Science Compared Every Diet and the Winner Is Real Food
David Katz
Flailing in the swell of bestselling diet books  infomercials for cleanses  and secret tips in glossy magazines  is the credibility of nutrition science. Watching thoroughly-credentialed medical experts tout the addition or subtraction of one nutrient as deliveranceâonly to change the channel and hear someone equally-thoroughly-credentialed touting the oppositeâit can be tempting to write off nutrition advice altogether. This month we hear something is good  and next we almost expect to hear itâs bad. Why not assume the latest research will all eventually be nullified  and just close our eyes and eat whatever tastes best? That notion is at once relatable and tragic  in that diet is inextricable from the amount of healthy time we spend on Earth. Improvements in diet are clearly associated with significant lengthening of lifespan and dramatic decreases in risk of most chronic diseases. Combining disease and longevity into the concept of healthspan  the number of healthy years of lifeâfundamentally more important but less readily quantifiable than lifespanâthe data in favor of optimizing our diets are even more compelling. No one is arguing that diet is less than extremely important to health and well-being  but seemingly everyone is arguing as to what constitutes the best diet. "A diet of minimally processed foods close to nature  predominantly plants  is decisively associated with health promotion and disease prevention." The voices that carry the farthest over the sea of diet recommendations are those of iconoclastsâthose who promise the most for the least  and do so with certainty. Amid the clamor   Dr. David Katz  is emerging as an iconoclast on the side of reason. At least  thatâs how  he  describes  himself . From  his  throne at Yale University's Prevention Research Center  where  he  is a practicing physician and researcher  said sea of popular diet media is the institution against which  he  rebels. Itâs not that nutrition science is corrupt  just that the empty promises of memetic  of-the-moment diet crazes are themselves junk food. To  Katz   they  are more than annoying and confusing;  they  are dangerous injustice. Scientific publisher Annual Reviews asked  Katz  to compare the medical evidence for and against every mainstream diet.  He  says they came to  him  because of  his  penchant for dispassionate appraisals. "I don't have a dog in the fight "  he  told me. âI donât care which diet is best. I care about the truth."
 Katz  and Yale colleague Stephanie Meller published their findings in the current issue of the journal in a paper titled  "Can We Say What Diet Is Best for Health?" In it  they compare the major diets of the day: Low carb  low fat  low glycemic  Mediterranean  mixed/balanced (DASH)  Paleolithic  vegan  and elements of other diets. Despite the pervasiveness of these diets in culture and media  Katz and Meller write  "There have been no rigorous  long-term studies comparing contenders for best diet laurels using methodology that precludes bias and confounding. For many reasons  such studies are unlikely." They conclude that no diet is clearly best  but there are common elements across eating patterns that are proven to be beneficial to health. "A diet of minimally processed foods close to nature  predominantly plants  is decisively associated with health promotion and disease prevention." Katz  Meller/Annual Reviews Among the salient points of proven health benefits the researchers note  nutritionally-replete plant-based diets are supported by a wide array of favorable health outcomes  including fewer cancers and less heart disease. These diets ideally included not just fruits and vegetables  but whole grains  nuts  and seeds. Katz and Meller found "no decisive evidence" that low-fat diets are better than diets high in healthful fats  like the Mediterranean. Those fats include a lower ratio of omega-6 to omega-3 fatty acids than the typical American diet.
