In recent years, studies have started pointing to nuts as a way to boost heart health, but most of them were observational with a limited sample size. Now, a systematic review of clinical trials spanning 25 years has confirmed that when it comes to cardiovascular health, nuts are the go-to food.
At Medical News Today, we've been unpacking the health benefits of nuts, one study at a time.
Now, scientists led by Marta Guasch-Ferré — a research associate in the Department of Nutrition at the Harvard TH Chan School of Public Health in Boston, MA — have carried out a large-scale review of numerous studies covering the link between nut consumption and heart health.
These "natural health capsules," as Guasch-Ferré called them in a study that MNT reported on last year, may do wonders for our cardiovascular system.
This is the main takeaway of the new review, which has been
Walnut-enriched diets protect the heart
This review updates the results of a previous meta-analysis that was published in 2009. It included 13 clinical trials.
Now, Guasch-Ferré and team have assessed the trials published since that point; this amounted to 26 randomized trials, summing up 1,059 participants with ages between 22 and 75.
The scientists evaluated the benefits of a diet rich in walnuts and compared it with low-fat, Western, Mediterranean, and Japanese diets.
Walnut-enriched diets provided a more significant reduction in cholesterol levels and other markers of cardiovascular health when compared with these control diets.
More specifically, a diet rich in walnuts had a 3.25 percent greater reduction in total cholesterol levels, a 3.73 percent greater decrease in low-density lipoprotein (LDL) cholesterol, and a 5.52 percent greater reduction of triglycerides.
Also, levels of apolipoprotein B — which is the main protein found in LDL, or "bad," cholesterol — were lowered by 4.19 more percentage points than in control diets.
Strengths and limitations of the study
Dr. Michael Roizen, the chief wellness officer in the Department of Preventive Medicine at the Cleveland Clinic in Ohio, weighs in on the findings.
"This updated review further strengthens the case that enjoying walnuts is a great (and tasty) way to add important nutrients to your diet while supporting the health of your heart."
Dr. Michael Roizen
But the review does have some caveats. The samples in most of the studies reviewed were fairly small, which may weaken the findings.
Also, some trials used a considerable amount of walnuts, which may be hard to stick to in a day-to-day setting, say the researchers.
Still, they highlight the fact that great benefits were noticed with even smaller amounts of walnuts — that is, fewer than 28 grams per day.
Finally, the research was funded by the California Walnut Commission, an agency of the State of California that works together with the Secretary of the California Department of Food and Agriculture to develop the nut market and support health research.