Better & Bolder the Blog

the only thing to say about nutrition

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What should be intuitive and easy – feeding ourselves well – has become complicated. Should you go low carb or high fat? Try intermittent fasting? Is there a best diet?

What does the science say about each of those things?

Science can’t find its own ass with both hands when it comes to nutrition.

The problem is less about corporate influence, though that gets in the way, too, than it is about the limits of current research. The effects of what we eat are often long-term, influenced by many factors. What I eat today reacts differently than eating the same thing last year: I’m older, maybe my stress level is higher or lower, maybe I’m exercising more or less, maybe I’ve moved to a new location or work in a new environment. And so on.

This JAMA Network article explores the disagreements over a 2019 publication of “several studies showing that the evidence linking red meat consumption with cardiovascular disease and cancer is too weak to recommend that adults eat less of it.”  This New York Times article by Aaron E. Carroll examines the same controversy.

Nutritional studies cannot include randomized trials. We can’t, for instance, feed 1000 toddlers high levels of meat, continue for 50 years, and then compare them to a group of low meat eaters. We can’t control everything else they eat or how often they exercise or get out into the sun. “Because of that,” Carroll reports, “we must rely on observational data; we ask people what they are eating and correlate that with outcomes.”

Observational studies have limitations. According to Carroll, “It’s hard to see big differences in death, cancer and heart attacks in even large groups of people, unless you follow them over long periods. But quantifying what people are eating over long periods is challenging, too, because often people don’t remember. Such studies are also difficult to interpret because of what are called confounding factors. Maybe people who eat more meat are poorer. Maybe they smoke, drink too much alcohol or don’t exercise. Those things would also lead to bad outcomes, and it’s hard to tease out individual components over time.”

The practical outcome of this is that we might get some useful information from these studies, but we must be very aware of the limitations of these studies. In the end, what’s good for one group may not be good for any one individual.

I could line up 100 studies showing too much meat is not good for us, and someone else lines up another 100 studies showing meat is fine. The point of the researchers who said there isn’t enough data to say we shouldn’t eat meat is sound: there isn’t enough evidence. That doesn’t mean high quantities of meat are good for us or not harmful, just that there isn’t enough data to say either way.

We all in the end need to be our own experiment of N = 1.  How do I feel when I eat more or less meat? What happens to my cholesterol and blood sugar numbers? Does my energy levels or sleep change? This may need to be tracked over months or years. I’m still figuring this out for myself. I’m certain — 100% positive — that whatever I figure out for myself is not something that will then be sure to work for others.