A huge study done back in 2010 involving 38,094 people, looked at the consumption of protein and related it to risk of developing diabetes. The researchers looked at the type of protein (animal vs. vegetable) and the total amount of protein. The results show that diets high in animal-protein (and total protein) were positively correlated with diabetes risk, and that vegetable protein had no relation to diabetes risk [1].
I found this interesting because most studies look at dietary-fat and diabetes. The majority of the studies conducted usually indicate that saturated animal-fat induces insulin-resistance. But this study controlled for fat intake… so how in the world could protein cause diabetes?
Perhaps the connection is with SHBG. A classic study done by Longcope et al. clearly showed (after multiple regression analysis) that dietary-protein was negatively correlated with SHBG [2]. So why is this important? Because, SHBG is a sensitive marker for insulin-sensitivity… anything that decreases SHBG, in essence, will also decrease insulin-sensitivity [3-7].
Since eating less protein increases SHBG, and since higher SHBG equals better sensitivity to insulin, perhaps vegetarians and vegans (who eat less protein by default) have higher SHBG and better insulin-sensitivity? Researchers have asked this question as well and have actually conducted studies to see if in fact, vegetarians and vegans do indeed have higher SHBG and insulin-sensitivity. The research confirms they do [8-20].
[1] Diabetes Care. 2010 Jan;33(1):43-8. Dietary intake of total, animal, and vegetable protein and risk of type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition (EPIC)-NL study. Sluijs I, Beulens JW, van der A DL.
[2] J Clin Endocrinol Metab. 2000 Jan;85(1):293-6. Diet and sex hormone-binding globulin. Longcope C, Feldman HA, McKinlay JB.
[3] Eur J Endocrinol. 2000 Jul;143(1):85-9. Sex hormone-binding globulin as a marker for hyperinsulinemia and/or insulin resistance in obese children.
Gascón F, Valle M, Martos R.
[4] Diabetes Care. 2004 Jan;27(1):278-80. The biological variation of sex hormone-binding globulin in type 2 diabetes: implications for sex hormone-binding globulin as a surrogate marker of insulin resistance. Jayagopal V, Kilpatrick ES, Jennings PE.
[5] Clin Endocrinol Metab. 1993 Feb;76(2):273-4. Sex hormone-binding globulin: a marker for hyperinsulinemia and/or insulin resistance? Nestler JE.
[6] Metabolism. 1998 Jan;47(1):70-4. Sex hormone-binding globulin and insulin resistance in African-American women. Sherif K, Kushner H, Falkner BE.
[7] Diabetes Obes Metab. 2004 Jul;6(4):259-63. Plasma sex hormone-binding globulin rather than corticosteroid-binding globulin is a marker of insulin resistance in obese adult males. Lewis JG, Shand BI, Elder PA.
[8] Diabet Med. 2011 May;28(5):549-59. Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with Type 2 diabetes. Kahleova H, Matoulek M, Malinska H.
[9] Eur J Nutr. 2006 Feb;45(1):52-4. No evidence of insulin resistance in normal weight vegetarians. A case control study. Valachovicová M, Krajcovicová-Kudlácková M, Blazícek P.
[10] Br J Nutr. 2006 Jan;95(1):129-35. Taiwanese vegetarians have higher insulin sensitivity than omnivores. Hung CJ, Huang PC, Li YH.
[11] Am J Clin Nutr. 2009 May;89(5):1588S-1596S. Epub 2009 Apr 1. A low-fat vegan diet and a conventional diabetes diet in the treatment of type 2 diabetes: a randomized, controlled, 74-wk clinical trial. Barnard ND, Cohen J, Jenkins DJ.
[12] Am J Med. 2005 Sep;118(9):991-7. The effects of a low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity. Barnard ND, Scialli AR, Turner-McGrievy G.
[13] Eur J Clin Nutr. 2004 Feb;58(2):312-6. Insulin sensitivity in Chinese ovo-lactovegetarians compared with omnivores. Kuo CS, Lai NS, Ho LT.
[14] Br J Nutr. 2010 Jul;104(2):222-6. Comparison of sex hormonal and metabolic profiles between omnivores and vegetarians in pre- and post-menopausal women. Karelis AD, Fex A, Filion ME.
[15] Nutr Res Rev. 2000 Dec;13(2):159-84. The effects of diet on circulating sex hormone levels in men. Allen NE, Key TJ.
[16] Br J Cancer. 2000 Jul;83(1):95-7. Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. Allen NE, Appleby PN, Davey GK.
[17] Obstet Gynecol. 2000 Feb;95(2):245-50. Diet and sex-hormone binding globulin, dysmenorrhea, and premenstrual symptoms. Barnard ND, Scialli AR, Hurlock D.
[18] Br J Nutr. 1990 Jul;64(1):111-9. Testosterone, sex hormone-binding globulin, calculated free testosterone, and oestradiol in male vegans and omnivores. Key TJ, Roe L, Thorogood M.
[19] J Steroid Biochem. 1989 Jun;32(6):829-33. Influence of diet on plasma steroids and sex hormone-binding globulin levels in adult men. Bélanger A, Locong A, Noel C.
[20] J Natl Cancer Inst. 1981 Oct;67(4):761-7. Diet and reproductive hormones: a study of vegetarian and nonvegetarian postmenopausal women. Armstrong BK, Brown JB, Clarke HT.
Edited by misterE, 03 August 2012 - 04:57 AM.
