Is Meat Unhealthy?
Does eating red meat decrease your lifespan? This is a discussion that has been going on for years, with vegetarians and vegans stating that meat is not only bad because of the cruelty to animals, but it will decrease your life. There have been a number of studies looking at this, and the results vary, but this week a new study showed -
After correction for measurement error, red meat intake was no longer associated with mortality, and there was no association with the consumption of poultry.
While this is good news to the lovers of red meat – those who love bacon had different news:
The results of our analyses suggest that men and women with a high consumption of processed meat are at increased risk of early death, in particular due to cardiovascular diseases but also to cancer. In this population, reduction of processed meat consumption to less than 20 g/day would prevent more than 3% of all deaths.
You have to wonder about a publication with editors that would let that statement slip. Imagine if we could prevent any death – but I suspect all members of that study will die. Besides the grammar, the real issue of the processed meat portion is the variable of smoking.
We cannot exclude residual confounding, in particular due to incomplete adjustment for active and passive smoking. The sub-group analysis for processed meat showed heterogeneity according to smoking, with significant associations only in former and current smokers and no significant associations in never smokers, which is compatible with residual confounding by smoking.
This is explained further in the article with these statistics:
There was also a statistically significant interaction between smoking and processed meat consumption (P-interaction 0.01), with mortality being significantly increased among former (HR = 1.68, 95% CI 1.29 to 2.18) and current smokers (HR = 1.47, 95% CI 1.18 to 1.83), but there was no association among never smokers (HR = 1.24, 95% CI 0.89 to 1.72).
Since the relative risk of smoking is 20, and the relative risk of this was 1.14 one must assume that smoking is bad for your health. So it may be the person’s smoked lungs rather than the smoked pork. Although clearly smoking was bad for the pig.
Increasing vegetables and fruits in the diet was almost a protective factor:
Those with a lower fruit and vegetable intake (below median intake) had a higher overall mortality in the highest consumption category of processed meat (160+ g/day) as compared to subjects with a fruit and vegetable intake above the median intake (P-interaction 0.001).
But the study was in contrast to the US study:
However, in contrast to the US cohorts , there was no statistically significant association of red meat consumption with risk of cancer or cardiovascular mortality. (see ref 7 and 8 below)
The problem with the US studies has more to do with the basis of their data gathering than anything else. We blogged about the topic of red meat related to mortality last year. The basis of those studies is this: a bunch of people are given a questionnaire about what they eat. They fill it out. Depending on the study, their health is followed for a number of years, and using statistical analysis determination is made about what factors influence their health.
Human beings are not hardwired to remember what they ate a year ago, even a week ago. The flaws in this type of study are the data gathering, expecting people to remember what they ate over the last year.
The European study avoided this by having clinics that did more measuring and in depth analysis, and their data has less flaws than the US Data, but still, the basis is sketchy.
All Meat is not the Same
The other missing piece is this: meat is processed differently by different places, and the meat is handled differently. Animals that are raised on grass have higher levels of Omega-3 fatty acids, where animals raised on grains have higher levels of Omega-6 fatty acids. If you process your meats in Italy, there is a different production than in Northern Germany, which is different than in Iowa – some being more prone to harsh chemicals that may (or may not) linger.
Vegetarians v Vegans
One study that looked at all groups- it turns out that Vegans and meat eaters live to be about the same age, those that have the best survival advantage were fish eaters. In fact, occasional meat eaters have a longer lifespan than vegans.
1. Meat consumption and mortality – results from the European Prospective Investigation into Cancer and Nutrition. Rohormann S, et. al. BMC Medicine 2013, 11:63
2.Food-Based Validation of a Dietary Questionnaire: The Effects of Week-to-Week Variation in Food Consumption. Salvini S, HunterDJ, Sampson L, et al:. International Journal of Epidemiology 18:858-867, 1989
3. Reproducibility and validity of dietary patterns assessed with a food-frequency questionnaireHu FB, Rimm E, Smith-Warner SA, et al:. The American journal of clinical nutrition 69:243-249, 1999
4. Lack of efficacy of a food-frequency questionnaire in assessing dietary macronutrient intakes in subjects consuming diets of known composition.Schaefer EJ, Augustin JL, Schaefer MM, et al: The American journal of clinical nutrition 71:746-751, 2000
5. Bias in dietary-report instruments and its implications for nutritional epidemiology.Kipnis V, Midthune D, Freedman L, et al: Public Health Nutrition 5:915-923, 2002
6.Red meat consumption and mortality: results from 2 prospective cohort studies. Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, Willett WC, Hu FB: Arch Intern Med 2012
7.Meat intake and mortality: a prospective study of over half a million people.Sinha R, Cross AJ, Graubard BI, Leitzmann MF, Schatzkin AArch Intern Med 2009, 169:562-571.
8. Is It Time to Abandon the Food Frequency Questionnaire? Kristal AR, Peters U, Potter JD: Cancer Epidemiology Biomarkers & Prevention 14:2826-2828, 2005
9.Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies. Key, T., et. al. Am J. Clin. Nutr March 2013, 97 (3)