Physiological significance of vitamin D produced in skin compared with oral vitamin D

Abstract

Since the discovery of vitamin D, it has been accepted that its physiological supply is either from food or by endogenous synthesis in skin exposed to solar UV light. Yet vitamin D is a component of very few foods and its supply as a natural nutrient is unable to maintain good vitamin D status for human populations. One aspect of vitamin D physiology that has been ignored is that the mechanisms for its transport and processing from these two sources are quite different. Excess intake of vitamin D causes hypercalcaemic toxicity. However, experiments with different animal species have shown that long-term supply of oral vitamin D in apparently non-toxic amounts causes atherosclerosis in large arteries. A mechanism for this toxicity is proposed. Alternative strategies for addressing widespread vitamin D deficiency by food fortification should be considered in light of the angiotoxicity caused by oral vitamin D in animal experiments.

Vitamin D status among residents of Molidawa Daur Autonomous Banner, Inner Mongolia, North China

“…23 The reason for this lag is related to 2 factors, one being the local temperature change and the other the physiological process of VD synthesis in the skin. 24 Although there are more sunshine hours from March to June each year, the average temperature from January to May was below 15°C, and the area of skin exposed to the solar UVB light was far less than that from June to September. This shows that the month of the year can change people's lifestyle through temperature fluctuations, which in turn affects the production of VD from solar UVB light.…”

“…The accumulation of VD supply through skin exposure to solar UVB light rarely causes hypervitaminosis D, whereas excessive intake of VD is potentially toxic. 24,25 Currently, the dose of VD supplementation in LVDS patients varies from region to region. 26,27 With the usage of VD supplementation, incidents of VDI (VDI: also called VD toxicity or hypervitaminosis D) are inevitable.…”

Sunscreen cosmetics as basic protection against photoaging

“…This effect can be achieved by exposing the body to solar radiation for about 10-15 minutes a day (for people with fair skin). Extending the time without using effective sun protection can have negative effects on the condition of the skin [4][5][6]. From a biochemical point of view, the initial symptom of the harmful effects of sunlight on the skin is the release of histamine in the body, which causes the dilation of blood vessels and causes erythema, and is accompanied by increased sweat secretion [7].…”

‘Big History’, history and citations in nutritional science

“…Limits are, however, increasingly unusual as more and more journals are exclusively online with a consequent reduction in the pressures on space. I note that there has been a limit on the number of references for ‘Perspectives’ papers in JNS , but we are able to remove this – as exemplified in a recent article on vitamin D ( 12 ) .…”