How to Personalize Your Nutrition Based On Genetics (Revised 3/19/15)

Patrick describes this as the foundational step — a first-pass screen that surfaces the handful of variants (from among 57,000) that are both common and readily modifiable through diet or supplementation. The $5 Promethease report will flag your MTHFR, APOE, FUT2, BCMO1, FADS2, CYP2R1, PEMT, and FOXO3 status in a single run. This is not a clinical diagnostic — it is a starting point for a more targeted conversation with your doctor and a smarter approach to supplementation.

Patrick explains the mechanism precisely: MTHFR converts 5,10-methyleneTHF into 5-MTHF, which then donates its methyl group to B12 (forming methylcobalamin), which then donates the methyl group to homocysteine to form methionine. If the MTHFR enzyme is 70 to 90% non-functional, this entire sequence stalls — even with adequate dietary folate intake. Supplementing 5-MTHF directly enters the pathway after the broken enzyme step, completely circumventing the bottleneck. The concurrent use of methylcobalamin (rather than cyanocobalamin) matters because the B12 acceptor in this pathway needs to already be in the active methyl-accepting form.

Patrick frames this as a clean nutrigenomics intervention: the problem is not dietary intake of B12 — it is the machinery for absorbing it. Switching delivery route from oral/GI to sublingual/mucosal solves the problem without requiring higher doses or more frequent testing. This is particularly important for vegetarians and vegans who already face higher B12 deficiency risk and may compound it with a FUT2 absorption deficit.

Patrick emphasizes that this is specifically relevant for vegetarians because they have deliberately removed direct marine omega-3 sources from their diet and rely on the ALA conversion pathway. Fish can eat algae and accumulate EPA/DHA precisely because fish have efficient FADS-equivalent desaturases. Microalgae oil gives vegetarians the same direct EPA/DHA source without the fish, while entirely bypassing the genetically variable FADS2 conversion step.

Patrick explains the biological logic: estrogen normally activates the PEMT gene, allowing women to synthesize their own choline even on a lower-choline diet. The PEMT variant breaks this activation, meaning the estrogen-choline link is severed. Post-menopausal women or women on estrogen-blocking therapies are therefore at greatest risk. Egg yolks are the highest-choline common food — a single yolk provides about a third of daily needs. Liver and other organ meats are also high in choline. For women who avoid eggs and organ meats (common in vegetarians), supplemental choline bitartrate or CDP-choline becomes important.

Patrick explains that APOE4 encodes a lipoprotein that circulates throughout the body and is also produced by astrocytes in the brain, where it transports fatty acids and cholesterol to neurons. The APOE4 isoform is structurally different from APOE2 and APOE3 in two amino acid positions that critically affect receptor binding affinity and lipid clearance rate. In the brain specifically, APOE4 impairs amyloid beta clearance, which is one reason why APOE4 is the largest genetic risk factor for late-onset Alzheimer's disease outside of rare deterministic mutations.

Patrick explains that folate serves two distinct roles: making thymine for DNA synthesis (intact in MTHFR variants) and generating methyl groups for turning genes on or off via epigenetics (impaired). The impairment in the second function leads to elevated homocysteine, which is independently associated with coronary artery disease, stroke, and vascular dementia. Studies demonstrate that supplementing with 5-methyltetrahydrofolate (the pre-converted active form) and methylcobalamin (active B12) successfully circumvents the enzyme bottleneck and lowers homocysteine even in people with severe MTHFR dysfunction. Knowing your MTHFR status allows you to choose the right supplement form rather than wasting money — or worse, creating a false sense of security — on folic acid.

Patrick frames FUT2 as an example of absorption-level genetic variation: you may be eating adequate B12 and even taking oral supplements, yet still be functionally deficient if your intestinal absorption machinery is genetically impaired. The actionable response is specific — not just 'take more B12' but take sublingual B12, which bypasses the intestinal absorption step entirely. This is a clean example of the nutrigenomics principle: same nutrient, same dose, completely different biological outcome depending on genotype.

Patrick notes that the fix for BCMO1 variant carriers is to either increase animal-source foods rich in preformed retinol (liver, eggs, dairy) or to supplement with the active form of vitamin A — retinol — rather than beta-carotene. She adds an important caution: unlike beta-carotene (which is essentially non-toxic), preformed vitamin A is fat-soluble and can accumulate to toxic levels at high doses, so supplementation requires care and should not be treated as casually as most micronutrients.

Patrick explains that the FADS variants can go in either direction — some increase and some decrease conversion efficiency. The problem direction is the decrease variant, because even with favorable genetics the conversion is poor; with unfavorable genetics it becomes negligible. The practical recommendation for vegetarians with low-efficiency FADS2 variants is to switch from ALA-based supplements (flaxseed oil, chia) to microalgae oil, which contains preformed EPA and DHA and does not require any enzymatic conversion. This is particularly important because the downstream products of EPA/DHA metabolism — resolvins, protectins, specialized pro-resolving mediators — are responsible for actively resolving inflammation, not just blunting it.

Patrick describes this as one of her personal favorite examples in nutrigenomics because the intervention is simple (supplement more D3, test your 25(OH)D levels regularly) but the genetic reason for under-response is invisible without genotyping. People with CYP2R1 variants who take the standard 1,000 to 2,000 IU/day dose may plateau well below 40 ng/mL, leaving them with the elevated all-cause mortality signature, even though their supplement habits appear adequate. The serum test is the essential feedback loop: know your level, know your variant, adjust dose until you land in the optimal 40–60 ng/mL range.

Patrick explains that FOXO3 is the human equivalent of DAF-16 in C. elegans, the first longevity gene identified. Its activity is regulated by insulin/IGF-1 signaling — when insulin is high, FOXO3 is phosphorylated and inactivated; when insulin is low (fasting, caloric restriction, exercise), FOXO3 moves to the nucleus and activates its longevity target genes. This means that beyond genetics, lifestyle factors that reduce chronic insulin signaling — intermittent fasting, aerobic exercise, carbohydrate moderation — functionally activate FOXO3 even in people without the favorable polymorphisms, partially mimicking the genetic advantage.