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Rapid Responses: Rapid Responses published:
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Essential fats may be the critical factor
- Eduardo N. Siguel (25 June 2009)
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Glycaemic Index and the Mediterranean Diet
- William T Neville (30 June 2009)
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Approach to the individual components of the Mediterranean diet as a mortality predictor
- Maria G Joyanes, Ingrid M. Outschoorn (1 July 2009)
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Glycaemic index
- Dr. Herbert Nehrlich (4 July 2009)
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Follow the Mediterranean diet
- Nan Li (9 July 2009)
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"Moderate alcohol intake"?
- Richard Watson (10 July 2009)
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Re: Glycaemic index
- William T Neville (13 July 2009)
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Re: Re: Glycaemic index
- Dr. Herbert Nehrlich (28 July 2009)
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Eduardo N. Siguel, Medical research PO Box 10187, Gaithersburg, MD 20898
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The data does not appear to accurately calculate the effect of fatty acid composition. According to my research, the fatty acid composition of tissues (using plasma as a biomarker), particularly the relative percents of essential vs. non essential fats (approximated by PUFA vs. NonPUFA) is a (or the) major nutritional predictor of acquired cardiovascular disease. Monunsaturated (MUFA) intake is far less relevant because the body seeks to maintain MUFA levels fairly proportional to PUFA. Humans can make MUFAs from saturated fatty acids. According to my research and models, MUFAs are made by the body to compensate for suboptimal levels of PUFAs. Eating more means the body makes less. Thus, I propose that the major factors accounting for lower cardiovascular disease in some Mediterranean populations is body tissue levels of essential fats (~ PUFA except for polyunsaturates of the w7 and w9 families). Diets high in fish or some vegetables provide adequate omega -3s; olives (and olive oil) provide omega-6s. The Lyon’s heart study achieved huge reductions in risk of myocardial infarction using a diet high in essential fats. I doubt that higher intake of MUFAs has substantial beneficial effects. Instead, the key are the vegetables, nuts and foods high in essential fats (and not excessive calories). References de Lorgeril M, Salen P, Martin J-L, Monjaud I, Delaye J, Mamelle N.
Mediterranean diet, traditional risk factors, and the rate of
cardiovascular complications after myocardial infarction: final report of
the Lyon Diet Heart Study. Circulation. 1999;99:779–785.
Siguel E, Lerman, RH. Altered Fatty Acid Metabolism in Patients With Angiographically Documented Coronary Artery Disease. Metabolism 1994; 43:982-93. Siguel, E. Deficiencies and Abnormalities of Essential Fats in Gastrointestinal and Coronary Artery Disease. Journal of Clinical Ligand Assay 2000; 23:104–11. Siguel, E. Clinical Impact of Methodological Issues in the Diagnosis of Deficiencies and Abnormalities of Essential Fats. Journal of Clinical Ligand Assay 2000; 23:112–21. Competing interests: Author has a patent to measure fatty acids |
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William T Neville, General Practitioner Abbey Road Surgery, 63 Abbey Road, Waltham Cross, Hertfordshire, EN8 7LJ
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This article and the Mediterranean Diet Score unfortunately do not consider one of the major benefits of a Mediterranean diet which is its low Glycaemic Index (GI). The resulting scores and conclusions therefore give an incomplete picture. If the GI were considered, a better explanation of the benefits of a Mediterranean diet would be apparent. GI is a measure of how rapidly carbohydrates are digested. High GI food causes a high, sharp rise in blood glucose and insulin which is harmful. Low GI food causes a low, sustained rise in blood glucose. A low GI diet may prevent or control a variety of conditions including diabetes, cardio-vascular disease, obesity, hyperlipidaemia, Alzheimer’s disease and breast cancer. Due to the high content of fruit, vegetables and legumes the Mediterranean diet has a low GI. Pasta has a low GI which is relevant to the Italian diet. The GI is therefore important for