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April 2005, Volume 27, No. 4
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Update Articles
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Medical nutrition therapy for diabetes mellitusRobert Y Chan 陳元略 HK Pract 2005;27:149-158 Summary Diabetes mellitus is a public health problem with an increasing incidence of about 10% in Hong Kong. Local doctors are beginning to take advantage of medical nutrition therapy (MNT), a professional dietetic service, which has produced some very convincing evidence of its effectiveness. This paper points out and analyses the modern approach of MNT and the value of using a multi-disciplinary team in the management of diabetes mellitus. 摘要 糖尿病是一個公共衛生問題，發病率在香港約為10%，並逐漸上升。 本地醫生開始使用一種專業飲食療法醫學營養療法(MNT)， 並取得很有說服力的結果。本文就MNT做了說明和分析， 同時多學科團隊在糖尿病管理方面闡述了的價值。 Introduction Professor Paul Zimmet (1998) estimated that there are approximately 100-million people around the world with the two main forms of diabetes, but current trends suggest that its incidence will get worse.1 Estimates from World Health Organization predict that by the year 2025, 300 million people around the world will be diagnosed with diabetes.2 The Asian/Pacific region accounts for 46% of the global burden of diabetes and China is estimated to contribute almost 38 million people to the diabetic population in the year 2025.3 The age-adjusted prevalence of diabetes mellitus in Hong Kong was found to be 7.7% whereas the crude prevalence ranged from less than 1% in subjects younger than 30 years to more than 20% in the middle-aged group. The 1995 population based survey involving 2900 subjects aged between 25 and 74 years showed an age-adjusted prevalence of 8.5%. These figures are consistent with an overall rising trend in the age-adjusted prevalence of diabetes mellitus.4 The rising prevalence of diabetes is of concern and likely to be related to over-nutrition - a result of energy intake in excess of the amount of physical activities performed in increasing number of populations.5 This local and global trends of both types of diabetes and obesity call for more attention to nutrition therapy and its recent developments. Lifestyle modifications (appropriate diet and increase in physical activities) and consequent reduction in weight, supported by a continuous education programme, were used to achieve a reduction of almost two-thirds of people in the progression to diabetes amongst susceptible groups in China over a 6 year period.6 Medical nutrition therapy Medical Nutrition Therapy (MNT) was introduced in 1994 by the American Dietetic Association to describe the nutrition therapy process. It is defined as the use of specific nutrition services to treat an illness, injury, or condition. It involves two phases:
"It is the position of The American Dietetic Association that medical nutrition therapy is effective in preventing disease complications, resulting in health benefits and cost-saving for the public. Therefore, MNT provided by dietetic professionals is an essential reimbursable component of comprehensive health care services". (ADA Position Statement). The Institute of Medicine of the National Academy of Sciences has recommended MNT - with physician referral - be a covered benefit under the Medicare programme in the U.S.A. Effectiveness of MNT The evidence for the effectiveness of MNT in diabetes management has been well documented by Pastors Joyce Green, Warshaw Hope, Daly Anne et al (Diabetes Care 2002;25:608-613). Johnson and Valera reported impressive outcomes in their study of 21 type-2 diabetic patients who were receiving MNT through supervision by a dietitian. After three individual visits within six months, blood glucose levels decreased by 33.3%, mean total weight reduction was 2.05 kg. Of the 85% of patients who were on oral medication or insulin at the initiation of the study, approximately half (44%) had less or no need for medication at the 6-month end-point of the chart audit.8 The New England Journal of Medicine reports that "aggressive therapy" including daily insulin injection, frequent blood glucose monitoring, diet and exercise therapy produced successful outcomes. After four years of this type of treatment, patients significantly lowered their risk of vision complications and saw the risk of kidney complications nearly cut in half. (New England Journal of Medicine 2000;329:977-986). The Diabetes Control and Complication Trial (DCCT) study (intensive therapy with dietetic intervention) is another convincing piece of evidence in support of MNT. This study involves the intensive treatment of 623 type-1 diabetic patients and a control group involving counselling by a dietitian. The study group achieved glycemic control with monthly nutritional intervention counselling by a dietetic professional.9 The process of MNT This usually follows four distinct steps:
The goals of MNT The goals are to assist individuals with diabetes make necessary changes in nutrition, food choices and preparation, exercise and lifestyle giving considerations to the continuing changes in our environment, in order to keep blood glucose within normal limits by using glucose monitoring records as a reference. The general goals applicable to most people with diabetes include:
