August 6, 2014

expert reaction to fatty acids and type 2 diabetes risk

A large study in The Lancet reported that saturated fatty acids can be associated with both an increased and decreased risk of developing type 2 diabetes, depending on the type of fatty acids present in the blood.

Prof Keith Frayn, Emeritus Professor of Human Metabolism, University of Oxford, said:

“This paper, based on a very large sample, provides robust evidence of associations between particular saturated fatty acids in the plasma and risk of developing type 2 diabetes.  However, as the authors themselves point out, levels of most saturated fatty acids in plasma (even when measured in a specific fraction such as phospholipids) are not a close reflection of dietary intake – the saturated fatty acids measured in this study are in the bloodstream and not in the diet.

“In the case of the ‘odd-numbered’ fatty acids (with 15 and 17 carbons), which are not synthesised in the human body, they may be a better indicator of dairy fat consumption.  Higher levels of these particular fatty acids have long been known to be protective against heart attack, and here the authors show protection against diabetes development.  But these results do not say that it would therefore be beneficial to ingest these particular fatty acids: it is quite possible, indeed probable, that these are simply markers of a particular dietary pattern that may involve other factors protecting against diabetes.”

Prof Tom Sanders, Head of Diabetes and Nutritional Sciences Division, School of Medicine, King’s College London, said:

“Generally, the size effects of these fatty acid on risk of type 2 diabetes is miniscule compared to the effects associated with being overweight.  This is an observational study, not a trial of modification of diet. However, the findings are in line with some other reports that suggest the consumption of dairy products is associated with a lower risk of type 2 diabetes.

“The odd-chain saturated fatty acids, which were found to be associated with a lower risk of type 2 diabetes, are made by microorganisms from substrates such as propionic acid, which arise during fermentation of carbohydrates.  Fat (including milk products) from ruminant animals (cows, sheep, goats) is not the only source of these branched chain fatty acids – the other major source of odd-chain fatty acids is fish, where they accumulate from algae in the food chain. Genetic factors may also play a role in determining the levels of branched chain fatty acids in blood.

“The levels of even-chain fatty acids such as lauric (12:0), myristic (14:0), palmitic (16:0) and stearic acid (18:0) in phospholipids are a poor reflection of dietary saturated fatty acid intake, as the authors acknowledge. We have shown minimal change in the levels of these fatty acids in blood when the dietary intake of saturated fatty acids is lowered in randomized controlled trials (Am J Clin Nutr September 2013 98: 677-683; doi:10.3945/ajcn.113.063644). However, higher levels of even-chain saturated fatty acids occur when intakes of polyunsaturated fatty acids are low, because the body compensates to replace polyunsaturated fatty acids, which cannot be made in the body, with saturated and monounsaturated fatty acids.”

‘Differences in the prospective association between individual plasma phospholipid saturated fatty acids and incident type 2 diabetes – EPIC-InterAct study’ by Nita Forouhi et al. published in the Lancet Diabetes & Endocrinology on Wednesday 6 August 2014.

Declared interests

Prof Keith Frayn has no conflict of interest with the findings of the paper nor with its authors.  He is a scientist working the area of fat metabolism and author of ‘Lipid Biochemistry: an Introduction’ (edn 5, Blackwell Science) and Metabolic Regulation: a Human Perspective’ (edn 3, Wiley).