Rickets is caused mainly by a lack of vitamin D, but low calcium intake may also contribute. The main source of vitamin D is the exposing skin to sunlight when the sun is high enough in the sky.
If the shadow is much longer than you, the sun is not high enough. Clothing, sunscreen and glass windows prevent the passage of ultraviolet sunlight waves that produce both sunburn and vitamin D. Changes in skin tone (different amounts of melanin) have appeared due to the changing balance between avoiding sun damage and get vitamin D that has occurred to human established beyond Ecuador.
Vitamin D production increases with the area of skin exposed to sunlight. The ideal duration of exposure of the skin to get the benefits without causing unnecessary damage is one third of the time it could cause us burns. For people with white skin in UK ideal exposure time varies from five minutes at noon in the summer to about twenty minutes late autumn, while people with darker skin require a longer exposure time.
In the UK there is a long "vitamin D winter" when the sun is not high enough in the sky, even at noon, to produce a useful amount of vitamin D. This is increased by a smaller amount of skin exposed once the temperatures begin to drop in the fall.
Amounts of vitamin D produced by exposure of the face, hands and arms to the sun for 5 minutes with clear skies and no sunscreen.
Amounts of vitamin D with 5 min. Exposure by skin type and sun angle
Vitamin D levels, therefore vary with the seasons, children are in late winter and higher in late summer. If sun exposure is good, this winter vitamin D is a diet which becomes important in providing a safety net preventing vitamin D reserves fall too low. The winter of vitamin D in Scotland is longer than in the south of the UK, increasing the risk of rickets and other health problems.
It is worth noting that even in countries without a winter of vitamin D deficiencies may have a limited exposure to sunlight. Furthermore, the ability to produce vitamin D by the action of sunlight on the skin decreases with age.
Only 2.5 micrograms per day of vitamin D is generally sufficient to prevent rickets, but larger amounts are beneficial differently. A recent review of studies on vitamin D supplements, with doses of 10 to 20 micrograms (mcg or mg), showed a 7% reduction in death rate caused by any cause. About 25 micrograms per day is enough to largely eliminate seasonal variations in vitamin D reserves in Europe and the United States. In recent years, many experts have suggested that 25 micrograms per day, the combined effect of the sun and diet, are needed to maintain healthy levels throughout the year.
There are two forms of vitamin D: vitamin D2 and vitamin D3. Vitamin D2 is generally from plant sterols, whereas D3 comes both from animal skins or wool as cholesterol (usually animal). Many studies using high doses of vitamin D indicate that the vegan form of vitamin D, vitamin D2 was less effective than vitamin D3. However, a conciencudo study published in 2008 has shown that a dose of 25 micrograms of vitamin D both are equivalent to increasing levels and there are no adverse interactions between them.
The normal amount of vitamin D in the diet in the UK is about 3 micrograms per day. The meat and fish together contribute half of this amount and eggs 10%. Milk provides virtually no vitamin D. The other main sources of the overall diet are fat spreads (margarine) enriched and fortified breakfast cereals. While fat spreads in the UK are enriched with vitamin D2 enriched breakfast cereals are often enriched D3 animal. Enriched soy milk can be a significant source for some people, but it is very easy for vegans - and indeed for all vegetarians - not having any supply of vitamin D in the diet, thereby increasing the risk of rickets and other health problems.
The first line of defense in maintaining healthy levels of vitamin D is a frequent exposure to sunlight - at least twice a week, and ideally every day - taking care not to burn. Horseback lunch in the fall involve few risks of excessive sun exposure, while increasing stores of vitamin D when they are most needed. Similarly, the spring walks to lunch quickly rebuild our reserves. Much less vitamin D occurs on cloudy days. So the sunny days of autumn and spring are interesting to go out at noon.
In the fall and spring in the UK increased sun exposure is safe without the use of sunscreen, but always use your own experience and judgment to avoid burns. It is safer to expose more skin in less time than less skin for a longer period.
The second line of defense is to use a vitamin D supplement providing effective sun exposure is limited. The Vegan Society supplement VEG 1 includes 10 micrograms of vitamin D2. It is twice the amount of most multivitamin supplements and reaches the highest recommendations from the United Kingdom (adults over 65). It is, however, lower than the US recommendations for adults over 70 (15 micrograms) and lower than the amount that is now widely recommended (25 micrograms combined diet and sun).
European insurance guidelines may set a limit cap of 25 micrograms per day, including those contributed by diet and supplement, for people up to 10 years and 50 micrograms after that age. US guidelines indicate the same quantities but with a threshold age of one year. There is no risk of overdose sunbathing and also taking supplements.
Amounts of vitamin D produced by exposure of the face, hands and arms to the sun for 5 minutes at noon on 21 each month with clear skies and no sunscreen.
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