Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Original Communication
  • Published:

Some problems with Cochrane reviews of diet and chronic disease

Abstract

The sum of evidence-based nutrition has to be more than a Cochrane-type meta-analysis of randomised controlled trials (RCTs). Most of the evidence base in nutrition is observational, especially cohort studies. RCTs of diet change through to disease outcome are uncommon and the change has usually been addition or removal of only a single food component. Trials with whole diets through to disease outcome are rare and dietary changes made by individuals are unlikely to be an exact copy of the prescription. It is hard to even imagine a trial in which half (randomised) of a large group of middle-aged people agree to avoid vegetables for 5 y and be followed up to see who will develop cancer. Most of the USA's health claims, permitted by the Food and Drug Administration, are not supported by RCTs. But where controlled trials of nutritional change and disease outcome have been achieved, they must be reviewed very carefully. Two Cochrane reviews on diet and cardiovascular disease (CVD), published in the widely read British Medical Journal (BMJ), were criticised after their publication and the conclusions have not been subsequently adopted by expert committees. The first of these reviews was ‘Dietary fat and prevention of CVD: a systematic review’. The second was ‘Systematic review of long term effects of advice to reduce dietary salt in adults’. A critique of these two Cochrane reviews is presented here as a contribution to our discussion of the potential of Cochrane methodology to the reliability of knowledge about diet and disease.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

References

  • Beard TC (2004): Salt Matters, A Consumer Guide pp 203–204. Melbourne: Lothian Books.

    Google Scholar 

  • Gillman MW, Cupples A, Millen BE, Ellison RC & Wolf PA (1997): Inverse association of dietary fat with development of ischaemic stroke in men. JAMA 278, 2145–2150.

    Article  CAS  Google Scholar 

  • Hooper L, Bartlett C, Davey Smith G & Ebrahim S (2002): Systemic review of long term effects of advice to reduce dietary salt in adults. Br. Med. J. 325, 628–632.

    Article  Google Scholar 

  • Hooper L, Summerbell CD, Higgins JPT, Thompson RL, Capps NE, Davey Smith G, Reimersma RA & Ebrahim S (2001): Dietary fat intake and prevention of cardiovascular disease: systematic review. Br. Med. J. 322, 757–763.

    Article  CAS  Google Scholar 

  • Hu FB, Sacks F & Willett WC (2001): Patient compliance should have been considered (letter). Br. Med. J. 323, 1001.

    CAS  Google Scholar 

  • Joint WHO/FAO Expert Consultation (2003): Diet, Nutrition and the Prevention of Chronic Diseases. WHO Technical Report Series 916. Geneva: WHO.

  • Keys A, Aravanis C, van Buchem FSP, Blackburn H, Buzina R, Djordjevic BS, Fidanza F, Karvonen MJ, Kimura MJ, Menotti A, Nedeljkovic S, Puddu V & Taylor HL (1981): The diet and all causes death rate in the Seven Countries Study. Lancet 2, 58–61.

    Google Scholar 

  • Law MR & Wald NJ (2003): Salt needs to be reduced in manufacturing and processed food. Br. Med. J. 326, 223.

    Google Scholar 

  • MacGregor GA & He FJ (2003): Front cover was highly misleading. Br. Med. J. 326, 222–223.

    Article  Google Scholar 

  • Mann J, Skeaff M & Truswell S (2001): Conclusion may have been underplayed (letter). Br. Med. J. 323, 1000–1001.

    Article  CAS  Google Scholar 

  • Miettinen M, Turpeinen O, Karvonen MJ, Pekkarinen M, Paavilainen E & Elosuo R (1983): Dietary prevention of coronary heart disease in women: the Finnish Mental Hospital Study. Int. J. Epidemiol. 12, 17–25.

    Article  CAS  Google Scholar 

  • National Health & Medical Research Council (1984): Report of the Working Party on Sodium in the Australian Diet. Canberra: Australian Government Publishing Service.

  • Perry IJ (2003): Critical faculties should always be exercised. Br. Med. J. 326, 223.

    Google Scholar 

  • Reddy WS & Katan MB (2004): Diet, nutrition and the prevention of hypertension and cardiovascular diseases. In Special Issue: Diet, Nutrition and the Prevention of Chronic Diseases: Scientific Background Papers of the Joint WHO/FAO Expert Consultation (Geneva, 28 Jan–1 Feb 2002) Public Health Nutr. 7, 167–186.

    Google Scholar 

  • Rose GA, Thomson WB & Williams RT (1965): Corn oil treatment of ischaemic heart disease. Br. Med. J. 1, 1531–1533.

    Article  CAS  Google Scholar 

  • Scientific Advisory Committee on Nutrition (2003): Salt and Health. London: The Stationery Office.

  • The National Diet–Heart Study (1968): Final report. Circulation 37 and 38 (Suppl 1), 1–428.

  • Truswell AS (1994): Review of dietary intervention studies: effect on coronary events and total mortality. Aust. N.Z. J. Med. 24, 98–106.

    Article  CAS  Google Scholar 

  • Truswell AS (2001a): Levels and kinds of evidence for nutritional science: a workshop report. Food Aust. 53, 272–276.

    Google Scholar 

  • Truswell AS (2001b): Levels and kinds of evidence for public health nutrition. Lancet 357, 1061–1062.

    Article  CAS  Google Scholar 

  • Truswell AS (2002): Evidence-based nutrition. Nutr. Diet. 59, 7–8.

    Google Scholar 

  • Truswell AS (2003): Limit saturated fat and moderate total fat intake. In National Health and Medical Research Council. Dietary Guidelines for Australian Adults pp 107–132. Canberra: Commonwealth Department of Health.

    Google Scholar 

  • Turpeinen O, Karvonen MJ, Pekkarinen M, Miettinen M, Elosuo R & Paavilainen E (1979): Dietary prevention of coronary heart disease: the Finnish Mental Hospital Study. Int. J. Epidemiol. 8, 99–117.

    Article  CAS  Google Scholar 

  • Watts GF, Lewis B, Brunt JN, Lewis ES, Coltart DJ, Smith LDR, Mann JI & Swan AV (1992): Effects on coronary artery disease of lipid-lowering diet, or diet plus cholestyramine, in the St. Thomas' Atherosclerosis Regression Study (STARS). Lancet 339, 563–569.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to A S Truswell.

Additional information

I have no sponsorship or conflict of interest in connection with this publication.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Truswell, A. Some problems with Cochrane reviews of diet and chronic disease. Eur J Clin Nutr 59 (Suppl 1), S150–S154 (2005). https://doi.org/10.1038/sj.ejcn.1602189

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/sj.ejcn.1602189

Keywords

This article is cited by

Search

Quick links