Plaque builds up in your arteries through a slow, multi-stage process that begins with damage to the inner lining of the artery wall. Cholesterol particles seep into the damaged area, trigger an immune response, and gradually form deposits that stiffen and narrow the vessel over years or decades. The earliest stages produce no symptoms at all, and the process can begin as early as your teens or twenties.
It Starts With Damage to the Artery Wall
Your arteries are lined with a thin layer of cells called the endothelium. Under normal conditions, this lining keeps blood flowing smoothly by releasing nitric oxide, a molecule that relaxes the artery walls and prevents blood cells from sticking. When the endothelium is injured or stressed, it stops producing enough nitric oxide. That single shift is one of the earliest detectable signs of the disease process, showing up before any plaque is visible on imaging.
The usual suspects behind this damage are high cholesterol, high blood pressure, smoking, diabetes, and chronic inflammation. Each of these stresses the artery lining in slightly different ways, but the result is the same: the endothelium becomes “leaky,” allowing cholesterol-carrying particles to slip through into the artery wall. It also becomes sticky, attracting immune cells and platelets to the area. A family history of early heart disease independently raises your risk as well, suggesting that some people inherit endothelial cells that are more easily damaged.
How Cholesterol Becomes Trapped
LDL cholesterol, the type labeled “bad” on your lab results, is the main raw material of arterial plaque. Once LDL particles cross the damaged endothelium and lodge in the artery wall, they undergo a chemical change called oxidation. All three cell types in the artery wall (endothelial cells, smooth muscle cells, and immune cells called macrophages) can trigger this oxidation.
This matters because macrophages can’t efficiently absorb normal LDL. They need it to be chemically altered first. Once LDL is oxidized, macrophages recognize it through a separate set of receptors and consume it in large quantities with no built-in shutoff. The macrophages gorge on oxidized LDL until they swell into what pathologists call foam cells, bloated with cholesterol. Clusters of these foam cells form the fatty streak, the earliest visible sign of atherosclerosis. Fatty streaks have been found in the arteries of children and teenagers, long before any health consequences appear.
From Fatty Streak to Mature Plaque
Fatty streaks don’t always progress, but when they do, the changes unfold over years. Researchers classify plaque development into roughly six stages. The first three, from scattered immune cells to small pools of fat within the artery wall, are always small and produce no symptoms. These early lesions can sit quietly for decades or begin advancing depending on your ongoing risk factors.
At stage four, the accumulated fat coalesces into a distinct core of dead cells, cholesterol crystals, and cellular debris deep within the wall. The artery can initially compensate by expanding outward, so blood flow isn’t yet restricted. By stage five, smooth muscle cells migrate into the area and begin producing collagen, elastin, and other structural proteins. This forms a fibrous cap over the fatty core, like scar tissue sealing off the damage. At this point, the artery can no longer expand to compensate, and the lumen (the opening blood flows through) starts to narrow noticeably.
Stage six is where things become dangerous. The plaque may crack, erode, or bleed internally. Any of these disruptions can trigger a blood clot that partially or completely blocks the artery.
What Plaque Is Actually Made Of
A mature plaque is not a simple glob of fat. About half of the lipid content consists of cholesterol esters, with free cholesterol making up roughly a quarter and the remainder split between phospholipids and triglycerides. Surrounding and covering this fatty core is a fibrous cap made of collagen and smooth muscle cells. Over time, calcium deposits accumulate within the plaque, essentially turning portions of a flexible artery into something resembling bone.
The composition of a plaque matters more than its size. A large, heavily calcified plaque with a thick fibrous cap and little inflammation can sit in an artery for years without incident. These stable plaques narrow the vessel and may cause symptoms like chest pain during exertion, but they rarely cause sudden heart attacks.
Why Some Plaques Rupture
The plaques most likely to cause heart attacks and strokes are not necessarily the biggest. They are the ones with a thin fibrous cap (65 micrometers or less, thinner than a human hair), a large core of dead cells and fat, and heavy infiltration by immune cells that weaken the cap from within. Researchers call these thin-cap fibroatheromas. Their calcium deposits tend to be scattered in small specks and fragments rather than laid down in solid sheets, which makes the structure less stable.
When the cap ruptures, the fatty core is exposed to flowing blood. The core is loaded with compounds that trigger clotting, including collagen and a protein called tissue factor. A blood clot forms rapidly at the rupture site. If the clot is large enough to block the artery, the result is a heart attack or, if it happens in an artery feeding the brain, a stroke. Stable plaques, by contrast, tend to have thick layers of dense collagen, heavy diffuse calcification, and far fewer inflammatory cells.
Can Plaque Be Reversed?
Yes, to a degree. Cholesterol-lowering medications, particularly statins at high doses, have been shown in randomized trials to shrink existing plaque. The effect is dose-dependent: the further you drive LDL cholesterol down, the more regression you see. In one landmark trial, high-dose statin therapy reduced total plaque volume by 0.4% over 18 months, while a lower-dose statin allowed plaque to grow by 2.7%. The difference is modest in absolute terms but clinically meaningful, especially because the medications also stabilize plaque by thickening the fibrous cap and reducing inflammation.
Current guidelines from the American Heart Association set LDL targets based on your overall risk. For people at intermediate risk of heart disease, the goal is LDL below 100 mg/dL. For those at high risk or who already have established heart disease, the target drops to below 70 or even below 55 mg/dL. Reaching these lower thresholds often requires combining a statin with additional medications.
No supplement, food, or exercise program has been proven to shrink plaque in the way that aggressive cholesterol lowering can. That said, the same lifestyle factors that damage the endothelium in the first place (smoking, poor diet, inactivity, uncontrolled blood sugar) continue to accelerate plaque growth if left unaddressed. Quitting smoking, regular aerobic exercise, and a diet low in saturated fat won’t erase decades of buildup, but they slow progression and reduce inflammation in existing plaques, making rupture less likely.
Dental Plaque Is a Different Process Entirely
If you searched this question with your teeth in mind, dental plaque forms through a completely different mechanism. It is a bacterial film, not a cholesterol deposit. Within hours of brushing, a thin protein layer from your saliva coats your teeth. Pioneer bacteria, primarily streptococcus species, attach to this layer through weak physical forces and then lock on more firmly by producing a sticky matrix of sugars and proteins. Once these early colonizers establish themselves, they create scaffolding that allows secondary species to join the community. The biofilm matures into a structured, three-dimensional colony with its own internal communication system.
If dental plaque is not removed by brushing or flossing, calcium and magnesium ions from your saliva gradually mineralize it into tartar (calculus), a hardite deposit that can only be removed by a dental professional. The bacteria within mature dental plaque, particularly anaerobic species that thrive in oxygen-poor pockets beneath the gumline, produce acids and toxins that cause cavities and gum disease.