people who wish to improve their health by switching to a Mediterranean diet. If they continue to eat the high GI food typical of a Western European diet they will not benefit. Such high GI food includes potatoes, most rice and most breakfast cereals. White bread, brown bread and even wholemeal bread have a high GI because they are made from finely milled flower. This high GI food needs to be replaced by low GI alternatives for example porridge, muesli, stone-ground bread, granary bread (made with malted or sprouted wheat) or bread containing soya and linseed. Eating fish, unsaturated fat, nuts, legumes, fruit and vegetables are important. But for a Mediterranean diet to benefit a wider population the consumption of high GI food needs to be decreased and replaced with low GI food. References: 1. Kelly SAM, Frost G, Whittaker V, Summerbell CD. Low glycaemic index diets for coronary heart disease. Cochrane Database of Systematic Reviews 2004, Issue 4. Art. No.: CD004467. DOI: 10.1002/14651858.CD004467.pub2. 2. Thomas DE, Elliott EJ, Baur L. Low glycaemic index or low glycaemic load diets for overweight and obesity. Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD005105. DOI: 10.1002/14651858.CD005105.pub2. 3. Thomas D, Elliott EJ. Low glycaemic index, or low glycaemic load, diets for diabetes mellitus. Cochrane Database of Systematic Reviews 2009, Issue 1. Art. No.: CD006296. DOI: 10.1002/14651858.CD006296.pub2. 4. Jenkins DJ, Wolever TM, Taylor RH, et al. (1981) Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr 34:362–6 Competing interests: None declared |
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Maria G Joyanes, Researcher CNA-AESAN Ministry of Health and Social Policy of Spain, Ingrid M. Outschoorn
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Reading your innovative approach to the individual components of the Mediterranean diet as a mortality predictor, your conclusion with respect to fish and dairy products is well explained. The diet score predictor of ethanol consumption relates to low and high doses, where red wine is the main source. We wonder if one can estimate the contribution of non- nutrients or if one can obtain more information indicating whether the ethanol is via fermentation or distilled, for the remainder of the intake. Finally, in the search for predictive factors, considering the results from other countries, these could be addressed with respect to ethnic and geographic variations. Gene and environment interaction measurements can be based on quantitative measurements of a few paired subjects across a generation? Joyanes M & Lema L. Criteria for optimizing the food composition tables in relation to studies of habitual food intakes. Crit Rev Food & Nutr Sci. 2006 Vol 46, Number 4, June:329-336(8) Zaridze D, Brennan P, Boreham J, Boroda A, Karpov R, Lazarev A, Konobeevskaya I, Igitov V, Terechova T, Boffetta P, Peto R. Alcohol and cause-specific mortality in Russia: a retrospective case-control study of 48 557 adult deaths. Lancet 2009 Jun 27;373(9682):2201-14 Competing interests: None declared |
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Dr. Herbert Nehrlich, Private Practice Bribie Island, Australia
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While the concept of the Glycaemic Index appears widely accepted, the real possibility exists that it is rather useless in real life as a predictor of the fate of carbohydrates ingested and of the influences on various bodily functions. To credit a favourable GI with the positive influences on health and thus dismiss the myriad of already identified factors such as presence of antioxidants, fatty acid mix and the exclusion by proxy of less nutritious food items stretches the imagination beyond the reasonable. After all, individual food items are rarely eaten by themselves. Man tends to eat his veggies along with his meats and desserts are not unheard of. The (very healthful) practice of liberally spreading butter onto vegetables or bread will render the GI quite useless and obsolete. Strange theories tend to originate in stubborn as well as innovative minds. The best treatment for them is the original Eskimo Diet. Tis the salt of course. Competing interests: None declared |
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Nan Li, Cardiovascular Disease Research Hangzhou, China
