Research shows that nuts play an important role in preventing type 2 diabetes [1], managing existing diabetes [2], and preventing or reducing the progression of diabetes-related complications [2].
Eating just one handful of nuts four times a week is associated with a 13% reduced risk of developing diabetes [1], and nuts can improve blood glucose levels and lower HbA1c for those with type 2 diabetes [2].

How do nuts help manage diabetes?

  • While nuts 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 [3]. 
  • Nuts contain mainly 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 [4].
  • Nuts are a good source of fibre. Diets high in fibre have been shown to help manage diabetes and metabolic syndrome, and can reduce the risk of developing diabetes [5, 6].
  • Most nuts are a rich source of magnesium, which can reduce the risk of developing type 2 diabetes. Magnesium also improves fasting blood glucose and blood lipid levels in people with diabetes [7].

Research supports eating at least 30g, or about one handful of nuts four times a week to reduce the risk of developing diabetes [1].

Studies have been conducted on many different tree nuts, all showing benefits. The take out? All nuts help prevent or manage diabetes, so enjoy a variety of nuts every day. However, it’s best to enjoy raw or roasted, unsalted nuts as your everyday choice, saving salted nuts for special occasions.

Did you know, people with diabetes are more than twice as likely to die from cardiovascular disease and are more likely to have abnormal blood lipids including high cholesterol and triglycerides and lower ‘good’ HDL cholesterol [8]? Carrying extra weight is also a major risk factor for developing type 2 diabetes, and can make managing diabetes more difficult.

Evidence shows that eating nuts regularly can reduce your risk of developing heart disease and can improve cholesterol levels [9, 10].  Nuts are also associated with reducing the risk of overweight/obesity, as well as decreasing body weight, BMI and waist circumference [11].

What the research says

The first population study to show an association between nuts and diabetes risk was the Nurses’ Health Study [12]. 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 [13]. 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 [14]. 

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 [1].

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 [2].

Preventing diabetes [13]

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

Managing diabetes [2]

  • 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 [1].
  • 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) [2]

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 [3]. 
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 [4].
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 [5, 6].
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 [7]. 

References

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. Salmeron, J., et al., Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care, 1997. 20(4): p. 545-50.
  6. 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.
  7. 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.
  8. Barr, E.L., et al., Risk of cardiovascular and all-cause mortality in individuals with diabetes mellitus, impaired fasting glucose, and impaired glucose tolerance: the Australian Diabetes, Obesity, and Lifestyle Study (AusDiab). Circulation, 2007. 116(2): p. 151-7.
  9. 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. 14(1): p. 207.
  10. Neale, E., et al., The effect of nut consumption on heart health: an updated systematic review of the literature. 2018. Nuts for Life, unpublished.
  11. Li, H., et al., Nut consumption and risk of metabolic syndrome and overweight/obesity: a meta-analysis of prospective cohort studies and randomized trials. Nutr Metab (Lond), 2018. 15: p. 46.
  12. Jiang, R., et al., Nut and peanut butter consumption and risk of type 2 diabetes in women. JAMA, 2002. 288(20): p. 2554-60.
  13. 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.
  14. 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.
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