Sugar has long been accused of causing diabetes. However if you have read the first part of this article on diabetes, one idea should be emerging out of the rather murky swamp of conflicting information. This is that sugar (and by extension, carbohydrates) are not the culprits when it comes to developing diabetes. Saturated fats, found mostly in animal-based foods, are certainly linked to the downhill spiral into insulin resistance, so much so that a simple reduction in the intake of saturated fat goes a long way towards decreasing diabetes risk (2). However, saturated fat may be telling just a part of the story. There is a distinct possibility that another factor, one that is closely affiliated with saturated fat, is exerting its own influence. Evidence is increasingly pointing to animal protein as the true offender. Further to this, plant-based eating has amassed a wealth of evidence of its own powerful protective role against the development of type-2 diabetes.
Once again we need to delve into the scientific evidence for illumination. To start with, studies on sugar intake have shown that moderate sugar intake is completely unrelated to the development of diabetes (3). On the other hand, eating meat is directly associated with increasing the risk of type-2 diabetes (4,11). The InterAct study of 2013 illustrates that for every 50 gm of meat eaten there is an 8% increase in diabetes risk. Interestingly, this study also shows an excess of diabetes in people who handle meat for a living (11). Another study compared a group of omnivores (people who eat all types of meat) and a group of vegans (people who eat no foods of animal origin), all of similar body weight, and found that the vegans showed not only lower insulin levels but also had significantly less fat trapped in their deep calf muscles. This was in spite of the fact that the vegans ate far more carbohydrates (9,10).
Why is meat-eating so closely linked to type-2 diabetes? There are many contributing factors but one of the most influential is inflammation which is known to be closely involved in the genesis of type-2 diabetes (12). Inflammation damages muscle cells and leads to accumulation of fat within muscles (5). It is the saturated fats and trans fats found in animal-sourced foods, not the polyunsaturated and monounsaturated fats found in plant-sourced foods, that lead to inflammation (18). Meat can cause inflammation in other ways besides through saturated fat content. Cooking kills most of the bacteria that are harboured by meat but the endotoxins produced by these bacteria are not destroyed by heat, leaving them available to be absorbed by the body. These endotoxins fire up our immune systems and result in inflammation (6,7). Heme iron, the type of iron found in meat, can give rise to inflammation by increasing the production of free radicals and oxidation (13). Highly inflammatory compounds known as AGEs (Advanced Glycation End-products) are found in many animal based foods but particularly in roasted, fried or broiled meats (15,16). Conversely, eating a high carbohydrate plant-based diet does not cause inflammation (14,23).
Besides inflammation there are a couple of other issues that weigh in here. Persistant organic pollutants (POPs) are organic chemicals such as pesticides and industrial chemicals that persist in the environment and build up in the food chain. The main exposure of POPs to humans is eating animal-sourced foods – meat, eggs, dairy and fish. Vegetables, grains and fruits have only miniscule amounts of POPs (20). Studies show that those with the highest levels of POPs have a much higher risk of diabetes (21,22). Also, eating excessive protein stimulates the aging enzyme, mTOR. When mTOR is activated, the functions of cells become accelerated and lead to early cell death. As you might expect, the unfortunate result is a shortened lifespan. Leucine, the amino acid that has the greatest stimulating effect on mTOR, is found in many foods but it exists in highest concentration in meat, eggs and dairy. Plant foods contain so much less leucine that a person would have to eat more than 100 apples to ingest the amount of leucine provided by one serving of meat. Over stimulation of the mTOR pathway is also associated with the development of diabetes (17).
A very recent study on this subject, published in March of 2017, strengthened the evidence showing that the source of protein being eaten is more important than the presence of carbohydrate in the diet when it comes to the development of diabetes. This study included 2,332 men between the ages of 42 and 60 years who did not have diabetes. During the 19 year follow-up, 432 of those men were diagnosed with type 2 diabetes. The men who ate the most plant protein were found to have a 35% lower risk of developing diabetes compared to the men who at the least plant protein. To quantify this effect, replacing only 1% of energy derived from animal protein with energy from plant protein was associated with an 18% decreased risk of type 2 diabetes (1). A study from 2012 looked into the difference in the amount of insulin the pancreas needs to make when dealing with carbohydrate versus protein containing foods. If a person eats a high glycemic carbohydrate food such as white rice, a certain amount of insulin is released from the pancreas to direct the digested sugars into the body tissues that are in need of energy. Adding tuna, a high protein food, to the rice might be expected to ease the insulin spike. Instead, it doubles. Twice as much insulin is released from the pancreas. The same thing happens with adding meat to white flour spaghetti. It appears the addition of animal protein makes the pancreas work twice as hard (19).
To sum all this up, high blood sugar is a symptom of diabetes; it is not the cause. It is becoming increasingly clear that animal protein is the nutrient that we should be concerned with. Based on the scientific evidence, you may greatly improve your chances of avoiding (or even reversing) type-2 diabetes by transitioning to a whole food, plant-based diet.
