Does the color of our skin depend on what we eat?

The question at the top of this post may seem stupid, but it has not an easy answer.

The color of our skin has served as the basis for numerous racist theories that have considerably animated (sarcasm) the history of humanity for millennia. All those who consider white skin to be synonymous with superiority will probably raise their hands to their heads when they learn that hommo sapiens emerged from Africa with dark colored skin. All, absolutely all the races on our planet, come from a few individuals of what today we would call the black race.

The color of the skin represents a protection against solar radiation. Living beings are especially sensitive to the ultraviolet type. Much of this radiation is filtered by ozone in the Earth's atmosphere, but a certain amount reaches the planet's surface, constituting a terrible danger: the ultraviolet spectrum can cause changes in the DNA of cells, causing cancer and other mutations. This is the which is why humans living in equatorial zones have dark skin due to melanin that acts as a defensive shield. If hommo sapiens arose from the equatorial zone of Africa, it is practically impossible that they possessed light skin. As they occupied more northerly latitudes, the solar radiation was weaker and the skin lightened. 

The mechanism that allowed this decoloring was the balance between Vitamin D and folic acid.

If human beings had kept dark skin at any latitude, growth problems would have occurred since vitamin D is responsible for the passage of calcium to the bones. Vitamin D is created from dietary ergosterol and cholesterol with the help of ultraviolet rays. Without sunlight, vitamin D is not produced. Therefore, the lighter our skin, in latitudes with low solar radiation, the more vitamin D will be produced.

However, even in areas of very northern latitude, few human beings have skin completely devoid of melanin. It happens that an excess of ultraviolet radiation affects folic acid, which acts actively in the reproduction process. In this way, folic acid is interested in our skin being dark, while vitamin D is interested in making it as light as possible.

As hommo sapiens left Africa to live further north, solar radiation decreased, so evolution selected those individuals with less dark skin so as not to have problems in the production of vitamin D, as long as the balance regarding folic acid was not excessively unfavourable. Folic acid is a water-soluble vitamin, but unlike other vitamins of the same type - such as vitamin C - it is stored in the liver and is less dependent on the sun.

Oddly enough, all the remote ancestors of the rosy Icelanders were men with very dark complexions and brown eyes. How long did it take for them to change color? Not too much. It is considered that evolution takes between two and two thousand five hundred years to change the coloration of the skin to adapt to the environment. And it is a process that can be reversed. If we were to bring a Scandinavian population to the center of Africa, it is likely that a couple of millennia, without even crossing with the original inhabitants of their environment, they would turn dark skinned. In the same way the black population that was brought from Africa to the United States will turn a much whiter color - if not white - over time. The reason why it has not happened yet is because they have been in the country for barely 300 years, insufficient for evolution to act. Elsewhere this color change is known to have occurred.

When the Aryans arrived in northern India, they displaced the original populations, who were originally very light-skinned, to the south. More than four thousand years have passed and today the inhabitants of southern India, exposed to a high level of ultraviolet radiation, have once again become very dark-skinned. In fact, in this country the division into castes is closely related to the color of the skin. The upper caste, the Brahmins, are almost as light-skinned as Europeans while the Untouchables are very dark.

Why the first sapiens are usually represented with white skin is due solely to a stupid anachronistic "white-centrism". For many it was already difficult to assume our relationship with primates to seriously consider that our remote great-grandparents were black. And so the museums and paleontology books are full of rosy African sapiens that only existed thousands of years after their arrival in Europe and Asia.

The question is, can we maintain  the color of our skin by regulating the amount of vitamin D and vitamin B9 (folic acid) that we take according to the latitude at which we are? Although theoretically we can supply our body with both vitamins in such a way that it is quite indifferent to the amount of solar radiation available, in the long term it is much more effective to allow natural genetics to regulate the color of the skin. The number of environmental and nutritional variables are so high that it is impossible to administer the adequate amount of vitamin that would allow us to maintain a certain skin color because nothing, much less something as stupid as maintaining skin color, is worth the effort. And you know, an excess of any vitamin, as well as its lack, can cause serious health problems.