I read that we gradually lose the ability to synthesize Vitamin D as we age and after 40 years old or so we are down to only 5% of our original capacity. Sorry I can't find the study again.
Anyone heard of this? If true, maybe I'm wasting a lot of time in the sun and tanning booth and should be just supplementing.
asked byTom_1 (99)
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on August 16, 2010
at 01:32 PM
The ability to synthesize Vitamin D in the skin from sunlight does decrease with age. I found This Study by Michael Holick comparing synthesis in young adults and older people. Unfortunately it will be behind a paywall for most people. I couldn't find any other studies measuring this directly.
Six healthy white subjects aged 20-30 and six older white subjects aged 62-80 with skin type III received whole body exposure to "sunlight" (32 mJ/em2) in a National Biologic light box emitting energy between 260 and 360 nm.2
Serum concentrations of vitamin D were measured for 7 days. In the young adults circulating vitamin D concentrations increased from 2-6 ng/ml to 30 ng/ml within 24 hours and slowly declined towards baseline by 7 days.
In the older volunteers, with the same skin type and exposed to the same amount of simulated solar radiation, circulating vitamin D rose from 1.5 to only 7.6 ng/ml.
The average production of Vitamin D from the same dose of UV light was quite abit lower in the older subjects compared to the young adults. However it is more like 30% than 5% even for 60-80 year olds so you will still be making Vitamin D if you are out in the sun. It would be cheaper and safer taking a supplement in addition to sunlight rather than spending money on tanning booths.
on August 16, 2010
at 03:44 PM
Not everyone loses the ability to synthesize and activate vitamin D, in other words it is not always age-related.
The kidneys are a prime site of activation ergo if significant kidney dysfunction is going on, vitamin D activation will also be compromised. The liver is another site -- the P450 enzyme system and other enzymes are involved. GLUTEN and high fiber diets KNOCK THIS OUT. Ergo happy wholediseasegrains are at the center of vitamin D deficiency combined with blatant sun-phobia with the overuse of sunscreen.
Drugs -- many drugs (birth control, statins, any sulfur-derived pharmaceutical which is A LOT OF PHARMACEUTICALS, diuretics/'water pills', etc) cause photo-hypersensitivity.
Lack of vitamin B3 -- induced by phytic acid by oats, grains, whole brown rice, etc (also known as the vampire condition -- pellagra) causes photosensitivity which again will affect and increase sun avoidance, further worsening vitamin D deficiency.