Reference Number: 670
Year: 2025
Link: Link to original paper
Nutrition: Vitamin D
Summary
Abstract
Vitamin D (VD) plays a critical role in human health, with deficiencies linked to a range of adverse outcomes, including compromised immune function and increased disease risk. While environmental factors such as sunlight exposure and diet influence circulating VD levels, genetic variation is a significant and underappreciated contributor to interindividual differences in serum 25-hydroxyvitamin D [25(OH)D] concentrations. This review provides a comprehensive summary of genetic variants in key genes involved in VD synthesis (e.g., DHCR7, cyp2r1, cyp27b1), transport (GC), and metabolism (cyp24a1, cyp3a4), as well as in cholesterol transport proteins (SCARB1, CD36, NPC1L1). We examine how single-nucleotide polymorphisms (SNPs) and rare mutations in these genes affect enzyme activity, VD bioavailability, and overall 25(OH)D status. Importantly, we highlight evidence supporting gene-by-environment interactions and population-specific allele frequencies that further shape individual VD responses. In the context of clinical nutrition and precision health, these findings support the development of genomic risk scores (GRSs) to identify individuals at risk for deficiency or toxicity and guide personalized VD supplementation strategies. Regular monitoring of serum 25(OH)D alongside genetic screening may improve clinical outcomes by helping to achieve optimal VD immunosufficiency while minimising the risk of adverse effects.
Summary of Findings
Vitamin D is essential for good health, especially for your immune system. You get it from sunlight, food, and supplements. But not everyone absorbs or processes vitamin D the same way—and your genes play a big role in that.
This paper explains how genetic differences between people affect how much vitamin D they make from sunlight or absorb from food. It focuses on how certain genes control the production, transport, and breakdown of vitamin D in the body.
Key Genes Involved
- DHCR7: This gene helps decide whether your body uses a substance called 7-DHC to make cholesterol or vitamin D. If your DHCR7 gene is less active, more 7-DHC is available to make vitamin D when your skin is exposed to sunlight.
- CYP2R1, CYP27B1, CYP24A1: These genes help convert vitamin D into its active or inactive forms. Variants in these genes can affect how efficiently your body processes vitamin D.
- GC (Vitamin D Binding Protein): This gene affects how vitamin D is carried in your blood. Some versions of the gene bind vitamin D more tightly, which can influence how much is available for your body to use.
- SCARB1, CD36, NPC1L1: These genes help absorb vitamin D from food in the gut. Variants here can affect how well your body takes in vitamin D from your diet.
Sunlight, Diet, and Skin Tone
The paper emphasizes that people living far from the equator (like in northern Europe) often don’t get enough sunlight in winter to make enough vitamin D. This is especially true for people with darker skin, which naturally blocks more UVB rays. In these cases, diet and supplements become more important—but again, genetics can affect how well your body absorbs and uses vitamin D from these sources.
Genetic Testing and Personalized Nutrition
The authors suggest that genetic testing could help identify people who are more likely to be vitamin D deficient—even if they get plenty of sun or eat well. For example, someone with certain gene variants might need higher doses of supplements to reach healthy vitamin D levels. This could lead to more personalized nutrition plans in the future.
What the Research Shows
The paper reviews dozens of studies that link specific genetic variants (SNPs) to vitamin D levels in the blood. It includes a detailed table listing these variants, the genes they affect, and what they do. Some variants are common in certain populations, which may help explain why vitamin D deficiency is more common in some groups than others.
Conclusion
Your genes can significantly influence how much vitamin D your body makes from sunlight or absorbs from food. Understanding these genetic differences could help tailor vitamin D recommendations to individual needs—especially for people at risk of deficiency due to where they live, their skin tone, or their diet.
Significance to the Baker
When we view vitamin D through the lens of the BALM protocol, a deficiency can ripple through all seven steps — particularly where food, fermentation, fibre, and emotional well-being intersect. The protocol’s emphasis on fermented wholegrain breads supports vitamin D metabolism by:
- Providing the prebiotic fibres that nourish vitamin D-enhancing gut microbes
- Offering a delivery vehicle for vitamin D-rich ingredients (eggs, fish, mushrooms, especially when exposed to sunlight)
- Supporting the fat absorption necessary for this fat-soluble vitamin
- Creating a circadian-supportive eating pattern that complements natural vitamin D rhythms
Regular midday sun (in the Northern hemisphere) or earlier in the South for 10-30 minutes without sunscreen can help with in-body production of vitamin D. Symbiotic eating of plant and animal sources of fats containing vitamin D are another option.
