Since my recent post on problems related to vitamin D deficiency and excess I received several questions. I have also participated in several discussions in other blogs related to vitamin D in the past few days.
There is a lot of consensus about vitamin D deficiency being a problem, but not much about vitamin D in excess being a problem as well.
Some bloggers recommend a lot of supplementation, which may be dangerous because: (a) our body evolved to obtain most of its vitamin D from a combination of sunlight exposure and cholesterol, and thus body accumulation regulation mechanisms are not designed to deal with excessive oral supplementation; and (b) vitamin D, like many fat-soluble vitamins, accumulates in fat tissue over time, and is not easily eliminated by the body when in excess.
The Vitamin D Council has the following general recommendation regarding supplementation:
There is a lot of consensus about vitamin D deficiency being a problem, but not much about vitamin D in excess being a problem as well.
Some bloggers recommend a lot of supplementation, which may be dangerous because: (a) our body evolved to obtain most of its vitamin D from a combination of sunlight exposure and cholesterol, and thus body accumulation regulation mechanisms are not designed to deal with excessive oral supplementation; and (b) vitamin D, like many fat-soluble vitamins, accumulates in fat tissue over time, and is not easily eliminated by the body when in excess.
The Vitamin D Council has the following general recommendation regarding supplementation:
Take an average of 5,000 IU a day, year-round, if you have some sun exposure. If you have little, or no, sun exposure you will need to take at least 5,000 IU per day. How much more depends on your latitude of residence, skin pigmentation, and body weight. Generally speaking, the further you live away from the equator, the darker your skin, and/or the more you weigh, the more you will have to take to maintain healthy blood levels.
They also provide a specific example:
For example, Dr. Cannell lives at latitude 32 degrees, weighs 220 pounds, and has fair skin. In the late fall and winter he takes 5,000 IU per day. In the early fall and spring he takes 2,000 IU per day. In the summer he regularly sunbathes for a few minutes most days and thus takes no vitamin D on those days in the summer.
For those who have problems with supplementation, here is what Dr. Cannell, President of the Vitamin D Council, has to say:
For people who have trouble with supplements, I recommend sunbathing during the warmer months and sun tanning parlors in the colder months. Yes, sun tanning parlors make vitamin D, the most is made by the older type beds. Another possibility is a Sperti vitamin D lamp.
One thing to bear in mind is that if your diet is rich in refined carbohydrates and sugars, you need to change that before you are able to properly manage your vitamin D levels. You need to remove refined carbohydrates and sugars from your diet. No more white bread, bagels, doughnuts, table sugar, sodas sweetened with high-fructose corn syrup; just to name a few of the main culprits.
In fact, a diet rich in refined carbohydrates and sugars, in and of itself, may be one of the reasons of a person''s vitamin D deficiency in the case of appropriate sunlight exposure or dietary intake, and even of excessive levels of vitamin D accumulating in the body in the case of heavy supplementation.
The hormonal responses induced by a diet rich in refined carbohydrates and sugars promote fat deposition and, at the same time, prevent fat degradation. That is, you tend to put on body fat easily, and you tend to have trouble burning that fat.
This causes a "hoarding" effect which leads to an increase in vitamin D stored in the body, and at the same time reduces the levels of vitamin D in circulation. This is because vitamin D is stored in body fat tissue, and has a long half-life, which means that it accumulates (as in a battery) and then slowly gets released into the bloodstream for use, as body fat is used as a source of energy.
It should not be a big surprise that vitamin D deficiency problems correlate strongly with problems associated with heavy consumption of refined carbohydrates and sugars. Both lead to symptoms that are eerily similar; several of which are the symptoms of the metabolic syndrome.
In fact, a diet rich in refined carbohydrates and sugars, in and of itself, may be one of the reasons of a person''s vitamin D deficiency in the case of appropriate sunlight exposure or dietary intake, and even of excessive levels of vitamin D accumulating in the body in the case of heavy supplementation.
The hormonal responses induced by a diet rich in refined carbohydrates and sugars promote fat deposition and, at the same time, prevent fat degradation. That is, you tend to put on body fat easily, and you tend to have trouble burning that fat.
This causes a "hoarding" effect which leads to an increase in vitamin D stored in the body, and at the same time reduces the levels of vitamin D in circulation. This is because vitamin D is stored in body fat tissue, and has a long half-life, which means that it accumulates (as in a battery) and then slowly gets released into the bloodstream for use, as body fat is used as a source of energy.
It should not be a big surprise that vitamin D deficiency problems correlate strongly with problems associated with heavy consumption of refined carbohydrates and sugars. Both lead to symptoms that are eerily similar; several of which are the symptoms of the metabolic syndrome.
I was just reading two posts by Hyperlipid (link below, two top posts) on vitamin D levels and cancer. To say that they were interesting is an understatement.
