Vitamin B12 is a vital nutrient for human health, playing a crucial role in several essential functions, including DNA synthesis, red blood cell production, nerve function, and energy metabolism, among others. Found predominantly in animal-based foods like meat, poultry, seafood, milk, cheese, and eggs, vitamin B12 can be more challenging for vegetarians and vegans to obtain through their diet, placing them at a higher risk of deficiency. However, older adults, individuals with digestive disorders such as Crohn’s disease or celiac disease, and those on certain medications may also be vulnerable. Additionally, genetics can predispose some people to lower-than-average vitamin B12 levels.
A deficiency in vitamin B12 can lead to serious, long-term neurological damage, manifesting as vision problems, memory loss, and muscle weakness.
Several genes play a key role in determining vitamin B12 levels in the body:
- FUT2: This gene encodes an enzyme called fucosyltransferase 2, which helps synthesize the H antigen, a crucial attachment site and carbon source for intestinal bacteria. Variations in FUT2 can impact B12 absorption, increase the likelihood of H. pylori infection, and hinder the secretion of gastric intrinsic factor, a substance essential for vitamin B12 absorption.
- TCN2: This gene provides instructions for making transcobalamin, a protein responsible for transporting vitamin B12 to cells. Genetic variations in TCN2 can reduce the concentration of transcobalamin, limiting the availability of vitamin B12 in the body.
Given these factors, it’s important to regularly monitor your vitamin B12 levels, especially if you’re at risk of deficiency. For vegetarians or vegans who in addition carry these genetic variations above, particularly care must be taken to ensure sufficient B12 and potentially choline are in the diet. Sources include fortified plant-based milks, fortified cereals, and nutritional yeasts.
Supplementation can help, but understanding your genetic makeup can further guide your choices. For instance, individuals with genetic variations in FUT2 or TCN2 may find that vitamin B12 supplements containing methylcobalamin (the active form of the vitamin) or co-methylcobalamin are most effectively absorbed. Ultimately, maintaining optimal vitamin B12 levels is crucial for long-term health, and knowing your individual needs is the key to making the right choices.
Our Fitgenes practitioner-only Health and Wellbeing Report includes testing of these two genes, among other genes involved in key biological functions such as inflammation, cardiovascular disease, and fat metabolism, and information on gene-specific interventions to maximise your health. For more information about this report, visit https://www.fitgenes.com/health-wellbeing/ or contact us at enquiries@fitgenes.com
Article author: Cristina Fortuno, PhD
Dr Fortuno is genetic scientist with focus on human health, and has a PhD (University of Queensland) in Human genetics.
References
Green R, Miller JW. Vitamin B12 deficiency. Vitam Horm. 2022;119:405-439. doi:10.1016/bs.vh.2022.02.003
Marques de Brito B, Campos VM, Neves FJ, Ramos LR, Tomita LY. Vitamin B12 sources in non-animal foods: a systematic review. Crit Rev Food Sci Nutr. 2023;63(26):7853-7867. doi:10.1080/10408398.2022.2053057
McGovern DP, Jones MR, Taylor KD, et al. Fucosyltransferase 2 (FUT2) non-secretor status is associated with Crohn’s disease. Hum Mol Genet. 2010;19(17):3468-3476. doi:10.1093/hmg/ddq248
Surendran S, Adaikalakoteswari A, Saravanan P, Shatwaan IA, Lovegrove JA, Vimaleswaran KS. An update on vitamin B12-related gene polymorphisms and B12 status. Genes Nutr. 2018;13:2. Published 2018 Feb 6. doi:10.1186/s12263-018-0591-
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