Health Aspects of Animal Foods

Other Aspects of Animal Foods: Humanitarian Concerns and Sustainable Agriculture

I want to cover this first before getting to health aspects because it can make the discussion of animal products more contentious. In addition to health issues, many choose to reduce animal food consumption for reasons such as wanting to avoid inhumane treatment of animals, or because of religious belief. I respect these reasons, and concern over inhumane treatment of animals leads me to support the Humane Farming Association. But these concerns can also cause the discussion about animal products to be more heated than other issues. Brian Kateman, in his book The Reduceitarian Solution, suggests that rather than present it as a black and white matter of vegans vs meat eaters, it would help if it we just stated that everyone could consider cutting back on animal products, which sounds reasonable to me.

There are also environmental issues. Animal agriculture, especially modern factory farming, is inefficient compared to growing plants. Traditionally, animals were grazed on land that was less suitable for farming, such as hillsides, but modern large scale animal production uses large amounts of prime land. Many are concerned that this type of practice is not sustainable for feeding the earth’s large and growing population. But it’s not just animal agriculture that’s inefficient. Giant fields of commodity crops like corn, wheat, potatoes, and soybeans are planted just to make snack foods, for example. So it helps to avoid processed foods, buy sustainably raised plant and animal foods, as well as consider “reduceitarianism”. I should point out that the paleo diet, while not necessarily being reduced in meat, takes the “reduceitarian” step of eliminating dairy products.

Ok, on to health…

Saturated Fat

I need to start by discussing saturated fat because it comes up a lot in discussing the health of animal-based foods.

Saturated fat has been almost universally considered a bad fat in the past, but with more recent evidence, many nutritionists are moderating that viewpoint. The link between saturated fat and atherothrombosis, the main danger in coronary artery disease, is not as clear cut as previously thought. However, as we’ll see, saturated fat also plays a role in other conditions.

Saturated Fat and Coronary Artery Disease

Coronary artery disease is caused by the formation and progression of coronary plaques (atherosclerosis). Plaques can be stable, and act like a “partially clogged pipe”, which can cause angina. Arteries are not really pipes, they are active flexible tubes, so it’s really more like “partially clogged flexible tube”. But in any case the most dangerous plaques are unstable plaques, which account for the vast majority of heart attacks [1] when they rupture (atherothrombosis) . The mechanism is like a pimple bursting, leading to a severe inflammatory response and possible complete blockage of an artery.

Increases in saturated fat in the diet are well known to correlate with increases in ldl cholesterol in the blood [2] and since ldl was felt to be a primary risk factor for coronary artery disease, this put blame on saturated fat. However, recent evidence shows it is more complicated. It appears that a key step in the initiation of plaque formation is the penetration of the arterial wall (the endothelium), and the greatest risk factor for that is ldl particle number: if you have high ldl but the ldl particles are all large (sometimes colloquially called fluffy), the ldl particle number will be low.

But if they are the smaller dangerous kind, the particle number, or ldl-p, will be high. The reason why it is small dense ldl that is dangerous is that penetration of the endothelium is actually caused by oxidized ldl [3], and small dense ldl is more likely to oxidize. When you get your cholesterol measured it is ldl-c. There is a test using nuclear magnetic resonance for ldl-p but it is not usually ordered by doctors (or paid for by insurance). However, a high ratio of hdl cholesterol to triglycerides correlates with larger ldl, so your ldl is likely to be benign if you have high hdl relative to triglycerides. This can happen for a diet high in saturated fat but low in carbs, especially refined carbs [4].

This would let saturated fat off the hook for heart disease. However, the combination of saturated fat and refined carbs could still be dangerous (for one thing it is known to be highly inflammatory) [5], and should be avoided. That should not be a problem if you eat a diet that minimizes refined carbs.

Even with this new evidence, there is also strong evidence that if you keep ldl very low (less than 70), it will not lead to coronary plaque [6]. So proponents of diets like wfpb, that still recommend keeping saturated fats low, are basing it on this cholesterol goal. They argue that the poor results for “normal” blood numbers mean that the standards are not strict enough.

It’s quite possible that both approaches are right. You can keep hdl high and triglycerides low by avoiding refined carbs, and eating plenty of good fat which drives up hdl, and not worry about saturated fat. Or you can keep ldl and triglycerides very low. Or you can do both (“belt and suspenders”) by following a version of wfpb which has reduced saturated fat but emphasizes more of the healthy fats like omega3 and monounsaturated discussed above.