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Though we are curious to know the mystery of the Mediterranean diet on reduction of overall mortality, the positive results from this cohort study do not show that it stands alone in various other diets. Large quantity of vegetables and moderate amount of red wine can be practically followed unless they are unique. Olive oil, a symbol of the Mediterranean diet, is inclined to help consumption of large quantity of vegetables and fruits. Therefore whether high ratio of monounsaturated lipid/saturated lipid can be replaced by high ratio of polyunsaturated lipid/saturated lipid is another issue. I think "anatomy" in the title indicates a static state of components of the Mediterranean diet, while the way of cooking is important and also deserves investigation. It is noted that young generations are more nutrition-orientated and gradually away from their grandma's kitchens, from which foods are much heavy, creamy and yummy. It calls for the clarification of contemporary and traditional Mediterranean diets, as traditional Mediterranean diets refer to diets before 1960s. There is apparent change in dietary patterns with time flying. Cereals but not pasta was one of the variables; probably the study was conducted in Greece not in Italy. Cereals has low glycemic index but its daily consumption was less than 200 grams. If we look at the nine components of the Mediterranean diet, we will find that carbohydrates (mainly from vegetables, fruits and cereals) occupied the biggest proportion (about 70%), and the protein proportion (mainly from fish and seafood, dairy products, meat and meat products) was relative small (about 15%). The absolute amount of lipid is large (about 70 - 90 grams/day), with a ratio of monounsaturated/saturated lipid about 1.7. As we know, many countries have their own recommended food pyramids. Here comes the question: which one contributes more: the amount of lipids or ratio of lipids? Interestingly, 66% of participants were over 45 years old and 60% of participants had a waist:hip ratio less than 0.9. It shows that following the Mediterranean diet is beneficial to control abdominal obesity. Thus it will be more informative if the relationship of BMI and the Mediterranean diet is presented in this study, as there are discrepancies between the relationship of BMI and the Mediterranean diets in various studies. Reference: 1. Simopoulos AP. The Mediterranean diets: What is so special about the diet of Greece? The scientific evidence. J Nutr. 2001;131(11 Suppl):3065S-73S. 2. Garcia-Closas R, Berenguer A, Gonzálz CA. Changes in food supply in Mediterranean countries from 1961 to 2001. Public Health Nutr. 2006;9(1):53-60. 3. Balanza R, García-Lorda P, Pérez-Rodrigo C, Aranceta J, Bonet MB, Salas-Salvad?J. Trends in food availability determined by the Food and Agriculture Organization's food balance sheets in Mediterranean Europe in comparison with other European areas. Public Health Nutr. 2007;10(2):168- 76. 4. Baldini M, Pasqui F, Bordoni A, Maranesi M. Is the Mediterranean lifestyle still a reality? Evaluation of food consumption and energy expenditure in Italian and Spanish university students. Public Health Nutr. 2009;12(2):148-55. 5. Romaguera D, Norat T, Mouw T, May AM, Bamia C, Slimani N, Travier N, Besson H,Luan J, Wareham N, Rinaldi S, Couto E, Clavel-Chapelon F, Boutron-Ruault MC,Cottet V, Palli D, Agnoli C, Panico S, Tumino R, Vineis P, Agudo A, Rodriguez L,Sanchez MJ, Amiano P, Barricarte A, Huerta JM, Key TJ, Spencer EA,Bueno-de-Mesquita HB, Büchner FL, Orfanos P, Naska A, Trichopoulou A, Rohrmann S,Kaaks R, Bergmann M, Boeing H, Johansson I, Hellstrom V, Manjer J, Wirfält E,Uhre Jacobsen M, Overvad K, Tjonneland A, Halkjaer J, Lund E, Braaten T, Engeset D, Odysseos A, Riboli E, Peeters PH. Adherence to the Mediterranean Diet Is Associated with Lower Abdominal Adiposity in European Men and Women. J Nutr. 2009:1. 6. Rossi M, Negri E, Bosetti C, Dal Maso L, Talamini R, Giacosa A, Montella M,Franceschi S, La Vecchia C. Mediterranean diet in relation to body mass index and waist-to-hip ratio. Public Health Nutr. 2008;11(2):214 -7. Competing interests: None declared |
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Richard Watson, General Practitioner and RCGP Scotland Clinical Lead, Substance Misuse 11 Craigallian Avenue, Glasgow, G72 8RW
