Carbohydrates & Cardiovascular Disease - Our response
2014 so far has been a rocky road for carbohydrates. The media has come out voicing concerns against the consumption of carbohydrates, especially sugar, in the diet. However, there is still much opposition to the issue of reducing carbohydrates in the diet, the latest being an article published in the Proceedings of the Nutrition Society by Ian Macdonald, a member of the European Scientific Advisory Council for Coca Cola Europe, The Nutrition Advisory Board for Mars Europe and the Mars Scientific Advisory Council for Mars, Inc.
This blog has been written in response this article:
Ian A. Macdonald. (2014) Dietary strategies for the management of cardiovascular risk: role of dietary carbohydrates . Proceedings of the Nutrition Society. Published online.
In this article, the author begins by stating that carbohydrates are necessary as a fuel due to the body’s dependence on glucose to supply the brain, red blood cells and other tissues with energy. By making such a statement, the author is deliberately neglecting the biochemical fact that the human body is able to run on other dietary fuels such as protein and fat. In light of this statement I refer you to the Biochemistry textbook written by Berg, Tymoczko & Stryer 2012(1). In particular refer you to Chapter 16.3 “Glucose can be synthesised from non-carbohydrate precursors”; Chapter 21 “Glycogen Metabolism”; Chapter 22 “Fatty Acid Metabolism”. This textbook is on the required reading list for the majority of university modules that deal with biochemistry and the human body.
The author also goes into the endocrine mechanism that controls carbohydrate intake in the human body. Unfortunately, the author deliberately neglects discussing the beneficial effects that carbohydrate restriction has on the human metabolism.
Mr Macdonald mentions the work and recommendations of the German Nutrition Society, which unsurprisingly, are similar to the British stance that carbohydrates are essential. There is no mention about other European nutrition societies and Government bodies, such as the Swedish Council on Health Technology Assessment (SBU) that has recommended a restriction in dietary carbohydrates. This stance has subsequently been adopted by the Swedish Government to form part of their public health advice on nutrition (Please see here). Why has this counter position, by a learned society, not mentioned in an article whose purpose is to shed light on the effect of dietary carbohydrates in relation to Cardiovascular Disease (CVD) from a public health perspective?
The author speaks at length about the confusion that can arise from studies that look at the relationship between dietary carbohydrates and CVD. What is interesting however is that not once was a study that looked at the effect of reducing dietary carbohydrate mentioned or discussed. In fact, it may seem that the author is intentionally avoiding discussing the myriad of studies that look at the metabolic and endocrine aspects of following a carbohydrate restrictive dietary regimen.
The validity of Randomised Controlled Trials (RCTs) are emphasised throughout the article as being the gold standard for research to help shed light on such issues. There have been RCTs and meta-analysis of RCTs, which have looked at the effects of restricting carbohydrate intake not only for weight loss, but also on the effects this approach has on CVD markers – the main focus of this article. Unfortunately the author fails to address the results obtained, using this scientific gold standard, of studies that have looked at carbohydrate restriction interventions. Please see Brehm et al 2003(2), Bueno et al 2013(3), Foster et al 2003(4), Gardner et al 2007(5), Hession et al 2006(6), Liu et al 2013(7), Yancy et al 2004(8).
An increasing amount of evidence, obtained predominantly via RCTs, are showing a beneficial effects that following a low carbohydrate dietary regimen has on blood serum cholesterol, markers which the author himself identifies as important markers for CVD prevention. Please see Aude et al 2004 (9), Brehm et al 2003(2), Dyson et al 2007(10), Forsythe et al 2008(11), Halton et al 2006(12), Keogh et al 2008(13), Liu et al 2013(7), Meckling et al 2004(14), Perez-Guisado et al 2008(15), Samaha et al 2007(16), Volek et al 2008(17), Volek et al 2009(18), Wood et al 2006(19).
