Between diet and exercise, the former is generally more divisive when it comes to right and wrong. If you’re like me, you find it particularly annoying when individuals debate dietary advice without the facts. “Show me the science,” is what I always say. And quite frankly, we should all demand the science and leave aside anecdotes and opinions.
In part one of this series, we looked at cholesterol and saturated fat – perhaps two of the most controversial dietary nutriments found in animal products. In this video, we will explore some of the lesser known risk factors associated with animal products to determine once and for all, “Are animal products healthy to eat?”
IGF, or insulin growth factor, is a set of polypeptide hormones that stimulate cell proliferation. IGF-3, for instance, proliferates only normal cells, whereas IGF-1 will proliferate both normal and malignant cancer cells, as shown by Allen et al. in 2002. The study outlines IGF-1’s connection to breast cancer while demonstrating that vegetarians and vegans have the lowest serum levels of the hormone respectively, ergo the lowest risk factor for cancer.
The study’s authors write,
“There has been some speculation that cow’s milk, which naturally contains bovine IGF-I and is identical to human IGF-I, may increase circulating IGF-I levels (20) and thus may affect cancer risk (21) . Indeed, two dietary intervention studies have found a dairy milk supplement to cause a 10% increase in serum IGF-I levels among adults (22) and children (23).”
Allen’s findings were corroborated by a 2009 paper published in Endocrine Reviews, in which Kleinberg, Wood, Furth, and Lee demonstrated a clear positive correlation between IGF-1 and breast cancer.
That same year, Rowlands et al. connected IGF-1 levels to prostate cancer, effectively showing that both men and women are adversely affected by the circulating hormone.
Naomi Allen, who pioneered the research into IGF-1 as a risk factor for cancer, demonstrated as far back as 2000 that vegan men have very low serum levels of IGF-1 but overall healthy levels of bioavailable androgens, the building blocks for hormones.
When we zoom out and look at the human population as a whole, centenarians, or individuals who live beyond 100, exhibit low levels of IGF-1 as shown in this 2009 review by Salvioli et al.
Methionine is an essential amino acid. However, overconsumption of methionine has been linked to cancer growth in a number of studies. The foods highest in methionine are meat, dairy, eggs, and fish.
Tumor cells are unable to proliferate beyond the G2 phase without methionine, a requirement called methionine dependence, which was noticed as early as 1993.
This study was followed up four years later by a closer look at humans, in which McCarty and colleagues found that low-methionine vegan diets prove to be a feasible life extension strategy.
More recently, a thorough look at the biochemistry revealed that reactions between glucose and methionine yielding gaseous sulfur-containing compounds give way to tumor malignancy, suggesting that limiting methionine intake could be a new approach to cancer treatment.
In case you have ever wondered, it is this sulfurous odor that is the primary reason dogs can detect cancer through their heightened sense of smell.
Phthalates are both natural and manmade acids that can be found in fatty animal foods such as milk, butter, and meat. They have been shown to disrupt the endocrine system through antiandrogenic pathways.
A 2006 cross-sectional study of Americans found that phthalates are positively associated with obesity, insulin resistance, and type 2 diabetes.
Four years later, Colacino, Harris, and Schecter conducted a similar national review and found equally alarming trends primarily linked to the consumption of poultry and other types of meat, but, to be fair, also found phthalate metabolites in tomatoes and potatoes.
In a 2009 study conducted by Durmaz et al., it was shown that phthalates cause pubertal gynecomastia, or the enlargement of male breasts in adolescence.
Swan and associates found that prenatal phthalate exposure impairs testicular function, stunts growth of the penis later in life, and contributes to an overall physical feminization of men. Suddenly, eating meat doesn’t seem so manly anymore.
That same year, Swan, along with a different team, published another paper on the matter, demonstrating a behavioral abnormality expressed in boys with higher phthalate exposure, stating that they are less prone to play outdoors, physically, aggressively, to take risks, and other male-typical play behavior, suggesting an overall docility and lower levels of testosterone.
This was corroborated by parallel findings in 2010 where Cho et al. found that phthalate exposure adversely affects neurodevelopment in children, while citing earlier findings that it has a positive association with delayed development of the reproductive system, reduced birth weight, allergies, and asthma.
The detrimental effects of phthalate exposure are thoroughly documented, with its toxicity often referred to as the “phthalate body burden” because the body is struggling to develop properly despite environmental and dietary exposure.
Animal proteins are often touted as healthier and more bioavailable than their plant alternatives. Is there any truth to this claim?
In 2016, Song et al. conducted the largest and longest-running study ever performed comparing animal and plant sources of protein in the human diet consisting of 131,342 participants running for 26 years and found a positive association between animal proteins and cardiovascular death as well as all-cause mortality and an equal and opposite lower risk of death with plant protein consumption.
In 2003, researchers found that soy protein promotes bone and calcium homeostasis in postmenopausal women, effectively strengthening bones in a section of the population particularly at risk for osteoporosis, whereas milk protein was found responsible for leaching 33% more calcium compared to baseline levels thereby increasing women’s risk for bone loss.
That’s great news for women who eat soy, but what about men? Won’t excessive consumption of soy protein lower testosterone in men? Not according to a peer-reviewed paper published in 2007 by Kalman et al. In fact, soy protein was shown to promote lean body mass in men, which also seems to contradict many people’s misconception about soy. This was further corroborated 3 years later by two separate studies [1, 2]. Soy protein has no effect on the reproductive hormones of men.
And while we are on the subject, according to a 2006 study, consumption of soy decreases prostate cancer risk in men and breast cancer risk in women.
