‘High protein diet as bad for health as smoking’ – 348 news articles UK/ 15,400 news articles worldwide
‘Saturated fat is not bad for health’, says heart expert’ – 67 news articles UK/ 2,640 news articles worldwide
Two very different headlines and both in the news last week. You can guess which of the two dominated conversations in the workplace, on radio and tv, at the supermarket checkout, even between random strangers on the street…. Yes, the ‘eating meat kills you’ line rears its ugly head again.
My first reaction to this headline was to take a look at the original paper, ‘Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population’. You can find it here.
The study combined data from 6,381 US men and women over 50 with ‘mouse and cellular studies’. Data collected from people was based on a 24 hour recollection of what they had eaten. This data showed an average consumption of 1,823 calories, the majority of which came from carbohydrates (51%), then fat (33%) and protein (16%), with most of it (11%) derived from animal protein. That is by any description a high-carbohydrate diet although 1,823 calories seems very low, so I wonder how accurately people reported their eating.
The people were followed up for 18 years and results showed 40% overall mortality (2553 people), 19% cardiovascular disease (CVD) mortality (485 people), 10% cancer mortality (255 people), and about 1% diabetes mortality (26 people). So, data from one day’s eating was extrapolated over an 18 year period to help us understand why people died. One day of eating sure gives us an awful of information, but on we go…
The results of this experiment are written here as follows:
‘Using Cox Proportional Hazard models we found no association between protein consumption and either all cause, CVD, or cancer mortality (Table S2). However, high and moderate protein consumption were positively associated with diabetes – related mortality. One explanation is that diabetes may be more prevalent in these groups, possibly because of a switch to a higher protein, lower fat, and lower carbohydrate intake following a diabetes diagnosis. Finally, high versus low protein consumption was found to be associated with an over ten-fold increase in the risk of diabetes mortality for subjects age 66 and over.
However, the much higher prevalence of subjects with a history of diabetes in the high protein group and the small number of subjects dying of diabetes in the low protein group may account for this, thus emphasizing the need for additional studies to determine the role of protein intake on diabetes incidence and mortality.’
From that, I take that there is NO association between high to moderate protein diets and death by cancer, CVD or all cause. Also, that any rise in diabetes deaths was so small and inconclusive that further studies are needed.
However, finding no overall link between protein consumption and these diseases, the study then goes on to isolate the findings according to age. They are broken down into two groups: 50–65 and those aged 66 or over. The people in the former group had ‘a 74% increase in their relative risk of all-cause mortality’ and were ‘more than four times as likely to die of cancer’ during the following 18 years. How this conclusively proves that moderate to high protein consumption causes cancer and death is a mystery. There could be a myriad of confounding factors and as we know so well, correlation is not causation. Nevertheless, the study finds that ‘high levels of animal proteins promote mortality and that plant-based proteins have a protective effect.’
The study then looked at IGF-1 (insulin-like growth factor), which is a hormone that regulates the effects of the growth hormone (GH) in the body. When we are young, we need this hormone to generate growth in our bones and organs but as we age, cell proliferation also carries with it the risk of genetic mutations that may lead to cancer, so there is an argument that high circulating IGF-1 levels pose a risk. Obviously we want the right amount of IGF-1 at the right time and not levels that are abnormally high. Dairy products have been linked to high IGF-1 levels and calorie restricted diets have been found to lower IGF-1 levels.
Levels of IGF-1 were only available for 2,253 people. Although the study states that for those in the 50-65 bracket on a moderate to high protein diet, the risks of all-cause and cancer mortality were increased further with high levels of IGF-1, it also confusingly states that ‘IGF-1 did not account for the association between protein consumption and mortality’. Next they ran ‘predicted hazard ratios’ on the IGF-1 and protein groups to calculate risks.
The data was then combined with ‘mouse and cellular studies’ to look at the effect of IGF-1 levels.
The mice in the high protein group were fed on Harlan AIN-93G (see contents here – just scroll down the page to find the AIN-93G pdf). The diet was 60% carbohydrates, 7% fat and 18% protein (from casein – a milk protein) and contained corn starch, Maltodextrin, Sucrose, Soybean Oil and Cellulose. The study states that ‘additional diets with contents ranging from 4%-18% kcal from protein were created using either the AIN-93G purified diet or the Soy protein diet (93G, G) as reference standards’.
How can we derive data regarding nutrition when mice are fed food filled with such as corn starch, Maltodextrin, Sucrose, Soybean Oil and Cellulose? How can we isolate protein as the culprit against the background of such a combination of other foodstuffs? What does this tell us about meat consumption when the protein used is casein? How can this tell us that consumption of beef in the context of a healthy, real food diet such as Paleo will give us cancer? I just don’t understand the giant leaps that this research makes. But once all of the confusing data, tenuous links, projections, risk analysis and hazard ratios are combined, we end up with a headline that equates high protein with cancer and ultimately that is what makes the news.
The study was funded by NIH/NIA grants to V.D.L. V.D.L has equity interest in a company called L-Nutra. The company make plant-based ‘anti-aging’ replacement meals that mimic the effect of a calorie restricted/fasting diet for chemotherapy patients or for anyone that wishes to ‘increase healthspan’. It makes sense that the research findings are clearly in favour of a predominantly plant-based diet, with the study stating that ‘… associations were either abolished or attenuated if the proteins were plant derived.’
The possibility of using calorie restriction as a way to treat cancer is certainly interesting. There is some very exciting research taking place by Professor Seyfried at Boston College using ketogenic diets (extremely high fat, moderate protein and very low carbohydrate) in conjunction with calorie restriction to treat cancer – see the Resources page. Calorie restriction may be easier in the context of a ketogenic diet as the body is satisfied with very high levels of fat and low levels of carbohydrates, removing the need to eat frequently. However, calorie restriction is not the crux of the argument put forward by this research. This study was clearly intended to promote a plant-based diet while vilifying protein-based diets. Sadly, those hysterical headlines are what people remember.
In the same week as the above story appeared, I was so pleased to see this article about a paper written for the BMJ journal Open Heart by Dr DiNicolantonio, of Ithica College, New York. Dr DiNicolantonio discusses the vilification of saturated fat and the dangers of high carbohydrates. Read the original paper here. It is an excellent summary of the misleading dietary advice adhered to over the last few decades. Many of the issues that Dr DiNicolantonio discusses are touched upon elsewhere on this site (and on other sites that I have recommended over in Resources) – the unfounded fears over saturated fat, the dangers of a high refined carbohydrate diet, the misinformation regarding cholesterol… So refreshing to see this reaching the news but as I said at the beginning of this post, you can guess which of the two stories generated the most publicity.
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