Dietary fats and stroke: Is there a link?

Scientists are puzzled…they don’t know how big—or small—a role certain “bad fats” play in raising stroke risk. What does this mean for you?

We know that some dietary fats—namely, saturated fats and trans fats—contribute to coronary artery disease. And we know that heart disease and stroke have important risk factors in common. So you might think it would follow that stroke is also linked with eating a diet high in saturated fats and trans fats.

In fact, the jury is still out on whether these fats are associated with the most common type of stroke (ischemic), which is caused by an obstruction in arteries to the brain from fatty deposits in the blood vessels. The scientific evidence doesn’t exist to justify a link—even though atherosclerosis (clogged, narrowed heart arteries) is thought to be a common cause of both ischemic stroke and heart disease.

Saturated fats are mainly found in meat and dairy products, although some plant-based foods (think coconut oil and palm oil) also contain this cholesterol-raising substance. Trans fats are created when hydrogen is added to vegetable oils. This process, known as hydrogenation, helps preserve the shelf life and flavor of foods.

Saturated fats raise levels of low-density lipoprotein (LDL, or “bad”) cholesterol and, as a result, coronary artery disease risk. Trans fats may be even more dangerous, because they not only raise LDL cholesterol but may also lower levels of “good” cholesterol (high-density lipoprotein, or HDL, cholesterol, which helps remove “bad” cholesterol from blood vessels). Trans fats also promote other unhealthy effects in the body that lead to heart disease.

Yet for all that, studies do not indicate that either of these types of fat is linked with stroke. In fact, research suggests that there may be a different—even opposite—pattern of risk related to dietary fat intake for ischemic stroke vs. coronary artery disease: Some studies have shown that people who eat very little saturated fat actually have high rates of stroke even though they have low rates of coronary artery disease.

Statins help prevent stroke…but why?
To add to the mystery, high cholesterol levels generally associated with saturated and trans fats—and heart disease—may not be associated with stroke. Yet statin drugs, which are powerful tools for lowering cholesterol, have been shown to reduce the risk of stroke!

Experts think statins may lower stroke risk by reducing the risk of heart attack and other dangerous events that, in turn, increase the chances of having a stroke. The answer could also lie in some other effect that statin drugs have—an effect that isn’t tied to the cholesterol-lowering properties of these medications.

Smart eating still counts!
To date, there simply hasn’t been enough solid research on dietary fat and stroke risk to draw any conclusions about a link. Because saturated fats and trans fats are known risk factors for coronary artery disease, it makes sense to steer clear of them.