No disrespect intended, I am biologically challenged, but I do not understand how anyone can have a Vitamin D deficiency when 15 minutes of sunlight a day on the skin creates all the Vitamin D anyone needs, and too much Vitamin D is very bad. I suppose it makes sense in the Winter months when everyone is inside for months, but usually, the sun shines every day, even in Winter.
I have discussed at length regarding this with endocrinologists.
There is no shortage for the source of Vitamin D - As you mentioned - UV from Sun, certain food and of course supplements. But the destination should be able to activate it. So, in my case my body is not able to activate the Vitamin D in the system properly and so is the case with most Vitamin-D deficient people.
>Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol[1].
Further, Vitamin D is necessary for calcium absorption in the gut. Hence, the lack of Vitamin D causes bone problems among other issues.
Latitude matters. The farther north you are the more time in the sun you’d need. In some far north places, the sun you do get is not strong enough to get any Vit D.
Not everyone can afford getting half naked under the sun on a daily basis.
It's easier to be deficient than you think. Do a blood test. You may get an unpleasant surprise.
I think about half of the population is either insufficient or deficient without supplementation.
It really depends on what counts as insufficient. There is enough debate in the scientific literature on what constitutes a "sufficient" level of Vit D for most healthy adults. If we set the sufficiency level of 25(OH)D of 20 ng/mL (50 nmol/L), most of the world's adult population would be in the healthy range. These levels can be achieved in a healthy Caucasian adult in a northern latitude in summer (eg, Edinburgh, Scotland) with as little as, say, two sessions of 10 minutes each in a week, exposing just the arms and legs.
Serum levels of Vitamin D also do not plummet with the winter months - it's more of a slow dip, and the seasonal low levels do not seem to negatively effect most adults.
Even during the nicest weather of the year, I don't typically spend 15+ minutes outside every single day, and even when I am outside, only my arms below the elbow and face are exposed.
It simply does not follow from "the sun shines" that "everyone basks in it all the time".
> usually, the sun shines every day, even in Winter.
Not in Vancouver!
And even on the few sunny winter days, the full daylight hours might typically be spent in an office. Even the commute happens in the dark.
I'm from South India and I know two people in my family with severe Vitamin D deficiency. Sunlight-> Vitamin D won't happen for most people with a white collar job even if you are near equator. Hospitals in India rarely offer that test as it's expensive. We insisted on getting one after severe back pain and other symptoms.
I've seen studies that show quite low levels of Vitamin D in even healthy rural south Indian farm workers. The average was ~ 20 ng/mL. The study authors speculate that the high levels of phytates in the typical Indian diet might be to blame.
I've seen that claim given as "15 minutes of full body exposure to noonday sun", which is obviously quite different from what most of us might get. Also I expect it depends on your skin tone. If anyone could dig up the original source for the 15 minutes claim I would be curious (tried a bit but have to get back to work).
Low magnesium impairs vitamin D activity and levels. Same occurs as a result of declining hGH/IGF-1 with age. Further, cholesterol within skin diminishes with age (and cortisol rises) lessening response to sunlight.
The further north, the less days of direct sunlight. Exposure would have to also be all over, but most are covered by clothing.
No disrespect intended, I am biologically challenged, but I do not understand how anyone can have a Vitamin D deficiency when 15 minutes of sunlight a day on the skin creates all the Vitamin D anyone needs, and too much Vitamin D is very bad. I suppose it makes sense in the Winter months when everyone is inside for months, but usually, the sun shines every day, even in Winter.