Energy stored in adipose tissue can be utilised to maintain cellular functions in cases of increased energy needs or to fuel adaptive thermogenesis in response to cold stress [ 63 ]. Notably, there is much skepticism, given that the most fatal forms of skin cancer peak after reproductive age, and it is therefore difficult to argue that a low occurrence of skin cancers in individuals of reproductive age alone would have had an impact on natural selection [ 42 , 43 ]. Vitamin D3 is the best kind of supplement to take. Vitamin D also regulates the permeability of this layer via involvement of VDR in the synthesis of long-chain glycosylceramides, which form part of the lipid-enriched membranes around corneocytes [ 49 ]. However, there are only a few foods that naturally contain any vitamin D. Notably, a high folate status correlates with increases in the expression of proteins involved in the activation and regulation of the complement system, an important non-specific skin defense mechanism [ 52 ].
Taking vitamin D supplements. The vitamin D—folate paradigm proposes that skin pigmentation evolved as a balancing mechanism to maintain levels of two key vitamins in human health: vitamin D and folate. Keywords: vitamin D, folate, skin pigmentation, ultraviolet radiation 1. However, it is proposed that a selective advantage of protecting older post-reproductive adults against skin malignancies can be seen when considering the importance of older generations for offspring survival in hunter—gatherer communities [ 44 , 45 ].
This is supported by a recent study reporting multiple loci involving the VDR gene that display strong latitudinal clines [ 73 ] and previous work of the present authors in showing positive associations between the carriage of several VDR variant alleles Fok1, Bsm1, Apa1, and Taq1 and latitude as a surrogate measure of UVR exposure [ 74 ]. As these mechanisms may been seen as relatively short-term responses to temperature changes, they are likely to be of greater importance in temperate UVR environments rather than environments of high UVR. This hypothesis is plausible, given that in maintaining levels of vitamin D and folate via skin pigmentation processes, the widespread action of these nutrients in maintaining reproductive success would have been preserved [ 26 , 27 ]. However, the feasibility of this theory is potentially limited, given that considerable discrepancies exist between studies examining ethnic differences in skin morphology. The table below shows the different skin types: Skin Type. However, it is proposed that a selective advantage of protecting older post-reproductive adults against skin malignancies can be seen when considering the importance of older generations for offspring survival in hunter—gatherer communities [ 44 , 45 ].
One animal experiment has demonstrated that co-consumption with vitamin K reduced adverse effects, but this has not been tested in humans. In a Chinese population at particular risk for esophageal cancer and with the high serum 25 OH D concentrations have a significantly increased risk of the precursor lesion. However, the levels found in India are consistent with many other studies of tropical populations which have found that even an extreme amount of sun exposure, does not raise 25 OH D levels to the levels typically found in Europeans. The folate status is also linked to the expression of multiple proteins involved in immune function, inflammation, and coagulation in human blood [ 52 ]. Skin colour is such an extensive polygenic adaptation to our environment that the explanation for its evolution is likely a complex picture that integrates these prominent theories and current unknowns. The main physiological function of vitamin D is in regulating calcium levels by influencing calcium absorption, storage, and retention in the intestines, bones, and kidneys.
The table below shows the different skin types: Skin Type. This is supported by nitric oxide dependent vasodilation shown to be reduced in darkly skinned populations [ 59 ]. However, there is significant overlap between these theories and the now known actions of vitamin D and folate in the skin. Where you live — the closer to the equator you live, the easier it is for you to produce vitamin D from sunlight all year round. Vitamin D elicits the majority of its functions through binding to these receptors, which act as transcription factors that modulate gene expression by binding to vitamin D response elements on target genes [ 1 ].
It has been argued that these variants, therefore, argue against the vitamin D—folate hypothesis and are adaptive measures to overcome skin pigmentation as a barrier for adequate vitamin D synthesis. The table below shows the different skin types: Skin Type. For most, the UVB-induced — nm synthesis of vitamin D is the major source of this nutrient [ 1 ], but levels produced following UVR exposure are determined by several factors. As these mechanisms may been seen as relatively short-term responses to temperature changes, they are likely to be of greater importance in temperate UVR environments rather than environments of high UVR. A link between the folate status and adverse pregnancy outcomes is well established, particularly with respect to the influence of this vitamin on the occurrence of neural tube defects [ 31 ].
In the summer, when the Earth rotates, the angle improves and more UVB reaches the places far away from the equator, allowing you to produce vitamin D outside of winter months.
This review provides key examples of overlap between the theories proposed as alternatives to the vitamin D—folate hypothesis and actions of vitamin D and folate in countering environmental stress. In almost every case, a low-calcium diet combined with corticosteroid drugs will allow for a full recovery within a month. It could be suggested that folate and melanin compounds are synergistic; melanin, on the one hand, protects folate from UVR-related degradation, which in turn supports the influence of folate in melanogenesis. However, the levels found in India are consistent with many other studies of tropical populations which have found that even an extreme amount of sun exposure, does not raise 25 OH D levels to the levels typically found in Europeans. These roles are consistent with precepts of other theories for the evolution of skin pigmentation, and they support the integration of these theories. Subsequently, vitamin D does not fit the classic definition of a vitamin, and it is often more accurately referred to as a pro-hormone or secosteroid.
Inuit compensate for lower production of vitamin D by converting more of this vitamin to its most active form. Metastatic calcification of the soft tissues Hypervitaminosis D symptoms appear several months after excessive doses of vitamin D are administered. The Vitamin D—Folate Hypothesis The vitamin D—folate hypothesis is one of the main theories potentially explaining the evolution of human skin pigmentation.