Nut Consumption: Time for New Recommendations?

Increased consumption of nuts is linked to decreased CVD and total cancer risk, as well as lower risk of death from diabetes, respiratory disease, and infections, according to a systematic review and meta-analysis published online in BMC Medicine.

Results also suggested that 4.4 million deaths in America, Europe, Southeast Asia, and the Western Pacific may be linked to low nut consumption.

“These findings support dietary recommendations to increase nut consumption to reduce chronic disease risk and mortality,” wrote first author Dagfinn Aune, a PhD candidate at Norwegian University of Science and Technology, Trondheim, Norway, and colleagues at Imperial College (London, UK).

Nuts provide a good source of dietary fiber, as well as magnesium, potassium, polyunsaturated fats, vitamin E, and antioxidants, which have been linked to lower risk of CVD and insulin resistance. Nuts also contain phytochemicals that may lower cancer risk. Although nuts are high in total fat, studies have suggested that nut intake is associated with less weight gain over time and decreased risk of obesity.

Past epidemiological studies have linked nut consumption to decreased risk for CVD and all-cause mortality, but have not systematically evaluated less common causes of death. The current meta-analysis expands on past studies by including 1.5 to 3 times more studies than previous meta-analyses, and twice the number of all-cause deaths.

In the study, researchers searched PubMed and Embase for prospective studies published from inception up to July 19, 2016. Retrospective studies were excluded due to the potential for recall bias. Cross sectional studies were excluded because of the inability to determine cause and effect. The final analysis included 29 studies (9 from the US, 6 from Europe, 4 from Asia, 1 from Australia). 

Key results for one serving (1 ounce, 28 g) per day increase in nut intake:

• CAD: 29% lower risk (RR 0.71 [95% CI: 0.63–0.80])

• Stroke: 7% lower risk (RR 0.93 [0.83–1.05])

• CVD: 21% lower risk (RR 0.79 [0.70–0.88])

• Total cancer: 15% lower risk (RR: 0.85 [0.76–0.94])

• All-cause mortality: 22% lower risk (RR 0.78 [0.72–0.84])

♦ Mortality from respiratory disease:  52% lower risk (RR 0.48 [0.26–0.89])

♦ Mortality from diabetes: 39% lower risk (RR 0.61 [0.43–0.88])

♦ Mortality from neurodegenerative disease: 35% lower risk (RR 0.65 [0.40–1.08])

♦ Mortality from infectious disease: 75% lower risk (RR 0.25 [0.07–0.85])

♦ Mortality from kidney disease: 73% lower risk (RR 0.27 [0.04–1.91])

• Similar results for tree nuts and peanuts

Researchers used data from the Global Burden of Disease Study 2013 to estimate the number of deaths in North and South America, Europe, Southeast Asia, and the Western Pacific attributable to low nut consumption, assuming a causal association between nut intake and the above findings. Results suggested that about 4.4 million premature deaths during 2013 in these regions could be attributed to nut intake below 20 grams per day.

Participants with higher nut intake tended to be nonsmokers, slimmer, more physically active. They also ate less red and processed meat and more fruits and vegetables than those who ate fewer nuts. The authors noted, however, that the findings persisted in studies that controlled for these factors. The association in this analysis was independent of BMI, they added, suggesting that the benefits of eating nuts may be independent of BMI.

They also noted that the decreased risk of diabetes mortality may be related to decreased risk of cardiometabolic risk factors and diabetes complications. Only a small number of studies evaluated mortality from respiratory disease, diabetes, and infections, and more studies are needed in this area.

Limitations include large variability in methodology between studies. Also, population-attributable risk calculations did not include data from Africa, the Middle East, and West-Asia, due to lack of studies in these regions. As such, these results may be conservative, according to the authors.

Take-home Points

• Meta-analysis of prospective trials suggests one serving per day increase in nut intake is associated with decreased risk of CAD, CVD, total cancer, all-cause mortality, and mortality from respiratory disease, diabetes, neurodegenerative diseases, infectious disease, and kidney disease.

• Assuming a causal association, 4.4 million premature deaths in North and South America, Europe, Southeast Asia, and the Western Pacific during 2013 may be attributable to low nut consumption.

• The results support dietary recommendation to increase nut intake.

Reference: Aune D, et al. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies. BMC Med. 2016 Dec 5;14(1):207.