How much vitamin d3 is produced by exposure to the sun?
A question that is often asked: is 4000 IU a high dose? The answer is yes and no.
As far as the dose of vitamin D3 is concerned available as a supplement it is very high because most general practitioner doctors only describe a dose of 400IU (Ie i/10) of our dose and market places like Amazon restrict us from selling any higher dose for fear of going over the normally recommended NHS limits.
In some countries for example in India they are so much higher doses over the counter where you can buy doses of 20,000 IU or above. This sounds totally ridiculous. However when you consider how much vitamin D3 is produced by sunlight you too might think that the dose is in fact reasonable, but maybe could be considerably higher especially if we answer the following question:
How much vitamin D3 is generated by one hour of sunlight?
The amount of vitamin D that is produced in the skin as a result of sun exposure can vary based on skin type. People with darker skin generally have higher levels of melanin, which is a pigment that helps to protect the skin from the harmful effects of the sun. Melanin absorbs UV radiation and reduces the amount of vitamin D that is produced in the skin. As a result, people with darker skin may require longer periods of sun exposure to produce the same amount of vitamin D as people with lighter skin.
According to one study, it is estimated that people with lighter skin (skin type I or II) may produce between 10,000 and 25,000 IU of vitamin D3 after one hour of sun exposure on the face, arms, and legs during the summer months (when the sun is highest in the sky). People with darker skin (skin type III to VI) may produce significantly less vitamin D under the same conditions.
It is important to note that these estimates are approximate and can vary widely depending on the specific circumstances. It is also important to be aware of the risks of overexposure to the sun, as excessive sun exposure can increase the risk of skin cancer.
Here is a reference for this information:
- Holick MF. Vitamin D: photobiology, metabolism, mechanism of action, and clinical applications. In: Feldman D, Pike JW, Glorieux FH, eds. Vitamin D. San Diego, CA: Academic Press; 1997:1-42.
Can you combine Vitamin D3 capsules to achieve a higher dose?
Yes, however we always recommend taking guidance from your health professionals to assess your particular circumstances for example your skin colour, your ability to access sunlight (certain skin conditions may restrict this), whereabouts you live and the season.
Do you have to take vitamin D3 every day?
As Vitamin d3 is a fat soluble vitamin you actually don't have to take it every day but you can bunch it up for example taking two or three in a day and then skipping for a those three days (or accordingly to the number you took).
More references are avaialbel here:
Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr. 2004 Mar;79(3):362-71. [PMID: 14985560]
Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30. [PMID: 21646368]
Webb AR, Kline L, Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab. 1988 Oct;67(4):373-8. [PMID: 3420491]
Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1678S-88S. [PMID: 15585788]