Sun vs Food: Which is best for optimizing your vitamin D levels?

  • icon

    Your vitamin D levels significantly affect your health. Scientists throughout the world have only recently discovered the magnitude of health benefits offered by vitamin D in the body. One of the most important findings regarding vitamin D is its role in cancer prevention, as vitamin D appears to be one of the strongest inhibitors of cancer cell growth. A common question I often come across is whether we can get enough vitamin D through our food.   

    Vitamin D food sources are very often not sufficient

    Vitamin D is only found in very few foods. Fatty fish, fish liver oil and eggs naturally contain vitamin D, but their levels are not enough to ensure a good vitamin D status. One egg yolk for example has an average of 50 IU of vitamin D. It is now believed that people who are not regularly exposed to the sun cannot get the right amount of vitamin D only from food.

    How much vitamin D3?

    The vitamin D we get from food or supplements is measured in IU (International Units). It can also be measured in micrograms (mcg or μg) and 1 mcg equals 40 IU. 

    Different organizations recommend different daily intakes. An increasing number of researchers that specialize in vitamin D believe that taking low amounts, 1000 IU or below isn’t enough and suggest taking 2000 – 5000 IU of vitamin D3 per day.

    Research published in recent years shows that even people who live in sunny areas such as the Mediterranean are very often deficient in vitamin D.  

    The latest information suggests that the optimal vitamin D blood level is at least between 40 and 60 ng/ml. It is recommended that you check your vitamin D levels approximately every six months. It takes at least three months for blood vitamin D levels to stabilize after a change in sun exposure or supplement dose.

    Once you reach sufficient levels, it would be wise to monitor your vitamin D blood levels regularly. You can then gradually reduce the dosage of vitamin D that you take until you find the vitamin D supplement dose that keeps your vitamin D status at the desired range.

    In people who are overweight, a large percentage of their vitamin D intake is stored in fat tissue so they might need 2 to 5 times more vitamin D intake compared to lean people. 

    Safe sun exposure for maximizing your vitamin D levels

    Sun produced vitamin D is the most natural and efficient way for optimizing the body’s vitamin D levels. Exposing bare skin in the sun can quickly produce significant levels of vitamin D, especially in the summer, according to John J Cannell, MD, founder and Executive Director of the Vitamin D Council. The Vitamin D Council, accessed at:, was founded in order to educate the public on the importance of safe sun exposure and vitamin D.

    You don’t need to tan or burn your skin to get vitamin D. According to the Vitamin D Council, you only need to expose your skin for around half the time it takes for your skin to turn pink and begin to burn.

    Extra caution is needed, however, to build sun exposure slowly and to match your exposure to your skin type. Exceeding this safe level of sun exposure and letting the skin burn causes harm and damage to the skin and in the long run leads to an increased risk of skin cancer.

    Key Facts about Vitamin D and sun exposure  

    According to the Vitamin D Council, the amount of vitamin D you get from exposing your bare skin to the sun depends on:

    • The time of day – your skin produces more vitamin D if you expose it during the middle of the day.
    • Where you live – the closer to the equator you live, the easier it is for you to produce vitamin D from sunlight all year round. People living further away from the equator have less UVB rays available, particularly during the winter time, so supplementation is necessary. For example in cities like New York, Boston, and in the Scandinavian countries, one cannot produce enough vitamin D from November to March.  
    • The amount of skin you expose – the more skin your expose the more vitamin D your body will produce.
    • The color of your skin – pale skins make vitamin D more quickly than darker skins. Melanin, the substance that affects how light or dark your skin color is, affects the amount of vitamin D you can produce. Melanin protects against skin damage from too much UVB exposure. Darker skins have more melanin and allow less UVB to enter the skin. With less UVB getting through the skin, less vitamin D is produced each minute. This is why if you’re dark skinned, you need more sun exposure to make vitamin D than if you’re fair skinned.

    Factors affecting the amount of vitamin D your body makes when exposed to the sun:

    • The amount of skin you expose. The more skin you expose, the more vitamin D you can produce.
    • Your age. As you get older, your skin has a harder time producing vitamin D.
    • Whether you’re wearing sunscreen. Sunscreen blocks a lot of vitamin D production.
    • The altitude you’re at. The sun is more intense on top of a mountain than at the beach. This means you make more vitamin D the higher up you are (at higher altitudes).
    • The weather. Less UVB reaches your skin on a cloudy day and your skin makes less vitamin D.
    • Air pollution. Polluted air soaks up UVB or reflects it back into space. This means that if you live somewhere where there is lots of pollution, your skin makes less vitamin D.
    • Being behind glass. Glass blocks all UVB, so you can’t make vitamin D if you’re in sunlight, but behind glass.

    What if food and sun are not enough?

    • You can also get vitamin D by taking supplements. This is a good way to get vitamin D if you don’t have the opportunity to spend at least 20-30 minutes every day in the sun or if you’re worried about exposing your skin.
    • Vitamin D3 is the bioactive form of the vitamin, so it is important to make sure you are supplementing with vitamin D3 and not with other forms of the vitamin like vitamin D2. It comes in a number of different forms, such as tablets, capsules or liquid, and it doesn’t matter what form you take. For most people vitamin D is easily absorbed in the body so you don’t need to worry about what time of day you take it or whether you take it with meals.

    If you take Vitamin D you also need vitamin K2

    • If you're taking vitamin D supplements you need to make sure you're also taking vitamin K2. Vitamin K2 deficiency may lead to vitamin D toxicity, which includes inappropriate calcification resulting in hardening of the arteries and promotion of heart disease and stroke.
    • According to Dr. Kate Rheaume-Bleue, a naturopathic physician and author of the book “Vitamin K2 and the Calcium Paradox”, lack of vitamin K2 increases the risk of osteoporosis, heart disease and cancer. 
    • Vitamin K2 is important because it moves calcium around the body. It removes calcium from areas where it shouldn't be, such as in your arteries and soft tissues. Vitamin K2 can only be found in fermented foods such as sauerkraut, kefir, and traditional sheep’s yogurt and can be also produced by beneficial bacteria in the gut.
    • The other main role of vitamin K2 is to activate proteins that control cell growth. According to Dr. Rheaume-Bleue this means that vitamin K2 has an important direct role to play in cancer protection.

    Take home message:

    • Very often, people’s vitamin D levels are low in Western countries.
    • It is advisable to check your vitamin D levels as part of your routine blood tests.
    • Aim to keep your vitamin D levels at least between 40 - 60 ng/ml year-round.
    • Very often, people’s diets are poor in vitamin D.
    • For most people, exposing their skin safely to the sun seems to be the best way for optimizing vitamin D levels.
    • Especially in winter time, you might want to consider using a vitamin D3 supplement to ensure good vitamin D levels.  


    2. Gorham ED, Garland CF, Garland FC, Grant WB, Mohr SB, Lipkin M, Newmark HL, Giovannucci E, Wei M, Holick MF.  Vitamin D and prevention of colorectal cancer.  J Steroid Biochem Mol Biol  2005; 97(1-2):179-194.
    4. Expert Review of Anticancer Therapy; Current progress in using vitamin D and its analogs for cancer prevention and treatment; June 2012, Vol. 12, No. 6 , Pages 811-837,  Florence SG Cheung, Frank J Lovicu, and Juergen KV Reichardt
    5. Sungmin Baek, Young-Suk Lee et al, Vitamin D3 regulates cell viability in gastric cancer and cholangiocarcinoma: Anatomy & Cell Biology 2011;44:204-209

    Subscribe to my nutrilosophy and get your Superfood Guide

    book small