Your heart health is declining, yet your doctor says everything looks normal.

Your APOE gene codes for a protein called apolipoprotein E. This protein is responsible for packaging cholesterol into particles that circulate through your bloodstream and delivering it to cells that need it. Think of apolipoprotein E as the delivery truck for cholesterol. Without it, cholesterol would just accumulate in your blood.

APOE comes in three main variants: e2, e3, and e4. Most people carry the e3 variant, which is neutral. But roughly 25% of people of European ancestry carry at least one copy of the e4 variant. Here’s the problem: the e4 variant reduces your liver’s ability to clear LDL cholesterol from your bloodstream by up to 40%, meaning more cholesterol circulates in your blood for longer, increasing the time it spends oxidizing and depositing in your artery walls.

If you carry the APOE e4 variant, you likely notice that your LDL cholesterol rises quickly even on a low-fat diet. Your doctor may have told you to cut saturated fat, and you did, and your LDL barely budged. That’s not a character flaw. That’s your APOE e4 driving cholesterol production regardless of your dietary choices. You may also have noticed that you seem to struggle more than your friends to keep your weight stable, and that you feel more brain fog after eating high-carbohydrate meals. All of these are connected to APOE e4.

Your MTHFR gene codes for an enzyme called methylenetetrahydrofolate reductase. This enzyme converts folate (vitamin B9) into its active form, which your cells then use to process homocysteine. Homocysteine is an amino acid byproduct of protein metabolism. Your body normally breaks it down quickly. But if your MTHFR enzyme isn’t working well, homocysteine accumulates.

The MTHFR C677T variant, carried by approximately 40% of people of European ancestry, reduces this enzyme’s activity by 40-70%. This means your cells are converting B vitamins into the usable forms they need at a fraction of the rate they should be, and homocysteine backs up in your bloodstream. Elevated homocysteine is an independent cardiovascular risk factor. It damages the inner lining of blood vessels, promotes inflammation, and increases clotting risk.

If you have the MTHFR C677T variant, you likely notice that you feel better on certain supplements and worse on others. Generic folic acid (the synthetic form of B9) may not help you feel more energized; you may even feel worse on it. Your doctor may have told you to take more vegetables, which is good advice, but you’re probably still tired because you can’t efficiently extract and use the folate from them. Your homocysteine level may even be elevated on standard blood tests, which your doctor may have shrugged off as not clinically significant. But at the cardiovascular level, elevated homocysteine is damaging your arteries.

Your ACE gene codes for angiotensin-converting enzyme, a key regulator of blood pressure. ACE converts angiotensin I into angiotensin II, a powerful hormone that tells your blood vessels to constrict and raises your blood pressure. Normally, this system is finely tuned. Your blood pressure rises when you need it to rise, and falls when you need it to fall. The ACE gene has a polymorphism called the I/D variant, referring to an insertion or deletion in the gene code.

If you carry the D/D homozygous genotype, roughly 25% of people carry this, you produce higher levels of ACE enzyme. This means your blood vessels get stronger constriction signals, your arteries are under more constant pressure, and your baseline blood pressure runs higher. You may also be more salt-sensitive than people with other genotypes, meaning sodium has a more dramatic effect on your blood pressure.

If you have the ACE D/D genotype, you likely know that your blood pressure has always run a bit high, even as a young person. You may have tried a low-sodium diet and noticed a real difference in your blood pressure readings, which is great. But you may also notice that you’re more prone to left ventricular hypertrophy (your heart muscle thickens from constant pressure), which increases your risk of heart attack and sudden cardiac death. Your cardiologist may have told you that your left ventricle is slightly enlarged and put you on an ACE inhibitor, which blocks this exact enzyme. That’s the right drug for you.

Your NOS3 gene codes for nitric oxide synthase, an enzyme that produces nitric oxide inside the cells lining your blood vessels. Nitric oxide is crucial. It tells your blood vessels to relax and dilate, allowing blood to flow freely. Without it, your blood vessels stay somewhat constricted, blood flow is restricted, and your blood pressure rises.

The NOS3 Glu298Asp variant is carried by 30-40% of the population. This variant reduces the amount of nitric oxide your blood vessels can produce, impairing their ability to dilate in response to exercise or demand, increasing both your resting blood pressure and your atherosclerosis risk. Your blood vessels become stiffer, less responsive, and more prone to plaque accumulation.

If you have the NOS3 Glu298Asp variant, you likely notice that your blood vessels feel tight. You may experience more blood pressure elevation during exercise than you’d expect. Your cardiologist may have noted that you have reduced arterial compliance or stiffness on imaging. You may also notice that you don’t feel the usual boost from exercise that other people describe. That’s because your blood vessels aren’t dilating properly to meet the increased oxygen demand. Medications like statins help, but they don’t restore nitric oxide production.

Your LPA gene controls the production of lipoprotein(a), often written as Lp(a). Lipoprotein(a) is a cholesterol-carrying particle that looks very similar to LDL cholesterol, but it’s genetically determined and almost entirely resistant to dietary changes. Think of Lp(a) as a sneakier cousin of LDL; it circulates in your blood doing damage, but standard diets and even statins barely touch it.

Roughly 20% of the population carries genetic variants that produce elevated Lp(a) levels. Elevated Lp(a) is one of the strongest independent cardiovascular risk factors known, increasing your heart attack and stroke risk by 2-10 fold depending on your level. And here’s the critical part: this risk is almost entirely genetic. You can exercise daily, eat a perfect diet, and still have dangerously high Lp(a) if your genes produce it.

If you have elevated Lp(a), you likely have a family history of early heart disease. Your parents or grandparents may have had heart attacks in their 40s or 50s despite having no other risk factors. Your doctor may have tested your LDL cholesterol and been satisfied with it, never mentioning Lp(a) at all. But your Lp(a) level may be three or four times the normal range. This is one of the most underdiagnosed cardiovascular risk factors in medicine. You can be doing everything right and still be at extreme risk.

Your PCSK9 gene codes for proprotein convertase subtilisin/kexin type 9, a protein that regulates LDL receptors on your liver cells. LDL receptors are like mailboxes on your liver’s surface. When an LDL particle approaches, the receptor grabs it and brings it into the cell, removing it from your bloodstream. PCSK9 works by telling these receptors to self-destruct and be recycled. The fewer receptors you have, the more LDL stays in your blood.

The PCSK9 R46L gain-of-function variant is carried by 1-3% of people, but when present, it has a dramatic effect. Gain-of-function variants cause your liver to destroy LDL receptors faster than normal, meaning your body cannot clear LDL cholesterol from your bloodstream efficiently, and your LDL levels soar. People with this variant often have LDL levels of 200-400 mg/dL even on a low-fat diet, and standard-dose statins barely move the needle.

If you have a PCSK9 gain-of-function variant, you likely have a lifelong history of high LDL cholesterol. Your parents may have had early heart disease. Doctors have probably been pushing statins on you for years. You may have tried statins and noticed they helped a little, but your LDL is still high. Or you may have noticed side effects and stopped taking them. Either way, you know something is wrong with your cholesterol metabolism that goes beyond diet. Your genetic issue is that your liver simply cannot clear cholesterol efficiently.