What Causes High LDL Cholesterol?

Updated July 2026

The title might make you expect a list of the usual suspects, like saturated fat or too little exercise. Those matter, but what I really want to explain is what happens inside your body that determines your LDL level, because this is the part patients are rarely told about. Several biological levers control your LDL, and understanding them will help you appreciate what your actions actually influence, and how.

How does your liver influence LDL?

Most of it comes down to a single enzyme. Your liver makes cholesterol using an enzyme called HMG-CoA reductase, and while its activity is strongly shaped by lifestyle, it is also set in part by your genes. That means at some point you hit a genetically determined floor that no amount of clean living can push past. Statins are HMG-CoA reductase inhibitors, so they dial that enzyme down and LDL falls. Here is the upside. Even if the high LDL on your lab test is genetic, because you have already removed the lifestyle contributors, just a small dose of a statin can produce a dramatic reduction.

How does digestion affect your LDL?

Through the way your body recycles bile. Every time you eat, bile is released into the intestine to break down food. Bile is rich in cholesterol, and your body makes it from circulating LDL. Because you always need bile at the ready, your body keeps its reserves full two ways, by pulling LDL back to the liver to make more, and by reabsorbing whatever bile it did not use. Interfere with that reabsorption and the liver has to pull more LDL out of your blood to make the next batch, so LDL drops. This is where fiber and plant sterols come in. Fiber traps bile and carries it out through the digestive system, and plant sterols crowd out bile at its absorption sites, so more of it is lost. Some people are especially efficient bile reabsorbers, and for them even a small nudge here can drop LDL sharply.

What do LDL receptors and PCSK9 do?

They set how quickly LDL is cleared from your blood. LDL leaves the bloodstream by latching onto receptors on your cells, so the more receptors you have, the less LDL is left circulating. A protein called PCSK9 breaks those receptors down. When PCSK9 is high, receptors are scarce and LDL runs high. The reverse is true too, as people born with very little PCSK9 keep very low LDL their whole lives and rarely develop heart disease. Newer injectable drugs, Repatha, Praluent, and Leqvio, all lower PCSK9, which raises receptor numbers and can bring LDL down dramatically. By the way, saturated fat can be a potent down-regulator of LDL receptors. This is why some people who go on a keto diet see their LDL numbers explode. Unsaturated fats have the opposite effect.

How does insulin raise your LDL?

By influencing LDL production. Insulin is released when blood sugar rises, and its job is to move that sugar into your cells. But insulin is a potent stimulator of HMG-CoA reductase, so when insulin runs high, LDL tends to climb with it. That is why people with insulin resistance, pre-diabetes and type 2 diabetes, who generally have higher circulating insulin levels, tend to have higher LDL, and why a diet heavy in simple, processed carbohydrates drives LDL up. It does not mean you should eat low-carb. Complex carbohydrates from whole foods digest slowly, which keeps blood sugar and insulin lower and quiets the insulin-LDL effect.

Why does menopause change your cholesterol?

Because estrogen up-regulates LDL receptor function, and menopause takes that away. Estrogen is protective in women, helping to lower LDL and raise HDL, the good cholesterol. When estrogen drops at menopause, most women see their cholesterol profile worsen, and some see sharp increases in LDL. As an aside, testosterone has less effect on LDL, but it can lower HDL, so men on testosterone replacement may see their HDL fall, which could potentially raise heart risk.

So what can you actually change?

All three of these levers are in your hands, as all are impacted by food. This is where Step One Foods helps, by concentrating fiber, plant sterols, unsaturated fats and complex carbohydrates so you can work with your own biochemistry rather than against it.

A partial response is still worth a great deal. Lowering your LDL with diet makes it easier for a drug to finish the job at a lower dose, and lower doses mean fewer side effects. Better food also does far more than move a cholesterol number. Most of us are not only trying to lower LDL, we are also trying to avoid cancer and dementia, and eating well helps with those goals too.

The bottom line

LDL cholesterol has many biochemical drivers, some of which are genetically determined. Medications target single pathways, while food targets all the pathways all at once. This makes food a powerful first step in managing LDL - as well as a wise adjunct to medications to ensure that every pathway is covered.

Not everyone with high LDL needs a drug, or even a perfect number. LDL is only one risk factor in a disease with many. So if your cholesterol is not perfect, you do not already have heart disease or diabetes, and you have maximized your diet, a coronary calcium scan can help decide whether a lifelong medication would actually benefit you for risk reduction today.

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