CARB QUALITY AND RISK OF METABOLIC SYNDROME

Carbohydrate quality may play a role in the development of metabolic syndrome, according to two recent systematic reviews and meta-analyses of observational studies.

Metabolic syndrome is a cluster of risk factors including:

• High blood pressure
• Raised blood glucose
• High waist circumference (excess weight around the middle)
• Abnormal blood fats, including high triglycerides and low HDL (‘good cholesterol’) levels

A diagnosis of metabolic syndrome is made when someone has at least three of these risk factors, and having the syndrome increases the risk of developing type 2 diabetes and cardiovascular disease (e.g., heart disease and stroke). It is estimated that around 20-25% of the world’s adult population has metabolic syndrome.

Diet and lifestyle changes play an important part in the management of metabolic syndrome, and are the first line of treatment. One aspect of diet that can affect metabolic syndrome risk is carbohydrate intake, and several studies have looked at whether dietary glycemic index (GI) and/or dietary glycemic load (GL) may influence risk.

Earlier this year, a group of researchers from Iran combined the findings from 12 observational studies involving over 36,000 people, looking at the relationship between dietary GI and/or GL and metabolic syndrome. They found a positive association between dietary GI and prevalence of metabolic syndrome. In other words, people with a higher GI diet were more likely to have metabolic syndrome. No association was seen between dietary GL and metabolic syndrome.

An earlier meta-analysis, published last year by a group of Chinese researchers, reported similar findings. This research combined the findings from eight observational studies involving almost 29,000 people. They found that compared to those with the lowest dietary GI, those with the highest dietary GI had a 23% greater chance of having metabolic syndrome. Each 5-point increase in dietary GI increased the risk of metabolic syndrome by 12%. Again, there was no significant association between dietary GL and prevalence of metabolic syndrome.

Both reviews only included observational studies, and most of these were of cross-sectional design. As such, they can only highlight associations and can’t prove that following a low GI or low GL diet will reduce the chances of developing metabolic syndrome, or not. However, together the findings suggest that the type of carbohydrates in the diet may affect the risk of developing metabolic syndrome. As is commonly the case, more research is needed.

Read more:

• Askari M, and colleagues. Glycemic index, but not glycemic load, is associated with an increased risk of metabolic syndrome: Meta-analysis of observational studies. Int J Clin Pract. 2021.
• Zhang JY, and colleagues. The association between glycemic index, glycemic load, and metabolic syndrome: a systematic review and dose-response meta-analysis of observational studies. Eur J Nutr. 2020.

Dr Kate Marsh is an is an Advanced Accredited Practising Dietitian, Credentialled Diabetes Educator and health and medical writer with a particular interest in plant-based eating and the dietary management of diabetes and polycystic ovary syndrome (PCOS).

Contact: Via her website www.drkatemarsh.com.au