Book review

review by ursula arens writer; nutrition & dietetics

P r o t e i n A h o l i C

author: garth daviS md publiSher: harperone 2015 iSbn: 978-0062279309 priCe: £14.88

the pendulum of judgment about fiend nutrients (in excess) has been swinging from carbohydrates to fats and back. until now, protein has enjoyed a virtuous halo. as the dangers of too much fat and/or too much carb have been so consistently communicated to the public, protein seemed the only dietary escape.

Ursula has spent most of her career in industry as a company nutritionist for a food retailer and a pharmaceutical company. She was also a nutrition scientist at the british Nutrition Foundation for seven years. Ursula guides the NHD features agenda as well as contributing features and reviews But now Dr Davis has pulled in this nutrient for critical inspection and chastisement.

Too much protein is not a good thing; it is bad. And many of the currently popular critiques of carbohydrates are muddled and misleading > come back potatoes (all is forgiven).

By chance, I was behind a very wellmuscled young man in the shopping queue this morning. My basket held an uninspiring mix of groceries and a newspaper. Of course I could not restrain myself from a quick auditory glance at his basket: it held many packets of skinless chicken breasts, bags of biltong and dozens of eggs. My guess is that he was the title of this book being reviewed, or, in the description of Dr Davis, an adherent of ‘Bro-Science’.

Dr Davis is a weight-loss surgeon, with a well-known health and weightloss clinic in Houston, Texas. This is not his first book: The Expert’s Guide to Weight-Loss Surgery was published in 2008 and is the most popular book on Amazon for patients considering this unfortunate choice. However, Dr Davis was uncomfortably exposed when a journalist phoned and asked him about his own health practices. “Oh, I run up and down stairs at the University,” was what he said. What he meant to say was, “I used to, occasionally walk some stairs at the University”. An immediate photo shoot was set up, leading the worst day of Dr Davis’s life. Squeezing into a tracksuit, he had to huff and puff at stair running for a photographer. Dr Davis was aware that he was overweight and unfit and he more than anyone in Houston should have known better. His subsequent medical check confirmed high blood pressure, elevated cholesterol and fatty liver. He was viewed as an expert on health and weight and felt like a hypocrite.

One reason he researched and wrote the book Proteinaholic, is because of the success of his previous book in which he advocated a diet high in protein and fat and low-ish in carbohydrate. He felt that he had contributed to misleading his patients and, because he is such a close witness to the distress of obesity, he felt doubly responsible to conveying his insights that have led to his current excellent health and super fitness. Photographers and stair runs are now welcome.

With the demonisation of fats and carbohydrates, Americans have been led to believe that protein is the answer. A survey by the Food Information Council reported that about 60% of Americans based all their meal choices around protein and that most were looking to consume ‘as much as possible’. Sales of protein bars and

drinks are doing well, beyond just the market of people seeking muscle gain or fat loss. The tags claiming protein content are also increasingly visible on UK food packaging.

But typical diets in the US are far from deficient in protein. Dr Davis reviews historic and current calculations for protein requirements, and most American diets contain nearly double the requirements: the RDAs are 46/56g for adult women/men, whereas latest US dietary surveys report intakes of 70/102g. There are some population subgroups that may benefit from greater intakes and Dr Davis describes the scientific data in depth. Infants, athletes, the bedridden and the elderly may all need more protein than the average citizen, but increases from 0.8g/kg reference levels are modest, with little data supporting requirements above 1.0g/ kg, so still comfortably within typical intakes (and no need for supplementary sources). He cites some studies concluding benefits from higher intakes of protein, but concludes that these are fully contradicted by other larger, better studies, and that the higher-proteinneeds studies are quoted in isolation from more comprehensive reviews. In contrast, there are few studies demonstrating inadequate intakes in US diets where energy intakes are achieved.

