The body of evidence about nuts and diabetes continues to grow, with new local and international research papers regularly published.

Key studies: Systematic reviews and meta-analyses

Nut consumption and type 2 diabetes risk: A systematic review and meta-analysis of observational studies. (2021).
This systematic review and meta-analysis (of eight observational studies) investigated the link between nut consumption and type 2 diabetes (T2D), by comparing the highest with the lowest nut intake groups within the studies. It found no association between consumption of nuts (including tree nuts or peanuts) and the prevalence and incidence of T2D. But the researchers found some evidence that peanut butter consumption may be inversely associated with T2D.

Nut consumption, body weight, and adiposity in patients with type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials. (2021)
The review paper, which collated the outcomes of 15 randomised controlled trials involving 899 people, found nut consumption has no effect, positive or negative, on body weight in people with type 2 diabetes. It also found no significant effects of nut-enriched interventions on body mass index, waist circumference or percent body fat. It backs up previous research that nut consumption does not lead to weight gain in the general population.

The effect of tree nuts on glycaemic outcomes in adults with type 2 diabetes mellitus: A systematic review. (2020).
This study pulled together the available research on the effectiveness of tree nuts on glycaemic outcomes in adults with type 2 diabetes. Fifteen randomised controlled trials were included, with a total sample size of 667. Consumption of mixed tree nuts showed reduction in both fasting blood glucose and glycated haemoglobin (mean differences of −0.26 mmol/L and −0.11%, respectively) at three months or earlier follow-up.

The effect of nuts on markers of glycaemic control: a systematic review and meta-analysis of randomized controlled trials. (2019).
Results from a recent systematic literature review and meta-analysis have found that nuts significantly decrease HOMA-IR and fasting insulin – suggesting that nuts improve insulin sensitivity.

Association between plant-based dietary patterns and risk of type 2 diabetes: a systematic review and meta-analysis (2019).
Greater adherence to plant-based eating patterns significantly associated with reduced risk of type 2 diabetes. Association strengthened with healthier plant foods including nuts, fruit and veg, wholegrains and legumes.

Meta-analysis of prospective studies on the effects of nut consumption on hypertension and type 2 diabetes mellitus. (2015).
Findings from this meta-analysis indicate that consumption of nuts (>2 servings/week) may be inversely associated with hypertension risk, but not with T2DM risk.

Nut consumption and risk of cancer and type 2 diabetes: a systematic review and meta-analysis. (2015).
Nut consumption may play a role in reducing cancer risk. Additional studies are needed to more accurately assess the relationship between nut consumption and the prevention of individual types of cancer, given the scarcity of available data. No significant association was found with type 2 diabetes.

Nut consumption and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a systematic review and meta-analysis. (2014).
Our meta-analysis indicates that nut intake is inversely associated with IHD, overall CVD, and all-cause mortality but not significantly associated with diabetes and stroke. The inverse association between the consumption of nuts and diabetes was attenuated after adjustment for body mass index. These findings support recommendations to include nuts as part of a healthy dietary pattern for the prevention of chronic diseases.

Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke, and diabetes: a systematic review and meta-analysis. (2014).
This systematic review supports inverse associations between eating nuts and incident IHD and diabetes, and eating legumes and incident IHD.

Nut consumption in relation to cardiovascular disease risk and type 2 diabetes: a systematic review and meta-analysis of prospective studies. (2014).
A higher consumption of nuts was associated with reduced risk of CAD and hypertension but not stroke or T2D. Large randomized controlled trials are warranted to confirm the observed associations.

Other evidence

The effects of almonds on gut microbiota, glycometabolism, and inflammatory markers in patients with type 2 diabetes: A systematic review and meta-analysis of randomised controlled trials. (2021).
This review, of randomised controlled trials (RCTs) published over almost 20 years, looked at the effect of almonds on gut microbiota, glycaemic control, and inflammatory markers, in people with type 2 diabetes. It found almond-based diets promoted the growth of short-chain fatty acid (SCFAs)-producing gut microbiota, and were effective in lowering glycated haemoglobin and body mass index (BMI) in people with type 2 diabetes, compared with control. The effects of almonds were not significant with respect to fasting blood glucose, 2-hour postprandial blood glucose, inflammatory markers (C-reactive protein and TNF-α), glucagon-like peptide-1 (GLP-1), homeostatic model assessment of insulin resistance (HOMA–IR), and fasting insulin.

Effect of almond consumption on metabolic risk factors – Glucose metabolism, hyperinsulinemia, selected markers of inflammation: A randomized controlled trial in adolescents and young adults. (2021)
This randomized controlled trial involved 219 Mumbai-based adolescents and young adults aged 16-25 years, with impaired glucose and/or insulin levels. They received either 56g almonds daily, or an iso-caloric cereal-pulse based snack (control group), over 12 weeks. Almond consumption significantly reduced HbA1c, total cholesterol and LDL-cholesterol. The inflammatory biomarkers TNF-α and IL-6 also decreased in the almond group, while increased in the control group. The researchers state that almonds can be part of food-based strategies for preventing pre-diabetes.

