Nuts about diabetes

Nuts are a nutritional powerhouse. Might they be a prevention powerhouse too? Delegates at the 38th International Symposium on Diabetes and Nutrition heard presentations on their role in preventing and managing metabolic syndrome and type 2 diabetes.

Nuts have long been known for their nutritional value but they’re now coming under the research spotlight for what specific role they can play within a healthy diet. Zhaoping Li, Professor of Medicine and Chief of the Division of Clinical Nutrition at the University of California, Los Angeles, USA, gave a fascinating presentation on nuts in the prevention of diabetes and metabolic syndrome.

When looking at what makes a healthy diet, said Professor Li, it’s not calories alone that matter, but dietary quality – i.e. what the diet is actually made up of. Nuts are a wise addition – they’re proven to be good for the heart, with a healthy fatty acid composition (predominantly monounsaturated), vitamin E, omega 3 fatty acids, phytosterols, antioxidants, potassium, magnesium and fibre. 

Professor Li highlighted four epidemiological studies involving thousands of people, which showed that the more nuts you consume, the lower your risk of metabolic syndrome. Metabolic syndrome, as we know, increases overall mortality and risk of heart disease, stroke and type 2 diabetes.

With regard to weight management, numerous studies reveal that tree-nut consumption is linked with lower BMI and a meta-analysis shows that they are beneficial in preventing weight gain.

In one 12-week study, pretzels and the same number of calories in pistachios were compared in a weight-loss programme, and the pistachio group lost a significant amount more weight (going back to Professor Li’s earlier point about calories versus dietary composition).

A more recent study, in 2021, compared mixed nuts and pretzels as part of a weight-loss diet – both lost weight but the mixed nuts were more successful in maintaining weight loss after the programme. The researchers think that one of the main mechanisms here was better satiety. For people with diabetes, nuts are a smart snack, said Professor Li. They are potential drivers for glycaemic control – a low glycaemic index food with a healthy fats, protein and fibre matrix. There is a host of studies looking at tree nuts’ effect on type 2 diabetes and metabolic syndrome.

A recent one replaced carbohydrates with nuts in patients with type 2 diabetes. After 12 weeks of 75 g of nuts a day in place of carbs, HbA1c was significantly improved compared with the group given the same calories with a muffin. Even a group given half nuts/half muffin for their calories showed better glucose control than the muffin-only group.

Another study compared pistachios and wholewheat bread (with equivalent calories) in women with gestational diabetes, and found that wholewheat bread produced a significant rise whereas the pistachios were able to maintain glucose in a normal range.

The PREDIMED study found that a Mediterranean diet supplemented with nuts or olive oil resulted in a lower risk of cardiovascular mortality than a control diet (advice to reduce dietary fat). To explore the potential mechanisms behind why this might be, recent studies using almonds showed that a daily dose significantly improves diversity of the gut microbiome and improves overall antioxidant capacity in the body.

In summary, she said, nuts significantly decrease risks for metabolic syndrome; potential mechanisms are maintaining a healthy weight, lowering blood glucose, increasing total antioxidant capability and preventing gut microbiome dysbiosis.

In his presentation, Professor Anoop Misra, Chairman at the Fortis-CDOC Center of Excellence for Diabetes, Metabolic Diseases and Endocrinology, looked at the role of nuts in the management of type 2 diabetes, taking the audience through the available research.

From these studies, he concluded that:

• Nut intake has beneficial effects on glucose-insulin metabolism, and also decreases hepatic fat in experimental studies
• Epidemiological data shows an inverse association between nut intake and type 2 diabetes and components of metabolic syndrome, especially in women
• In short-term intervention studies, pre-prandial intake of nuts decreases post-prandial hyperglycaemia
• In studies of 4-6 months’ duration, intake of nuts decreased blood glucose levels, triglycerides and inflammatory markers, and increased GLP-1 levels
• Overall, the data indicates the potential of nut intake in the prevention and management of type 2 diabetes
• Further robust and long-term data is required

The opinions expressed in this article are those of the author, Dr Eleanor D Kennedy.