ReplyDeletehttp://high-fat-nutrition.blogspot.com/search?q=vitamin+D
If I understand the posts correctly, the main message is that blood levels of vitamin D may be low or high, but they need to be kept at a constant level. Erratic supplementation leads to an increased risk of cancer, even if that leads to high levels of blood vitamin D on average.
Not as simple as one would think … life is not simple.
"Were ancestral Europeans deficient for vitamin D?
ReplyDeleteThere are several problems with the vitamin-D hypothesis. First, if lack of this vitamin created the selection pressure that led to white European skin, why are Europeans genetically polymorphic in their ability to maintain blood levels of vitamin D? At least two alleles reduce the effectiveness of the vitamin-D binding protein, and their homozygotes account for 9% and 18% of French Canadians (Sinotte et al., 2009). If lack of this vitamin had been so chronic, natural selection would have surely weeded out these alleles. And why does European skin limit vitamin-D production after only 20 minutes of UV-B exposure? (Holick, 1995). Why is such a limiting mechanism necessary?" Why are Europeans white? .
Black-White Differences in Cancer Risk and the Vitamin D Hypothesis.
"Europeans are white-skinned because their ancestors had to maintain the same level of vitamin-D synthesis at latitudes where UVB radiation is much weaker. This leaves unexplained the much darker skin of indigenous peoples at similar latitudes in northern Asia and North America. More importantly, it posits vitamin-D metabolism as a ‘given’ that human skin color has to adjust to, when in fact this metabolic pathway is just as amenable to natural selection as everything else.[...]
ReplyDeleteFor instance, many populations have long been established at latitudes where vitamin-D synthesis is impossible for most of the year. Some of these populations can get vitamin D from dietary sources (e.g., fatty fish) but most cannot. In these circumstances, natural selection seems to have adjusted their metabolism to reduce their vitamin-D requirements. We know that the Inuit have compensated for lower production of vitamin D by converting more of this vitamin to its most active form (Rejnmark et al., 2004). They also seem to absorb calcium more efficiently, perhaps because of a different vitamin-D receptor genotype (Sellers et al., 2003). Even outside the Arctic zone, there seem to be differences in vitamin-D metabolism from one population to another. In particular, vitamin-D levels seem to be generally lower in darker-skinned populations. [Here is confirmation of that even within populations the lighter skinned have lower vitamin D levels Pigmentation and Vitamin D Metabolism in Caucasians: Low Vitamin D Serum Levels in Fair Skin Types in the UK.]
Population differences in vitamin D metabolism (scroll down a bit)
Ken:
ReplyDeleteThere is a tremendous among of genetic variation among Europeans today. This applies to almost any modern human group. Genetic variation is in part due to people from different backgrounds having children.
Genetic variation that makes a difference to vitamin D levels would by subject to selection Northern Europeans have white skins. If the trait of having lower vitamin d levels is in 20 % of such people (French Canadians) how does this square with selection for maximun fitness. I sounds to me that there are advantages to lower D levels. Vitamin D and aging.).
ReplyDelete" Calcidiol serum concentrations show a U-shaped risk of prostate cancer suggesting an optimal serum concentration of 40-60 nmol/L for the lowest cancer risk. Therefore, it is necessary to study several common aging-associated diseases such as osteoporosis, hypertension and diabetes known to be vitamin D-dependent before any recommendations of an optimal serum concentration of calcidiol are given.
If you are saying that the D reducing aleles are not native to Europe why have they not been eliminated. An analogy with sickle cell anemia: alleles for this would be eliminated outside the area where they paid off in fitness terms.
"People from different backgrounds having children" - yes a possible explaination but are you really suggesting that 20% of French Canadians a have a non European grandparent.
Cavalli-Sforza - The price of collaboration?
That should be:-
ReplyDeletebut are you really suggesting that the average French Canadian has a non European grandparent.
Ken:
ReplyDeleteI posted recently on vitamin D and aging:
http://healthcorrelator.blogspot.com/2010/01/vitamin-d-deficiency-seasonal.html
As to your question: grandparent, no, but ancestor, very likely.
There are other evolutionary processes that can account for some of the data you mentioned, such as genetic drift and the evolution of conflicting genes (as in costly traits). I posted about these also:
http://healthcorrelator.blogspot.com/2010/01/how-long-does-it-take-for-food-related.html
http://healthcorrelator.blogspot.com/2010/01/evolution-of-costly-traits-challenge-to.html
We would have to look at each individual case, and try to understand it. The cases that you point out are intriguing, and I hope to be able to take a more careful look at them soon.
The two evolutionary processes that I mentioned above are relatively simple versions of more complex population genetics models that Luca Cavalli-Sforza and others studied.
There is also a new field of research known as evolutionary graph theory that leads to even more intriguing results.
Interesting post and I've been reading a lot about this matters because I am a study of Nutrition and Vitamin D insufficiency can result in thin, brittle, or misshapen bones, while sufficiency prevents rickets in children and osteomalacia in adults, and, together with calcium, helps to protect older adults from osteoporosis.
ReplyDelete23jj