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Nuts and DiabetesA FACTSHEET FOR HEALTHCARE PROFESSIONALS

Diabetes is Australia’s fastest growing chronic disease, with prevalence more than tripling over the last 25 years. It is estimated that more than 1.2 million Australians have known diabetes, and another 2 million are at high risk of developing diabetes[1].

Diet plays an important role in the prevention of type 2 diabetes, in managing existing diabetes and in preventing or reducing the progression of diabetes-related complications.

The first population study to show an association between nuts and diabetes risk was the Nurses’ Health Study[2]. 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[3]. 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[4].

What the research says

More current research continues to strengthen these findings, with meta-analyses showing that nuts can help prevent the risk of developing type 2 diabetes[5], as well as manage existing diabetes by improving HbA1c and fasting glucose levels[6].

  • 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[5].
  • 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[6].

Key results

Prevention of diabetes[5]

  • 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[6]

  • 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 -0.15 mmol/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[5].
  • 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)[6].

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[7].

Rich source of healthy fats

  • Nuts contain mainly the healthy unsaturated fats (monoand polyunsaturated fats), and are low in saturated fats. Replacing saturated and trans fats with unsaturated fats improves insulin sensitivity and reduces type 2 diabetes risk[8].

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[9, 10].

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[11].

For good health,
enjoy a healthy handful
of nuts every day.

What does all this mean?

The body of evidence supports regular nut consumption for reducing the risk of developing diabetes, as well as for managing existing diabetes.

To put it simply, nut intake is good for both preventing and managing diabetes.

In addition to reducing diabetes risk and diabetes management, there is also strong evidence for nuts in reducing the risk of heart disease[12], overweight and obesity[13], supporting brain health and reducing the risk of cancer[14].

What your clients need to know

A 30g serve of nuts a day is helpful to prevent the development of, and assist with the management of diabetes.

A 30g serve also aligns with the Australian Dietary Guidelines serve size guidelines. The Australian Dietary Guidelines recognise nuts as being highly nutritious, and in playing an important role in a healthy balanced diet[13].

Metabolic syndrome (MetS) – a clustering of cardiovascular disease risk factors including elevated blood glucose, dyslipidaemia, hypertension and abdominal obesity. Individuals with metabolic syndrome have a greater risk of developing cardiovascular disease and type 2 diabetes.

Being overweight or obese, particularly around the abdomen is a major risk factor for type 2 diabetes. People with diabetes are more than twice as likely to die from cardiovascular disease and are more likely to have abnormal blood lipids. So how does this impact nut consumption?

Research supports regular nut consumption for reducing the risk of developing heart disease[12] and for reducing cardiovascular risk factors[16], as well as for reducing the risk of overweight/obesity[13], and for showing significant reductions in body weight parameters[13].

References

  • Sainsbury, E., et al. Burden of diabetes in Australia: it’s time for more action. The Boden Institute, University of Sydney. July 2018
  • Jiang, R., et al., Nut and peanut butter consumption and risk of type 2 diabetes in women. JAMA, 2002. 288(20): p. 2554-60.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • Salmeron, J., et al., Dietary fiber, glycemic load, and risk of NIDDM in men. Diabetes Care, 1997. 20(4): p. 545-50.
  • 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.
  • 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.
  • 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.
  • 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.
  • Wu, L., et al., Nut consumption and risk of cancer and type 2 diabetes: a systematic review and meta-analysis. Nutr Rev, 2015. 73(7): p. 409-25.
  • National Health and Medical Research Council. Australian Dietary Guidelines. Canberra: National Health and Medical Research Council. 2013
    https://www.eatforhealth.gov.au/sites/default/files/files/the_guidelines/n55_australian_dietary_guidelines.pdf
  • Neale, E., et al., The effect of nut consumption on heart health: an updated systematic review of the literature. 2018. Nuts for Life, unpublished.
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