Eating nuts every day may help reduce the risk of metabolic syndrome in young adults by improving waist circumference, lipid biomarkers, and/or insulin levels, finds a new study (1).  

The first-of-its-kind randomised trial, recently published in the journal Nutrients, adds to growing evidence on the cardiometabolic benefits of daily nut consumption.

Metabolic syndrome is thought to affect more than one in three Australians (2).

About the study

Researchers at Vanderbilt University Medical Centre enrolled 84 young adults (aged 22-36 years) in their study.

Participants were either overweight or obese, and had at least one metabolic syndrome (MetS) risk factor – abdominal obesity, high triglycerides, low HDL (good) cholesterol, high blood pressure, or high blood glucose levels.

They received guidance on food choices and portions, to meet each participant’s kilojoule goal for weight maintenance.

The difference was that some were randomly assigned to eat, twice daily, 33.5g mixed tree nuts* (around a handful), while others had a carbohydrate-rich snack (such as pretzels, or muesli bars) – with the same kilojoules, protein, fibre, and sodium as the nuts.

Over the 16-week study, the researchers tracked measures, such as body weight, waist circumference, blood pressure and lipid levels. They also calculated participant’s MetS risk scores, by assigning one point for each metabolic syndrome risk factor, at baseline and at the end of the study period.  

* The tree nuts snacks were comprised of a mix of unsalted raw cashews, pistachios, hazelnuts, macadamia nuts, pecans, walnuts, and almonds.

This is the first trial comparing consumption of tree nuts as snacks versus typical carbohydrate snacks on cardiometabolic measures in young adults at risk of MetS.

The key findings

Daily consumption of tree nuts as between-meal snacks significantly reduced total MetS risk scores in young adults (by 67% in females, and 42% in males).

Tree nut consumption improved diet quality, with a 31% higher ratio of unsaturated to saturated fat intake, and a 29% lower total sugars intake, compared with the carbohydrate snack group. The nut group also had significant increases in their vitamin E, folate, vitamin B6, calcium, magnesium, potassium, and zinc intakes.

At the end of the study, the nut group had significantly reduced waist circumference (which differed from the change in the carbohydrate group), primarily in female participants. And in males in the nut snack group, blood insulin levels were reduced, compared with the carbohydrate group.

Tree nuts also significantly reduced triglycerides (TG) and the TG/HDL cholesterol ratio (by around 11%), with the TG/HDL ratio considered a more robust biomarker for identifying MetS than other lipid ratios, and a reliable biomarker for identifying insulin resistance.  

The study also found no change in body weight in the young adults consuming nuts twice daily as a snack.

Did you know? Feeding trials have shown that nuts promote satiety – reducing hunger and desire to eat, while increasing the sensation of fullness – particularly when eaten as a snack between meals (3,4).

What is metabolic syndrome?

MetS is a cluster of risk factors that together increase a person’s risk of stroke, heart disease, type 2 diabetes, and chronic kidney disease (2,5).

These risk factors include high blood pressure, elevated fasting glucose levels, excess body fat around the waist, and abnormal cholesterol or triglyceride levels.

How do nuts help lower the risk?

Evidence from nutrient analysis studies suggests that nuts offer substantial protective cardiometabolic health benefits, due to their unique nutritional make up (6).

The fatty acids in nuts are mainly the heart-healthy monounsaturated and polyunsaturated types. Nuts are also rich sources of protein, fibre, vitamins E and K, minerals, carotenoids, tocopherols, polyphenols, and phytosterols.

These components may displace the intake of nutrients often linked with increased cardiometabolic disease risk, such as saturated fats and sugars. In other words, opting for nutrient-rich nuts as a snack improves overall diet quality.

The bottom line

This first-of-its-kind study found that snacking on nuts daily significantly reduced metabolic syndrome risk in young adults, compared with a typical carbohydrate-rich snack.

And adding a handful of nuts (twice a day, in this case) improved diet quality.

It’s yet another reason to encourage more Australians, including millennials at risk for MetS, to eat a handful of nuts each day!