If you’ve ever wondered why you feel happy after spending an afternoon outdoors, the answer could be as simple as sun exposure. Vitamin D, supplied by sunlight, contributes to many aspects of our physical and mental wellbeing.
But many people do not get enough vitamin D. In fact, vitamin D deficiency is commonly reported worldwide. Read our guide to find out why vitamin D is so important to your health and how to make sure you’re getting enough.
What is vitamin D?
What are the primary sources of vitamin D?
Why is vitamin D important?
Who is most likely to suffer from vitamin D deficiency?
What are the symptoms of vitamin D deficiency?
Testing for vitamin D deficiency
How to get more vitamin D
Vitamin D supplement FAQ
Dietary sources of vitamin D
Vitamin D is an essential nutrient required for healthy bones, teeth, immunity, and overall health.¹ Unfortunately, in the past several decades, vitamin D deficiency has become a global epidemic, leading to increased risks of:² ³
- Bone fractures
- Infectious disease
- Muscle weakness
- High blood pressure
- Heart disease
- Multiple sclerosis
- Certain cancers
Vitamin D contributes to the body’s ability to absorb calcium, which is why you’ll find many milk products fortified with it. It also aids cellular communication and immunity. Getting the right amount of vitamin D is crucial for physical and mental health.
The primary source of vitamin D is the sun. Direct, bare-skin sun exposure to UVB light provides adequate vitamin D for many people. Still, there are several reasons for deficiencies, including variations in skin type and residence location. Vitamin D supplements are the secondary source of attaining this nutrient, followed by diet. Few food sources provide adequate amounts of vitamin D, but you will find it in:¹
- Fortified milk and milk alternatives (almond, soy, oat, etc.)
- Fortified breakfast cereals
- Beef liver
- Egg yolks
- Fatty fish (salmon, tuna, trout, mackerel)
- Fish liver oils
Vitamin D plays a vital role in many bodily functions, from cellular communication to calcium absorption. It supports bone and heart health and assists with blood sugar regulation. Some of the fundamental reasons to ensure you’re getting sufficient vitamin D include:
Vitamin D promotes bone health and prevents rickets in children. It prevents a similar condition in adults called osteomalacia.
Vitamin D aids in calcium absorption and helps prevent osteoporosis, which is the loss of bone density. Older individuals and those with weaker bones should supplement vitamin D to prevent fractures.
Communicating with parathyroid glands
Vitamin D works with parathyroid glands in balancing calcium in the body. When your body is producing insufficient amounts of vitamin D, the parathyroid glands leach calcium from the bones to keep it balanced in the blood.
Protection against disease
Vitamin D protects against high blood pressure and some cancers, including those affecting the colon, prostate, and breasts.
Those with dark skin
Pale people absorb sunlight and produce vitamin D faster than darker-skinned individuals. Thus, vitamin D deficiency is more common for those with darker skin.
This is because melanin, the pigment that determines skin color, prevents ultraviolet UVB rays from penetrating and absorbing into the skin. People with more melanin need more sun exposure to attain the same amount of vitamin D as someone who is fair-skinned.
Those who live far from the equator
People who live in the upper regions of North America, including parts of the United States and Canada, experience less sun exposure, which often leads to vitamin D deficiency. This applies globally as well: the further you live from the equator, the less direct sunlight you receive, and in turn, you produce less vitamin D.
Sun exposure varies with the seasons, with those living in regions near the American Northeast (New York, Boston, etc.) unable to produce much vitamin D from November through March. You can produce vitamin D almost year-round in southern regions, including Florida.
In the southern hemisphere, you experience less sun exposure in June in places like Buenos Aires. In Cape Town, there’s little sun exposure between mid-May and August, for example.
As we age, our skin becomes thinner and less capable of producing vitamin D from sunlight. Older individuals are also prone to weaker bones, so vitamin D supplementation is essential in preventing fractures.
Babies and pregnant people
When you’re pregnant, your body can become depleted of vitamin D, leading to a deficiency in both you and your child. Vitamin D supplementation is recommended for those who are pregnant or nursing.
Vitamin D is crucial for children, as a deficiency can lead to rickets, a softening and weakening of bones that can lead to pain and deformity.
