Key points

The first population study to show an association between nuts and diabetes risk was the Nurses’ Health Study [1]. In the cohort of nearly 84,000 women, both total nut intake and peanut butter intake were associated with a reduced risk of type 2 diabetes, with a 27% and 21% lower risk, respectively, when consuming a handful (~30g) five or more times per week. A further analysis from the same cohort, specifically looking at walnuts showed similar findings [2]. The more recent PREDIMED study found those consuming more than 3 serves of nuts/week had a 22% lower prevalence of diabetes than those consuming less than one serve of nuts/week [3]. 

Evidence from a systematic literature review and meta-analysis of five prospective cohort studies and one RCT, showed that consuming a 30g handful of nuts four times per week was associated with a 13% reduction in the risk of type 2 diabetes [4].

Evidence from a meta-analysis of twelve randomised controlled trials showed that nuts lowered HbA1c and fasting glucose, but not fasting insulin or HOMA-IR, compared to control diets in people with type 2 diabetes [5].

Prevention of diabetes [4]

  • Per 28g serves, 4 times per week, there was a 13% reduction in the relative risk of diabetes (RR 0.87, 95% CI). 

Management of diabetes [5]

  • HbA1c – diets emphasising tree nuts significantly lowered HbA1c in comparison to controlled diets (mean difference -0.07%, 95%CI)
  • Fasting glucose – diets emphasising tree nuts significantly lowered fasting glucose in comparison to control diets (mean difference -0.15mmol/L ,95%CI)

How many nuts and for how long?

  • To prevent diabetes, a handful of nuts (~30g) at least 4 times per week is recommended [4].
  • To manage diabetes, RCTs that compared a diet emphasising the intake of tree nuts in comparison to diets without tree nuts, matched for energy, the dosage of nuts ranged from 28-85g per day, for a median duration of 8 weeks (3 weeks or longer) [5]

Potential mechanisms of action

Nuts have a unique nutrition profile, containing many nutrients that may benefit metabolic health, including unsaturated fatty acids, protein, fibre, minerals, antioxidants and phytochemicals. The low carbohydrate and high unsaturated fat content of nuts produces lower postprandial glucose and insulin responses, which is thought to be important for reducing diabetes risk over time. 

Glycaemic Index (GI) lowering effect

While nuts themselves are not low GI (they don’t have enough carbohydrate), they have a GI lowering effect, meaning that they reduce the overall GI of a meal [6]. 

Rich source of healthy fats

Nuts contain mainly the healthy unsaturated fats (mono- and polyunsaturated fats), and are low in saturated fats. Replacing saturated and trans fats with unsaturated fats improves insulin sensitivity and reduces T2DM risk [7].

Nuts are a good source of fibre

Diets high in fibre have been shown to help in managing diabetes and metabolic syndrome and can reduce the risk of developing diabetes [8, 9].

Most nuts are a rich source of magnesium

Magnesium intake has been inversely associated with type 2 diabetes risk and supplementing magnesium intake has been shown to improve fasting blood glucose and HDL levels in those with diabetes [10]. 

References

  1. Jiang, R., et al., Nut and peanut butter consumption and risk of type 2 diabetes in women. JAMA, 2002. 288(20): p. 2554-60.
  2. Pan, A., et al., Walnut consumption is associated with lower risk of type 2 diabetes in women. J Nutr, 2013. 143(4): p. 512-8.
  3. Ibarrola-Jurado, N., et al., Cross-sectional assessment of nut consumption and obesity, metabolic syndrome and other cardiometabolic risk factors: the PREDIMED study. PLoS One, 2013. 8(2): p. e57367.
  4. Afshin, A., et al., Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke, and diabetes: a systematic review and meta-analysis. Am J Clin Nutr, 2014. 100(1): p. 278-88.
  5. Viguiliouk, E., 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): p. e103376.
  6. Kendall, C.W., et al., The glycemic effect of nut-enriched meals in healthy and diabetic subjects. Nutr Metab Cardiovasc Dis, 2011. 21 Suppl 1: p. S34-9.
  7. Riserus, U., W.C. Willett, and F.B. Hu, Dietary fats and prevention of type 2 diabetes. Prog Lipid Res, 2009. 48(1): p. 44-51.
  8. Salmeron, J., et al., Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care, 1997. 20(4): p. 545-50.
  9. Salmeron, J., et al., Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. Jama, 1997. 277(6): p. 472-7.
  10. Dong, J.Y., et al., Magnesium intake and risk of type 2 diabetes: meta-analysis of prospective cohort studies. Diabetes Care, 2011. 34(9): p. 2116-22.
Back Download PDF
Print

Follow Us

Join our mailing list

For up to date information & the latest research articles