Scientists from Penn State found that walnuts, a diet low in saturated fats, may help lower blood pressure, especially in people with a high heart disease risk.
Walnuts contain a lot of polyunsaturated fatty acids, which are healthier than saturated fats.
In addition, walnuts have alpha-linolenic acids (ALA), which may have anti-inflammatory effects that keep blood vessels healthy, in addition to having favorable effects on blood lipids (cholesterol and triglycerides).
Previous research has shown that walnuts provide benefits to heart health, but it is unclear whether these effects are attributable to their fat content.
In the study, researchers examined 45 people with a high risk of heart disease.
These people ate a 2‐week standard Western diet and three types of diets that replaced saturated fat in the western diet with unsaturated fat for 6 weeks.
The first was a walnut diet, the second was a diet matching the fat content with the walnut diet but with no walnuts, and the third was an oleic acid–replaced‐ALA diet, which substituted the amount of ALA from walnuts with oleic acid.
Oleic acid is an omega-9 fatty acid. It can be made by the body. It is also found in foods. The highest levels are found in olive oil and other edible oils.
Oleic acid is most commonly used for preventing heart disease and reducing cholesterol.
The researchers found that the walnut diet was linked to lower diastolic blood pressure compared with the oleic acid–replaced‐ALA diet.
Diastolic blood pressure is the pressure in the arteries when the heart rests between beats. This is the time when the heart fills with blood and gets oxygen
The walnut diet also strongly lowered brachial and central arterial pressure.
In addition, all diets lowered total cholesterol, LDL (low‐density lipoprotein) cholesterol, and HDL (high‐density lipoprotein) cholesterol.
Based on the findings, the team concluded that all moderate‐fat, high‐unsaturated‐fat diets could provide heart health benefits.
The greater improvement in diastolic blood pressure in the walnut diet suggests the benefits of walnuts as a whole‐food replacement for saturated fat.
One limitation of the study is that it only tested 45 people. The researchers suggest that this might make it hard to detect the differences between diets.
Future research with much more participants (e.g., more than 500) is needed to explore the differences between diets.
The research is published in the Journal of the American Heart Association and was conducted by Penny Kris-Etherton et al.
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