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50g of ethanol a day is 6.2 UK units. Current guidance is that a man should not drink more than 4 units per day and have at least 2 alcohol free days per week. Round here we would call that level of drinking hazardous, or risky. Is it possible to break down the figures for alcohol in more detail? That is to look at those who said they drank 1-3 units per day compared to those who said they drank 3-6? Probably not, but it might be illuminating. In a British context the problem with advocating daily drinking as part of a Mediterranean diet is that daily drinkers are rarely light drinkers and light drinkers are rarely daily drinkers. The harm caused by alcohol here far outweighs any benefit. Also, the authors do acknowledge the problem that they assume that peoples habits remained unchanged for over a decade. Perhaps alcohol intake is more likely to alter than the other dietary components? Competing interests: None declared |
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William T Neville, General Practitioner Abbey Road Surgery, 63 Abbey Road, Waltham Cross, Hertfordshire, EN8 7LJ
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Dr Herbert Nehrlich’s letter illustrates a widespread scepticism and lack of knowledge about glycemic index (GI). Despite increasing evidence of benefit, the role and importance of a low GI diet remains controversial. David S Ludwig uses the GI in the Optimal Weight for Life Program at the Children's Hospital Boston and has summarised the current position on the GI in the Lancet (1). Health professionals in Europe and the USA have advocated a low fat diet and dietary fat has decreased, but obesity has increased. This is because the fat has been replaced by high GI carbohydrate. After a high GI meal insulin levels rise excessively which promotes fat storage. Furthermore, high GI food causes a rapid rise in blood glucose, there is then a rapid fall, the appetite is stimulated and overeating follows. Hundreds of clinical trials have shown benefit from a low GI diet, very few have shown a neutral effect and none have shown harm. Animal studies support the use of a low GI diet. Two groups of rats were fed on either a low GI diet or a high GI diet for 18 weeks (2). The rats given high GI food had more body fat and less lean body mass. The rats with the high GI diet showed disrupted pancreatic islet cell architecture and raised triglycerides levels consistent with the high levels of type 2 diabetes and myocardial infarction observed in humans who eat a high GI diet. A recent study shows a possible mechanism by which eating low GI food keeps people feeling fuller for longer (3). A low GI meal is digested more slowly and causes a reduced appetite. The gut hormone glucagon-like peptide 1 (GLP-1) is known to reduce appetite. Twelve volunteers compared eating a low GI meal and a high GI meal. After the low GI meal subjects had 20% higher GLP-1 levels and 38% lower insulin levels compared with when they ate a high GI meal. The Mediterranean diet is a good way of achieving low GI eating. The low GI diet addresses the underlying physiological cause of diseases arising from excessive swings in postprandial glycaemia. Greater use of a low GI diet would be valuable in the prevention and treatment of diabetes, heart disease, and obesity. References: 1. Clinical update: the low-glycaemic-index diet. David S Ludwig. The Lancet. London: Mar 17-Mar 23, 2007. Vol. 369, Iss. 9565; p. 890 (3 pages) 2. Effects of dietary glycaemic index on adiposity, glucose homoeostasis, and plasma lipids in animals. Dorota B Pawlak, Jake A Kushner, David S Ludwig. The Lancet. London: Aug 28-Sep 3, 2004. Vol. 364, Iss. 9436; p. 778 (8 pages) 3. Effect of single high vs low glycemic index (GI) meal on gut hormones. Endocrine Abstracts (2009) 19 OC17. A Norouzy, A Leeds, P Emery, I Bayat Competing interests: None declared |
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Dr. Herbert Nehrlich, Private Practice Bribie Island, Australia
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Dr. Neville's comments do little to help the uninformed or to lessen the controversy. It is indeed astonishing how one can talk about "increasing evidence of benefit" when the subject is an index that appears severely flawed in its essence. Low (refined) carbohydrate consumption is indeed of benefit and few would dispute that. To use an index such as the GI (Glycaemic Index) which is subject to influences like food combining practices means that one is content to ignore confounders . It has been my experience that the GI is a tool utterly unsuited and impractical when it comes to evaluation of the effects of various food items on the "human condition". Competing interests: None declared |
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