Tuesday, February 12, 2013

Cherry Picking Data

It seems that some people following low-carbohydrate diets believe that Dr. Michael Greger "cherry picked" the studies he cited in his presentation "Uprooting the Leading Causes of Death."  

Greger cited research showing that a plant-based diet can prevent and reverse cardiovascular disease, cancer, diabetes, dementia, and ten other leading causes of death.  Only if there existed a similar or greater amount and quality of data that a meat-based low carbohydrate diet could prevent and reverse these same diseases, we could justifiably accuse him of "cherry picking" the data.  

Those who accuse Greger of "cherry picking" his research have or want to give the impression that Greger has presented only his personal interpretation of the evidence on human health and diet.  However, the scientific data in favor of a plant-based diet began accumulating more than 100 years ago, and has increased in quantity and quality since then, with the result that all major public health organizations, such as the National Heart, Lung, and Blood Institute, the National Cancer Institute, the American Institute for Cancer Research, the World Cancer Research Fund, the American Heart Association, and the National Academies of Science in all industrialized nations have all recommended a reduced intake of animal flesh, fat, eggs, and dairy products and an increased intake of whole plant foods.  

All of these organizations make these recommendations in favor of eating more plants (carbohydrates) and less animal products (fat and protein) because, so far, we don't have any high quality data supporting the claim that low carbohydrate, flesh-based diets have similar effects to plant-based diets.  On the contrary, the preponderance of evidence, most of it produced by people who have not declared any commitment to animal rights, points in the direction of the conclusion that meat-based low carbohydrate diets promote the major causes of death.  

I think the evidence stacks in favor of eating plants and against eating flesh because, like other primates,  humans have a psychophysiology adapted by natural selection to plant-based diets.  We have specific heritable characteristics naturally selected to improve our ability to acquire, digest, and metabolize plant foods, including sensory (e.g. color vision, sugar taste receptors), locomotive (e.g. plantigrade stance), digestive (e.g. grinding molars, salivary amylase), and metabolic (e.g. ability to convert carotene to retinol, inability to produce ascorbic acid) characteristics.

Further, we have some specific, heritable characteristics which actually make us maladapted to consumption of animal flesh, such as our lack of the uricase enzyme for metabolizing uric acid (a genetic mutation dating to about 13 million years ago) [1], our loss of immunological tolerance for Neu5Gc sialic acid (ingested from animal flesh) about 2.5 to 3.0 million years ago [2], and our stomach's inability to produce adequate acid to destroy pathogens delivered by flesh [3] resulting in the six to eight million annual cases of food-borne infections contracted from eating (mostly cooked) animal products that occur in the U.S. alone.   

If you want to see what "cherry picking" looks like in practice, I suggest that you read Big Fat Fake at Reason.com to learn how the journalist Gary Taubes quoted out of context the words of experts he interviewed, in order to make it look like they endorsed low carbohydrate diets (when they did not) his New York Times article "What If Its All Been a Big Fat Lie?"   RichieFruitbat also briefly discussed this in the following video:

For an in-depth look at some "cherry picked" research, watch the following four videos produced by Plant Positive, wherein he dissects the data in all of the studies that "Diet Doctor" Andreas Eenfeldt, M.D. picked and listed on his website as the best support for his recommendation to eat a low carbohydrate diet.




Healthy Longevity said...

Thanks for this post Don! I believe that the low carbers have to resort to referring to such studies as being cherry picked as they find it too difficult to provide an adequate explanation as to why so many studies produced findings that contradict their claims.

Lighthouse keeper said...

Harriet Hall at science based medicine has just launched a similar criticism of Dr Greger Don. I know plant positive has questioned her judgement in one of his videos, what do you make of her latest piece?

Don said...

Personally, I don't find anyone who associates with Quackwatch credible.

