Last month, a striking article in The New York Times led us – and many major media outlets – astray.
The Times' Gina Kolata covered a paper in the journal Nature Medicine, which seemed to explain the statistical links between red meat and cardiovascular disease (CVD) seen in some large epidemiological studies.
It's important to note that most of the epidemiological evidence shows no clear link between fresh, unprocessed red meat and risk of CVD.
And the never-credible notion that the saturated fat and cholesterol in red meat causes CVD has been buried under a mountain of contrary data … with even its most prominent proponents admitting defeat.
The studies that do find a link between red meat and risk of CVD are riven with “confounding” factors … that is, the strong tendency for red-meat-lovers to have risk factors for CVD (drink, smoke, eat little fiber and few fruits or vegetables, and lead sedentary lives).
Trust, but verify
Sadly, this isn't the first time that a study damning red meat relied on selective reporting of the data in the authors' abstract (summary) … or was hyped in major media outlets.
For example, on March 18, we published “Processed Meat May Speed Death
”, which covered a large epidemiological study from Europe (called EPIC), linking diets high in baloney, hot dogs, and company to higher risk of premature death.
After reading the full study, we rejected the authors' conclusions, in “Processed Meats … Really so Risky?
”. As we wrote, we were “too ready to accept the authors' summary [abstract] at face value ...”.
You'll find our detailed rebuttal of that study's conclusions under the heading “EPIC study suffered from tangle of habits”.
The need to make this reversal underscores the readiness of researchers and medical reporters to spin the story told by the data.
Carnitine study doesn't support beef avoidance
This time, a major journal published a study claiming to find a novel reason why red meat could harm cardiovascular health.
As we wrote in “The Real Heart-Attacker in Red Meat?
”, researchers from the famed Cleveland Clinic reported that diets high in carnitine promote the growth of bacteria turn it into a compound called TMAO, which has previously been linked to atherosclerosis.
That part of the study revealed metabolic processes of real interest.
But their conclusion that beef promotes cardiovascular disease (CVD) doesn't stand up to scrutiny. Tthe authors indulged in incomplete reporting of their data … while the press indulged in hype, leading to two unsupported conclusions:
Incredibly, the authors failed to mention that many other foods – including fish and plant foods clearly linked to lower risk of heart disease – have more carnitine and/or TMAO than beef does.
And many studies – including randomized clinical trials – have indicated that carnitine supplements improve outcomes in patients with cardiovascular disease.
But the devil of the carnitine study lies in its details, and a UCONN doctoral candidate in nutrition named Chris Masterjohn analyzed them in great depth, adding data from earlier studies on other foods.
His rebuttal relies on the authors' own data and that of prior TMAO researchers, and is very credible.
After we read it, any conclusion that eating red meat – especially beef – raises heart disease risk via TMAO production vanishes into thin air.
As Masterjohn says, a 1999 study in six human volunteers measured excretion of TMAO after consumption of a handful of supplements and 46 different foods.
By comparison, the new paper in Nature Medicine reported TMAO excretion results for just one food (red meat) fed to two (urine measurement of TMAO) or six volunteers (blood measurement of TMAO).
And a 1983 study found that eight ounces of carnitine-rich foods (like red meat) produced no more TMAO than common fruits and vegetables, while seafood produced big increases in TMAO.
Don't be alarmed by the fact that some seafood causes people to produce more TMAO than beef does.
There's no link between dietary carnitine, TMAO, and CVD … while seafood and its omega-3s have been proven heart healthy by thousands of lab, epidemiological, and clinical studies. In other words, this whole episode seems to have been a “red-meat red-herring”.
Masterjohn C. Does Carnitine From Red Meat Contribute to Heart Disease Through Intestinal Bacterial Metabolism to TMAO? April 10, 2013. Accessed at http://www.westonaprice.org/blogs/cmasterjohn/
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Zeisel SH, Wishnok JS, Blusztajn JK. Formation of methylamines from ingested choline and lecithin. J Pharmacol Exp Ther. 1983 May;225(2):320-4.
Zhang AQ, Mitchell SC, Smith RL. Dietary precursors of trimethylamine in man: a pilot study. Food Chem Toxicol. 1999 May;37(5):515-20.