Risks of a high-protein diet outweigh the benefits

Sir

Alastair Robertson of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) says that the CSIRO's high-protein Total Wellbeing diet is “based on peer-reviewed science within robust experimental frameworks” (“Diet's healthy blend of science and practicality“ Nature 439, 912; 200610.1038/439912c). These small studies reported no significant difference in weight loss between a high-protein meat-based diet and a control diet with lower protein content. The exception was a small sub-group of women with high triglyceride levels, who lost more weight over 12 weeks with a high-protein diet.

Longer-term trials of high-protein diets are more controversial, but some studies by the CSIRO and others show that such results do not last, and that weight loss and sustainability are not superior to diets that focus on a reduction in fat and overall energy intake (see G. D. Brinkworth et al. Int. J. Obes. 28, 661–670; 2004). Robertson's claim that the Total Wellbeing diet can “contribute to reducing obesity in Australia” is hype, not science. The diet is not a more viable option than current dietary recommendations.

Recent cohort and laboratory studies (T. Norat et al. J. Natl Cancer Inst. 97, 906–916; 2005, and M. H. Lewin et al. Cancer Res. 66, 1859–1865; 2006) also highlight the potential increased risk of colorectal cancer with a high intake of red and processed meat — both prominent in the CSIRO diet. Add the high financial and ecological costs of diets high in meat, and they are not justified in the absence of any superior weight-loss benefit.