1. Berg, Tymoczko & Stryer (2012) Biochemistry 7th Edition. WHFreeman.
2. Brehm BJ, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrinol Metab, 2003, 88:1617–1623
3. Bueno N.B, Vieira de Melo I.S, Lima de Oliveira L, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. BJN, 2013, 110, 1178–11874. Foster GD, et al. A randomized trial of a low-carbohydrate diet for obesity. NEJM, 2003, 348:2082-2090
5. Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, Kraemer HC, King AC: Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA 2007, 297(9):969-977.
6. Hession M, Rolland C, Kulkarni U, Wise A & Broom J. Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calorie diets in the management of obesity and its comorbidities. Obesity Reviews, 2008, 10 (1): 36-50.
7. Liu X, Zheng G, Xingwang Y, Li H, Chen X, Tang L, Feng Y, Shai I, Stampfer M.J, Hu F.B., Lin X. Effects of a low-carbohydrate diet on weight loss and cardiometabolic profile in Chinese women: a randomised controlled feeding trial. BJN, 2013, 110, 1444–1453
8. Yancy WS, Jr., Olsen MK, Guyton JR, Bakst RP, Westman EC: A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia: a randomized, controlled trial. Ann Intern Med 2004, 140(10):769-777.9. Aude YW, et al. The national cholesterol education program diet vs a diet lower in carbohydrates and higher in protein and monounsaturated fat. Arch Intern Med. 2004, 164:2141-2146
10. Dyson P.A., Beatty S., & Matthews D.R. A low-carbohydrate diet is more effective in reducing body weight than healthy eating in both diabetic and non-diabetic subjects. Diabetic Medicine, 2007, 24: 1430-1435.
11. Forsythe CE, Phinney SD, Fernandez ML, Quann EE, Wood RJ, Bibus DM, Kraemer WJ, Feinman RD, Volek JS: Comparison of low fat and low carbohydrate diets on circulating Fatty Acid composition and markers of inflammation. Lipids 2008, 43(1):65-77.
12. Halton T.L, Willett W.C, Liu S., Manson J.E, Albert C.M, Rexrode K, Hu F.B. Low-Carbohydrate-Diet Score and the Risk of Coronary Heart Disease in Women. NEJM, 2006, 355:1991-200213. Keogh JB, et al. Effects of weight loss from a very-low-carbohydrate diet on endothelial function and markers of cardiovascular disease risk in subjects with abdominal obesity. Am J Clin Nutr, 2008, 87 (3):567-576
14. Meckling KA, et al. Comparison of a low-fat diet to a low-carbohydrate diet on weight loss, body composition, and risk factors for diabetes and cardiovascular disease in free-living, overweight men and women. J Clin Endocrinol Metab, 2004, 89: 2717–2723
15. Pérez-Guisado J, Muñoz-Serrano A & Alonso-Moraga A. Spanish Ketogenic Mediterranean diet: a healthy cardiovascular diet for weight loss. Nutrition Journal 2008, 7:30
16. Samaha F.F, Foster G.D, Makris A.P. Low-carbohydrate Diets, Obesity, and Metabolic Risk Factors for Cardiovascular Disease. Current Atherosclerosis Reports, 2007, 9:441–447
17. Volek JS, Fernandez ML, Feinman RD, Phinney SD: Dietary carbohydrate restriction induces a unique metabolic state positively affecting atherogenic dyslipidemia, fatty acid partitioning, and metabolic syndrome. Prog Lipid Res 2008, 47(5):307-318.
18. Volek JS, Phinney SD, Forsythe CE, Quann EE, Wood RJ, Puglisi MJ, Kraemer WJ, Bibus DM, Fernandez ML, Feinman RD: Carbohydrate Restriction has a More Favorable Impact on the Metabolic Syndrome than a Low Fat Diet. Lipids 2009, 44(4):297-309.
19. Wood RJ, Volek JS, Liu Y, Shachter NS, Contois JH, Fernandez ML. Carbohydrate Restriction Alters Lipoprotein Metabolism by Modifying VLDL, LDL, and HDL Subfraction Distribution and Size in Overweight Men. J. Nutr., 2006, 136 (2): 384-38