Vitamin D is unique in being generated in our skin following ultraviolet radiation (UVR) exposure. Ongoing research into vitamin D must therefore always consider the influence of UVR on vitamin D processes. The close relationship between vitamin D and UVR forms the basis of the “vitamin D–folate hypothesis”, a popular theory for why human skin colour has evolved as an apparent adaption to UVR environments. Vitamin D and folate have disparate sensitivities to UVR; whilst vitamin D may be synthesised following UVR exposure, folate may be degraded. The vitamin D–folate hypothesis proposes that skin pigmentation has evolved as a balancing mechanism, maintaining levels of these vitamins. There are several alternative theories that counter the vitamin D–folate hypothesis. However, there is significant overlap between these theories and the now known actions of vitamin D and folate in the skin. The focus of this review is to present an update on the vitamin D–folate hypothesis by integrating these current theories and discussing new evidence that supports associations between vitamin D and folate genetics, UVR, and skin pigmentation. In light of recent human migrations and seasonality in disease, the need for ongoing research into potential UVR-responsive processes within the body is also discussed.

Data provide strong evidence that surface UV-irradiance reduces long-term systemic folate levels, and that this is influenced by the C677T-MTHFR gene variant. We speculate this effect may be due to 677TT-MTHFR individuals containing more 5,10CH -H PteGlu, and that this folate form may be particularly UV labile. Since UV-irradiance lowers RCF in an MTHFR genotype-specific way, there are likely implications for human health and the evolution of skin pigmentation.

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Objective: To test the "vitamin D-folate hypothesis for the evolution of human skin pigmentation."Methods: Total ozone mapping spectrometer (TOMS) satellite data were used to examine surface UV-irradiance in a large (n = 649) Australian crosssectional study population. Genetic analysis was used to score vitamin D-and folate-related gene polymorphisms (n = 22), along with two pigmentation gene variants (IRF4-rs12203592/HERC2-rs12913832). Red cell folate and vitamin D 3 were measured by immunoassay and HPLC, respectively.Results: i. Ultraviolet radiation (UVR) and pigmentation genes interact to modify blood vitamin levels; Light skin IRF4-TT genotype has greatest folate loss while light skin HERC2-GG genotype has greatest vitamin D 3 synthesis (reflected in both TOMS and seasonal data).ii. UV-wavelength exhibits a dose-response relationship in folate loss within light skin IRF4-TT genotype (305 > 310 > 324 > 380 nm). Significant vitamin D 3 photosynthesis only occurs within light skin HERC2-GG genotype, and is maximal at 305 nm.iii. Three dietary antioxidants (vitamins C, E, and β-carotene) interact with UVR and pigmentation genes preventing oxidative loss of labile reduced folate vitamers, with greatest benefit in light skin IRF4-TT subjects. The putative photosensitiser, riboflavin, did not sensitize red cell folate to UVR and actually afforded protection. iv. Four genes (5xSNPs) influenced blood vitamin levels when stratified by pigmentation genotype; MTHFR-rs1801133/rs1801131, TS-rs34489327, CYP24A-rs17216707, and VDR-ApaI-rs7975232.v. Lightest IRF4-TT/darkest HERC2-AA genotype combination (greatest folate loss/lowest vitamin D 3 synthesis) has 0% occurrence. The opposing,

These findings demonstrate novel relationships between skin color and folate-related genes, with trends suggesting folate genotypes are selected to maintain homeostasis in the folate system under differing UVR conditions.

Background: Most Australians do not meet vegetable intake recommendations. Vegetables are most often consumed in evening meals. However, they often require preparation and therefore cooking skills. Convenience cooking products such as meal bases/concentrates and ready-made sauces are increasingly common and popular and may help address the barriers to vegetable consumption in terms of cost and time. These products also typically provide recipes, which include vegetables, and as such, may help address the barriers of cooking skills, confidence, and creativity. However, the relationships between the use of these products, cooking confidence, and cooking creativity remain unknown. Methods: Australian adults were surveyed (snowball recruitment, n = 842) on their use of convenience cooking products (meal bases/recipe concentrates, simmer sauces, marinades, and other cooking sauces), cooking confidence (7 item scale) and creativity (6 item scale), and demographic information. Results: Overall, 63.2% of participants reported using convenience cooking products. Those using these products had lower mean cooking skills confidence and creativity scores than those who did not, in all product categories assessed. Among users, those who reported "always" following the recipes provided had lower mean cooking confidence and creativity scores than those who followed the recipes less regularly. Conclusions: Therefore, improving the vegetable content of recipes provided with these products may be a tool to increase vegetable intake by users with lower cooking skills (confidence and creativity). This may complement traditional approaches such as education in improving vegetable intake.

Background: The frequency of vitamin D-associated gene variants appear to reflect changes in long-term ultraviolet B radiation (UVB) environment, indicating interactions exist between the primary determinant of vitamin D status, UVB exposure and genetic disposition. Such interactions could have health implications, where UVB could modulate the impact of vitamin D genetic variants identified as disease risk factors. However, the current understanding of how vitamin D variants differ between populations from disparate UVB environments is limited, with previous work examining a small pool of variants and restricted populations only. Methods: Genotypic data for 46 variants within multiple vitamin D-related loci (DHCR7/NADSYN1, GC, CYP2R1, CYP11A1, CYP27A1, CYP24A1, VDR, RXRα and RXRγ) was collated from 60 sample sets (2633 subjects) with European, East Asian and Sub-Saharan African origin via the NCBI 1000 Genomes Browser and ALFRED (Allele Frequency Database), with the aim to examine for patterns in the distribution of vitamin D-associated variants across these geographic areas. Results: The frequency of all examined genetic variants differed between populations of European, East Asian and Sub-Saharan African ancestry. Changes in the distribution of variants in CYP2R1, CYP11A1, CYP24A1, RXRα and RXRγ genes between these populations are novel findings which have not been previously reported. The distribution of several variants reflected changes in the UVB environment of the population's ancestry. However, multiple variants displayed population-specific patterns in frequency that appears not to relate to UVB changes. Conclusions: The reported population differences in vitamin D-related variants provides insight into the extent by which activity of the vitamin D system can differ between cohorts due to genetic variance, with potential consequences for future dietary recommendations and disease outcomes.