girl going into sunshine

Getting vitamin D is as easy as taking a walk in the sun since vitamin D is made in our skin under the influence of UVB sunrays. The problem is that we have been told that direct sun exposure without protection is bad for us. On the other hand, new research about vitamin D benefits in preventing many diseases, including cancer, is constantly emerging.

The question is how can you get enough safe sun exposure and benefit from vitamin D for your overall health?

Why is vitamin D important?

Vitamin D has been traditionally linked to bone health. It helps maintain normal levels of calcium and phosphorus in our blood and helps our body to absorb that calcium. Adequate calcium absorption is crucial for bone development in children as well as for bone mineralization. Without vitamin D our bones would become brittle and thin. Vitamin D prevents rickets in children (soft and weak bones) and osteomalacia in adults (weak bones and muscles).

Lately, vitamin D has been linked to many other important processes in our body. Ongoing research is conducted in many fields to find out about all the benefits of vitamin D.

What is vitamin D?

Vitamin D is a fat-soluble vitamin our body can produce by itself when exposed to sunlight. Under the influence of UVB radiation, vitamin D3 (cholecalciferol) is synthesized in the skin. There is also another form of vitamin D- vitamin D2 (ergocalciferol) which is present in plants, mushrooms, and yeasts. Both vitamin D2 and vitamin D3  can’t be used by our bodies in the direct form but have to enter the circulation system to be transported to the liver. In the liver, vitamin D is transformed to 25-hydroxyvitamin D (calcidiol; calcifediol). This is the substance that is actually measured in your blood when you test for vitamin D levels. From the liver 25-hydroxyvitamin D travels to the kidneys where it is once more hydroxylated to 1,25-dihydroxyvitamin D (calcitriol). This is the final active form of vitamin D that is used by our bodies in many different processes.

Risk groups for vitamin D deficiency

Certain groups of people are in higher risk for vitamin D deficiency. These people need to test their vitamin D levels regularly, especially in winter and take supplements if necessary.

  • Older people
    old couple
    The older you are the higher the probability that you are vitamin D deficient, since older people tend to be less outside. Also the older you are the slower vitamin D is synthesized in your skin, making it necessary for older people to be more often in the sun. Older people should check their vitamin D levels to see if they need supplementation. A proper vitamin D status is very important for this group since it maintains good bone health and helps in the prevention of osteoporosis.
  • Dark skinned people
    dark skinned woman

    People with darker skin need 2-3 times more sun exposure than light skinned people. That’s because vitamin D is naturally synthesized much slower in their skin than with people who have a pale skin tone.
  • Overweight and obese people
    obese people
    People who are overweight or obese need 2-3 times more sun exposure or supplementation to achieve the same levels of vitamin D as normal weight people. You can check out if your overweight or obese here.
  • Breastfed babies
    breastfeeding baby
    Vitamin D supplementation with 400 IU per day is recommended for children who are exclusively breastfed. Although breast milk is the best food for babies it is low in vitamin D. Since you can’t take newly born babies outside into the direct sunlight supplementation is recommended by pediatricians to secure optimal bone and muscle development. Children who are bottle fed get their vitamin D inside their formula milk.
  • People who always wear sunscreen or don’t expose their skin to the sun
    Sunscreen doesn’t allow for UVB rays to penetrate the skin and form vitamin D. It is necessary to get into the sun for brief periods of time without any sunscreen or clothes on your skin. You can protect your face since the skin is very thin in this area but try to get some sun exposure without protection. If you are afraid of skin cancer talk to your doctor about safe sun exposure and try the dminder app that will send you a message when it is unsafe to be in the sun. You can always take supplements if you don’t want to go outside into the sun.

How much vitamin D do you need?

The recommendations for vitamin D intake can vary quite a lot depending on the source. The reason is that the recommended dietary allowance or RDA is established by the Food and Nutrition Board on the basis for maintaining bone health in healthy people. It seems that much higher levels are needed for overall health, especially if you want to benefit from vitamin D for the above listed conditions.

Here is the list of RDA by age and sex measured in IU (international units):

0-12 months*400 IU400 IU
1-13 years600 IU600 IU
14-18 years600 IU600 IU
19-50 years600 IU600 IU
51-70 years600 IU600 IU
>70  years800 IU800 IU
 * Adequate Intake (AI): established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy.

 source: Dietary Reference Intakes for Calcium and Vitamin D

These levels can be seen as the required minimum to avoid rickets and osteomalacia. New data indicates that these levels should be up to 10 times higher.