Obesity correlates with a high prevalence of vitamin D deficiency, contributing to negative overall health impacts, including psychiatric, autoimmune, and neurodegenerative diseases.⁴
Those living in polluted or sun-deprived environments
Living in urban areas with significant smog cover or foggy areas with little sunlight can lead to vitamin D deficiency. Individuals living in environments without much sun exposure should consider vitamin D supplements and incorporate more fortified foods into their diet.
Symptoms of vitamin D deficiency include the following:³
- Achy bones
- Muscle weakness and cramps
- Mood changes and depression
Some individuals may not experience any symptoms yet have a deficiency. Others may feel significantly debilitated from a lack of vitamin D. The only way to know if you have a deficiency is to ask your doctor to test you.
Your doctor can perform a vitamin D test that indicates your 25(OH)D levels. This simple blood test is easy and might be a standard assessment for blood work during your yearly physical. Today, you can also purchase at-home testing kits from many providers. These kits generally involve taking a finger-prick sample that you mail to the lab. You’ll receive your results in 2-3 weeks in most cases.
What do the numbers mean?
Having too little or too much vitamin D in your blood can indicate health risks. You should discuss your results with your doctor to determine the best path forward.⁵
- High vitamin D saturation: above 50ng/mL
- Adequate levels: 20 to 50ng/mL
- Inadequate levels: 12 to 20ng/mL
- Deficient levels: 12ng/mL or below
Direct sunlight exposure with at least 25% of your body uncovered is the best way to naturally produce vitamin D. However, several factors will affect how much vitamin D your body makes.
Time of day
Noontime is the best time of day for attaining the direct UVB sunlight needed to produce vitamin D. Most individuals need about six minutes of direct midday sunlight in the summertime to make 1,000IUs in a place like Miami, for example.
Time of year
You’ll need to spend more time under direct sun exposure in the winter to achieve the same vitamin D production. For instance, the same person who needs just six minutes of direct midday sun in the summertime in Miami would need at least 15 minutes of exposure in winter to produce 1,000IUs.
You’ll need considerably more sun exposure to produce vitamin D if you have darker skin. Someone with dark skin likely needs double the time in the sun as someone with pale skin to achieve the same goals.
A person with fair skin needs six minutes of direct sunlight at noon in Miami in the summertime to produce 1,000IUs of vitamin D. If that same individual lived in Boston, they’d need approximately one hour in the sun to make the same amount. And in the winter, individuals in Boston of all skin types are mainly incapable of producing vitamin D from sun exposure.
The more skin you expose to direct sunlight, the more vitamin D you produce.
Older skin has more difficulty producing vitamin D than young skin.
High-SPF sunscreens block UVB rays, greatly diminishing the amount of vitamin D your body produces.
Cloudy or foggy weather allows fewer UVB rays to reach your skin, diminishing vitamin D production.
The higher the altitude of your location, the better your sun exposure gets. You produce more vitamin D on a mountaintop than on a beach.
Smog and poor air quality limit vitamin D production, as pollution reflects UVB rays into the atmosphere.
Exposure to the sun through glass blocks UVB rays, preventing vitamin D production.
Lastly, you don’t want to overdo it. You should aim to get half the sun exposure that it would take for a sunburn.
Indoor tanning beds are one option for individuals who live in locations where sun exposure is limited. Keep in mind: while the body does produce vitamin D from tanning beds, dermatologists no longer recommend their use based on skin cancer risks.⁶
Notes on skin protection
Spending too much time in the sun can burn the skin and increase the risk of skin cancer. You should spend a moderate but frequent time in sunlight, no more than half the time it takes you to burn, and then cover up and move to the shade.
Sunscreen that blocks UVA and UVB light may be necessary for fair-skinned and sun-sensitive individuals, but it has not proven effective in preventing basal cell carcinoma. Babies and young children are prone to burning in the sun, so dermatologists recommend giving them supplements instead of risking sun damage. The same applies to anyone with a history of cancer or sun sensitivity.
Vitamin D supplements are an effective solution for most individuals with a deficiency. You’ll see the daily recommended allowances for different age groups in the chart below.⁵
|Age||Daily recommended intake|
The recommended allowances above are from the Food and Nutrition Board and are the official recommendations from the US government. Other organizations, including the Vitamin D Council, recommend higher dosages.
The chart below indicates the upper limits for vitamin D supplementation. Again, these levels vary by organization. This chart shows limits set by the US Food and Nutrition Board.⁵
|Age||Tolerable upper intake levels|
Vitamin D is fat-soluble, so your body has difficulty getting rid of excess. And while these upper limits may seem like a lot, it’s essential to keep in mind that the body produces as much as 25,000IUs of Vitamin D from full-body sun exposure.