The Mediterranean diet  which is additionally defined by high intake of fiber  moderate alcohol and meat intake  antioxidants  and polyphenols  does have favorable effects on heart disease  cancer risk  obesity  metabolic syndrome  and "is potentially associated with defense against neurodegenerative disease and preservation of cognitive function  reduced inflammation  and defense against asthma." They also found carbohydrate-selective diets to be better than categorically low-carbohydrate diets  in that incorporating whole grains is associated with lower risks for cancers and better control of body weight. Attention to glycemic load and index is "sensible at the least." Eating foods that have high glycemic loads (which  Katz  says is much more relevant to health outcomes than glycemic indexâin that some quality foods like carrots have very high indices  which could be misleading) is associated with greater risk of heart disease. Finally  in a notable blow to some interpretations of the Paleo diet   Katz  and Meller wrote  "if Paleolithic eating is loosely interpreted to mean a diet based mostly on meat  no meaningful interpretation of health effects is possible." They note that the composition of most meat in today's food supply is not similar to that of mammoth meat  and that most plants available during the Stone Age are today extinct. (Though it wouldn't surprise me to learn that Paleo extremists are crowd-funding a Jurassic Park style experiment to bring them back.)
Just because  Katz  is not one to abandon  his  scientific compass under duress of passion does not mean  he  is without passion  or unmoved by it in  his  own ways. The subjects of media headlines and popular diet books are dark places for  Katz . "Itâs not just linguistic  I really at times feel like crying  when I think about that weâre paying for ignorance with human lives "  he  told me. "At times  I hate the people with alphabet soup after their names who are promising the moon and the stars with certainty. I hate knowing that the next person is already rubbing his or her hands together with the next fad to make it on the bestseller list." "Thatâs an excellent idea  and yet somehow it turns out to be extremely radical." "The evidence that with knowledge already at our disposal  we could eliminate 80 percent of chronic disease is the basis for everything I do "  Katz  said. Just as  he  was finishing  his  residency in internal medicine in 1993  influential research in the Journal of the American Medical Association ("Actual Causes of Death in the United States") put diet on a short list of the lifestyle factors blamed for half of deaths in 1990. "Here we are more than 20 years later and weâve made just about no progress." A nod to the fact that popular media is not totally lost   Katz  borrows from the writer Michael Pollan  citing a seminal 2007 New York Times Magazine article on "nutritionism" in concluding that the mantra  "Eat food  not too much  mostly plants" is sound. "Thatâs an excellent idea  and yet somehow it turns out to be extremely radical."
Flailing in the swell of bestselling diet books  infomercials for cleanses  and secret tips in glossy magazines  is the credibility of nutrition science. Watching thoroughly-credentialed medical experts tout the addition or subtraction of one nutrient as deliveranceâonly to change the channel and hear someone equally-thoroughly-credentialed touting the oppositeâit can be tempting to write off nutrition advice altogether. This month we hear something is good  and next we almost expect to hear itâs bad. Why not assume the latest research will all eventually be nullified  and just close our eyes and eat whatever tastes best? That notion is at once relatable and tragic  in that diet is inextricable from the amount of healthy time we spend on Earth. Improvements in diet are clearly associated with significant lengthening of lifespan and dramatic decreases in risk of most chronic diseases. Combining disease and longevity into the concept of healthspan  the number of healthy years of lifeâfundamentally more important but less readily quantifiable than lifespanâthe data in favor of optimizing our diets are even more compelling. No one is arguing that diet is less than extremely important to health and well-being  but seemingly everyone is arguing as to what constitutes the best diet. "A diet of minimally processed foods close to nature  predominantly plants  is decisively associated with health promotion and disease prevention." The voices that carry the farthest over the sea of diet recommendations are those of iconoclastsâthose who promise the most for the least  and do so with certainty. Amid the clamor   Dr.  [TGT]   is emerging as an iconoclast on the side of reason. At least  thatâs how  he  describes  himself . From  his  throne at Yale University's Prevention Research Center  where  he  is a practicing physician and researcher  said sea of popular diet media is the institution against which  he  rebels. Itâs not that nutrition science is corrupt  just that the empty promises of memetic  of-the-moment diet crazes are themselves junk food. To  Katz   they  are more than annoying and confusing;  they  are dangerous injustice. Scientific publisher Annual Reviews asked  Katz  to compare the medical evidence for and against every mainstream diet.  He  says they came to  him  because of  his  penchant for dispassionate appraisals. "I don't have a dog in the fight "  he  told me. âI donât care which diet is best. I care about the truth."