I couldn’t resist including this- apparently saturated fat helps may help prevent baldness? 🙂

Saturated Fat and Other Diseases

Ingestion of excess saturated fat contributes to lipotoxicity, a metabolic syndrome that may be involved in “several inflammatory pathways, contributing to disease progression in chronic inflammation, autoimmunity, allergy, cancer, atherosclerosis, hypertension, and heart hypertrophy as well as other metabolic and degenerative diseases” [9,10].

Dietary saturated fat correlates negatively with binding of insulin-like growth factor-1 (igf-1) which contributes to cancer risk [11,12]. However, this was found in population-based studies and it is not clear whether the people were also consuming refined carbohydrates. We already know that combination is bad, so this is not necessarily evidence that saturated fat alone is a cancer risk factor.

Ldl is positively correlated with calcification of heart valves [13]. Not enough is known at this point, it may be that it is ldl particle number that really matters, not ldl, as seems to be the case for atherosclerosis. But the mechanism must differ at least somewhat with that for atherosclerosis, because valve calcification does not respond to statin therapy [14].

This seems to be an overlooked area for research. In the US about 80,000 to 85,000 heart valve replacements are done per year. At least half of these probably involve using tissue valves as replacements, so there are 40,000 or so of those a year. You’d have to track the recipients down and follow them in a longitudinal study, occasionally auditing their diet, and monitor how quickly their new valves calcify. I’m officially volunteering for such a study.

In the meantime, because not enough is known at this point, I’ve decided to be conservative and stay low on saturated fat, since I have a replacement tissue valve that I’d like to maximize the life of. So, sadly, butter is not back for me, except as a special treat.

Animal Foods

The discussion in this post is about excess consumption of animal foods. As discussed previously, there are populations known to have good health and longevity that get up to 15% of their calories from animal products. How far above that is the line for “excess” is a controversial point.

I invite your feedback on this if you disagree or think I have missed something. I try to keep an open mind on these issues but it’s impossible to read everything in the nutrition literature.

Health Issues

A main concern in the past about animal foods (except fish) has been saturated fat intake. The saturated fat and heart disease connection is less clear than previously thought, as we saw. If you are still concerned with other diseases and saturated fat, you can go with leaner choices of animal foods.

Paleo authors [15] and others like Dr. Mark Hyman [16] suggest healthy options for animal foods (grass-fed beef, eggs from pasture-raised chickens, etc.), which improves their omega3 content, among other benefits. I agree this is a good idea. Paleo advocates argue that despite containing  significant amounts of meat, their diet is anti-inflammatory overall because it contains lots of anti-inflammatory plant foods, and minimizes dairy and grains, which are pro-inflammatory [15]. I don’t know to what extent these mitigate the health concerns about to be discussed.

All animal foods (dairy, meat, eggs, and fish) have some negative effects on gut bacteria, which has important health effects [17]. For example, they can cause the gut bacteria to produce the toxic compound TMAO, which has various disease risks. They are also implicated in inflammatory bowel disease because “Diets rich in animal protein and animal fat cause a decrease in beneficial bacteria in the intestine” [18]. IBS can also be caused by grain sensitivity, however, which I’ve covered in my post on grains and legumes. Replacing some of the protein in the diet from animal foods with plant-based protein is associated with significantly lower all-cause mortality [19].

Dairy

Both wfpb and paleo advocates consider dairy to be an unhealthy food. It is inflammatory, and there are other health issues with dairy in the nonfat portion of it (such as skim milk). Ironically, despite it being touted as good for the bones, increased dairy consumption correlates with higher rates of bone fractures and osteoporosis [20]. Dairy is also a significant source of estrogen, associated with acne and male infertility [21], and increased cancer risk [22].

Americans are eating 7 times as much cheese (and 1.5 times as much meat) as 100 years ago [23]. This is also triple the amount of cheese consumed in the early 1970s [24]. Processed foods are a significant hidden source of cheese [24], so if you avoid them you will automatically reduce your cheese consumption as a side effect.

Meat

Many authors argue that meat is now ok because the saturated fat picture is not as clear cut as it once was. It is also a concentrated source of protein and other nutrients. However, there are other health issues specifically related to meat.

