Nuts Tied to Lower CVD Risk in Type 2 Diabetes

Veronica Hackethal, MD

February 25, 2019

Eating nuts may decrease the risk of cardiovascular disease (CVD) and death in people with type 2 diabetes, according to a study published online in Circulation Research.

The researchers found that higher levels of nut consumption — especially tree nuts like walnuts, cashews, and almonds — were tied to greater reductions in cardiovascular risk.

"Our findings provide new evidence that supports the recommendation of including nuts in healthy dietary patterns for the prevention of CVD complications and premature deaths among individuals with diabetes," first author Gang Liu, PhD, of the Harvard T.H. Chan School of Public Health, Boston, Massachusetts, said in a press release.

And even if people already ate nuts before their diabetes diagnosis, increasing nut consumption after diagnosis still showed cardiovascular benefits.

"It seems never too late to improve diet and lifestyle after diagnosis among individuals with type 2 diabetes," Liu added.

Nuts provide an excellent source of healthy nutrients, such as unsaturated fatty acids, plant proteins, fiber, minerals, vitamins, and anti-inflammatory phytochemicals.

Looking at Nut Consumption Specifically in Those With Diabetes

Past studies have linked consumption of nuts to a reduction in a variety of cardiovascular risk factors, such as high blood pressure, abnormal lipid levels, insulin resistance, and inflammation. The PREDIMED trial, one of the largest randomized controlled trials to evaluate the impact of nuts on cardiovascular health, found a reduced risk of CVD in those randomized to a Mediterranean diet plus nuts compared with controls, as reported by Medscape Medical News.

But that study generated controversy when it was retracted because of an error in analysis. Addressing the error yielded similar results, and the New England Journal of Medicine re-published the study.

Still, the role of nuts on cardiovascular health remains under debate. That's especially true for people with diabetes, who are already at increased risk for CVD. Few studies have looked at the issue in this specific population.

To shed more light, Liu and colleagues examined data from two prospective studies: one included data from 1980-2014 from the Nurses' Health Study and the other from 1986-2014 from the Health Professionals Follow-Up Study.

The analysis included 16,217 people who had diabetes at baseline or were diagnosed with it during the studies. Participants answered questions about nut consumption using validated food frequency questionnaires every 2 to 4 years.

Results showed that eating five or more 28-g servings of nuts per week was linked to a 17% lower risk of CVD, a 34% lower risk of CVD death, a 20% lower risk of coronary heart disease (CHD), and a 31% lower risk of death from all causes compared with eating less than one serving per month.

For each one serving increase in total nuts per week, the risk of CVD decreased by 3% and the risk of death from CVD decreased by 6% (P linearity < .001).

More specifically, eating higher levels of tree nuts was linked to a lower risk for CVD, CHD, death because of CVD, cancer, and all-cause death (all P trend < .001).

These observations did not apply to peanuts. The only outcome that was significantly reduced with increasing levels of peanut consumption was all-cause death (P trend < .001).

Increasing Nut Consumption After Diabetes Diagnosis Adds Benefits

People who started eating more nuts after their diabetes diagnosis had additional benefits of an 11% lower risk of CVD, 15% lower risk of CHD, 27% lower risk of death from CVD, and 27% lower risk of death from all causes compared with people who did not increase their nut consumption after diagnosis.

Again, tree nut consumption was linked to even greater reductions in risk in this group.

Results were unchanged after adjusting for several established risk factors for CVD, including diabetes duration, body mass index, medication use, nut consumption before diabetes diagnosis, exercise, and diet.

The authors note that the reason for the difference between tree nuts and peanuts is unclear but may have to do with higher levels of healthy nutrients in tree nuts.

Peanuts are actually legumes, not nuts, and so have a different nutritional composition.

A potential limitation is the observational nature of the study, and so the results do not prove that eating nuts directly caused the reduction in CVD risk in people with diabetes, say the researchers.

Also, study participants were all health professionals, and the findings may not be generalizable to a wider population.

In addition, accuracy of specific nut intake and portion sizes relied on self-report, which may have been prone to error. Finally, the study could not account for the impact of preparation methods (raw, roasted, salted) on CVD outcomes.

The study was funded by the National Institutes of Health. Hu and Li have reported receiving grants from the California Walnut Commission. The other authors have reported no relevant financial disclosures.

Circ Res. 2019. Published online February 19, 2019. Abstract

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