Weekly Blog

Oct 23

If you're a fan of steak, you've probably felt alienated by recent trends in health advice. Headlines, ranging from links to chronic disease to harsh environmental impacts of industrial-scale beef production, have generally trended negative. And while our goal in this blog is to stick to the facts, we know dietary dogma is often emotionally charged, so we'll try to steer clear (not a cow pun).

Of course, those who look beneath the surface tend to find the topic of red meat consumption a bit more nuanced. Those in favor point to a reasonably solid evolutionary case: higher fat and protein concentrations almost definitely played an important role in fueling our species' rise to the most dominant position in the food chain - so it can't be inherently bad. On the other hand, those opposed argue that times were quite different "back then". Our predecessors were required to MOVE (a lot) just to stay alive, succeeding for less than 40 years on average - which suggests that our diets should likely also modernize to match the very different risk picture we currently face. The new, modern challenge is staying healthy enough to actually enjoy the extra +/- 30 years of life gained through public health and medical progress since the early 1900s - something that most current research suggests conflicts with a diet heavy in red meat. At some level, both groups are probably right. However, we are still learning exactly why.

In June of this year, a team from UC San Diego summarized the role of red meat in human evolution in the Quarterly Review of Biology, asking if it was both a blessing and a curse in a publication that has wrestled with broad topics in the biological sciences since 1926. It still took 40 pages. To summarize further, there are 5 key points worth knowing. The first four were not surprising based on what we've blogged about in prior months and years:

1. Ancestral diets included meat but were way different: Dining on mass-produced steaks and burgers today - accessible almost anytime, anywhere, with very little exertion required - is a wildly different experience than hunting with irregular success and eating organs, fat, and marrow (in addition to muscle tissue).

2. Dosage Matters: There may be a consumption threshold. Swapping even a single serving for plant-based protein (nuts, seeds, beans, etc.) lowers the risk of premature death from major diseases we face by as much as one-third, including heart disease, diabetes, and colorectal cancer. According to this model, lowering consumption by 30% from current averages would save hundreds of thousands of lives globally each year. 

3. Heme Iron is double-edged: Dosage matters here too. While low doses likely protected early humans from anemia, too much of a good thing becomes a bad thing - in this case, becoming a source of free radicals that damage DNA and increase cancer risk.

4. A heavy ecological burden: Whether through deforestation, greenhouse gas and fresh-water contamination, or the risk of "super-bugs" associated with routine antibiotic use in high-density facilities, the trade-offs required to produce the 12 million tons of beef supplied in the US (and 77 million tons globally) may outweigh the reward.

However, the 5th key point was new to me - something I had not previously heard or understood: part of the reason red meat consumption may increase health risk relates to a genetic change. Approximately 2 million years ago, our ancestors stopped producing a cellular molecule called Neu5Gc, and sometime after that our immune systems began recognizing it as foreign, producing antibodies against it. Animals, however, did not experience this same genetic mutation, so when we consume red meat, we have a low-grade inflammatory reaction (called "serum sickness" when first described about 125 years ago), similar to what we might expect when exposed to the common cold. Consuming it regularly - say, several times per week or even multiple times per day - triggers chronic inflammation, which promotes plaque and tumor growth and has been linked with cognitive decline. Then, a few months later at the annual conference of the European Association for the Study of Diabetes, a massive review of dietary and medical records of nearly 90,000 people further linked Neu5Gc to type 2 diabetes.

As described in a press release here and in preliminary findings here, even after statistically scrubbing other known risks like physical activity, overall diet, smoking status, and other health conditions, the highest consumers of red meat (and thus the highest exposure to Neu5Gc) had a staggering 41-63% greater risk of developing diabetes during the 7.2-year follow-up period than those in the lowest consuming group, while those in the middle had a much more modest risk increase (+10%) - lending strong support to the theory of an inflammatory threshold. On the other hand, this is still only an observational analysis which cannot reliably point to a cause, so more study is needed to confirm the findings.

The bottom line here is that if you're a high consumer of red meat (1 or more daily servings), it may be time to consider shifting a few per week from food for FUEL to food for thought. 

Have a great weekend,

Mike E.