Nuts May Reduce Cancer, but Not Diabetes, Risk

A systematic review and meta-analysis has some surprising results

By Eliza Klearman, ND, LAc

Printer Friendly PagePrinter Friendly Page

Reference

Wu L, Wand Z, Zhu J, Murad AL, Prokop LJ, Murad MH. Nut consumption and risk of cancer and type 2 diabetes: a systematic review and meta-analysis. Nutr Rev. 2015;73(7):409-425.

Design

A systematic search and meta-analysis was performed on cohort and case-control studies and clinical trials that could provide data related to nut consumption and association with type 2 diabetes mellitus (DM2) or specific cancers.

Studies

Eligible studies included epidemiological studies (case-control and cohort) or clinical trials that reported an association between nut consumption and the outcome of DM2 or specific cancers. This meta-analysis included 36 observational studies with a total of 30,708 individuals from the general population who were followed for between 4.6 and 30 years.

Outcome Measures

Nut consumption vs diagnosis with DM2 or cancer

Key Findings

Individuals in the highest category of nut consumption compared to those in the lowest category had a significantly lower relative risk (RR) of colorectal cancer (RR:0.76), endometrial cancer (RR:0.58), and pancreatic cancer (RR:0.68). Overall, nut consumption was significantly associated with a reduced risk of cancer incidence (RR:0.85; 95% confidence interval:0.76-0.95). No significant association was found with other specific cancers or DM2. 

Practice Implications 

This meta-analysis is the first of its kind to summarize the available evidence on the associations between nut intake and cancer incidence. The most relevant finding is the 15% reduced risk for incident cancers overall in those with the highest nut consumption vs those with the lowest. 
 
The finding of no association between nut consumption and diabetes comes as something of a surprise. In a series of articles, Kendall and colleagues have reported that nuts, in particular almonds,1,2 and pistachios,3 have a low glycemic effect, little effect on postprandial serum glucose levels, and a dose-dependent effect on insulin response.1 Others have reported that eating nuts is associated with lower levels of inflammatory cytokines and higher levels of adiponectin,4 traits one would expect to be associated with decreased DM2 risk. These and other actions associated with nut consumption, when taken together, suggest consumption might lower DM2 risk. The absence of association seen in these results is contrary to other reviews that suggest there is an inverse relationship between incident diabetes and nut consumption.5,6 It also should not detract from the evidence for better glycemic control in those with an established diagnosis of diabetes.7
Advising patients to eat more nuts may make a significant difference in their health.
The health benefits of nuts go beyond cancer prevention. Previous studies have suggested that nut consumption may lower risk of coronary disease,8 sudden cardiac death in men9 and women,10 and the risk of developing gallstones in men11 and women.12 Eating nuts does not appear to have a negative impact on body weight, insulin resistance, or energy balance.13
 
In past issues of the Natural Medicine Journal, we have reviewed studies that have reported an association between eating nuts and lower risk of heart disease, stroke, Alzheimer’s disease, erectile dysfunction, and overall mortality. This new study provides evidence that we might use to justify telling patients that eating nuts may also lower their risk of getting cancer.
 
Advising patients to eat more nuts may make a significant difference in their health. A good recommendation to patients is that they should eat 1 oz to 1.5 oz of nuts four to five times a week. 

About the Author

Eliza Klearman, ND, LAc, received her doctorate of naturopathic medicine and master of science degree in Oriental medicine from the National College of Natural Medicine, Portland, Oregon. She now has a private practice in Eagle, Colorado, and works for the Fit for Survival program through the Shaw Cancer Center in Edwards, Colorado.  

References

  1. Kendall CW, Esfahani A, Josse AR, Augustin LS, Vidgen E, Jenkins DJ. The glycemic effect of nut-enriched meals in healthy and diabetic subjects. Nutr Metab Cardiovasc Dis. 2011;21(Suppl 1):S34-S39.
  2. Josse AR, Kendall CW, Augustin LS, et al. Almonds and postprandial glycemia—a dose-response study. Metabolism. 2007;56(3):400-404.
  3. Kendall CW, Josse AR, Esfahani A, Jenkins DJ. The impact of pistachio intake alone or in combination with high-carbohydrate foods on post-prandial glycemia. Eur J Clin Nutr. 2011;65(6):696-702.
  4. Ros E. Nuts and novel biomarkers of cardiovascular disease. Am J Clin Nutr. 2009;89(5):1649S-1656S.
  5. Salas-Salvadó J, Bulló M, Babio N, et al. Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes Care. 2011;34(1):14-19. 
  6. Pan A, Sun Q, Manson JE, Willett WC, Hu FB. Walnut consumption is associated with lower risk of type 2 diabetes in women. J Nutr. 2013 Apr;143(4):512-518. 
  7. Viguiliouk E, Kendall CW, Blanco Mejia S, et al. Effect of tree nuts on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled dietary trials. PLoS One. 2014;9(7):e103376. 
  8. Fraser GE, Sabate J, Beeson WL, Strahan TM. A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Arch Intern Med. 1992;152(7):1416-1424.
  9. Hu FB, Stampfer MJ, Manson JE, et al. Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. BMJ. 1998;317(7169):1341-1345.
  10. Albert CM, Gaziano JM, Willett WC, Manson JE. Nut consumption and decreased risk of sudden cardiac death in the Physicians’ Health Study. Arch Intern Med. 2002;162(2):1382-1387.
  11. Tsai CJ, Leitzmann MF, Hu FB, Willett WC, Giovannucci EL. A prospective cohort study of nut consumption and the risk of gallstone disease in men. Am J Epidemiol. 2004;160(10):961-968.
  12. Tsai CJ, Leitzmann MF, Hu FB, Willett WC, Giovannucci EL. Frequent nut consumption and decreased risk of cholecystectomy in women. Am J Clin Nutr. 2004;80(1):76-81.
  13. Rajaram S, Sabate J. Nuts, body weight and insulin resistance. Br J Nutr. 2006;96 Suppl 2:S79-S86.