 Katz  and Yale colleague Stephanie Meller published their findings in the current issue of the journal in a paper titled  "Can We Say What Diet Is Best for Health?" In it  they compare the major diets of the day: Low carb  low fat  low glycemic  Mediterranean  mixed/balanced (DASH)  Paleolithic  vegan  and elements of other diets. Despite the pervasiveness of these diets in culture and media  Katz and Meller write  "There have been no rigorous  long-term studies comparing contenders for best diet laurels using methodology that precludes bias and confounding. For many reasons  such studies are unlikely." They conclude that no diet is clearly best  but there are common elements across eating patterns that are proven to be beneficial to health. "A diet of minimally processed foods close to nature  predominantly plants  is decisively associated with health promotion and disease prevention." Katz  Meller/Annual Reviews Among the salient points of proven health benefits the researchers note  nutritionally-replete plant-based diets are supported by a wide array of favorable health outcomes  including fewer cancers and less heart disease. These diets ideally included not just fruits and vegetables  but whole grains  nuts  and seeds. Katz and Meller found "no decisive evidence" that low-fat diets are better than diets high in healthful fats  like the Mediterranean. Those fats include a lower ratio of omega-6 to omega-3 fatty acids than the typical American diet.
The Mediterranean diet  which is additionally defined by high intake of fiber  moderate alcohol and meat intake  antioxidants  and polyphenols  does have favorable effects on heart disease  cancer risk  obesity  metabolic syndrome  and "is potentially associated with defense against neurodegenerative disease and preservation of cognitive function  reduced inflammation  and defense against asthma." They also found carbohydrate-selective diets to be better than categorically low-carbohydrate diets  in that incorporating whole grains is associated with lower risks for cancers and better control of body weight. Attention to glycemic load and index is "sensible at the least." Eating foods that have high glycemic loads (which  Katz  says is much more relevant to health outcomes than glycemic indexâin that some quality foods like carrots have very high indices  which could be misleading) is associated with greater risk of heart disease. Finally  in a notable blow to some interpretations of the Paleo diet   Katz  and Meller wrote  "if Paleolithic eating is loosely interpreted to mean a diet based mostly on meat  no meaningful interpretation of health effects is possible." They note that the composition of most meat in today's food supply is not similar to that of mammoth meat  and that most plants available during the Stone Age are today extinct. (Though it wouldn't surprise me to learn that Paleo extremists are crowd-funding a Jurassic Park style experiment to bring them back.)
Just because  Katz  is not one to abandon  his  scientific compass under duress of passion does not mean  he  is without passion  or unmoved by it in  his  own ways. The subjects of media headlines and popular diet books are dark places for  Katz . "Itâs not just linguistic  I really at times feel like crying  when I think about that weâre paying for ignorance with human lives "  he  told me. "At times  I hate the people with alphabet soup after their names who are promising the moon and the stars with certainty. I hate knowing that the next person is already rubbing his or her hands together with the next fad to make it on the bestseller list." "Thatâs an excellent idea  and yet somehow it turns out to be extremely radical." "The evidence that with knowledge already at our disposal  we could eliminate 80 percent of chronic disease is the basis for everything I do "  Katz  said. Just as  he  was finishing  his  residency in internal medicine in 1993  influential research in the Journal of the American Medical Association ("Actual Causes of Death in the United States") put diet on a short list of the lifestyle factors blamed for half of deaths in 1990. "Here we are more than 20 years later and weâve made just about no progress." A nod to the fact that popular media is not totally lost   Katz  borrows from the writer Michael Pollan  citing a seminal 2007 New York Times Magazine article on "nutritionism" in concluding that the mantra  "Eat food  not too much  mostly plants" is sound. "Thatâs an excellent idea  and yet somehow it turns out to be extremely radical."