Dr. Neville Wilson
6 March 2014.
Another meat bashing report has hit the world headlines, issuing public health warnings about the dangers of animal protein ingestion.
Data from the NHANES ( National Health and Nutritional Examination Survey ) study has revived the popular myth that red meat from animals is not only harmful to health, but equivalent in risk raising potential to the smoking 20 cigarettes a day.
There can be no question about the destructive effects on the human body of cigarette smoke inhalation, but equating the outcome of red meat ingestion with the consequences of smoking is pushing the fallacious idea beyond the limits of common sense, credibility and good science.
Valter Longo is a co-researcher in the recently published study (1) that assessed the clinical outcome of consuming varying levels of animal protein, categorized as high intake, moderate intake and low intake.
The associated risks for animal protein intake were assessed in a cohort of 6318 adults over the age of 50 years, allocated to daily protein portions of 20% of total caloric intake, labeled as high intake, 10% to 19% as moderate intake, and below 10% as low intake.
The health risks of animal protein consumption, according to the authors, is a greater likelihood of death from cancer and other causes, when the protein is derived from milk, meat and cheese, and according to their conclusions and recommendations, dietary protein should ideally be plant based to minimize such risks to health.
The authors postulate that human protein intake should ideally be restricted to 0,8 gm/kg body weight, with 9%-10% of calories derived from protein.
They reported an average daily caloric intake of 1823 kcal per participant in their study, apportioned to 51% for carbohydrates, 33% for fat, and 16% for protein, with 2/3 from an animal source and 1/3 from plants.
Recommendations by these researchers to restrict animal protein intake to 9% or 10% runs counter to the recorded dietary benefits of the Inuits, who enjoyed good health on a balance of 75% to 80% fat intake, and 20% to 25% protein intake, as did modern day hunter-gatherer populations, according to anthropological reports, and modern day consumers of high fat and protein intake.
The basis for the scaremongering headlines, given media prominence in the wake of the study report, do not justify the criticisms offered by the authors, of the Atkins or the Paleo diets, in which the dietary composition of meat, eggs and animal protein has consistently led to improved levels of health, successful weight loss management, and cancer protection.
Conjugated Linoleic Acid (CLA) is a unique fatty acid found almost exclusively in ruminant animal and dairy fats, has been shown in recent studies to afford protection against the advancement of certain cancers and body fat reduction.
The sensationalist headlines and dietary warnings, in the wider media and internet, are reminiscent of several previous warnings, similarly aimed to discredit the health benefits of animal meat consumption.
The Harvard School of Public Health (2) issued similar health warnings in 2012, when the results of frequency food questionaires (FFQ), obtained from 37,698 men, and 83,644 women, over a period of 22 to 28 years, were reported, supposedly reflecting details of their daily dietary intake, as reported every 4 years over the study period.
The lead researcher, Dr. Frank Hu, committed the unpardonable sin of assuming that recollections, by participants, of their dietary intake, and details of food source, over such a lengthy period, were appropriately identified, and therefore accurately reported.
His conclusions that the study “provides clear evidence that regular consumption of red meat, especially processed red meat, contributes substantially to premature death” are invalid, and are assumptions based on reported recollections of participants over a protracted period of time.
It is common knowledge that FFQs are not accurate, and that poor recollection, recall bias, and even ignorance of the food content, by those completing food questionaires every 4 years, are likely to produce skewed and distorted conclusions.
A Validation Study, examining the purported merits of the FFQ in the Harvard study, found that several food groups, like processed meats, eggs, butter, high fat dairy products ) were underestimated by the participants, when compared to the diet records, and others, presumed to be “healthy foods” were overestimated. (3)
Such overestimates and underestimates of food intake, based on perceptions of health, would invariably lead to the creation of a data bank which is purely speculative, and far removed from reality !
An earlier Cleveland University Study (4) from also warned of the dangers of eating carnitine from animal red meat.
I have discussed the weaknesses of this study elsewhere. (www.drnevillewilson.com)
The Present Study :
The fearsome warnings, that are now being circulated, are repetitions of a recurring theme aimed at vilifying animal meat products, and glorifying the purported superiority of plant based products as healthy dietary choices.
The fact that Valter Longo is the founder of L-Nutra, a Company that promotes plant based nutritional supplements, represents a significant conflict of interest within the context of denigrating the nutritional value of a non-plant food source such as animal protein.
The conclusions by Longo and his colleagues are not the result of a carefully designed clinical study. They are, instead, data collected from an observational study, which is no more than a correlation, and cannot prove causation, when analyzing outcomes against a given diet.
At best, an observational study of this nature can only produce a working hypothesis, or a theory, which nevertheless remains untested and unproven, and without any proof of cause and effect.
The Growth Hormone Factor :
Researcher Valter Longo and his co-researchers concluded, on the basis of experiments with mice, that a growth hormone, IGF-1 was associated with increased risk for cancer, and that since IGF-1 levels decline after age 65 years, the risk for developing cancer was likely to be reduced after age 65 years, but increased before the age of 65 years.
A further assumption is made by the researchers, that men over the age of 65 are likely to consume more dietary protein, creating a scenario where increased protein intake, in the presence of decreased IGF-1, pose a lesser risk, than when increased protein intake is combined with higher levels of IGF-1, between the ages of 55 and 65 years.
