Thickening of the walls of arteries in the neck may be related to low levels of a substance called lutein, commonly found in spinach, broccoli and other dark green vegetables, according to researchers at the Keck School of Medicine of USC and the UCLA School of Medicine.

The study on lutein and atherosclerosis – the buildup of plaque on artery walls that can lead to heart attacks and strokes – helps explain why fruit- and vegetable-rich diets seem to protect cardiovascular health, the researchers recently reported in the journal Circulation. The researchers monitored 480 men and women between ages 40 and 60 in Los Angeles.

Atherosclerosis accounts for more than 1.5 million heart attacks and 600,000 strokes every year in the United States.

“Scientific knowledge of the long-term effects of diet on cardiovascular disease is still rudimentary, but there is mounting evidence that increased intake of vegetables and fruits is protective against cardiovascular disease,” said James Dwyer, USC professor of preventive medicine. “Unlike the use of supplements, such as beta carotene, increased intake of vegetables and fruit is also very unlikely to yield surprise adverse effects.”

Findings suggest that increased intake of the dark green leafy vegetables, such as spinach, kale and collard greens, may prevent – or at least slow – the progression of the underlying disease that leads to most heart attacks and strokes. Fortunately, such foods can easily be incorporated into a normal American diet.

“They can be eaten raw in salads, cooked by themselves or served as additions to many recipes,” Dwyer said. “Cooking these greens may reduce the bioavailability of the lutein somewhat, but most of its impact on blood levels is retained after cooking.”

Lutein is in a class of compounds known as carotenoids, which are found in many foods. Other studies have suggested that lutein may be important in eye health. However, another carotenoid tested in the study, beta carotene, was not found to help protect against atherosclerosis – a finding consistent with previous studies.