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Dietary carbohydrates: role of quality and quantity in chronic disease

18 / 09 / 18

Finding:

Humans have thrived on diets with widely varying carbohydrate content. Carbohydrate quality rather than amount has a major influence on risk for numerous chronic diseases.

Summary:

Influx of rapidly digestible, high GI carbohydrates has contributed to obesity and cardiometabolic disease in developed nations, and traditional starch diets have contributed to rising risk of chronic disease in rapidly urbanising developing countries.

A strong case can be made for high glycemic load (GL) grains, potato products and added sugars (especially in drinks) being causally related to diabetes, cardiovascular, and some cancers, while other vegetables, fruits, legumes and whole grains are protective. However, metabolic effects of total and high GI carbohydrate may vary among individuals, depending on the degree of insulin resistance, glucose intolerance or other inherited or acquired biological predispositions.

Despite new knowledge and areas of broad consensus, many controversies remain.

Carbohydrate controversies

  • Would reduction in total carbohydrate help control body weight in the general populations and susceptible sub groups?
  • What is the role of a low-carbohydrate diet in prevention and treatment of metabolic syndrome and type 2 diabetes, and in management of type 1 diabetes?
  • Does ketosis from severe carbohydrate restriction provide unique metabolic benefits and in what clinical settings would it be advisable?
  • To what level should added (or free) sugars be restricted for optimal health in individuals and in populations?
  • Would substitution of fructose with glucose-based sweeteners provide metabolic benefit or harm?
  • Would substitution of free sugars with poorly digestible sugars, sugar alcohols or artificial sweeteners provide health benefits or harms (eg unexpected effects on microbiome)?
  • Would increased intake of resistant starch provide health benefits?
  • What are the health effects of substituting whole grains with other high carbohydrate (fruits, legumes) or high fat (nus, seeds, avocado) whole plant foods?
  • What are the long-term effects of different types of carbohydrates on population risk of cancer, neurogenerative diseases and cognitive function?
  • Which carbohydrate foods will provide an optimal combination of health benefits, environmental sustainability, cost and public acceptability?

Citation: Ludwig DS, Hu F, Tappy L. Brand-Miller J. Dietary carbohydrates: role of quality and quantity in chronic disease. BMJ 2018; 361: k2340