Research suggests eating nuts may be crucial in cutting the risk of metabolic syndrome. But what is metabolic syndrome? And how can lifestyle changes, including a daily handful of nuts, help protect against the serious health problems that stem from it?

What is metabolic syndrome?

Australian health authorities define metabolic syndrome (MetS) as a cluster of risk factors that together increase a person’s risk of stroke, heart disease, type 2 diabetes and chronic kidney disease (1,2).

These risk factors are:

• Raised triglyceride levels
• High blood pressure
• Excess abdominal weight
• Low HDL (good) cholesterol levels
• Elevated fasting glucose levels.

These factors underlying MetS (which is also known as ‘syndrome X’ or ‘insulin-resistance syndrome’) are increasing across the globe. And MetS itself is thought to affect more than one in three Australians.

How to prevent metabolic syndrome

A healthy lifestyle is crucial to prevent or delay the onset of MetS, and to help manage it for those with existing MetS.

An international panel looked into the evidence on how a range of lifestyle factors impact MetS (3). Their findings are summarised below (Table 1).

Table 1: Dietary patterns, foods and nutrients in the prevention of metabolic syndrome (3)

Nuts and metabolic syndrome

Within their wider lifestyle recommendations, the international panel advises eating 1 to 1.5 serves of nuts daily.

Nut consumption reduces heart disease risk, has a favourable effect on type 2 diabetes, blood pressure, and triglycerides, and is linked with reduced adiposity, which are all factors in metabolic syndrome (3).

They found epidemiological and clinical trial evidence of a beneficial effect of nut consumption on MetS components, and also on the full syndrome itself (4-10). And they say there is probably an added benefit if nuts are incorporated into a Mediterranean-type dietary pattern.

Some key studies include:

• A 2018 meta-analysis, of six prospective cohort studies with 420,890 subjects and 62 randomised feeding trials with 7,184 participants, showed that for every 1 serving/week increase in nut consumption, the risk of metabolic syndrome was reduced by 4% (10).

• The well-regarded PREDIMED trial found, after 4.8 years of follow-up, that participants with MetS at the start of the study, who were allocated to the Mediterranean diet plus a daily serve of mixed nuts, had a 28% higher rate of MetS reversal, compared with those in the control group (not supplemented with nuts) (8).

• The Tehran Lipid and Glucose study showed reduced incidence of MetS with tree nut consumption of five or more servings per week (13). This population-based prospective study involved 1,265 adults, aged 19–74 years, who were followed over 6.2 ± 0.7-years.

A 2022 systematic review and meta-analysis, of 10 randomised controlled trials, summed up the evidence to date on the impact of nut consumption on components of metabolic syndrome, in healthy adults with overweight/obesity (12). Among the findings, incorporating nuts into the diet significantly reduced serum triglycerides and LDL-cholesterol, but had no effect on glycaemic markers or blood pressure.

How are nuts protective?

Nuts are rich in beneficial unsaturated fatty acids, fibre, antioxidant vitamins and minerals, and bioactive phytochemicals (like polyphenols and phytosterols).

It’s thought that this unique combination of nutrients and bioactive compounds helps protect against inflammation and oxidative stress, benefits endothelial function, and favourably alters the gut microbiota – which, in turn, impact the factors underlying MetS (9,10).

Did you know? Nut consumption is associated with a 15% reduction in the incidence of cardiovascular disease and a 23% reduction in dying from it (11).

The bottom line

Lifestyle changes, including a healthy diet and regular physical activity, are crucial in reducing the odds of developing metabolic syndrome.

The Mediterranean-type diet – based around plant-based foods (like whole grain cereals, legumes, nuts, fruits and vegetables), fish, extra virgin olive oil and low-fat dairy foods – can help prevent and treat metabolic syndrome.

And research tells us that a daily handful of nuts benefits many metabolic syndrome components, and the full syndrome itself.