Does a gluten-free diet increase your risk of diabetes?

Recently a study was presented at a meeting of the American Heart Association reporting low gluten diets increased the risk of developing Type 2 diabetes. When this was distilled into media sound bites, the message implied gluten-free diets paved the way for diabetes. Is this correct? Should we ditch our kale smoothies and quinoa porridge for breakfast and start scoffing the Weet-Bix and vegemite on toast?

The association between low gluten and diabetes

Nutrition research is complex and contains many variables and potential confounders. Data for the research was obtained from the Nurse’s Health Study where 200,000 nurses were followed for 30 years and asked to complete food surveys every 2-4 years. The weakness with epidemiological studies is they rely on people’s memories of what they ate. This leaves a lot of room for error to creep in. My experience with getting clients to complete a 7-day food diary tells me the bias is in favour of a healthier recall than it was in reality. Hey, I would be totally guilty of this! Epidemiological studies only reveal association and not cause and effect. Dr William Davis gives a detailed overview on this issue.

So study design aside, what could be the reason low gluten intake had an association with an increased risk of Type 2 diabetes?

Gluten-free does not mean healthy

The public perception that gluten is having a severe impact on health has created a growing market for gluten-free foods.¹ Gluten-free foods are viewed as a “healthy” choice even for those with no symptoms or diagnosis of coeliac disease or wheat allergy. Unfortunately, many of these commercial gluten-free products are highly processed and contain ingredients like cornstarch, sugar, saturated fat and additives which have little nutritional value².

The missing fibre

Eliminating grains from your diet can also reduce the amount of a particular type of fibre – prebiotics or resistant starch. Prebiotic fibre is essential to nourish the good bacteria in your digestive tract. Research reveals it is not enough to “seed” our digestive tract with probiotics, we also need to “feed” them to help them produce short chain fatty acids³. These fatty acids help regulate insulin and blood sugar⁴. A deficit of these in people who eliminate or reduce gluten may explain the reason for the increased incidence of Type 2 diabetes. This can also be a problem with people following a Paleo or very low carbohydrate diet.

The good news is grains are not the only source of prebiotics and resistant starch. Here are some alternative options for you.

Prebiotics

Vegetables:

Jerusalem artichokes, chicory, garlic, onion, leek, shallots, spring onion, asparagus, beetroot, fennel bulb, green peas, snow peas, sweetcorn, savoy cabbage

Legumes

Chickpeas, lentils, red kidney beans

Fruit

Custard apples, nectarines, white peaches, persimmon, tamarillo, watermelon, grapefruit, pomegranate  Dried fruit (e.g. dates, figs)

Nuts and Seeds

Cashew, pistachio

Resistant Starch is found in green bananas, cold (white) rice, cold cooked starchy vegetable such as potato and sweet potato.

So what’s the moral of the story? Gluten and Grain-free diets done correctly can be a healthy choice and won’t necessarily increase your risk of getting Type 2 diabetes. Just make sure you include your prebiotic fibres to feed your beneficial gut bugs

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References:

1. Australian Food News. Global gluten-free market set to grow. http://ausfoodnews.com.au/2010/07/13/global-gluten-free-market-set-to-grow.html. Published 2010.
2. Pellegrini N, Agostoni C. Nutritional aspects of gluten-free products. J Sci Food Agric. 2015;(November 2014). doi:10.1002/jsfa.7101.
3. Hawrelak J, Crittenden RG. Probiotics, prebiotics and synbiotics. J Complementary Med. 2007;(6):28-35. www.ebscoehost.com.
4. Fernandes J, Su W, Rahat-Rozenbloom S, Wolever TMS, Comelli EM. Adiposity, gut microbiota and faecal short chain fatty acids are linked in adult humans. Nutr Diabetes. 2014;4(e121):2-7. doi:10.1038/nutd.2014.23.