1 Virtanen, H.E., Koskinen, T.T., Voutilainen, S., et al. Intake of different dietary proteins and risk of type-2 diabetes in men: the Kuopio Ischaemic Heart Disease Risk Factor Study. British Journal of Nutrition. Mar 2017; 117(6): 882-893.
2 Taylor, R. Pathogenesis of type 2 diabetes: tracing the reverse route from cure to cause.
Diabetologia. 2008 Oct; 51(10):1781-9.
3 Janket, S.J., Manson, J.E., Sesso, H., Buring, J.E. A prospective study of sugar intake and risk of type 2 diabetes in women. Diabetes Care. 2003 Apr; 26(4):1008-15.
4 Song, Y., Manson, J.E., Buring, J.E. et al. A prospective study of red meat consumption and type 2 diabetes in middle-aged and elderly women: The women’s health study. Diabetes Care 2004; 27(9): 2108-2115.
5 Coletta, D.K., Mandarion, L.J. Mitochondrial dysfunction and insulin resistance from the outside in: extracellular matrix, the cytoskeleton, and mitochondria. Am J Physiol Endocrinol Metab. 2011 Nov; 301(5):E749-55.
6 Ghanim, H., Abuaysheh, S., Sia, C.L. et al. Increase in plasma endotoxin concentrations and the expression of Toll-like receptors and suppressor of cytokine signaling-3 in mononuclear cells after a high-fat, high-carbohydrate meal: implications for insulin resistance. Diabetes Care. 2009 Dec; 32(12):2281-7.
7 Erridge, C., Attina, T., Spickett, C.M., Webb, D.J. A high-fat meal induces low-grade endotoxemia: evidence of a novel mechanism of postprandial inflammation. Am J Clin Nutr. 2007 Nov; 86(5):1286-92.
8 Anderson, J.W., Ward, K. High-carbohydrate, high-fiber diets for insulin-treated men with diabetes mellitus. Am J Clin Nut 1979; 32(11): 2312-2321.
9 Goff, L.M., Bell, J.D., So, P.W., Dornhorst, A. Veganism and its relationship with insulin resistance and intramyocellular lipid. Eur J Clin Nutr. 2005; 59(2): 291-298. 2005.
10 Gojda, J., Patkova, J. et al. Higher insulin sensitivity in vegans is not associated with higher mitochondrial density. Eur J Clin Nutr. 2013; 67(12): 1310-1315.
11 InterAct Consortium – Bendinelli, B., Palli, D, Masala, G. et al. Association between dietary meat consumption and incident type 2 diabetes: the EPIC-InterAct study. Diabetalogia, 2014
12 Pickup, J.C. Inflammation and activated innate immunity in the pathogenesis of type 2 diabetes. Diabetes Care. 2004 Mar; 27(3):813-23.
13 Bao, W., Rong, Y., Rong, S., Liu, L. Dietary iron intake, body iron stores and the risk of type 2 diabetes: a systematic review and meta-analysis. BMC Med. 2012 Oct 10; 10:119.
14 Montonen, J., Boeing, H.,Fritsche,A. et al. Consumption of red meat and whole-grain bread in relation to biomarkers of obesity, inflammation, glucose metabolism and oxidative stress. Eur J Nutr. 2013 Feb; 52(1):337-45.
15 Peppa, M., Goldberg, T., Cai, W. et al. Glycotoxins: a missing link in the “relationship of dietary fat and meat intake in relation to risk of type 2 diabetes in men”. Diabetes Care. 2002 Oct; 25(10):1898-9.
16 Koschinsky, T., He, C.J., Mitsuhashi, T. et al. Orally absorbed reactive glycation products (glycotoxins): an environmental risk factor in diabetic nephropathy. Proc Natl Acad Sci U S A. 1997 Jun 10; 94(12):6474-9.
17 Zoncu, R., Efeyan, A., Sabatini, D.M. mTOR: from growth signal integration to cancer, diabetes and ageing. Nat Rev Mol Cell Biol. 2011 Jan; 12(1):21-35
18 Rosqvist, F., Iggman, D.,Kullberg, J. et al. Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral fat accumulations in humans. Diabetes 2014.
19 Hu, E.A., Pan, A., Malik, V., Sun,Q. White rice consumption and risk of type 2 diabetes: meta-analysis and systematic review. BMJ 2012; 344:e1454
20 World Health Organization; Persistent Organic Pollutants (POPs). July 2008
21 Magliano, D.J., Loh, V.H., Harding, J.L. et al. Persistent organic pollutants and diabetes: a review of the epidemiological evidence. Diabetes Metab. 2014 Feb; 40(1):1-14.
22 Ngwa, E.N., Kengne, A., Tiedeu-Atogho, B. et al. Persistent organic pollutants as risk factors for type 2 diabetes. Diabetology & Metabolic Syndrome 2015; 7:41
23 Turner-McGrievy, G.M., Wirth, M.D., Shivappa, N. et al. Randomization to plant-based dietary approaches leads to larger short-term improvements in Dietary Inflammatory Index scores and macronutrient intake compared with diets that contain meat. Nutr Res. 2015 Feb; 35(2):97-106.