Evolution of vitamin D pathyway genes


Yuen, A. W. C. and N. G. Jablonski (2010). “Vitamin D: In the evolution of human skin colour.” Medical Hypotheses 74(1): 39-44.

Nina Jablonski has been interested in evolution of human skin and skin color for a while and have wrote some interesting articles on this topic.  This is one of her recent articles and in the article, Jablonski and Yuen review recent medical literatures showing association between hypovitamin D and health status.  They use these lines of evidence to suggest that lighter skin color is selected outside of Africa to increase the production of vitamin D.

Followings are diseases and other health issues that are associated with low Vitamin D level;

Low fertility

Infectious diseases

Bone metabolism and factures

Cancers

Cardiovascular disease

Autoimmune disease

Dental health problems

Higher mortality

These potentially reduce reproductive success of individuals with low vitamin D level.  People with dark skin living in the area without enough daily sunlight in high latitude usually have hypovitamin D and they have higher risk of developing these diseases and health issues.  Some of these conditions decrease the chance of successfully having children, while others decrease the chance of surviving until reproductive age or increase the chance of death before the end of reproductive age.  Also, longevity is important for reproductive success of individuals, since in many societies, the elderly individuals usually have a role taking care of young children.

However, this article does not explain the mechanism of natural selection.  For example, which genes were involved to produce light skin?  Which genetic variants were selected?  How about genes involved in vitamin D pathway?  Human geneticists began to understand the genes and genetic variants for skin pigmentations, but I have found only a few literatures that address the evolutions of genes in vitamin D metabolism, or vitamin D pathway, and it is poorly understood.  Some genetic variants that are associated with vitamin D level have been found, but only a few of them have been conformed in multiple studies.  Many studies are conducted with White or Europeans populations, but African Americans or other minority groups are rarely included. 

If the efficiency of vitamin D metabolism and utilization is important in Europe or other areas in higher latitude, genetic variants that increase the efficiency were positively selected, and genetic variants that decrease the efficiency were negatively selected, so there should be little variation on the vitamin D pathway genes among the Europeans and other populations from higher latitude.  On the other hand, natural selection should not have acted on or should be relaxed in the populations from the areas with enough daily sunlight or populations, in which people consume vitamin D rich food.  In these populations, more variation on the vitamin D pathway genes should be observed and some of mutations may reduce the efficiency.

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2 thoughts on “Evolution of vitamin D pathyway genes

  1. PROFESSOR Frank Garland, and his brother, Cedric, recommend [...] taking 50,000 units of vitamin D per week for eight to twelve weeks followed by maintenance on 1,000 to 2,000 units a day”.
    ACCORDING Cedric F. Garland, Dr. P.H., FACE, Department of Family and Preventive Medicine and Moores Cancer Center of the University of California, San Diego (UCSD), “It is projected that raising the minimum year-around serum 25(OH)D level to 40-60 ng/ml (100-150 nmol/L) would prevent approximately 58,000 new cases of breast cancer and 49,000 new cases of colorectal cancer each year, and three quarters of deaths from these diseases, in the US and Canada.”
    Plasma vitamin D and mortality in older men: a community-based prospective cohort study.
    “There was a U-shaped association between vitamin D concentrations and total mortality. An approximately 50% higher total mortality rate was observed among men in the lowest 10% (98 nmol/L [or 39 ng/ml]) of plasma 25(OH)D concentrations compared with intermediate concentrations. Both high and low concentrations of plasma 25(OH)D are associated with elevated risks of overall and cancer mortality.
    Dr. Frank C. Garland, 1950-2010
    “Tuesday, August 17 at UCSD Thornton Hospital after contending with a nearly year-long illness.“

    “African Americans … are more likely to be vitamin D deficient due to their darker skin pigmentation’s ability to block the sun’s rays”
    It is not true that melanin blocks the wavelengths which synthesize vitamin D . The value of melanin as a sunscreen (2010).
    “epidermal melanin is not a neutral density filter providing no or minimal protection for the induction of erythema at 295 and 315 nm and some protection at 305 and 365 nm”
    It does block 305nm but around that wavelength is the most damaging A UVB Wavelength Dependency for Local Suppression of Recall Immunity in Humans Demonstrates a Peak at 300 nm. also see Erythema curve. Note the relative danger curve ( yellow) peaks at around 305nm
    T the blocking of a limited spectra of vitamin D synthesizing UVB doesn’t matter the other wavelengths get through. Blood vitamin D levels in relation to genetic estimation of African ancestry “found novel evidence that the level of African ancestry [rather than skin pigmentation] may play a role in clinical vitamin D status”.
    There is a negative feedback system; evolution has has got vitamin D levels just right
    Klotho protein deficiency and aging.
    “α-Klotho protein is shown to function in the negative feedback regulation of vitamin D3 synthesis These observations indicated that abnormal vitamin D3 metabolism is the main cause of aging phenotypes.″
    Klotho was named after one of the Moirae or fates, supplementing vitamin D is indeed a fateful step.

    Many people of tropical ancestry have a optimum homeostasis of vitamin D which is below the new IoM levels, but if they’re wise they’ll not take supplements

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