleepiness (EDS). This is a symptom of hypersomnia often linked to chronic fatigue.

Even vitamin D blood levels that aren't extremely low can hurt your energy levels, as noted by another 2013 study involving 80 women. At the end of the study, researchers reported that vitamin D sufficient (those with blood levels over 30 ng/ml) participants were less likely to experience fatigue than their vitamin D insufficient (with blood levels between 21 and 29 ng/ml) counterparts.

The good news is that getting enough vitamin D from the sun or taking supplements can ameliorate fatigue and excessive tiredness. This seems to be corroborated by the same 2010 study mentioned above, in which a 28-year-old lady managed to alleviate these symptoms by improving her vitamin D blood levels to 39 ng/ml in a period of 4 months.

It’s important to note that tiredness and fatigue can have multiple other causes, including sedentary lifestyle, high-carbs diet, sleep deprivation, poor hydration, and food intolerances.

2. Weakened immune system

If you get sick frequently, one possible reason could be low levels of vitamin D in your body. That’s because vitamin D deficiency may result in a weak immune system. Scientists speculate that this is due to vitamin D’s direct interactions with disease-fighting immune cells like T cells and B cells.

By extension, vitamin D deficiency lowers your immune system's capacity to activate these cells that fight off invaders, leaving your body prone to fungal, viral, and bacterial infections. A host of observational studies have noted a strong relationship between low blood levels of vitamin D and pneumonia, bronchitis, chronic lung disorder, and other respiratory tract infections.

On a positive note, a handful of studies — including an often-cited 2015 randomized controlled trial — have also demonstrated that vitamin D supplementation may help lower the risk of these respiratory tract infections.

3. May lead to bone and back pain

Vitamin D deficiency can have a negative impact on your skeletal health. After all, the micronutrient plays a major role in the absorption of two pro-bone health minerals, phosphorus, and calcium.

Low bone calcium reserves, as a result of low vitamin D levels in the body, can cause low bone density and osteoporosis. This can lead to chronic joint, back, and general bone pain.

In one study involving 9,000 women, scientists witnessed that those with vitamin D deficiency were more likely to complain of back pain than vitamin D-sufficient participants. This highlights the need to obtain an adequate amount of vitamin D from the sun, natural food, and supplements.

4. May lead to depression

If you suffer from unending bouts of depression and mood problems, you may be vitamin D deficient. This seems to be the conclusion of one 2013 study published in the Journal of Nutrition, Health, and Aging.

Likewise, research has shown that vitamin D may play a role in helping lower depressive symptoms, especially in older adults.

5. Slow healing of wounds

It’s thought that vitamin D’s ability to fight infection and control inflammation may contribute to proper wound healing. So, if your wounds heal too slowly after an injury, infection, or surgery, you may have an insufficient or deficient level of vitamin D in your body.

A randomized controlled trial study found that low vitamin D levels hampered certain wound healing aspects in patients recovering from periodontal surgery. In a 2016 lab experiment, scientists established that the vitamin might help elevate the production of beta compounds that aid the formation of new skin during the wound-healing process.

6. May risk of fractures, falls, and osteoporosis

As we’ve repeatedly stated, vitamin D is a crucial micronutrient that promotes bone metabolism and dietary calcium absorption.

Most elderly individuals diagnosed with osteoporosis, bone loss, or low bone density may be quick to take calcium supplements. However, they may also be suffering from vitamin D deficiency. This may put them at higher risk of fractures, falls, and skeletal deformities.

So, getting enough vitamin D from the sun and taking vitamin D supplements may aid in bone strength that can prevent falls and fractures.

7. Unexplained muscle pain

Vitamin D, or its active form, to be exact, is fundamentally a messenger that plays a crucial role in facilitating healthy communication between the brain and various body parts, including the muscles. That said, vitamin D is essential for muscle health, because without robust communication between the brain and the body we wouldn't be able to tell the muscles when to move.

Against this background, it doesn’t surprise doctors that vitamin D deficiency has been cited as a potential cause of unexplained muscle pain in both kids and adults. In fact, in one 2014 study carried out in Switzerland, researchers found that 71 percent of those with chronic muscle pain had low vitamin D levels. They believe that nociceptors might have something to do with it.

Nociceptors are vitamin D receptors present in nerve cells. And they are responsible for pain sensation, which may help explain why not getting enough vitamin D may lead to muscle pain.

Although existing research is fairly inconclusive, some studies have noted significant improvement in some forms of pain with high-dose vitamin D supplements in deficient individuals. In one particular study that appeared in Medical Principles and Practice, vitamin D supplementation lowered pain scores for children with growing muscle pains by around 57 percent.

Can you get too much vitamin D, and can vitamin D toxicity be harmful?

Let’s get one thing straight: you can’t get too much vitamin D from the sun - that is, before you suffer the consequences like a sunburn. However, if you decide to take vitamin D supplements, 10 mcg should be plenty for most kids and adults.

You can safely take up to 100 mcg (4,000 IU) without any notable side effects. In fact, some studies have even demonstrated that a daily vitamin D supplement of up to 10,000 IU doesn’t result in any harm to healthy people.

The truth is, vitamin D toxicity is very rare and much of the information about taking too much vitamin D is too, according to Mayo Clinic Proceedings. It’s often linked to hazardously high blood levels of phosphates and calcium, as well as extremely low levels of parathyroid hormone.

Vitamin D toxicity only occurs when you take unreasonably high doses of vitamin D supplements, either intentionally or accidentally. Here we are talking about taking 50,000–1 million IU every day for several weeks, if not months. 

Even then, the majority of symptoms are rarely severe or life-threatening. They may include high blood pressure, constipation, abdominal pain, vomiting, depression, drowsiness, poor focus, and confusion. However, people suffering from certain conditions that impede kidney or liver function may have worse outcomes in case of vitamin D toxicity.


Unfortunately, roughly 2 in every 5 Americans are deficient in vitamin D. Low levels of vitamin D in the body can have adverse effects that include:

  • Excessive fatigue and tiredness
  • Getting sick often due to a weakened immune system
  • Bone softening, bone loss, and back/bone pain
  • Muscle pain
  • Depression and anxiety
  • Slow-healing wounds
  • Increased risk of falls, fractures, and bone thinning (osteoporosis)

Turns out, the best way to meet your daily recommended intake is to get vitamin D from the sun. You can enhance this process by:

  • Exposing more skin to rev up vitamin D production
  • Getting 10-30 minutes of summer sun exposure thrice per week
  • Darker-skinned people should stay out in the sun for longer
  • Not using sunscreen for between 10 and 15 minutes for optimal vitamin D levels
  • Going out especially during midday to achieve optimum results
  • Taking necessary safety precautions to avoid sunburns and skin damage. The bottom line is that you should cover up with appropriate wear, use sunglasses, seek shade, and apply sunscreen if you plan to stay in the sun for long.

Although vitamin D toxicity is quite rare, it can happen if you take extremely high doses of the supplement over an extended period, causing phosphorus and calcium to accumulate in the body to toxic levels (hypercalcemia). But this only occurs if you take colossal amounts of vitamin D supplements, often in the 50,000-1 million IU neighborhood.

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