While APOE4 is the most important genetic risk factor discussed throughout this site, it is only one piece of a much larger genetic puzzle.

Over the past decade, researchers have identified numerous genetic variants that may influence inflammation, lipid metabolism, methylation, detoxification, hormone function, insulin sensitivity, nutrient requirements, and the brain’s ability to repair and protect itself. Individually, most of these variants exert only a modest effect. Together, however, they may help explain why people respond differently to the same foods, supplements, medications, and lifestyle interventions.

The goal of genetic testing is not to predict your future or provide a list of things to worry about. Rather, it can offer clues about potential strengths, vulnerabilities, and areas where a more personalized approach may be beneficial.

I view genetics as a roadmap, not a destiny. In most cases, biomarkers, imaging, symptoms, and real-world results are far more important than the presence of any single genetic variant. Still, understanding a handful of well-studied genes may provide valuable insights and help guide more individualized decisions.

Below are some of the genetic variants most commonly discussed within the APOE4 and longevity communities, along with the versions that may warrant additional attention.

Gene	SNP	Variant Worth Attention	Why It May Matter
MTHFR	rs1801133 (C677T)	TT (AA)	Reduced methylation efficiency; may contribute to elevated homocysteine and increased need for methylfolate and B vitamins. (I’m T/T)
MTHFR	rs1801131 (A1298C)	CC (GG)	May modestly affect methylation pathways, particularly when combined with C677T variants. (I’m T/T)
PEMT	rs7946	TT (AA)	May increase dietary choline requirements and reduce phosphatidylcholine production. (I’m T/T)
FADS1	rs174547	TT (AA)	Less efficient conversion of plant omega-3 fats into EPA and DHA, increasing reliance on marine sources. (I’m C/T)
ABCA1	rs2230806 (R219K)	GG (CC)	May be associated with less efficient cholesterol transport and ApoE lipidation compared with the K variant. Particularly relevant for APOE4 carriers. (I’m C/T)
PON1	rs662 (Q192R)	TT (AA)	Different variants may influence LDL oxidation and detoxification capacity. Interpretation depends on context and is not simply “good” or “bad.” (I’m T/T)
KLOTHO	rs9536314 (KL-VS)	Absence of the KL-VS heterozygous variant	Lacks the potential cognitive resilience and longevity benefits observed in some KL-VS carriers. (I’m G/T)
TREM2	rs75932628	T allele present	Rare variant associated with significantly increased Alzheimer’s disease risk and altered microglial function. (I’m C/C)
COMT	rs4680 (Val158Met)	AA (TT) – Slow COMT (Met/Met)	Slower breakdown of dopamine and catecholamines; may influence stress sensitivity, mood, and cognitive performance. (I’m G/G)
GSTP1	rs1695	GG (CC)	May reduce detoxification capacity and antioxidant defenses. (I’m A/A)
APOE	rs429358 / rs7412 “C”	One or two APOE4 alleles	Strongest common genetic risk factor for late-onset Alzheimer’s disease; influences lipid transport, inflammation, and brain metabolism. (I’m C/C / C/C)

DIO1

rs2235544

T allele / risk variant

May influence conversion of T4 to T3 and reverse T3 patterns; relevant when thyroid labs and symptoms do not match neatly.

DIO2

rs225014

GG / risk variant

May reduce local intracellular T3 availability in some tissues, including brain; relevant for people who do not feel well on T4-only thyroid replacement.

LPA

rs10455872

G allele present

Strongly associated with elevated Lp(a) levels and increased cardiovascular risk. One of the best-studied genetic determinants of Lp(a).

LPA

rs3798220

C allele present

Associated with markedly elevated Lp(a) levels and increased cardiovascular risk in many populations.

**Note:** Genetic variants are not destiny. Most exert only modest effects individually and should be interpreted alongside biomarkers, symptoms, lifestyle, and overall health status. The goal of genetic testing is not to predict the future, but to identify potential areas where a more personalized approach may be beneficial.

MTHFR and Homocysteine

Among the many genetic variants discussed in the health and longevity community, MTHFR is one of the most common and most frequently misunderstood.

The MTHFR gene helps convert folate into its biologically active form, which is needed for methylation – a process involved in DNA repair, neurotransmitter production, detoxification, and cardiovascular health.

Individuals carrying one or more MTHFR variants may have a reduced ability to process folate efficiently, potentially leading to elevated homocysteine levels. However, the gene itself is not the problem – elevated homocysteine is.

For that reason, I believe it is far more important to measure homocysteine than to focus solely on genetic results. Many people with MTHFR variants maintain excellent homocysteine levels, while others without these variants may have elevated levels due to diet, nutrient deficiencies, kidney function, medications, or other factors. Variants are extremely common.

Elevated homocysteine levels have been independently associated with an increased risk of cognitive decline and Alzheimer’s disease, while vitamin B12 deficiency can contribute to elevated homocysteine as well as neurological symptoms that may mimic or worsen cognitive impairment.

Some studies have also reported associations between certain MTHFR variants and an increased risk of several cancers, including breast cancer, although the relationship is complex and appears to be influenced by numerous genetic, nutritional, hormonal, and environmental factors.

If homocysteine is elevated, nutrients that support methylation may be helpful, including:

• Methylfolate (5-MTHF)
• Methylcobalamin (Vitamin B12)
• Riboflavin (Vitamin B2)
• Pyridoxal-5-phosphate (Vitamin B6)
• Trimethylglycine (TMG)

My target: Homocysteine below 7 µmol/L, with many prevention-focused clinicians aiming for a range of approximately 5–7 µmol/L.