You're Taking Minerals, But Your Genes May Block Absorption.

Your VDR gene codes for the vitamin D receptor, a protein that sits on cell membranes and inside cells, waiting for vitamin D to dock. When vitamin D binds to this receptor, it triggers a cascade of genetic switches that control everything from calcium absorption to immune function to mitochondrial energy production. Without a functioning VDR, vitamin D cannot do its job, no matter how much you have circulating in your blood.

Common variants in VDR, including BsmI, FokI, and TaqI, are carried by roughly 30-50% of the population depending on ancestry. These variants reduce the sensitivity of the VDR receptor. What that means in practical terms is your cells respond less robustly to vitamin D signaling, requiring higher circulating levels to achieve the same biological effect. You can be supplementing at 5,000 IU per day and feel as deficient as someone with a 25 ng/mL level.

You might notice this as fatigue, especially in winter; muscle weakness or aches; slow recovery from exercise or illness; mood changes; or difficulty maintaining immune function despite taking vitamin D. If you’ve been supplementing vitamin D and not feeling the expected benefit, a VDR variant is a key culprit.

HFE is the iron regulation gene. It codes for a protein that works with other molecules to sense how much iron is in your body and signal to your gut whether to absorb more or hold back. It’s like a thermostat for iron homeostasis. When HFE is working normally, this system prevents you from absorbing excessive iron (which is toxic) while also preventing deficiency.

The C282Y variant causes homozygous iron overload (hemochromatosis), which is rare. More common is the H63D variant, carried by roughly 15-20% of people with European ancestry. H63D doesn’t cause outright overload, but it mildly dysregulates iron absorption, often tipping the scales toward either chronic iron loss or difficulty absorbing adequate iron. Combined with heavy menstruation, blood donation, or vegetarian diets, an H63D variant can accelerate iron depletion.

You experience this as fatigue that doesn’t improve with sleep, shortness of breath with exertion, hair thinning or loss, difficulty concentrating (brain fog), cold hands and feet, and frequent infections. If you’ve been supplementing iron and not feeling better, or if iron supplements cause constipation and you stop taking them, an HFE variant may be limiting your ability to hold onto the iron you do absorb.

TMPRSS6 regulates hepcidin, a hormone that acts as a master switch for iron absorption. When hepcidin levels are high, your gut blocks iron absorption (which can happen with inflammation or iron overload). When hepcidin is low, your gut absorbs more iron. TMPRSS6 mutations interfere with the system that normally senses whether you need more iron and signals hepcidin to drop. It’s like breaking the feedback loop that tells your gut when to open the iron gate wider.

The rs855791 variant is present in roughly 45% of the population. People carrying this variant have baseline lower iron absorption and lower ferritin levels, making them susceptible to iron-deficiency anemia even on a decent diet. The problem is that standard bloodwork often doesn’t catch this vulnerability until you’re already symptomatic.

You notice this as chronic fatigue, pale skin, shortness of breath or heart palpitations with moderate exertion, difficulty with concentration, and persistent heavy or unusual menstrual periods in women. Your ferritin might be in the “normal” range (say, 20-30 ng/mL), but you feel symptomatic because your cells need more. If you’ve been told your iron is “fine” despite feeling exhausted, a TMPRSS6 variant may explain why you need more aggressive repletion than the standard recommendations suggest.

SLC30A8 codes for a zinc transporter protein that pumps zinc from the bloodstream into pancreatic beta cells (which produce insulin) and into other tissues that depend on zinc for enzyme function and immune defense. Zinc is essential for over 300 enzymes in your body. Without adequate intracellular zinc, your immune system weakens, your metabolism slows, and your ability to regulate blood sugar deteriorates.

The R325W variant, identified by rs13266634, carries the W allele in roughly 30% of the population. This variant impairs the efficiency of zinc transport into cells, reducing intracellular zinc availability even when blood zinc levels appear adequate. The effect is subtle but cumulative. Over time, your cells become functionally zinc-deficient, even though serum zinc tests might show normal levels.

You experience this as frequent infections or slow wound healing; weak or brittle nails with white spots; hair loss or slow hair growth; persistent skin issues like dermatitis or eczema; brain fog or difficulty with memory; and in some cases, insulin resistance or elevated blood sugar despite maintaining a reasonable diet. If you’ve noticed these patterns and standard micronutrient testing came back normal, an SLC30A8 variant is worth investigating.

MTHFR codes for the methylenetetrahydrofolate reductase enzyme, which converts dietary folate and folic acid into methylfolate, the active form your cells actually use. This enzyme is essential for the methylation cycle, a fundamental biochemical process that regulates neurotransmitter synthesis, DNA repair, immune function, and detoxification. Without functioning MTHFR, you have plenty of folate in your diet and bloodstream but very little of it in the active form your cells need.

The C677T variant is carried by roughly 40% of the population with European ancestry. Homozygous carriers (two copies) have 65-70% reduced enzyme efficiency; heterozygotes (one copy) have roughly 35% reduced efficiency. The effect is functional folate deficiency despite normal dietary intake and normal lab measurements of serum folate. Your body is absorbing folate; it’s just not converting it into the form cells can use.

You notice this as persistent fatigue unresponsive to sleep; brain fog or difficulty concentrating; mood instability, anxiety, or depression; migraines; joint or muscle aches; slow wound healing; and in women, heavy or irregular periods. If you’ve taken standard folic acid supplements (like in prenatal vitamins or B-complex formulas) and felt worse or unchanged, an MTHFR variant is likely why.

COMT codes for catechol-O-methyltransferase, an enzyme that breaks down dopamine, norepinephrine (adrenaline), and estrogen. It’s your body’s cleanup crew for these critical neurotransmitters. COMT variants don’t directly control mineral absorption, but they dramatically affect how well your body tolerates and utilizes minerals, especially when combined with other genetic variants. A slow COMT means you clear catecholamines slowly, making you more sensitive to stimulation. A fast COMT means you burn through them quickly and may feel low energy or motivation without stimulation.

The Met158Val variant, carried by roughly 30-40% of the population, creates a “slow” COMT variant that reduces dopamine and norepinephrine clearance by 25-40%, making you more sensitive to stress, caffeine, and supplemental stimulants. The interaction with mineral absorption becomes clear when you realize that people with slow COMT variants often become over-stimulated by high-dose mineral supplementation or by any supplement that boosts catecholamines. They need lower, divided doses and more gentle mineral forms.

You notice this as anxiety or jitteriness after starting new supplements; sensitivity to caffeine; difficulty tolerating iron or zinc at typical doses; mood reactivity; sleep disruption; and a tendency toward perfectionism or difficulty relaxing. If you’ve felt worse after starting mineral supplementation rather than better, a slow COMT variant may be amplifying the stimulant effect and making you intolerant to the dose you’re taking.