In their study of 6381 men those between the age of 55 to 65 were at a greater relative risk for developing cancer with an increased protein intake, while no such risk was evident in the over 65 year old group, who consumed high levels of animal protein.
The study data shows that men in the older group were at the lowest risk when consuming the highest levels of protein, (greater than 20% of daily calories ) compared to either moderate (10% -19%) or low levels (< 10%) of protein intake.
A more fitting and accurate media report would have been the findings that increased animal protein intake over the age of 65 affords greater protection against cardiovascular disease and cancer.
The erroneous media statements that harm derived from animal meat consumption equates with harm derived from smoking 20 cigarettes a day is entirely speculative and misleading, and not in the best interests of public health education, given the established risks to human health from active or passive cigarette smoking.
The weakness of this study is characterised by the absence of other relevant data, such as the source of the animal meat consumed, whether it was processed, derived from grain fed or from grass fed animals, and the lifestyle factors of the participants, recognizing that non-meat eaters (vegetarians) are frequently more health conscious than meat eaters, and usually avoid dietary and lifestyle habits that may be detrimental to health.
The absence of these important details invites speculation about potential confounders that may have contributed to the greater risks to health in the group aged 50 to 65.
We have not been given information about other important factors pertaining to the habits of these subjects, such as smoking, levels of physical activity, alcohol consumption, or ingestion of other high caloric foods, or to their medical conditions and possible use of medication, as acknowledged in the BMC report.
Not only does protein from animal meat contribute to an increased risk for cancer and death, according to Prof. Longo, but, in his view, plant based diets provide greater protection, and should be adopted instead of meat based diets.
The conclusions, based on this premise, are that “low protein is associated with a major reduction in IGF-1, cancer and overall mortality in 65 and younger but not older population”.
These conclusions are not supported in a review of prospective studies examining a potential relationship between red meat and colorectal cancer, in which the researchers conclude “the current available epidemiological evidence is not sufficient to support an independent positive association between red meat consumption and colorectal cancer” (5).
Furthermore, the purported benefits of consuming a plant based, or vegetarian type diet, may be due to factors other than the diet itself, as concluded by researchers in their 1994 British Medical Journal report, who wrote, “data do not justify advice to exclude meat from the diet since there are several attributes of a vegetarian diet, apart from not eating meat, which might reduce the risk”. (6)
REAL MEAT VS PROCESSED MEAT:
The conventional arguments in support of animal meat avoidance have been linked to the presumed saturated fat content of animal meat, and it’s purported risk for raising blood cholesterol levels.
The weakness of this argument lies in the false assumptions that raised cholesterol is a risk factor for heart disease, and in the failure to recognize that where cholesterol is raised, it is the protective cholesterol containing lipoproteins HDL, which may be raised, and which correlates with protection against heart disease, and not increased risk !
Furthermore, a meta-analysis of 21 studies involving a follow-up of 347,747 subjects over a 5 to 23 year period showed “ no association between saturated fat intake and increased risk of coronary heart disease, stroke or cardiovascular disease” (7)
Few people recognize the fact that animal meat invariably comprises a mix of fats, and that bacon, for example, is comprised of 50% monounsaturated fat (mostly in the form of healthy oleic acid, and 3% palmitoleic acid, 40% saturated fats, and 10% poly-unsaturated fat, including healthy levels of vitamin A and vitamin D.
In an earlier study (4) meat phobic researchers sought to implicate carnitine, an amino-acid component of red meat, as the culprit in heart disease, and the many weaknesses of this study have been exposed by several analysts.
My own criticism of this study can be found at www.drnevillewilson.com- Carnitine and Red Meat.
An important distinction must be made between meat derived from grass fed animals, and that produced from corn and soy fed animals, and used in the industry of processing and preservation of a wide range of commercially marketed meat based products.
The high levels of nitrites and nitrates, utilized in the meat industry as preservatives, have a propensity to form cancer producing nitrosamines, which do not occur in the unprocessed meat derived from grass fed animals.
The distinctive differences between grass fed animal meat and factory farmed processed meat is not always considered in studies which condemn animal meat. Failure to make this vital distinction leads to unwarranted fears about risks to health when consuming unprocessed animal meat.
Ina systematic review and meta-analysis of 1,598 abstracts from 20 studies researchers have concluded, “ consumption of processed meats, BUT NOT RED MEATS, is associated with higher incidence of coronary heart disease and diabetes” (8)
Despite the 2005 USA Dietary Guidelines for Americans to moderate their intake of red meat, (9) the purported harmful relationship between meat consumption and coronary heart disease, stroke and type 2 diabetes are not well supported by the body of critical literature.
And more recently, in the EPIC cohort, a high consumption of processed meat was related to moderately high all-cause mortality. After correction for measurement error, red meat intake was no longer associated with mortality, and there was no association with the consumption of poultry. Processed meat consumption was associated with increased risk of death from cardiovascular disease and cancer” (10)
The CIRC study researchers, whose fearsome warnings of greater risks to health for middle aged men eating animal derived protein, have misunderstood and misinterpreted their own findings.
According to their data, they should have highlighted the facts that over the age of 50 years, there was no association between protein intake and all cause mortality, or death from cancer.
Dr. Neville Wilson.
6 March, 2014.
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- USA Dietary Guidelines, 2005.
- EPIC cohort, 7/03/2013, BMC Medical.