From her article: " Esselstyn studied only a small number of patients who already had heart disease, and he treated them with statin drugs in addition to diet, and their diet included skim milk and low-fat yogurt. " This statement has two things wrong: not all of E's patients used statins, and E excluded dairy products from their diets shortly after starting the study.

She completely ignores the background data E provides as rationale for his approach, with which the NHLBI ATP agreed, specifically, that populations with TC<150 and LDL<70 do not have cardiovascular disease.

Basically, she takes Greger's presentation out of context, the context being the large amount of supportive research he cites in his dozens of videos.

Most important to me, she seems to have no grasp of the evolutionary context of humanity. She appears to believe in what I call the omnivore fallacy: the idea that any animal that we can observe eating flesh has specific biological adaptation to that habit so IS (biologically) an omnivore.

To summarize, I would say she has the logic of a technician who believes only what she learned in school and knows how to keep those beliefs protected from challenging information, much like the highly logical scientists who constructed very logical, evidence-based defenses of geocentric astronomy and vigorously resisted Galileo's heliocentric theory. Thus she really just functions as a defender of outdated dogma.

I won't go further here. This could turn into a full blog post on her credibility and faulty logic masquerading as "science based medicine."

Frank said...

Don said..

''This could turn into a full blog post on her credibility and faulty logic masquerading as "science based medicine."''

I for one sure would like to read that!

Overall, the only thing I agree with her from her article, and this is the reason the other day I wrote that I agree with Charles, is the fact that Dr. Greger tends to overstate the evidence. He sometime talks too much in absolust term, which hurt his scientific credibility. There was a comment section on his website where even his own follower where in disagrement with the conclusion he came at from a published study. He speaks too much in black and white when, as usual, science is always an area of grey.

Don't get me wrong, as you Don I think it's easy to see the whole picture and understand that a plant-based diet is clearly the way to go. I think Harriet is just pointing this very fact and I think it this a valid cristism, hence why I wish he would not do it as critrics of vegan could not use that agaisnt it.

But she come off as having her own bias. She probably eat meats and don't want to give it up. And probably, as most people, equals vegan with new-age weirdos.

I think many authors in the scientific community agree with the fact that one of our earliest ancestor was an herbivor. But we're talking about million of years ago here. Maybe she did not think about going that far.

She also wrote, talking about the various diet approach ''supported'' by science out there

''If the evidence were really so clear-cut in favor of veganism, we wouldn’t have all these differing approaches.''

Seriously? How hard is it to imagine that people can distort science in order to sell a book or an ideology? The science could be perfecly clear (it is, actually) and we still would have people taking advange of layman ignorance into having them believes anything using ''science''.

She also perpetuate the Eskimos myth, that they show it's possible to do well on a meat-based diet. She's in great need to listen to Plant Positive slide on Eskimos.

Overall, I just wish most vegan would be as evidence-based as possible and would not overstate the evidence, as to not hurt the vegan scientific credibility. Plant-positive did a very good job at that, and he's always saying that vegan is not a necessity in itself. This is the kind of discourse that will help it being accepted if the evidences ever turn out to be indeed really clear, which I, personally, am not so sure yet they are. I'm still ovo-lacto with even occasional meat consumption, and i'm not quite yet convince to go fully vegan.

But that a diet should be majorly(as in 85-90%) plant-based is a no brainer. And that meat is overall unhealthy is another one.

Sagar Bansal said...

Pls comment on this:

Lighthouse keeper said...

Thank you for replying at length to my previous comment Don. One noticed Dr Hall seems to grant Gary Taubes a level of credibility on the face of it in this piece . His hypothesis has been taken to task in great detail by Evelyn Kokur at The Carbsane Asylum and in the new Plant Positive material in a science based manner and found to be wanting.
Also the " Here are some comments recently posted by vegans on facebook " section is just fatuous.

Ajit Varsani said...

How is he cherry picking when he clearly states the studies he gets his information from in full? You can go over the studies yourself to check if you really really want to. Somehow I doubt anyone would as it would involve too much work.