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Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study

BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e4026 (Published 26 June 2012) Cite this as: BMJ 2012;344:e4026

Re: Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study

Dear editor-in-chief.

I saw this article referred to (but not actually cited) in a 'Mirror' report bought to my attention by a family member this week. The title and conclusions of this paper are misleading and inappropriate in my professional opinion. A 'Low carbohydrate diet of the Atkins' or ketogenic style' is <20g CHO.day-1. The tenth percentile (at the low end of intake) reported in this study was 123+ g.day-1. This is patently not a low CHO diet. Secondly, the assumption (and statement by the authors to the effect) that reduced CHO is meaningfully correlated with increased protein intake is demonstrably incorrect as the correlations between 'low carb / high protein score' and either macro nutrient intake were feeble at best, (r=0.37 for protein and r= -0.30 for CHO). The risk ratio for all CVD (increase per 2 point on the 'low carb / high protein score') were also feeble at best 1.05 (1.02-1.08); amounting to an actual incidence of +4 to 5 per 10,000 woman-years. In real terms given the mean of ~15-years of follow up, this is an increase in ''risk'', (actually an association only with "who knows what" given the correlations reported above) can be calculated as (5/10,000) x (15/10,000) = 0.00000075 per 2-point increase in ''low carb / high protein score''. Why is this not reported in the study with a clear statement that the 'independent variable' is actually a composite of two other poorly related variables; such that the value of this study is basically none whatsoever?

Regards,

B. Kay.
Lecturer in Clinical Physiology
de Montfort University
Leicester LE1 9BH
United Kingdom.

Competing interests: No competing interests

29 January 2015
Bartholomew Kay
Lecturer in Clinical Physiology
de Montoft University
The Gateway, LE1 1BH, Leicester, UK