Replacing the consumption of red meat with other major dietary protein sources and risk of type 2 diabetes mellitus: A prospective cohort study. (2020).
Pooled analyses from well-known, large prospective studies (the Health Professionals Follow-up Study, Nurses’ Health Study and Nurses’ Health Study II) found that a decrease in intake of red meat during a four-year period, together with an increase in another major protein food, was associated with a lower risk of type 2 diabetes in the subsequent four-year period. The hazards ratio per one serving/day was 0.83 for nuts, 0.82 for poultry, 0.87 for seafood, 0.82 for low-fat dairy, 0.82 for high-fat dairy, 0.90 for eggs, and 0.89 for legumes. The associations were present for both unprocessed and processed red meat, although stronger for the replacement of processed red meat.

Association of dietary patterns with the newly diagnosed diabetes mellitus and central obesity: A community based cross-sectional study (2020).
Researchers investigated the association of dietary patterns with the risk of diabetes and central obesity in a middle-aged Chinese population. They extracted four major dietary patterns using factor analysis: vegetables–fruits food pattern (fruit, vegetables, wheat, beans, nuts and dairy); rice–meat pattern; seafood–eggs pattern; and sweet–fast food pattern. The findings indicated low risk of insulin resistance, diabetes mellitus, and central obesity with the vegetable-fruits pattern, while an inverse relation with the sweet–fast food pattern.

Replacement of red and processed meat with other food sources of protein and the risk of type 2 diabetes in European populations: The EPIC-InterAct Study (2020).
This study modelled the association between replacing red and processed meat with other protein sources and the risk of type 2 diabetes and estimated its population impact. Replacing red and processed meat with cheese, yogurt, nuts, or cereals was associated with a lower rate of type 2 diabetes. The researchers concluded that substituting red and processed meat with other protein sources may contribute to the prevention of incident type 2 diabetes in European populations.

A shift toward a plant-centred diet from young to middle adulthood and subsequent risk of type 2 diabetes and weight gain: The Coronary Artery Risk Development in Young Adults (CARDIA) Study. (2020).
A prospective study, conducted in the US, followed adults ages 18–30 years in 1985–1986 through to 2015–2016. The researchers looked at the associations between change in plant-centred diet quality over 20 years and diabetes – as well as change in BMI, waist circumference and weight. Plant-centred diet quality was measured using the A Priori Diet Quality Score (APDQS). During a mean follow-up of 9.3 (± 1.7) years, participants with the largest increase in APDQS over 20 years had a 48% lower risk of diabetes over the subsequent 10 years, compared with participants whose APDQS score remained stable. Young adults who increased plant-centred diet quality also gained less weight by middle adulthood.

Brazil nut prevents oxidative DNA damage in type 2 diabetes patients (2020).
This study assessed the ex vivo antioxidative effects of selenium through Brazil nut consumption and its potential in preventing oxidative DNA damage induced by hydrogen peroxide (H2O2). The researchers also measured the potential of selenium to prevent oxidative damage to DNA induced by H2O2 in the blood of type 2 diabetes patients, collected before and after six months of supplementation with Brazil nuts. The researchers concluded that supplementation with Brazil nuts significantly increased serum selenium levels, and could decrease oxidative DNA damage in people with type 2 diabetes, likely through the antioxidative effects of selenium.

Effects of daily consumption of cashews on oxidative stress and atherogenic indices in patients with type 2 diabetes: a randomized, controlled-feeding trial. (2019).
A recent RCT concluded daily consumption of cashews significantly reduced insulin and LDL: HDL cholesterol ratio in patients with diabetes.

Mixed nut consumption may improve cardiovascular disease risk factors in overweight and obese adults. (2019).
Supplementation of 42.5g/day of mixed nuts into a usual diet significantly decreased insulin levels, glucose, BMI and body weight, compared to an isocaloric pretzel snack in an 8-week RCT.

The impact of nuts consumption on glucose/insulin homeostasis and inflammation markers mediated by adiposity factors among American adults. (2018).
Participants with a higher nut intake had a more cardioprotective profile of glucose/insulin homeostasis and inflammatory markers. The authors suggest the low GI and anti-inflammatory effects of nuts provides reasons for their inclusion in diets aimed at reducing the risk of type 2 diabetes, impaired glucose metabolism and CVD.

Nuts, inflammation and insulin resistance. (2010).
As chronic inflammation is a key early stage in the atherosclerotic process that predicts future CVD events and is closely related to the pathogenesis of insulin resistance, many recent studies have focused on the potential effect of nut consumption on inflammation and insulin resistance. Through different mechanisms, some components of nuts such as magnesium, fibre, alpha-linolenic acid, L-arginine, antioxidants and MUFA may protect against inflammation and insulin resistance.

The effect of nuts on inflammation. (2008).
The relationship observed between frequent nut consumption and the reduced risk of cardiovascular mortality and type 2 diabetes in some prospective studies could be explained by the fact that nuts are rich in all of these modulator nutrients. In fact, frequent nut consumption has been associated with lower concentrations of some peripheral inflammation markers in cross-sectional studies. Nut consumption has also been shown to decrease the plasma concentration of CRP, IL-6 and some endothelial markers in recent clinical trials.


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