Of Meat and Mortality – Part 2: NHANES
[This post was updated on April 10, 2013 to reflect further analysis.]
This is Part 2 of the recent studies looking at meat intake and mortality rates (click here for Part 1: EPIC).
The second study comes from the National Health and Nutrition Examination Survey (NHANES) III. NHANES is a nutrition survey that is done every few years in the USA to see how the nation is eating (1). For this arm of the study, about 17,500 people were included, a number dwarfed by the over 448,000 people in the EPIC study reviewed in Part 1.
I was particularly interested in this study because I thought the meat intake categories would be much higher than in EPIC. That is not the case, as the highest red meat intake category was ≥ 45 times per month, which comes to about 1.5 times per day, as compared to about 2 servings per day in EPIC.
In the model that adjusted only for age, sex and ethnicity, high red meat and processed meat consumption was significantly associated with increased total mortality (red meat: 1.57, 1.07–2.30; processed meat: 1.27, 1.06–1.54). However, in the fully adjusted model there were no statistically significant associations for red meat, processed meat, or fish consumption with total mortality.
In the fully adjusted model, they adjusted for smoking, alcohol, physical activity, socioeconomic status, marital status, fruit and vegetables, use of aspirin and ibuprofen, hormone replacement therapy, oral contraceptives, mineral and vitamin supplements, family history of diabetes and high cholesterol, and – get this – body mass index (BMI), history of hypertension, diabetes, and hypercholesterolemia (high cholesterol).
Adjusting for these last few items would remove any association with mortality for meat if meat causes death through increasing BMI, raising blood pressure, increasing diabetes risk, or increasing cholesterol – the very things considered to be how meat would cause an increase in mortality.
But even more odd is that had they run such a model, it might have shown that more red meat decreases mortality. As red meat intake went from ≤ 6 times per month to over 45 times per month, BMI went down in men and women, the percentage with a history of high blood pressure went way down in men and women, the percentage with diabetes went way down in men and slightly up in women, and the percentage with high cholesterol went way down in men and women!
In other words, according to this study, adding red meat an extra 40 times per month lowers cholesterol, blood pressure, BMI, and a man’s chance of getting diabetes.
The lowest category of red meat had a fairly large number of participants (18% for men, 28% for women), whereas eating red meat ≥ 45 times per month had very few (3.3% for men, 1.4% for women). And except for BMI, that lowest category is where there is a high level of those diseases mentioned above.
It seems to me that there must be some sort of reverse causation going on here where the people with those diseases were eating less red meat in response to having those diseases and then dying sooner. It’s interesting to note that the low red meat eaters were not likely to eat more poultry.
This underlines the benefit of starting with a population that is free of disease for a prospective study.
Stay tuned for Part 3!
Reference
1. Kappeler R, Eichholzer M, Rohrmann S. Meat consumption and diet quality and mortality in NHANES III. Eur J Clin Nutr. 2013 Mar 13. | link
April 8th, 2013 at 11:27 am
Always good to repeat Ginny’s point:
http://www.theveganrd.com/2011/08/bad-news-for-red-meat-is-bad-news-for-chickens.html
or
http://bit.ly/13c6ehM
April 8th, 2013 at 11:33 am
I almost put in my article that you would be happy to hear this news about red meat! I’m just analyzing the research to see where it leads. At least 2 more papers to go.
April 8th, 2013 at 12:10 pm
a new study shows a relation between carnitine, gut microflora, and atheroscelerosis. one vegan volunteered to eat a steak for the experiment–vegans apparently do not harbor the bacteria that metabolize carnitine. a fascinating study–check it out if you haven’t already
http://www.nature.com/nm/journal/vaop/ncurrent/full/nm.3145.html
April 8th, 2013 at 2:26 pm
Thanks, Sharky. I’ve been hearing about it for the past two days and read one article and the abstract. I’m skeptical, but will be looking into it further.
April 9th, 2013 at 12:15 am
Jack, it is 45+ servings per *month*.
April 9th, 2013 at 12:24 am
Hmm. Table 1 says times per week, but the text on p. 2 says times per month. And Table 2 says times per month. I guess it was a typo in Table 1 where I was taking this info about BMI, diabetes, etc. I’ll have to correct that tomorrow.
April 9th, 2013 at 9:17 am
My own belief from studying the nutritional epidemiology literature is that the vast majority of these studies are hopelessly confounded by residual confounding variables. Really only randomized data – like PREDIMED – can make any clear distinction between association and causation. People who eat meat differ in countless ways from those who eat less or no meat, and these ways are not statistically adjusted for, because they are not even measured. I am certain meat-eaters even have different driving habits than non-meat eaters, and potentially that could affect road traffic accidents and all cause mortality (I am just providing an example). My guess is they drive bigger cars and are less careful – but who knows? No one measures these things.
There are likely millions of prognostically important differences that don’t get addressed in these studies.