I've been watching for several years now (I adopted the diet myself in 2010), and all of the negative critiques tend to fall into (a) critiques from non-experts, (b) critiques from experts in unrelated fields, (c) health experts who agree that his recommendations have merit, but that they're impractical for the general public to follow.
I produce for you a book written by a relevant expert with ~2.5 times as many references as The China Study (2034 vs 758) who advocates eating an ancestral diet (lean unprocessed meat/fish, fruit, nuts, vegetables/root vegatables) (1). A list of individuals with relevant graduate degrees who more-or-less agree with him can be found in this list of speakers at a paleo conference he spoke at. His recommendations are at least as similar to the recommendations the Mayo clinic returned for me as Campbell's.
That is, I can make a symmetrical argument for a significantly different diet (2), complete with experts and evidence and stuff.
So, to address your questions directly: you should believe that nutrition is a young and complex field, and therefore shouldn't have everything all figured out; my take is that you may do well to replace grains with root vegetables, since that's something everyone agrees is good (plus they're really tasty!); this isn't good enough to inform your dietary choices because I just used a symmetrical argument for a diet that has nonnegligible discrepancies with the diet Campbell recommends; and I don't know how to dig out a signal that experts, to my knowledge, haven't managed to dig out without becoming an expert.
(FWIW, I spent about 5 years as a vegetarian, followed by 1.5 years doing the paleo thing, and now subsist entirely off DIY soylent, which combines the virtues of deriving all its protein from animal sources and being processed.)
(1) Interestingly, Campbell's and Lindeberg's diets can be eaten simultaneously, and this intersection is 100% in-line with what the Mayo clinic recommended me. The difference is that Campbell allows grains and beans, and Lindeberg allows (unprocessed) lean meats, fish, and eggs.
(2) Again, there's substantial overlap, but also substantial disagreement: Lindeberg, for instance, observe the Inuit derive something like 98% of their calories from animal sources and are virtually untouched by Western disease, and concludes that very high consumption of (unprocessed) animals is perfectly fine, whereas Campbell claims that humans should eat minimal amounts of animal.
Separate topic!
(FWIW, I spent about 5 years as a vegetarian, followed by 1.5 years doing the paleo thing, and now subsist entirely off DIY soylent, which combines the virtues of deriving all its protein from animal sources and being processed.)
What I find alarming about soylent-like diets is the idea that you can completely capture human nutritional needs as a table of micronutrients quantities to fill, and then go out and source those individual micronutrients, combine them, and drink.
Aren't you discounting the importance of the configuration of these...
There's a book called The China Study. It's written by the "Professor Emeritus of Nutritional Biochemistry at Cornell University, and his son Thomas M. Campbell II, a physician". Based on what I know about the words "professor" and "emeritus" and "cornell", I assume this is written by an authority in the field of nutrition.
When it was published in 2005 it recommended clearly crazy stuff: by minimizing or eliminating the consumption of animal based foods as well as refined/processed foods (e.g. adopt a "whole food plant-based diet"), you could greatly reduce your risk of diseases of affluence like heart disease, diabetes, some cancers, etc. The book follows his 60+ year career through cancer experiments on animals, conducting a pretty large epidemiological study (the China-Cornell-Oxford study), and then discusses some important clinical trials that support his recommendations. He also surveys some nutrition literature that corroborates his research.
Some other experts vocally support him; further, his recommendations don't seem to be a radical departure from either public health recommendations or prior research in the field. The FDA MyPlate, and also the UK's health initiatives ("5 fruits/vegetables a day"), as well as the Harvard School of Public Health's recommendations and others all seem to be moving in his general direction, although seemingly filtered by politics (e.g. telling Americans to stop eating meat entirely seems like political suicide, so baby steps in the direction seem more expedient; but I'm conjecturing this).
The book is widely dismissed as vegan propaganda, but the author says he's not advocating a vegan diet and in fact criticizes vegan diets as only minimally healthier than the "standard American diet". He also conducted experiments which subjected animals to carcinogens, which is not a very vegan thing to do. He does not admit to being vegan. He even observes that the evidence says restricting animal based calories to under 10% of total calories offers almost all of the health benefits as restricting them to 0%, but says as a practical matter this is much harder to stick to (e.g. you may only eat a 3mm slice of chocolate cake is much harder than simply saying no to chocolate cake). He also admits he had a bias when he entered the field of nutrition, but a bias in favor of attempting to justify the use of dairy to cure malnutrition (he came from a family of dairy farmers). He said when he discovered that his research did not support his dairy bias he abandoned his dairy bias (and would later shut down his diary farm).
Anyway, the China Study is widely criticized, but not by people in his field? I've been watching for several years now (I adopted the diet myself in 2010), and all of the negative critiques tend to fall into (a) critiques from non-experts, (b) critiques from experts in unrelated fields, (c) health experts who agree that his recommendations have merit, but that they're impractical for the general public to follow.
(C is worthwhile, but this is a problem for public health authorities to worry about. I'm much more interested in what any sufficiently motivated individual can elect to do to maximize their health)
So, this is the part that I find most surprising. There are lots of people who are PhDs of exercise, anthropology, or economics who criticize his recommendations, but I have a hard time finding a mass gathering of nutrition scientists coming out of the woodwork to shoot down his recommendations.
What should I believe? Here are things I've considered.
1. Science is crap. Don't believe expert predictions about the natural world.
2. No no, just nutrition science is crap. Don't believe any expert predictions about nutrition.
3. Nutrition science isn't crap, but the Campbells are rogue and the community of nutrition scientists have better things to do than debunk pop culture books.
4. Nutrition scientists **are** criticizing him in droves, I just don't come across them because I have confirmation bias blinders on.
5. "Nutrition scientist" is a made up discipline, and I've been tricked!
I'm more or less at a loss on how to make progress on these points. Am I missing something crucial?
What's the LW take on this? Why isn't this good enough to inform your dietary choices? Assuming you don't plan to become an expert in the field of nutrition yourself, what's a better way to inform your dietary choices?
EDIT: I would just like to thank everyone who responded. I've tried to discuss this in many forums, both IRL and on the internet and it's almost always a disaster unlike here on LW. Your measured, insightful responses are an enormous relief. You've given me a lot of food (ha!) for thought.