Vitamin D toxicity occurs when an individual intakes 40,000IU daily for over two months. And the Food and Nutrition Board allows pregnant or lactating women to intake higher amounts than non-pregnant individuals.
People with certain diseases and health conditions benefit from intaking higher levels of vitamin D, including those with prostate cancer and multiple sclerosis. If you live with these conditions or others that may benefit from a higher vitamin D intake, you should consult your doctor to determine a safe amount. Higher intake levels may also mean more frequent tests to ensure that your blood levels stay within a healthy range.
The Vitamin D Council and other organizations recommend taking Vitamin D3 supplements over Vitamin D2 supplements because the body more readily absorbs them. Vegans and vegetarians should be aware that Vitamin D3 supplements are not vegetarian. For these individuals, Vitamin D2 supplements may be a viable option.
Lastly, cod liver oil supplements contain vitamin D, but they also include high levels of vitamin A, which can be harmful.
Can I take a vitamin D supplement and still go in the sun?
Yes. The Vitamin D Council recommends getting adequate sunlight and taking vitamin D supplements on days when you experience less sun exposure.⁷ For instance, if you work a 9-5 office job, you’d take supplements on weekdays and spend time on your weekends outdoors without supplementation.
What if I have trouble absorbing vitamin D from supplements?
Some individuals struggle with vitamin D absorption. You can try several solutions: (1) Let the vitamin D supplement absorb orally by holding it under your tongue. (2) Rely more on sun exposure for vitamin D production. (3) Increase your daily intake. You may want to discuss this option with your doctor and set up testing to make sure you’re not getting oversaturated.
Can anyone take vitamin D supplements?
Vitamin D supplements are safe for most adults and children. However, individuals with certain medical conditions and those taking medications should discuss supplementation with their doctor. Medications that can interact with vitamin D supplements include digoxin and thiazide diuretics. Medical conditions that may limit vitamin D supplementation include Hodgkin’s lymphoma, kidney disease, liver disease, and hormonal diseases. You might need to take more vitamin D if you take certain medications, as they interfere with absorption. These medications include phenytoin, carbamazepine, primidone, and barbiturates.
How do I take these supplements?
Vitamin D supplements can be taken at any time, with meals or on an empty stomach.
Can I get vitamin D from my diet?
It is rare to get enough vitamin D from your diet, but some foods provide it. See more details in the next section of this guide.
Vitamin D does not occur naturally in many foods, so supplementation is essential if you live in an area with poor sunlight exposure. The chart below shows some foods that contain vitamin D.³
|Food||Vitamin D in IUs|
|Cod liver oil (1tbsp.)||1360|
|Canned tuna (3oz)||154|
|Fortified orange juice (8oz)||137|
|Fortified milk and milk substitutes (8oz)||120|
|Beef liver (3oz)||42|
|Egg yolk (one)||41|
|Swiss cheese (1oz)||6|
 Vitamin D: Fact sheet for consumers (2021, March 22). National Institutes of Health, Office of Dietary Supplements. Retrieved May 17, 2022, from https://ods.od.nih.gov/factsheets/VitaminD-Consumer/.
 Holick, M., Chen, T. (2008, April). Vitamin D deficiency: A worldwide problem with health consequences. PubMed Central. Retrieved May 17, 2022, from https://pubmed.ncbi.nlm.nih.gov/18400738/.
 Vitamin D deficiency. Cleveland Clinic. Retrieved May 17, 2022, from https://my.clevelandclinic.org/health/articles/15050-vitamin-d–vitamin-d-deficiency.
 Vranić, L., Mikolašević, I., and Milić, S. (2019, September) Vitamin D deficiency: Consequence or cause of obesity? Medicina (Kaunas), PubMed Central. Retrieved May 18, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780345/.
 Vitamin D: Fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements. Retrieved May 18, 2022, from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.
 Vanchinathan, V. and Lim, H. (2012, April). A dermatologist’s perspective on vitamin D. Mayo Clinic Proceedings. PubMed Central. Retrieved May 17, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498088/.
 Vitamin D. International Center for Well-Being. Retrieved May 18, 2022, from https://icwb.com/vitamin-d.