Healthy fats and type 2 diabetes: a meta-analysis

We are aware that fat is may not be the nutritional disaster it was once considered to be – woohoo! And a recent study looking into dietary fat and risk of type 2 diabetes further supports the notion that increasing our fat intake could be a good thing.

But it depends on the type of fat.

It has been suggested higher consumption of veg, fruit and whole foods, including monounsaturated and polyunsaturated fats, can be beneficial for reducing risk of type 2 diabetes.¹

These fats are common to the Mediterranean style diet, which is correlated with reducing risk of various disease states, including type 2 diabetes, and weight loss.

So, what does this latest study have to say?

The study

Fat has been the bad guy for decades, associated with all manner of chronic disease and weight gain, including risk for type 2 diabetes.

A meta-analysis released in PLoS Medicine summarised 102 randomised control trials that included a total of 4,660 people. The trials provided food to participants, measuring types of fat (saturated, polyunsaturated and monounsaturated) and carbohydrate consumed, and their impact on biomarkers such as insulin production, insulin sensitivity and blood glucose control.²

The findings imply that while replacing refined carbohydrates with saturated fat has been seen to help, it isn’t the best option for a positive impact on blood glucose. Instead consuming polyunsaturated fat in place of heavily processed carbohydrates, like refined grains, sugars and starches, and saturated fats, seems to be optimal when improving insulin sensitivity and secretion, and lowering blood glucose.

They summarised that for every 5% increase in total energy consumed by polyunsaturated fats in place of carbohydrates and saturated fats, a drop of 0.1% in the HbA1c blood biomarker for glucose was found. And every 0.1% drop in that biomarker contributes to a 22% decreased incidence of type 2 diabetes, and a 6.8% decrease for developing cardiovascular disease.

Pretty powerful findings, especially considering there are so many conflicting studies over fats and carbs, type 2 diabetes and heart disease!

Great for polyunsaturated fats, but where do monounsaturated fats fit in all this?

Consumption of monounsaturated fats seems to be correlated with improved insulin secretion, according to the meta-analysis. Monounsaturated fats can be found in a wide array foods, like meat, dairy, nuts and olive oil, and when trialled in past, each of these food groups have had good or bad impacts on risk for type 2 diabetes and cardiometabolic effects.

The positive or negative impacts may be dictated by how processed the food is. For example, the authors noted that increased intake of processed meat is linked with increased type 2 diabetes risk; dairy as neutral or beneficial; and nuts and olive oil get the cardiometabolic thumbs up.

Even though these are technically all sources of monounsaturated fats, food is a complex combination of compounds and nutrients, and these, along with how refined or processed the foods is, can influence a positive or negative health effect.² 

What to take from all this

The important takeaway from the study is reducing refined grains, sugars and starches intake, and increasing polyunsaturated fat intake, like those in vegetables and fish, may be beneficial in reducing risk of type 2 diabetes. And whilst inclusion of animal fats, including saturated fat, is better than eating super-refined carbohydrates, be sure to limit processed meats and instead choose high quality sources of lean meat, that is grass-fed, free-range or organic, eat it in moderation, and serve alongside a heap of vegetables.

Essentially, we want to consume real, whole food, and avoid the highly processed versions of meats, grains and other foods. So choose brown rice over white; choose steamed chicken over chicken nuggets. And limit those added sugars! If you have questions pertaining to your individual situation, please see your healthcare practitioner about specific dietary advice.

So, want to boost your intake of polyunsaturated fats? Here are some suggested foods to include in your day:

• Extra virgin olive oil (first cold pressed is best!)
• Nuts
• Seeds
• Avocado
• Olives
• Fish, especially oily fish like mackerel, sardines, herring, salmon and tuna.

By Angela Johnson (BHSc. Nut. Med.)

References:

1. Xi, P & Liu, RH 2016, ‘Whole food approach for type 2 diabetes prevention’, Molecular Nutrition & Food Research, [Epub ahead of print].
2. Imamura F, Micha R, Wu JHY, de Oliveira Otto MC, Otite FO, Abioye AI, et al. 2016, ‘Effects of Saturated Fat, Polyunsaturated Fat, Monounsaturated Fat, and Carbohydrate on Glucose-Insulin Homeostasis: A Systematic Review and Meta-analysis of Randomised Controlled Feeding Trials’, PLoS Medicine, vol 13, no. 7.