I’ve been reading a lot about nutrition lately, as part of my program to age gracefully. I thought I was acquiring information that would help me preserve my good health, and I guess I was. But it turned out my real subject was how scientific blind spots—confirmation bias, foregone conclusions, beliefs that resist reality-testing—obscure the most valuable information. It’s hard to know whom to trust.
I began with a book that was highly touted as earth-shaking, starting with the title: The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss and Long-term Health. T. Colin Campbell’s (the author’s) scientific credentials are pretty impressive: Jacob Gould Schurman Professor Emeritus of Nutritional Biochemistry at Cornell University; the study was a 20-year collaboration with Cornell, Oxford and the Chinese Academy of Preventive Medicine. The book is crammed with detailed, closely footnoted descriptions of research supporting its conclusions, fully blurbed by Nobel laureates and the like.
So what are those conclusions? Dr. Campbell asserts that over-consumption of animal-based protein underlies almost all of the major diseases besetting Americans and others who eat like us. He says that by reducing our intake of animal protein to 5 percent or less of our total protein consumption, by instead following a plant-based diet rich in complex carbohydrates and colorful fruits and vegetables, we will virtually eliminate our susceptibility to cancers and heart ailments most common in the West.
What’s more, his entire story is framed by scientific and health authorities’ suppression of the relevant research and their compliant surrender to meat and dairy lobbies and those they’ve funded to legitimate their claims to dietary superiority. Campbell seems to be one of those characters who moved through life rising easily, and therefore expected to be treated fairly by the scientific establishment. The shock at what he found instead permeates every page.
I was totally convinced. I stocked my pantry with all sorts of whole grains, soy products and the like. I love to cook, so over the nearly three months we’ve tried this, I had great fun retooling all sorts of recipes for a vegan diet. Truly, when it comes to the aesthetics of eating, neither my husband or myself missed a thing.
There’s only one hitch: both of us have gained weight, my husband more than I, but I’ve put on enough to set off alarm bells. So a few weeks ago, we decided to cut our consumption: we must eating too many snacks or something, we reasoned, we must be having too much fun experimenting with new recipes. My husband’s metabolism has always been the type most irritating to the female of the species: if he noticed his belt was getting a little tight, he’d just skip his midnight snack for a few days and any extra poundage would slide right off. Only this time it didn’t. This time, he ate far less than any calculation would say his body needs to maintain, and nothing happened. I needed another book.
Good Calories, Bad Calories caught my eye. It’s written by a well-respected science journalist, Gary Taubes. A lot of it reads more like a textbook than a best-seller, evidently because, like Campbell, Taubes believes that grounding his book in research is the best way to support his theses. Taubes does not set himself up as a diet guru, despite the book’s title—there isn’t a single meal plan or recipe in the 450-page-plus volume. Instead, he painstakingly shows how countless scientific studies have disproved some of the pet theories of the scientific establishment, yet this well-documented countervailing work has had no impact on the certainties asserted by scientific and health authorities—to the contrary, it’s been actively suppressed.
Along the way, Taubes shows how some of the most treasured medical truths of our time have long been proven falsehoods: there isn’t any proven causal relationship between cholesterol and heart disease, for instance; nor has fat consumption been proven to cause breast cancer; nor has fiber been shown to have any preventive effect on colon cancer. Taubes shows how these false ideas were picked up by influential people, how circumstance, ambition and resistance to questioning scientific pieties gave them the ring of truth and a life of their own. Consumption of refined carbohydrates, on the other hand, has been shown to be directly causative of a whole string of diseases that tend to proceed in sequence: diabetes, heart, cancer… And for the same reasons, that information has not been given the attention and research it warrants. The documentation is there, chapter and verse, so before you reply that so many trustworthy authorities have reached the opposite conclusion, check it out.
Taubes’ overall point is that extensive double-blind studies of diet are needed to definitively establish relationships between things like fat, fiber, carbohydrates and disease. In the meantime, his explorations of weight reduction convinced me that my husband and I had put on weight because going vegan radically shifted the balance of carbohydrates in our diet. He cites study after study in which the orthodoxies of calorie reduction are disproven (including some in which animal and human subjects gain weight on less food, as their bodies compensate for changing insulin levels); and numerous studies in which high-protein, high-fat and low-carbohydrate diets resulted in weight loss, regardless of caloric intake.
So, it turns out that following the first book’s advice caused our problem: you see, animal protein is pretty much protein and fat, while all the vegan sources of protein (soy, seitan, legumes, etc.) also contain carbohydrates. Trying to get enough protein entailed a proportion of carbohydrates sufficient to push our bodies into fat-storage mode. So we’re reintroducing animal products for a while to take off the weight, and then, I expect, returning to a dietary regime that incorporates a sustainable proportion of non-animal protein, keeping our carbohydrates relatively low. I don’t expect we’ll be vegan again, and I worry that the life-extension benefits of The China Study will be diminished as a result. (Unfortunely, Taubes’ book didn’t focus on the health impact of animal protein and Campbell’s didn’t focus on excess carbohydrate consumption, so it will have to wait for another book to see if there’s a better way to reconcile the two.) But I feel better now, and that matters a lot.
All the time I was reading these books, here’s what I was thinking: both books’ treated questions that can be answered by close application of the scientific method, fair and rigorous testing over time on a reasonable scale, without any interference by funders or researchers whose agendas might skew the results. Yet in both cases, there was active opposition to the needed research and suppression of studies that hinted at results that could upset the heavily defended consensus. I consider myself an informed consumer of health information, yet if prior to reading either book you had tested me on the basic causes of heart disease, obesity and so on, I would have produced a string of wrong (if widely accepted) answers.
How much more so with conventional assertions about war, poverty, social exclusion, race, education, culture—you name it? In a funny way, these books strengthened my resolve to question orthodoxies and foregone conclusions wherever I find them. The world is full of reminders of the value of keeping one’s mind uncolonized by received opinion, of keeping one’s eyes open so long as we draw breath.