“Suggestive evidence that soy-rich diets decrease prostate cancer risk, accords well with the observation that ERbeta appears to play an antiproliferative role in healthy prostate. In the breast, ERalpha promotes epithelial proliferation, whereas ERbeta has a restraining influence in this regard – consistent with the emerging view that soy isoflavones do not increase breast cancer risk, and possibly may diminish it.”
Additionally, they found that soy is negatively associated with blood clot-related disorders such as pulmonary embolisms or strokes.
“Hepatocytes do not express ERbeta; this explains why soy isoflavones, unlike oral estrogen, neither modify serum lipids nor provoke the prothrombotic effects associated with increased risk for thromboembolic disorders.”
In 2009, Maruyama, Oshima, and Ohyama traced consumption of bovine milk to decreased testosterone as a result of the exogenous estrogen inherent in cow’s milk.
When it comes to muscular gains, a 2013 study compared whey and rice protein side by side for performance and strength training and found no distinguishable difference between the two groups, concluding that rice protein was just as effective at building muscle as whey.
In 2015, Babault, et al. found that pea protein actually promoted a greater increase in muscle gains as compared to whey protein and a placebo control.
A causal link between consumption of milk protein and s-insulin and insulin resistance was established in late 2004, characterizing a risk factor for type 2 diabetes.
Most people, by now, are aware of the dangers of heavy metal bioaccumulation in seafood, like mercury, lead, and arsenic (1, 2) for instance, so we are not going to cover that here. However, most people are not aware of a similar phenomenon that occurs in the bones of livestock. It is this reason that bone broth, as advocated heavily in the paleo diet community, has alarmingly high levels of lead, as demonstrated by Monro, Leon, and Puri in 2013. It is worth noting that the study used organic free-range chickens.
Iron is found in two forms – heme iron which comes from animal sources and non-heme iron which we get from plant sources.
Iron is an essential nutrient but overconsumption can lead to death. A 2010 study by Sharp supported earlier findings that unfortunately, the body has no mechanism of ridding itself of excess iron so choosing your dietary sources is extremely important.
For this exact reason, iron absorption is regulated by the intestines as shown in this 2005 study by Steele, Frazer, and Anderson.
West and Oates found in their hallmark 2008 study that heme iron has the ability to bypass the body’s regulatory mechanism, thereby disposing the body to toxic overload.
In a 2012 study by Ward and associates, the researchers demonstrated that heme iron, the type found only in animal products, causes DNA damage and leads to oxidative stress which directly feeds cancer cells. It has been shown repeatedly to promote esophageal cancer by catalyzing endogenous formation of N-nitroso compounds, which are the potent carcinogens also found in cigarettes.
A meta-analysis of 59 epidemiological studies from 1995-2012 by Fonseca-Nunes et al. corroborated this finding 2 years later that heme iron is a significant risk factor for various forms of cancer because it is a prooxidant.
Bao and colleagues reported in their 2012 meta-analysis that heme iron is also a significant risk factor for type 2 diabetes.
According to Yang and associates as published in 2014, there is no safe level of heme iron intake. As little as 1mg/day, or only 5% of the daily requirement of iron, was shown to increase risk for coronary heart disease by 27%.
They concluded, “This meta-analysis suggests that heme iron intake was associated with an increased risk of CHD.”
Various sources of heavy metals in meat comprise an overall elevated risk factor as compared to plant foods. This includes hunters who prefer to shoot and kill their own wild game, as studies have shown that bullet fragments elevate lead exposure to dangerous levels, such as this study from 2009.
According to a study published in 2013, the dangers of meat consumption include,
“Issues like the presence of various toxic contaminants, including the most commonly found persistent organic pollutants or POPs (dioxins, polychlorinated biphenyls (PCBs); polyaromatic hydrocarbons (PAH) in smoked products, heteroaromatic amines (HAA) in cooked products, and leukotoxin diols in comminuted meat products. A number of other potentially toxic compounds are also possible to identify and quantify in meat and meat products.”
This includes aflatoxins, nitrites and nitrates, choline, carnitine, methylamines, endotoxins, parasites, etc.
You might be thinking, “Fine, I’ll just cook my meat until all the parasites are killed.” Unfortunately, that does not solve anything. In a paper published in 2009, it was shown that consumption of meat causes endotoxemia, an instantaneous inflammatory response caused by dead bacteria that are carried by lipid cells to reach the stomach. These dead bacterial cells are not destroyed by cooking, stomach acid, or pancreatic enzymes.
Additionally, cooking meat creates genotoxic carcinogens, such as PhIP which has been linked to breast cancer and other forms of cancer, as demonstrated by Lauber and Gooderham in 2011.
I simply cannot cover every risk factor for animal products in this video series alone, but I tried to hit on the major ones here to convey the general idea that animal products are unfit for human consumption. For every study I referenced throughout this video, there are easily hundreds more backing up each one.
It is paramount that the roots of knowledge grow deep in the minds of the uninformed if we wish to dispel dietary dogma from discussion. You can no longer deny it; Animal products contain a multitude of things that have been empirically shown to adversely affect our health. You may have noticed that of all the risk factors we just explored, none of them mattered whether or not the animal product in question was organic, free range, or growth hormone or antibiotic-free. These meaningless distinctions seem to disarm and allure consumers into thinking they are somehow safer.
There is, of course, a much larger ethical argument which we chose not explore here. Additionally, choosing not to use animal products not only behooves you, it is vastly more sustainable for the environment as animal agriculture is the primary reason for deforestation, species extinction through habitat destruction, ocean dead zones, and excessive water consumption and water pollution.
Also, if you are contemplating switch to a plant-based diet but are worried about nutritional deficiencies, check out my video entitled Vegan Deficiencies.