Meat contains multiple carcinogens, such as from environmental pollutants like PCBs, which are concentrated because it is further up the food chain [25]. As we saw, it also has various deleterious effects on the gut bacteria. Consumption of meat and other animal products cause an inflammatory response which may be caused by endotoxins in the food, including bacteria that were killed in cooking but still cause an immune response [26].

Fish

Fish are a good source of protein, and fatty fish like salmon are a good source of omega3 fatty acids. The main health concerns about fish are pollution including mercury and other heavy metals. I recommend Food, What The Heck Should I Eat?, by Dr. Mark Hyman, for good advice on healthy choices for fish (as well as other animal foods).

References

  1. Falk, E “Pathogenesis of Atherosclerosis”, Journal of the American College of Cardiology, 2006
  2. Clarke, R, “Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies”, BMJ, 1997
  3. Li, D, Mehta, J, ” Oxidized Ldl, A Critical Factor In Atherogenesis”, Cardiovascular Research, 2005
  4. Hays J, et al,  “Effect of a high saturated fat and no-starch diet on serum lipid subfractions in patients with documented atherosclerotic cardiovascular disease.”, Mayo Clin Proc., 2003
  5. O’Keefe, J, Bell, D, “Postprandial Hyperglycemia/Hyperlipidemia (Postprandial Dysmetabolism) Is a Cardiovascular Risk Factor”, Am J Card, 2007
  6. O’Keefe, J, et al. “Optimal low-density lipoprotein is 50 to 70 mg/dl Lower is better and physiologically normal”, Journal of the American College of Cardiology, 2004
  7. Min, J, et al, “Monitoring the formation of cholesterol oxidation products in model systems using response surface methodology”,  Lipids in Health and Disease, 2015
  8. Echarte M, Ansorena D, Astiasarán I, “Consequences of microwave heating and frying on the lipid fraction of chicken and beef patties.”, J Agric Food Chem., 2003
  9. Estadella, D, et al, “Lipotoxicity: Effects of Dietary Saturated and Transfatty Acids”, Mediators of Inflammation, 2013
  10. Kennedy A, et al, “Saturated fatty acid-mediated inflammation and insulin resistance in adipose tissue: mechanisms of action and implications.”, J Nutr., 2009
  11. Heald A, et al, “The influence of dietary intake on the insulin-like growth factor (IGF) system across three ethnic groups: a population-based study.”, Public Health Nutr., 2003
  12. Werner, H, Bruchim, I, “The insulin-like growth factor-I receptor as an oncogene”, Arch Physiol Biochem., 2009
  13. Pohle, K, et al, “Progression of Aortic Valve Calcification”,Circulation, 2001
  14. Loomba R, Arora R, “Statin therapy and aortic stenosis: a systematic review of the effects of statin therapy on aortic stenosis”, Am J Ther., 2010
  15. Cordain, L, The Paleo Diet, Wiley, 2002
  16. Hyman, M, Food: What the Heck Should I Eat?, Little, Brown and Company, 2018
  17. Tuohy, K, Fava, F, Viola, R, “’The way to a man’s heart is through his gut microbiota’—dietary pro- and prebiotics for the management of cardiovascular risk.”, Proc Nutr Soc., 2014
  18. Chiba M, et al, “Missing environmental factor in inflammatory bowel disease: diet-associated gut microflora.”, Inflamm Bowel Dis., 2011
  19. (146) Song, M, et al, “Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality,” JAMA Internal Medicine, 2016
  20. Michaelsson, K, et al, “Milk intake and risk of mortality and fractures in women and men: cohort studies”, BMJ, 2014
  21. Jensen, et al, “High dietary intake of saturated fat is associated with reduced semen quality among 701 young Danish men from the general population.”, Am J Clin Nutr., 2013
  22. Melnik, B, et al, “The impact of cow’s milk-mediated mTORC1-signaling in the initiation and progression of prostate cancer”, Nutrition & Metabolism, 2012
  23. www.ers.usda.gov/amber-waves/2010/march/guess-who-s-turning-100tracking-a-century-of-american-eating
  24. Moss, M, Salt Sugar Fat: How the Food Giants Hooked Us, Random House, 2013
  25. Hernandez A, et al, “An estimation of the carcinogenic risk associated with the intake of multiple relevant carcinogens found in meat and charcuterie products.”, Sci Total Environ., 2015
  26. Erridge C, “The capacity of foodstuffs to induce innate immune activation of human monocytes in vitro is dependent on food content of stimulants of Toll-like receptors 2 and 4.”, Br J Nutr., 2011

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