May 6, 2004 -- Want to get those arteries in shape? Or give them an overhaul? Grab a handful of walnuts.
Just like oily fish -- salmon, mackerel, and bluefin tuna -- walnuts and some other plant foods contain omega-3 fatty acids, says researcher Sheila G. West, PhD, with Pennsylvania State University, in a news release. Studies have shown that walnuts can indeed improve high cholesterol.
She presented her findings at the American Heart Association's 5th Annual Conference on Arteriosclerosis, Thrombosis, and Vascular Biology being held this week in San Francisco.
One omega-3 fatty acid -- alpha-linolenic acid -- has been shown to reduce heart disease, says West. In an earlier study, West found that alpha-linolenic acid can significantly reduce C-reactive protein and LDL "bad" cholesterol, two markers for heart disease.
In West's current study, she looks at direct effects on arteries.
Walnuts vs. All-American Diet
The study involved 13 adults with high cholesterol who were randomly assigned to eat three different diets for six weeks each -- with a two-week break in between each diet.
One diet was the average high-fat, high-cholesterol American diet. The other two diets had similar total fat counts as the American diet. But they were low in saturated fat and cholesterol, which are more abundant in animal products, and high in polyunsaturated fatty acids.
In both of the high-poly diets, volunteers got half of their total fat from walnuts and walnut oil:
- The "regular" high-omega-3 diet contained varying amounts of walnuts and walnut oil -- specifically, ¼ cup walnuts and 1 tablespoon walnut oil, according to a news release.
- The "high-dose" omega-3 diet contained walnuts, walnut oil, but flax oil, too (West's paper does not indicate how much flax oil they got).
At the study's end, the volunteers fasted for 12 hours -- then had an ultrasound test to measure how well their blood vessels responded to changes in blood flow. This artery function has been linked to heart disease risk. Their blood was also tested for high cholesterol.
"Cholesterol levels improved after both of the intervention diets, in which saturated fat had been replaced by plant omega-3 fatty acids," says West in a news release. "But only the higher-dose alpha-linoleic acid diet improved artery function."
The high-dose group had a sevenfold improvement in artery function, compared with the all-American diet group, says West. While it's a small study, her findings indicate that walnuts and other plant-based omega-3 oils offer an important benefit to arteries.
The study was funded by the California Walnut Commission.