An Issue of BMJ with Multiple Studies on Diet

This News Blog often contains information about diet and health. For example, we have cited evidence that salt is enemy number one [1]; trans-fats are unremittingly bad news [2]; and large amounts of sugar are harmful.[3] After that the risks become really rather small – relative risks of about 20%. Fruit, and more especially vegetables, are good news. Milk is an unhealthy drink in adults (never intended for that purpose and galactose is harmful, unless removed during a fermentation process).[4] Three further studies of diet were included in a single recent issue of the BMJ.[5-7]

The first study by Etemadi, et al. looked at meat consumption in a large cohort of people (n= 536,969) who gave detailed dietary histories.[5] The evidence corroborates other studies in showing that red meat is harmful, increasing relative risk of death by about 20% in high meat eaters compared to moderate meat eaters. The difference is greater if the comparison is made with people who obtain almost all of their meat in the form of fish and chicken. The causes of death that showed greatest increases in risk with high red meat consumption were cancer, respiratory disease and liver disease. Surprisingly, perhaps, increased risk from stroke was nugatory. The increased risk in unprocessed meat is probably related to haem iron, and in processed meat to nitrates/nitrites – there are all pro-oxidant chemicals. Of course this is an association study, so some uncertainty remains. The main problem with meat, as the BMJ Editor points out,[8] is the harmful environmental effects; apparently animal husbandry contributes more to global warming than burning fossil fuels. I take the environmental effects seriously – perhaps we will one day vilify meat farmers more vociferously than we currently vilify tobacco farmers. After all, individuals don’t have to smoke, but cannot protect themselves from the harmful effects of pollution.

Meanwhile, for those who are interested, the other two relevant articles in this issue of the BMJ looked at avoiding gluten in people who do not have celiac disease (no benefit and evidence points towards harm),[6] and the beneficial effect of a low salt and fat diet on gout.[7]

— Richard Lilford, CLAHRC WM Director

References:

  1. Lilford RJ. Effects of Salt in Diet. NIHR CLAHRC West Midlands News Blog. 17 October 2014.
  2. Lilford RJ. On Diet Again. NIHR CLAHRC West Midlands News Blog. 23 October 2015.
  3. Lilford RJ. How Much Sugar is Too Much? NIHR CLAHRC West Midlands News Blog. 25 September 2015.
  4. Lilford RJ. Two Provocative Papers on Diet and Health. NIHR CLAHRC West Midlands News Blog. 12 December 2014.
  5. Etemadi A, Sinha R, Ward MH, Graubard BI, Inoue-Choi M, Dawsey SM, Abnet CC. Mortality from different causes associated with meat, heme iron, nitrates, and nitrites in the NIH-AARP Diet and Health Study: population based cohort study. BMJ. 2017; 357: j1957.
  6. Lebwohl B, Cao Y, Zong G, Hu FB, Green PHR, Neugut AI, Rimm EB, Sampson L, Dougherty LW, Giovannucci E, Willett WC, Sun Q, Chan AT. Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ. 2017; 357: j1892.
  7. Rai SK, Fung TT. Lu N, Keller SF, Curhan GC, Choi HK. The Dietary Approaches to Stop Hypertension (DASH) diet, Western diet and risk of gout in men: prospective cohort study. BMJ. 2017; 357: j1794.
  8. Godlee F. Red meat: another inconvenient truth. BMJ. 2017; 357: j2278.
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