According to the NOVA classification system, the phrase ‘ultra-processed foods’ encompasses a wide range of foods and beverages, including (but not limited to): carbonated soft drinks; sweet or savoury packaged snacks (e.g., corn chips, potato crisps, etc…); ice cream, chocolate, candies (confectionery); mass-produced packaged breads, buns, cookies (biscuits), pastries, cakes and cake mixes; breakfast ‘cereals’, ‘cereal’ and ‘energy’ bars; margarines and spreads; processed cheese; ‘energy’ drinks; sugared milk drinks, sugared ‘fruit’ yoghurts and ‘fruit’ drinks; sugared cocoa drinks; meat and chicken extracts and ‘instant’ sauces; and many ready-to-heat products including pre-prepared pies and pasta and pizza dishes; poultry and fish ‘nuggets’ and ‘sticks’; sausages, burgers, hot dogs and other reconstituted meat products; and powdered and packaged ‘instant’ soups, noodles and desserts.
GI, GL and risk of type 2 diabetes
Regular readers of GI News will recognise that many of these foods and beverages contain refined carbohydrates (i.e., maltodextrins, starches and sugars) and are either high in glycemic index (GI) and/or glycemic load (GL). They will also know that there is a large body of compelling evidence that dietary patterns high in glycemic index and load increase the risk of developing type 2 diabetes by up to 89%.
‘ultra-processed foods’ and risk of type 2 diabetes
A recent systematic review and meta-analysis by Delpino and colleagues investigated the association between the consumption of ‘ultra-processed foods’ and the risk of developing type 2 diabetes in adults. Overall, it included 18 prospective cohort studies with nearly 1.1 million participants living in China, Europe, Japan, South Korea and the USA. Despite using the umbrella term ‘ultra-processed foods’, most of the included studies only looked at the consumption of processed meats including bacon, bologna, Chinese sausage, chorizo, corned beef, ham, hot dogs, salami, salted meat/preserved meat, sausage, smoked meat/bacon, Spam, Vienna sausages or Wiener sausage, however. Despite this major limitation, the authors concluded that compared with non-consumption, moderate intake of ‘ultra-processed food’ increased the risk of type 2 diabetes by 12%, whereas high intake increased the risk by 31%.
It’s important to note that the association between excessive consumption of processed meats and risk of type 2 diabetes has long been recognised, with high intakes increasing the risk by 41%.
It’s also important to note that of the 18 prospective cohort studies included in the Delpino and colleagues systematic review, only 3 actually used the NOVA classification system. These 3 studies included 146,497 people, with all of them living in Europe. There were no significant association for moderate intakes of ‘ultra-processed foods’ in the 3 included studies. However, for high intakes (the highest tertile or quartile for the study population), the risk of diabetes increased by 48% (Note: results from 2 studies, only). Unfortunately, none of the studies adjusted for dietary GI or GL, suggesting that the results may be significantly confounded by these important risk factors (amongst others).
Given the focus on processed meats in the overall analysis, and lack of adjustment for GI and/or GL in the studies that used the NOVA classification system, it is difficult to conclude that ‘ultra-processed foods’ increase the risk of developing type 2 diabetes based on the current evidence.
- Livesey and colleagues. Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: Assessment of Causal Relations. Nutrients. 2019.
- Delpino and colleagues. Ultra-processed food and risk of type 2 diabetes: a systematic review and meta-analysis of longitudinal studies. Int J Epidemiol. 2021
- Aune and colleagues. Meat consumption and the risk of type 2 diabetes: a systematic review and meta-analysis of cohort studies. Diabetologia. 2009
Dr Alan Barclay, PhD, is a consultant dietitian and chef with a particular interest in carbohydrates and diabetes. He is author of Reversing Diabetes (Murdoch Books), and co-author of 40 scientific publications, The Good Carbs Cookbook (Murdoch Books), Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment Publishing).