Real Food is the Winner of the Diet Roundup

by Kirke on April 29, 2014

 

It should come as no surprise that the recently published article “Can We Say What Diet Is Best for Health” has not been more widely covered by the media. There are no immediately obvious sensational breakthroughs, nothing to market, no miracle weight loss cookbook to sell, no magic supplement to bottle, no appearance on the Dr. Oz show. Instead, all we have is common sense, a rare and seemingly useless commodity in today’s world. The Annual Review of Public Health asked Dr. David L. Katz and Stephanie Meller to weigh medical evidence for or against current popular diets. The results are in, and they are reassuringly bland.

Any diet of whole foods directly from nature and predominantly plants is supportive of health at any age. That’s it.

Katz and Meller summarized:

The evidence revealed by this study is that we should 1) eat minimally processed foods close to how they came from nature and/or food made from those foods 2) eat mostly plants 3) eat animals that were fed those foods As Dr. Katz and Meller see it, in the absence of any rigorous, long term studies comparing contenders for best diet laurels using methodology that precludes bias and confounding, claims of superiority for any one specific diet over others are greatly exaggerated. Rather, the evidence supports a theme of healthful eating, while allowing for variations on that theme. “A diet of minimally processed foods close to nature, predominantly plants, is decisively associated with health promotion and disease prevention and is consistent with the salient components of seemingly distinct dietary approaches.” That sounds like a food scientist’s version of Michael Pollan’s now well known axiom “Eat food. Not too much. Mostly plants.” Perhaps more eloquent was Pollan’s tweet in response to the Katz-Meller paper: “duh!”

…claims of superiority for any one specific diet over others are greatly exaggerated

Those who know food intimately have long known that eating healthfully is really a simple task, and is only complicated in having to choose one of the myriad of ways to achieve the goal. Marion Nestle writes in her book “What to Eat,” “The range of healthful nutrient intake is broad, and foods from earth, tree, or animal can be combined in a seemingly infinite number of ways to create diets that meet health goals.” She further points out that this not some new revelation, quoting cardiologist Ancel Keys and his wife with their advice from 1959, “Do not get fat; if you are fat, reduce. Favor fresh vegetables and fruit. Avoid heavy use of salt and sugar. Get plenty of exercise and outdoor recreation…and do not worry.” In the landmark 1993 paper “Actual Causes of Death in the United States” the longevity and quality of life was distilled into three ultimate determinants: feet, forks and fingers, signifying exercise, diet, and smoking, respectively. Forks won the booby prize as the principle influencing factor, contributing to half of deaths in 1990. Ever since that report, the devastating toll from lifestyle-generated chronic diseases has continued to mount. What has taken epidemiologists so long to give the average consumer a hand in sorting out the hullabaloo of supposed healthy diets flooding the media? Perhaps we have been waiting for a passionate yet sensible pair of scientists like Katz and Meller to come along.

Seven Mainstream Diets Analyzed

In their study, Katz and Meller selected seven mainstream diet categories to analyze and compare while explaining their rationale.

  • Low Carbohydrate Diet
  • Low Fat Diet, including Vegetarian
  • Low Glycemic
  • Mediterranean
  • Mixed, balanced
  • Paleolithic
  • Vegan

Low Carbohydrate Diet

They give appropriate attention to the wide advocacy of low carbohydrate diets, particularly those used for weight loss. Citing multiple intervention studies, they concede the diet’s “potentially beneficial metabolic effects.” However, they note the inability of researchers to unbundle the inevitability of weight loss that results from macronutrient restriction, especially restriction of carbohydrates, which constitute the “majority of calories in almost all omnivorous species.” Other than classifying the diets as being less than 45% carbohydrate, the precise definition of a low carbohydrate diet is amorphous. For example, the Atkins Diet originally emphasized unrestricted meat and dairy consumption, one of its most popular selling points. The newly revised eco-Atkins diet is based on high-protein plant foods rather than animal foods. The authors found that many low-carbohydrate diets still tend to default to a high meat consumption diet; this emphasis is “an inefficient basis for feeding a global population now in excess of seven billion. Ethical concerns have been raised about meat-eating in general and in particular with regard to the treatment of animals associated with feeding multitudes, along with concerns about the environmental costs of heavily animal-based diets.” Katz and Meller go on to explore what version of a low carbohydrate diet is the most efficacious. “A truly low-carbohydrate diet would be low in all sources of carbohydrate, including vegetables, fruits, whole grains, and to a lesser extent, beans and legumes. Proponents of such diets generally note the particular variant they favor does not limit vegetables or beans. Such diets are then not truly low carbohydrate by rather carbohydrate selective.” The eco-Atkins diet, they conclude, might offer recourse for those who choose to partake in a low-carbohydrate dietary pattern based on high-protein plant foods while mitigating the environmental and sustainability challenges of an animal based diet. The authors suggest that when considering a low carbohydrate diet a consumer should assess the composition of each version individually, keeping in mind that research shows that the purported benefits of carbohydrate restriction might be best achieved by choosing superior carbohydrate sources.