Another way of determining vitamin D intake is by measuring serum 25-hydroxyvitamin D (25(OH)D) levels. This substance indicates how much vitamin D is circulating in our blood, regardless if it was synthesized from sun exposure or taken as a supplement. There is no official recommendation for serum 25(OH)D levels but several studies have reported that levels between 30 ng/ml – 60 ng/ml seem to lower risks for developing certain diseases like cancer and autoimmune diseases. Even higher levels are recommended for treatment of this diseases.

The current conclusion of the committee of the Institute of Medicine for serum 25(OH)D levels, based on reviewed data from different researches are very conservative.

Recommended doses of serum 25(OH)D levels by the Institute of Medicine

nmol/L*ng/ml*Health benefits
<30 <12Not sufficient vitamin D. These levels cause the development of rickets and osteomalacia.
30-50 12-20These levels are not sufficient for good bone and overall health.
>50 >20Levels considered adequate for bone and overall health.
>125 >50Possible contraindications are possible at levels higher than 125 nmol/L. These doses are not recommended for healthy adults.
  * 25(OH)D levels are expressed in nmol/L and ng/ml. 1 nmol/L = 0.4 ng/mL

Many researchers believe that these levels are still far too low to prevent disease. Research of GrassrootsHealth, for example, suggests a level between 40-60 ng/ml for optimal health. They have developed a chart that is helpful when you want to know how much vitamin D you need to accomplish higher levels of vitamin D.

GrassrotsHealth chart

It has been noticed that the population which gets plenty of sunshine, like outdoor workers or people living in tropical climates have levels of 50-70 ng/ml of 25(OH)D. On this basis, the present recommendation is to have levels of 50-70 ng/ml for optimal health. Which means that if you have levels under 50 ng/ml you are considered deficient in vitamin D.

vitamin D levels

 source: Holick MF. Calcium and Vitamin D. Diagnostics and Therapeutics. Clin Lab Med. 2000 Sep;20(3):569-90)

It is important to notice that vitamin D intake depends on body size. The more body weight you have the more vitamin D you need. Depending on your BMI, if you are overweight (BMI 25-30) or obese (BMI >30) you need 2-3 times more vitamin D to achieve the same level as normal weight (BMI 18.5-25).

How to get enough vitamin D

There are many ways you can boost your vitamin D intake. The simplest by far is adequate sun exposure. But in places above 40 deg latitude, it’s difficult to obtain enough sunshine during november-march. That’s why it’s important to monitor if you’re getting enough vitamin D during the whole year, not only during summer. Here are the most effective ways to avoid vitamin D deficiency.

  • Sunshine
    people in sun and water

    Exposing your self to sunshine is the most effective, least expensive and comfortable way to synthesize vitamin D. Dr. Holick, the leading scientist on vitamin D, recommends to expose yourself to the sun for about half the time you need to get a mild sunburn about 2-3 times a week.Since you need UVB exposure to make vitamin D it is important to know that UVB rays don’t go through glass. That means you have to go outside for a brief time from until 10.00 am to 3.00 pm to get enough vitamin D. Vitamin D can’t be made in your skin if you are wearing sunscreen. A factor with SPF 30 will inhibit vitamin D production by 90%. For optimal vitamin D production, it is best to go out into the sun for brief periods of time with your face protected and arms, legs, back or belly exposed.
  • Tanning beds
    tanning bed
    Tanning beds are an option if you can’t get enough sun exposure. You have to be very careful when choosing this option since it is confirmed that sunbeds can cause skin cancer. First of all, you have to choose a tanning bed that emits UVB and UVA rays since UVA rays won’t give you vitamin D. Second choose tanning beds that use electronic ballasts to generate light, since magnetic ballasts have been linked to skin cancer. Ask about those two things before you choose to go into a tanning bed. Additionally, shorten your UV skin exposure to half the time that is recommended for tanning to be on the safe side.
  • Foods high in vitamin D
    Although not many foods contain natural vitamin D there are a few sources which are rich in vitamin D. It is however difficult to eat amounts that would result in 50-70 ng/ml of serum 25(OH)D.Rich sources are:

    Food sourceIU/ 100 gr
    Cod liver oil10 000 IU
    Raw herring1628 IU
    Canned salmon466 IU
    Canned trout604 IU
    Raw mackerel360 IU

    source: USDA food composition database

  • Fortified products
    milk with vitamin D
    Since rickets was a public health issue in the beginning of the 20th century governments in many countries including the US and Canada have fortified milk with vitamin D to prevent such conditions, including osteomalacia. Since then a variety of food is fortified with vitamin D including milk, cereals, infant formula, some orange juices, eggs yolk, soy milk. Milk is fortified with 100 IU/ cup with vitamin D in the US. Egg yolks contain about 40 IU/ egg if the chicken was fed with vitamin D. Some kinds of margarine are also fortified, but you have to check the label to be sure. Margarine, on the other hand, is not recommended as a source of fat since it is full of trans fats. It’s better to skip this food even if fortified. Consuming fortified food is a good way to additionally boost your vitamin D intake. You should still have on mind that these foods won’t give you the necessary amount of vitamin D. If you stay indoors often or wear sunscreen all the time it is possible that you are vitamin D deficient, despite consuming vitamin D fortified foods.
  • Supplements
    vitamin D
    If you can’t go out into the sun or don’t get enough sun exposure, which is the most natural way to get enough vitamin D, supplements are an option. Most supplements contain about 400IU of vitamin D. Check the label of the supplement and take the recommended dose. Talk to your doctor if you want to take higher levels than prescribed on the label.
    Choose a supplement that contains vitamin D3 (cholecalciferol) since it seems to be more potent and better absorbed by the body than vitamin D2 (Vitamin D3 Is More Potent Than Vitamin D2 in Humans, The Journal of Clinical Endocrinology and Metabolism). GrassrotsHealth has published charts that can help you determine how much IU (International units) vitamin D you should take per pound of body weight, depending on the level of vitamin D you want to achieve.IU vitamin D per pound

Does vitamin D deficiency really exist?

Although getting enough vitamin D is as easy as to go for a walk in the sun many people are deficient in vitamin D. A study in Australia concluded that one third of the population is vitamin D deficient. This is a paradox since Australia has enough sunshine during the whole year. In this study, researchers defined vitamin D deficiency as levels below a concentration of 50 nmol/l 25(OH)D. This is still much lower than the present recommendation of GrassrotsHealth (40-60 ng/ml which is about 100-150nmol/l).

Go into the sun? Won’t that give me skin cancer?

girl getting uvb exposed

How come that so many people are deficient in vitamin D? Simply people stay much more indoors during summer, especially from noon to 5.00 pm, to minimize the risk of skin cancer. Even if they go outside they use sunscreen to protect themselves. This makes it impossible for our body to make and store vitamin D. I am not suggesting that you should go unprotected into the sun for long periods of time, especially during the summer. But 2-3 times a week for about half the time you need to get a mild sunburn is enough to meet your vitamin D needs- that’s the recommendation of Dr.M.F.Holick.
These levels of sun exposure won’t give you skin cancer, on the other hand, you could tremendously benefit from them keeping in mind all the processes vitamin D is involved in our body.
As Dr.Holick states in his book The vitamin D solution  “Exposure of a person in a bathing suit to a minimal erythemal dose of sunlight, which is typically no more than 15-20 minutes on Cape Cod in June or July at noontime, is the equivalent to taking 20,000 IU of vitamin D orally.” 20,000 IU of vitamin D is a high concentration and you don’t need to aim for such high levels. You can cut the time in half to still get adequate sun exposure and high levels of vitamin D. Just take care not to get a sunburn.

40th latidude

If you live in a sunny climate and take care of adequate sun exposure, you don’t really need to supplement for vitamin D. Excess vitamin D that hasn’t been used by the body is stored in fat tissues and is released when needed.  If you’re living above 40 deg latitude you could need vitamin D supplementation in winter since UVB radiation is low during winter time. You can test your 25-hydroxyvitamin D levels with a simple blood test to be sure if you’re deficient during winter time. Ask your doctor about this test.

Get help for safe sun exposure

You can also check the current UV-index for your region, for example on, to see if exposing yourself to the sun is going to help you make vitamin D. For example when the UV index is 0 or 1 your skin won’t be able to make vitamin D because the radiation is too weak. Only at levels from UV index 3 and above vitamin D formation in the skin is possible. The dminder app can help you with determining how much sun exposure you need to achieve vitamin D production, depending on your location, the angle of the sun, skin exposure, skin type, age, weight, and weather.

The current recommendations for vitamin D levels are based on preventing bone diseases and not promoting overall health. Considering the emerging evidence of vitamin D benefits for our health it is crucial to boost our vitamin D production. The easiest way to do this is by getting direct safe sun exposure. If done the right way we don’t need to fear the negative effects of the sun and enjoy all the positive effects vitamin D has on our body.

Photo credit: Vitamin Packaging by Colin Dunn, Milk Vitamin D by Rupert Ganzer, Horse Mackerels by frankenschulz, Illusive Photography