Interest in protein as a dietary theme to allow weight control developed strongly via Dr Atkins. There are many permutations to his original diet book published in 1972, with the latest variants described as paleo diets. Dr Davis challenges the romantic concepts of healthy primitive man and is also very mocking of rose-tinted descriptions of the health of the Masai tribes in Kenya and Inuits in Canada, much cited by those advocating eating diets high in animal flesh. Any differences in health compared to US citizens are despite, not because of, high intakes of meat, and differences are dramatically explainable by amounts of foods consumed and energy expenditures. Besides which, the health and life expectancies of both these particular population groups are poor; infection and environmental dangers kill them before chronic diseases can appear, so there is little valid data for comparison. Also, there are many other healthy, mainly starch-eating population groups that form valid contrasts to data cited by the protein-plus theorists.

The largest section of the book, pages 115 to 236, is a discussion and review of high intakes of protein in relation to diabetes, hypertension, heart disease, cancer and obesity risk. The difficulty of tackling these conditions in relation to protein is that there are thousands of studies and research parameters include meat and non-meat diets (but higher in fruits and vegetables). The complexity is untangling what effects may be specific to high intakes of protein, high intakes of meat and/or high intakes of veg. Dr Davis fully sets out these webs of influence and attempts to carefully follow through what the data shows (and what it does not show). He finds many repeated examples of incorrectly and over cited studies and other equally valid and meticulous studies that appear lost in public debate. He seems to particularly admire the European Prospective Investigation into Cancer (EPIC) studies, but pulls in a wealth of many other robust data to demonstrate the adverse effects of too much protein. His references, from Abelow on cross-cultural association between dietary animal protein and hip fracture, to Zur Hausen on reasons to suspect bovine infectious factors in colorectal cancer, are authoritative and comprehensive and allow detailed scrutiny of his claims.

So, for example, what is the evidence on protein and cancer? Dr Davis describes both probable risks due to animal proteins in the diet and also reviews the epidemiological observations. He does not say that animal protein causes cancer, but he does say that animal protein causes various reactions in the body that have been shown to be carcinogenic, and that animal protein has been strongly correlated with some cancers. He cites a study in which the breast

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tissue of women undergoing breast reduction surgery not related to any medical condition was examined. The study found a correlation between intakes of heterocyclic amines (HCAs), found in cooked meat, and the presence of pre-cancer DNA adducts in breast tissue. Or are intakes of heme iron, found in meat, linked to the development of unstable N-nitroso compounds, which may increase the risks of gastrointestinal cancer?

Another smoking gun is insulin-like growth factor 1 (IGF1). Many studies have correlated increased intakes of animal protein with increased circulating IGF1 and increased IGF1 with higher rates of certain cancers. Plus, high protein diets have shown reduced (protective) butyrate production in the colon, although this could rather be because of concomitant lower starch intakes. Further culprits in relation to cancer risk are described as acidosis, methionine, Neu5Ge, changes in hormone levels, slaughter house chemicals and thermo-resistant viruses. He concludes the cancer chapter with reviews of epidemiological data in relation to particular individual cancers, with reference especially to the much discussed associations between red and processed meat and the increased risk of colorectal cancers.

Nine tenths of the book Proteinaholic, is excellent. The book provides a very readable and comprehensive review of nutrition science data and provides a detailed ‘meaty’ discussion of interpretation and application to public health messages. Dr Davies has delved deep into the research, and has pulled together a rich text for dietitians and nutritionists to consider and to use in support of challenging proteinmisinformation.

One tenth of the book is awkwardly evangelical. If you went out to lunch with Dr Davies, you would not actually be able to see him over his salad plate, which consists of three cups of kale, broccoli, mushrooms, artichoke, topped with chickpeas, almonds and flaxseeds… and a baked potato.

A final chapter of meal plans, written with Dana McDonald, who describes herself as a ‘rebel dietitian’, is really too earnest and cranky to be helpful to the average reader. Not eating meat does not mean that you need to live on hemp seeds or sprouted pulses or coconut palm sugar. Healthy diets do not need the inclusion of bizarre and unfamiliar ingredients, and are an unfortunate conclusion to an excellent book.

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NHDmag.com October 2015 - Issue 108 49