Low Fat and Vegetarian Diets

When analyzing Low Fat and Vegetarian Diets, Katz and Meller cite the large body of evidence showing the health benefits of the diets. They also note the growing signs that despite government recommendations encouraging fat restriction, total calorie intake of the US population has increased due to the rise in availability of high-starch and high sugar low fat foods. The authors claim that idealized versions of low fat and vegetarian diets tend to overlap in that both emphasize wholesome, minimally processed plant derived foods. While noting shortcomings when both diets are poorly composed, they find that when assessing “nutritionally replete, low fat, plant based diets, the literature lends strong support for favorable effects across a wide array of health outcomes.” When consumers utilize idealized versions of low fat or vegetarian diets, they tend to consume more fiber from whole grains than the general population, and the benefits that result are widely supported by research. However, they conclude that “there is no decisive evidence that low fat eating is superior to diets higher in healthful fat in terms of health outcomes over the life span.”

“there is no decisive evidence that low fat eating is superior to diets higher in healthful fat…”

Mediterranean Diet

The Mediterranean dietary pattern acclaimed by chefs, nutritionists, as well as indigenous populations circling the Mediterranean Sea, features a range of foods that include olive oil, vegetables, fruits, nuts and seeds, legumes, selective dairy intake, whole grains, seafood and limited meat consumption. The diet is associated with increased longevity, preserved cognition and lower risk of heart disease, cardiovascular disease, obesity, insulin resistance, and cancer. Got a villa in Italy? The authors acknowledge these benefits are difficult to unbundle from the effects of cultural context and its confounding effects. (Read: Life is good on the Mediterranean Sea.)

Low Glycemic Diet

A Low Glycemic Diet focuses on lessening dietary glycemic load by limiting foods with a high glycemic index. The glycemic index is a method of classifying foods according to their potential to raise blood glucose. Glycemic load is the product of the glycemic index (GI) and the amount of carbohydrate (in grams) of the portion. GI×Carbs (g)=Glycemic load. This diet seems to make sense in a time when diabetes is reaching epidemic proportions. While the authors’ study of this strategy shows some resulting health benefits, they also expressed concern that the diet’s application in popular culture has resulted in some very questionable practices, such as the elimination of carrots due to their high glycemic index. “Evidence that health benefits ensue from jettisoning fruits or relatively high-glycemic-index vegetables from the diet does not exist.”

“Evidence that health benefits ensue from jettisoning fruits or relatively high-glycemic-index vegetables from the diet does not exist.”

They conclude that the most important quality of a low glycemic diet is that it incorporates minimally processed, direct from nature foods, while avoiding refined starch and added sugars. Dietitians find the glycemic index to be of little use primarily because it is wildly counter-intuitive. For example, we all know that ice cream is a high-sugar food and reasonably should rate a stratospheric glycemic index score. But ice cream is listed lower on the index than bake potatoes. Potatoes are primarily starch, and upon ingestion your blood sugar will rise promptly. On the other hand, ice cream’s carbohydrates are accompanied by a large amount of fat, which slows GI motility, decreasing the rate of absorption into the blood. If the potato is consumed with a generous pat of butter and a dollop of sour cream, the resulting glycemic response might be more equivalent.

Mixed/Balanced Diet

The Mixed/Balanced Diet category is meant to cover dietary patterns that conform to authoritative dietary guidelines such as the DRIs (Dietary Reference Intakes) of the Institute of Medicine and other governmental agencies. Katz and Meller primarily concentrated on reviewing the Diabetes Prevention Program (DPP) and the DASH (Dietary Approaches to Stop Hypertension) diet. The DASH diet, first studied in the 1990’s, has consistently been shown as the healthiest diet by any metric. It is largely a plant based diet with small portions of lean meat and low-fat dairy. DASH gained instant fame when it was shown to lower blood pressure among subjects within two weeks of starting the program. The criticisms the authors raise are the controversial dairy intake of 2-3 servings per day, albeit non-fat, and the lack of head to head comparisons with other diets. The DPP diet is similar to the DASH diet with tighter restrictions on refined starch and added sugars. The DPP diet did succeed in reducing the occurrence of diabetes by 58% among those studied who were at high risk. Notably absent was any mention of The Academy of Nutrition and Dietetics’ “My Plate Dietary Guidelines,” formerly known as the “Food Guide Pyramid.”

Paleo Diet

Fans of the Paleo Diet might be discouraged with some of Katz’s and Meller’s conclusions. They found it difficult to apply what is a debatable standard as to what actually was our ancestral dietary pattern.

Fans of the Paleo Diet might be discouraged with some of Katz’s and Meller’s conclusions.

