Sunlight is often called the best natural source of vitamin D, and for good reason. When your skin is exposed to ultraviolet B (UVB) rays from the sun, your body produces vitamin D on its own. This is the only vitamin your body can make directly from sunlight. While the sun is not a source of other vitamins, vitamin D from sun exposure is essential for bone health, immune function, and many other processes in the body.
What Vitamins Do Sun Give You?
The sun gives you vitamin D, specifically vitamin D3 (cholecalciferol). This is the form your skin produces when UVB rays hit it. Vitamin D3 is then converted in the liver and kidneys into the active form your body uses. No other vitamins are produced by sun exposure. Claims that sunlight provides vitamin C, B vitamins, or other nutrients are not supported by science.
Vitamin D functions more like a hormone than a typical vitamin. It regulates calcium and phosphorus absorption, which keeps bones and teeth strong. It also supports muscle function and helps the immune system fight off infections. Research consistently shows that maintaining adequate vitamin D levels is important for overall health.
How Much Sun Do You Need for Vitamin D?
There is no single number that works for everyone. The amount of sun exposure needed to produce adequate vitamin D depends on your skin tone, age, latitude, season, time of day, and how much skin is exposed. A general rule often cited in clinical guidance is that 10 to 30 minutes of midday sun exposure on bare skin several times per week is enough for many people. But this is not a guarantee for everyone.
People with darker skin need more sun exposure to produce the same amount of vitamin D as people with lighter skin. Melanin reduces the skin’s ability to produce vitamin D from sunlight. Older adults also produce less vitamin D from sun exposure than younger people. Cloud cover, air pollution, and sunscreen use all reduce the amount of UVB that reaches your skin.
The key challenge is balance. Too little sun means low vitamin D. Too much sun increases the risk of skin cancer. Most dermatology organizations advise against relying on unprotected sun exposure as your primary vitamin D source because of skin cancer risk. They recommend getting vitamin D from food and supplements instead, while using sun protection when outdoors.
Signs You Might Be Low in Vitamin D
Vitamin D deficiency is common, especially in northern climates and during winter months. Many people have no obvious symptoms. When symptoms do appear, they can be vague and easy to miss.
- Bone pain or achiness
- Muscle weakness
- Fatigue that does not improve with rest
- Frequent infections or slow healing
- Mood changes, including low mood
Severe deficiency leads to rickets in children and osteomalacia in adults. Both conditions involve soft, weak bones. This is well established in medical literature. If you suspect you are low in vitamin D, a blood test can measure your level. The test measures 25-hydroxyvitamin D, and most labs consider levels below 20 ng/mL deficient. Levels between 20 and 30 ng/mL are often considered insufficient.
Food Sources of Vitamin D
Very few foods naturally contain vitamin D. This is why sunlight and supplements matter so much. The best natural food sources are fatty fish and fish liver oils.
- Salmon — wild-caught has more vitamin D than farmed
- Trout
- Sardines
- Mackerel
- Canned tuna
- Cod liver oil
- Egg yolks — small amounts
- UV-exposed mushrooms — the only good plant source
Many foods are fortified with vitamin D in the United States. Cow’s milk is almost always fortified. Some brands of plant milks, orange juice, yogurt, and breakfast cereals also add vitamin D. Check the nutrition label to know for sure. Fortified foods help, but it can still be hard to reach recommended levels through food alone.
Vitamin D Supplements: What to Know
Supplements are the most reliable way to correct a deficiency. Vitamin D3 is the form most commonly recommended because it is the same form your skin produces. Vitamin D2 (ergocalciferol) comes from plants and is also effective, though some research suggests D3 maintains blood levels slightly better.
Standard supplement doses range from 400 IU to 2,000 IU per day for general health in adults. For treating a confirmed deficiency, doctors often prescribe higher doses for a limited time. Do not take high doses without medical supervision. Vitamin D is fat-soluble, meaning your body stores it. Taking too much over time can cause toxicity, leading to dangerously high calcium levels in the blood.
No clinical guidelines currently exist for a specific sun-exposure dose to produce a target vitamin D level. The evidence simply does not support a precise formula. If you are concerned about your vitamin D status, a blood test is the only accurate way to know where you stand. From there, a healthcare provider can recommend the right amount to take.
Sun Safety and Vitamin D: Finding the Balance
Skin cancer is the most common cancer in the United States, and UV radiation from the sun is the main cause. The American Academy of Dermatology advises that you should not get vitamin D from unprotected sun exposure. Instead, they recommend vitamin D from food and supplements, along with sun-protective behaviors like wearing sunscreen, hats, and protective clothing.
This advice conflicts with the idea that some sun is good for you. The reality is nuanced. Brief, incidental sun exposure during daily activities provides some vitamin D for many people. The risk of skin cancer increases with cumulative sun exposure over a lifetime. Short periods of sun exposure are less risky than prolonged sunbathing, but no amount of unprotected exposure is completely risk-free.
If you choose to get some sun for vitamin D, keep it short. A few minutes on your arms and legs a few times per week may be enough for lighter-skinned individuals. People with darker skin may need longer. Then apply sunscreen or cover up. Never let your skin burn — burning significantly increases skin cancer risk.
Who Is Most at Risk for Vitamin D Deficiency?
Some groups are at higher risk and may need supplements regardless of sun exposure.
- People living far from the equator, especially in winter
- People who spend most of their time indoors
- People with darker skin living in northern climates
- Older adults — skin produces less vitamin D with age
- People with conditions that affect fat absorption, such as Crohn’s disease or celiac disease
- People who are obese — body fat can trap vitamin D
- People who always wear sunscreen or full coverage clothing outdoors
If you fall into any of these categories, a blood test is a reasonable step. Deficiency is easy to fix with supplements. The risk of deficiency is far more common than the risk of toxicity from normal supplement use.
Frequently Asked Questions
Can you get all your vitamins from the sun?
No. The sun only provides vitamin D, specifically vitamin D3. Your body cannot produce any other vitamin from sunlight.
How long should I sit in the sun for vitamin D?
For many light-skinned people, 10 to 30 minutes of midday sun on bare skin a few times per week may be enough, but this varies widely. Darker skin, older age, latitude, and season all change how much time is needed.
Is sunscreen blocking vitamin D production?
Sunscreen does reduce vitamin D production because it blocks UVB rays. However, most people do not apply enough sunscreen or reapply it often enough to fully block all UVB, so some production still occurs.
What is the best way to get vitamin D in winter?
Food and supplements are the most reliable sources in winter. Sunlight is often too weak to produce vitamin D in northern latitudes during colder months.
