What Vitamin Do You Get From The Sun?

The sun is your body’s main natural source of vitamin D. When ultraviolet B (UVB) rays from sunlight hit your skin, your body produces vitamin D on its own. This nutrient is essential for strong bones, a working immune system, and many other vital functions.

How Does Your Body Make Vitamin D From Sunlight?

Sunlight triggers a chemical reaction in your skin. UVB rays convert a form of cholesterol in your skin into vitamin D3, also called cholecalciferol. This inactive form travels to your liver and kidneys, where it becomes active vitamin D that your body can use.

This process does not happen instantly. Your skin needs direct exposure to UVB rays. Glass blocks UVB, so sitting by a sunny window does not help your body produce vitamin D. The same applies to sunscreen with a high SPF, which blocks most UVB rays.

Your body has a built-in safety mechanism. After about 20 to 30 minutes of sun exposure, your skin stops producing vitamin D. This prevents vitamin D toxicity from sun exposure alone. You cannot overdose on vitamin D from the sun, but you can damage your skin.

How Much Sun Do You Need for Vitamin D?

There is no single answer that fits everyone. The amount of sun exposure needed depends on your skin tone, where you live, the season, the time of day, and how much skin is exposed.

People with lighter skin need roughly 10 to 15 minutes of midday sun several times a week. People with darker skin need more time because higher melanin levels slow vitamin D production. Melanin is the pigment that gives skin its color, and it acts as a natural sunscreen.

Location matters significantly. If you live north of roughly Atlanta, Georgia, your skin may not produce vitamin D from sunlight between November and February. The sun’s angle is too low, and UVB rays do not reach the ground effectively.

Time of day also matters. UVB rays are strongest when the sun is highest in the sky, typically between 10 a.m. and 3 p.m. Morning and evening sunlight contains mostly UVA rays, which do not produce vitamin D.

What Does Vitamin D Actually Do?

Vitamin D is often called the sunshine vitamin, but its role goes far beyond bones. It helps your body absorb calcium and phosphorus from food. Without enough vitamin D, your bones can become thin, brittle, or misshapen.

Vitamin D also supports muscle function and the immune system. Some research suggests it helps regulate mood and may play a role in preventing certain chronic diseases, but the evidence for these broader effects is still developing.

Severe vitamin D deficiency causes rickets in children and osteomalacia in adults. Rickets leads to soft, weak bones and skeletal deformities. Osteomalacia causes bone pain and muscle weakness. These conditions are rare in the United States but still occur.

Low vitamin D levels are linked to a higher risk of falls in older adults. Studies have shown that vitamin D supplements combined with calcium can reduce fracture risk in older people, particularly those living in care facilities.

What Happens If You Get Too Little Sun?

Many Americans do not get enough vitamin D. The National Health and Nutrition Examination Survey has found that a significant portion of the population has insufficient levels, though the exact numbers vary depending on how deficiency is defined.

People at higher risk for deficiency include those who spend most of their time indoors, people living in northern latitudes, older adults whose skin produces less vitamin D, and people with darker skin living far from the equator.

Certain medical conditions also increase risk. Crohn’s disease, celiac disease, and other conditions that affect fat absorption can reduce vitamin D absorption. Obesity is linked to lower vitamin D levels because body fat sequesters vitamin D rather than releasing it into circulation.

Symptoms of deficiency are often subtle. Fatigue, bone pain, muscle weakness, and mood changes can all signal low vitamin D, but these symptoms have many other causes. The only reliable way to know your level is a blood test.

How Do You Know If Your Vitamin D Is Low?

A simple blood test measures your vitamin D level. The test checks for 25-hydroxyvitamin D, the main form of vitamin D circulating in your blood.

Most laboratories define deficiency as a level below 20 nanograms per milliliter (ng/mL). Levels between 20 and 30 ng/mL are considered insufficient. Levels above 30 ng/mL are generally considered adequate for most people.

Routine screening for vitamin D deficiency is not recommended for everyone. The U.S. Preventive Services Task Force has concluded there is not enough evidence to recommend universal screening in adults without symptoms. Your doctor may order the test if you have risk factors or symptoms.

If your level is low, your doctor may recommend a supplement. The recommended daily allowance for most adults is 600 IU (international units) per day, and 800 IU for adults over 70. Some people need higher doses to correct a deficiency, but this should be determined by your doctor.

Can You Get Vitamin D From Food Instead?

Very few foods naturally contain vitamin D. Fatty fish like salmon, trout, and sardines are among the best sources. Cod liver oil contains very high amounts but should be consumed carefully because of its high vitamin A content.

Many foods are fortified with vitamin D. Cow’s milk in the United States is fortified with 100 IU per cup. Some orange juices, plant milks, yogurts, and breakfast cereals are also fortified, but amounts vary by brand.

Food alone rarely provides enough vitamin D. You would need to drink four cups of fortified milk daily to approach the recommended 600 IU, and that still might not be enough for someone with low levels. Mushrooms exposed to UV light are a notable plant-based source, but amounts vary widely.

For most people, a combination of sensible sun exposure and dietary sources is the practical approach. When that is not possible, supplements are a reliable alternative.

What Are the Risks of Too Much Sun?

Sun exposure carries real risks that outweigh the vitamin D benefit. Ultraviolet radiation from the sun is a known carcinogen. It causes most skin cancers, including melanoma, the deadliest form.

Skin damage from UV radiation is cumulative. Each sunburn increases your risk of skin cancer. Even without burning, repeated exposure accelerates skin aging, causing wrinkles and age spots.

The American Academy of Dermatology recommends getting vitamin D from food and supplements rather than unprotected sun exposure. This position reflects the strength of the evidence linking UV radiation to skin cancer.

If you choose to get vitamin D from the sun, keep sessions short. Expose your arms and legs for about half the time it takes your skin to turn pink. Then apply sunscreen or cover up. Never allow your skin to burn.

Who Should Avoid Sun Exposure for Vitamin D?

People with a history of skin cancer should avoid intentional sun exposure entirely. The same applies to people with conditions that increase sun sensitivity, such as lupus, or those taking medications that cause photosensitivity.

Certain medications make your skin more vulnerable to UV damage. Antibiotics like doxycycline, some blood pressure medications, and certain acne treatments can increase sun sensitivity. Check with your pharmacist if you are unsure about your medications.

People with very fair skin that burns easily should also be cautious. Their skin produces vitamin D quickly, but they also carry the highest risk of skin damage. A few minutes of exposure may be enough.

For anyone who cannot safely get sun exposure, supplements are the clear answer. Vitamin D supplements are inexpensive, widely available, and effective at raising blood levels. The evidence for their safety and efficacy is well established.