They suggest replacing the hunter-gatherer term often used by Paleo diet advocates with the term gatherer-hunter, which might more accurately describe the probable 50% portion of the diet consumed by our ancestors that consisted of gathered plant foods. Furthermore, the meat hunted back in that time, such as mammoth flesh, bears little resemblance to the composition of meat found today, although proponents of grass fed livestock would argue their range fed meat might more closely mimic prehistoric game. On a positive note, while the diet seems to come out of left field compared to other contending diets, the authors found that a true facsimile of the Paleolithic diet would be low in fat, low in objectionable carbohydrates, high in vegetables, fruits, nuts and seeds, high in fiber, and low glycemic. That’s pretty trendy sounding for the Stone Age.

Vegan Diet

The Katz-Meller review of the Vegan Diet largely deals with the importance of the in- depth nutrition knowledge a consumer needs to make this diet a healthy one. They concede that a diet consisting totally of plant foods is associated with multiple health benefits including weight loss, reduced inflammation, lessening of cardiac and cancer risks and improved insulin sensitivity. As with other specialized diets, the authors bemoan the lack of data from intervention trials that are free from bias and that directly compare the diet with others. They perceive as strengths that veganism is frequently adopted by those who are nutritionally educated and health conscious, and that it is associated with positive health outcomes. They find a weakness in that if the diet is casually or incompetently adopted, it can lead to nutrient deficiencies.

Picking the Author’s Brain

It is helpful to be able to pick the brain of an author when gleaning conclusions from his or her research. In James Hamblin’s review of this dietary review found in the pages of The Atlantic, Dr. Katz commented forthrightly on his and Meller’s work. On the subject of Katz’s dismay with the way the media and some popular diet books dice the important subject of everyone’s nutrition, Hamblin quotes the author “It’s not just linguistic, I really at times feel like crying, when I think about that we’re paying for ignorance with human lives.

I really at times feel like crying, when I think about that we’re paying for ignorance with human lives.

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.” And “the evidence that with knowledge already at our disposal, we could eliminate 80% of chronic disease is the basis for everything I do.” Referring to the 1993 study “Actual causes of Death in the United States” previously mentioned, Katz laments, “Here we are more than 20 years later and we’ve just about made no progress. I think Bertrand Russell nailed it when he said that the whole problem with the world is that fools and fanatics are so sure, and wise people always have doubts, something like that.” While the wise Dr. Katz may have his doubts, he has put those aside, spending two years developing an application to diminish confusion and increase options for consumers. Named NuVal, it’s a system that would give each food product a numeric value from 1-100, simplifying current complicated nutrition panels by distilling the information down to one number. The system is currently in 1600 stores and is being utilized by school districts as well.

Chef’s View

As a confessed foodite, I can’t think of anything more straight forward than: eat whole foods, as close to nature as possible. Or: Eat food. Not too much. Mostly plants. Sometimes the more simple the message, the more difficult it is to disseminate and assimilate. Dietitians are taught to advise clients to shop the periphery of a grocery store. That is where a shopper will invariably find the Real Whole Foods; whole meats, whole dairy, and whole produce. This remains an excellent guideline. I believe it is impractical to think consumers will totally give up the convenience of packaged foods. Many of those found in grocery store aisles contain quality, utilitarian food stuffs that I readily admit to using myself, like good tomato sauce or line caught tuna fish. The idea is to lean in towards the real, whole food, and maybe that will lead us all in the right direction.

  References Hamblin, J. (2014, March 24). Science compared every diet, and the winner is real food. Retrieved March 28, 2014, from http://www.theatlantic.com/health/archive/2014/03/science-compared-every-diet-and-the-winner-is-real-food/284595/ Katz, D.L., & Meller, S. (2014). Can we say what diet is best for health? Annual Review of Public Health, 35, 83-103. http://dx.doi.org/10.1146/annurev-publhealth-032013-182351 http://www.davidkatzmd.com/bio.asp McGinnis, J. M., & Foege, W. H. (1993). Actual causes of death in the United States. Journal of the American Medical Association, 270(18), 2207-2212. Nelms, M. N., Sucher, K., Lacey, K., & Roth, S. L. (2007). Nutrition therapy and pathophysiology (2nd ed.). Belmont, CA: Wadsworth. Nestle, M. (2006). What to eat. New York, NY: North Point Press. Whitney, E., & Rolfes, S. R. (2005). Understanding nutrition (10th ed.). Belmont, CA: Thomson Wadsworth. 118-119

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{ 2 comments… read them below or add one }

Heather May 13, 2014 at 12:27 pm

Well written Kirk…you’ve tackeled one of the most complex discussions of the day in such an eloquent fashion. Well done.

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Kirke May 13, 2014 at 12:45 pm

Thank you so much Heather. Your comment means a lot to me, coming from someone I highly respect.

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