The common cold - it's a white thing?

[Neon Beach]

The common cold - it's a white thing?

Posted on: October 1, 2007 10:08 AM, by Razib

Vitamin D deficiency and skin color are two biological topics I've focused on a lot. The latter may have a relationship to the former insofar as light skin is better at synthesizing Vitamin D at low radiation levels (i.e., at high latitudes). Additionally, some of the genes that are under recent natural selection (within the last 10,000 years), such as OCA2 & SLC24A5, are related to pigmentation (specifically, the lightening of skin or eye color). At my other blog I've reproduced some ethnographic data which shows deviation from expectation of skin color in various populations assuming that UV radiation is the independent variable (and generating the slope using the observed values of indigenous populations). It won't be a surprise to some of you that I suspect that perhaps Vitamin D deficiency due to a shift toward a high carbohydrate diet might have resulted in lighter skin emerging to compensate for the loss of natural intake via food. But is Vitamin D deficiency that bad? Rickets is an extreme case, and there is evidence for its influence in increasing mortality in relation to chronic end-of-life disease (cancer, etc.). There is some data which suggests birth defects, and that's pretty important, as it hits fitness at a critical point. But there's something else....



Epidemic influenza and vitamin D:

...Solar radiation triggers robust seasonal vitamin D production in the skin; vitamin D deficiency is common in the winter, and activated vitamin D...acts as an immune system modulator, preventing excessive expression of inflammatory cytokines and increasing the 'oxidative burst' potential of macrophages. Perhaps most importantly, it dramatically stimulates the expression of potent anti-microbial peptides, which exist in neutrophils, monocytes, natural killer cells, and in epithelial cells lining the respiratory tract where they play a major role in protecting the lung from infection. Volunteers inoculated with live attenuated influenza virus are more likely to develop fever and serological evidence of an immune response in the winter. Vitamin D deficiency predisposes children to respiratory infections. Ultraviolet radiation (either from artificial sources or from sunlight) reduces the incidence of viral respiratory infections, as does cod liver oil (which contains vitamin D). An interventional study showed that vitamin D reduces the incidence of respiratory infections in children. We conclude that vitamin D, or lack of it, may be Hope-Simpson's 'seasonal stimulus'.

The article above is focused on why flu (and cold) breaks out during winter; the basic model is that elevated Vitamin D synthesis during periods of high radiation (e.g., summer) tends to beef up the immune system and so allow one to globally resist infection more effectively.

[Sunsally]

My post on this:


Very interesting - thank you!

What is frustrating is the complete "Chicken Little" approach to the sun SO many have right now -- including medical professionals! The "sun scare" movement has gotten people convinced that it is DANGEROUS to be in the sun - and instead has them hiding inside and slathering the largest organ of their body (their skin) in chemicals, some untested, some with known carcinogenic properties!

Why? Well - some would suggest it is because the "backers" of this have significant financial ties to it's success. Fears of "skin cancer" are driving people to the doctor for insurance paid "treatments" for "pre-cancerous" skin (Pre-cancerous -- as in -- "maybe this could turn into cancer someday, perhaps"). While there, they are convinced that "normal aging" is suddenly "unacceptable" - and botox, chemical peels and other lucrative 'services' are recommended.

Meanwhile - the major money behind sites like The Skin Cancer Foundation are a whole HOST of companies that make money from people staying out of the sun. Companies that sell sunscreen and self-tanning lotions, special "sunproof" clothing and housing products, and the drug companies who make a FORTUNE off of cold "remedies"!

10-20 minutes of full body UV exposure 4-7 times/week will provide adequate Vit D production to reduce the Vitamin D deficiency that is linked to higher rates of breast and colorectal cancers, MS, and even the common cold!

Time for the "sunscare" proponents to be put aside and the shift back to real science to come through!



AGAIN - this was a VERY well written article that continues to pound the message -- people NEED UV exposure for their health!

[Neon Beach]

[Sunsally]

Why thank you, thank you very much (in an Elvis voice!)

I had put down the link to this site, but it didn't print out so I added another comment with a link to this.

Thanks for continuing to find these and post them so we can comment!

[Neon Beach]