Can sunlight produce enough vitamin D for your body?
06 October 2011
It’s possible...but unlikely. Here are the facts that explain why
Full-body exposure of pale skin to summer sunshine for 30 minutes without clothing (85% of you body exposed) or sunscreen can result in the synthesis of between 10,000 and 20,000 IU of vitamin D.
However:
- A given area of skin can only produce a certain amount of vitamin D
- After repeated exposure to sun, the pigment melanin accumulates (you get a tan), which decreases the vitamin D uptake
- Dark skin can reduce vitamin D production by 50 fold. Aged skin (over 70 yrs) reduces vitamin D production by up to 4 fold.
- In NZ a “vitamin D winter” occurs for around 4-6 months in which weather conditions make it impossible to produce enough vitamin D from sunlight
- If you are on cholesterol lowering drugs your vitamin D production from sunlight will be compromised.
- Mid-day sun is most effective for producing vitamin D – this is also the hottest time to be out.
- Sun tan lotion, clothing, glass, smog or fog will stop UV-B sun rays (which produce vitamin D) – slip, slop, slap kills your vitamin D production
The bottom line is unless you are a fisherman, farmer, or otherwise outdoors and exposed regularly to sunlight you are unlikely to obtain adequate amounts of vitamin D from the sun.
Our ancestors ate vitamin-D-rich foods including the intestines, organ meats, skin and fat from certain land animals, as well as shellfish, oily fish and insects. Modern diets usually do not provide adequate amounts of vitamin D partly because of the trend to low fat foods and partly because we no longer eat vitamin-D-rich foods.
Your diet and supplementation with cod liver oil is the most effective way of ensuring that your vitamin D levels are taken care of.