Designing a MNT plan Following the initial assessment of the diabetic patient, the patient's lifestyle, his/her food choices, nutritional needs and activities are considered in compiling the dietetic MNT plan. In designing the plan, practical implementation strategies-compliance, how likely and to what extent the patient would follow his/her instructions, consideration should be given to patients' behaviours that need to change and improve in the right order of priority. For example, the nutritional composition of the diet, the need to exercise and weight control may take priority over the practice of small regular meals. The aim is to introduce minimum disruption to established lifestyle. It is important to stress the importance of change to improve. No change means no improvement in the outcome. The dietitian considers the various nutrients the composition of which is important towards achieving the set goal (balanced nutrition makes the patient feel better in most patients who suffer from some form of nutritional inadequacies).15 The transformation of this set of scientific data into different tasty dishes on the dinner table tests the skills of practice in many dietitians. Nutrients I want to discuss the nutrients which have generated many research reports and some controversies in view of the increasing incidence of diabetes mellitus and the concomitant increased demand for service. Carbohydrates Glycolytic process provides glucose (energy) to the muscle and brain cells in the body, and carbohydrates are rich sources of some B group vitamins, minerals and fiber. As dietetic intervention programmes for diabetes and weight control share some common therapeutic features, the amount (in percentage of the diet) of carbohydrate is very important as it contributes directly to blood glucose levels and thus to glycemic control.16,17 High carbohydrates versus low carbohydrates
Low carbohydrates regimens are promoted by a large group of professionals on the assumption that low/moderate carbohydrate diets produce low glycemic response, and may help to improve glycemic control. Arguments supporting the low carbohydrates camp include:
However, the Physicians Committee for Responsible Medicine (PCRM) headed by Dr Neal D. Barnard has been speaking about the dangers of high protein, low-carbohydrate diet since its founding in 1985. Dietary proteins usually include saturated fat (fat from animal source) and excessive amount of dietary cholesterol. Example of this type of protein foods include red meat, offal meat and egg yolks. High protein diets are contraindicated for patients with renal failure and uraemia. Individual needs MNT recognizes that patients have different nutritional needs, and the initial assessment by a dietitian can accurately decide a plan for an individual patient with or without the help of nutritional analysis software. The total carbohydrate content in the nutrition plan is now recognized as more important than the types of this nutrient; complex carbohydrates found in potatoes, vegetables, cereals, etc which are richer in vitamins, fiber and other nutrients, are better than simple carbohydrates and thus they are better food choices. To minimize the hyperglycaemic spikes in the blood glucose curve, the timing of meals and the carbohydrate load of each meal should be accurately spaced out. In practice, the portions of carbohydrate foods should be served at approximately the correct intervals. This means that a patient who has worked with his/her dietitian and the diabetic treatment team will calculate how many grams of carbohydrate portions he/she should eat throughout the day. The dietitian helps the patient to "translate" these units of carbohydrates into tasty and acceptable meals from which the patient can happily choose from day to day. How much carbohydrate should an adult diabetic eat? This is a highly controversial issue, and I would advise patients to accept a level that has been proven to be safe and effective, and meet his/her individual needs. The 2005 Dietary Guidelines for Americans recommend 45 to 65 percent carbohydrates of total calories.15 The American Diabetic Association (ADA) has conducted a number of studies among type-1 and -2 diabetics, and has come to the conclusion that the total amount of carbohydrate in meals and snacks is more important than the source or the type. The daily carbohydrate load should be evenly distributed throughout the three major meals and between meal snacks. Glycemic index Although low glycemic index diets (GI) reduce postprandial glycemia, the ability of individuals to maintain these diets long-term (and therefore achieve glycemic benefit) has not been established. Dr Jennie Brand-Miller, (professor of human nutrition at Australia's University of Sydney and recognized as one of world's leading glycemic index researchers) recently said that dietitians recommend the best diet for people with diabetes is one that is balanced, varied, and that the patient should keep track of total carbohydrates consumed. But she had changed her attitude in recent years and she thought it was not ethical anymore to recommend high GI foods, because these may be doing more harm than good for diabetes and lipid control. Furthermore, it is difficult to predict the impact of a carbohydrate food as an ingredient in a meal even when we know the GI of that ingredient. What really satisfies? Research nutritionists are now focusing their attention on the "satiety index" which may have application in the planning of diabetic diets especially those ones which need calorie restriction. Studies by Australian researcher Dr Susanna Holt and her associates at the University of Sydney have developed one of the most exciting diet concepts ever. Holt's tool ranks different foods on their ability to satisfy hunger. Foods high in satiety value (index) but low in calories and saturated fat may be the foods of choice as part of the diabetic diet.
Carbohydrate exchanges 15 Grams (U.S.A. and Australian Standard); 10 Grams (Hong Kong Hospitals Standard given in Brackets) Cooked Rice 1/3 Cup (14g); Pasta/Noodles Cup (14g); Breakfast Cereals 2/3Cup (16g); Bread 1Slice (9g). Baked Beans, Corn, Potato, Peas, Soybeans, Cup (50g). One exchange of cooked rice for example contains 15g of carbohydrates (USA standard; 10g of carbohydrates Hong Kong standard). Calories and carbohydrate counts are given in calorie counters, available in news agents and bookshops.19 Some vegetables such as potatoes, corn, peas, and baked beans are rich in carbohydrate and the carbohydrates contents should be counted in designing the daily menu. Borushec's calorie counter includes a Carbohydrate Counter. (Allan Borushek, Family Health Publications, PO Box 3100, Nedlands, WA 6006, Australia.) Milk allowance Dietary Guidelines for Americans 2005 recommends 3 cups of milk or equivalent dairy products such as yoghurt, cheese or junket in the above 1200 to 1800 calorie range. Dairy products are excellent sources of calcium. Lau Edith M.C. of the CUHK, (March 1995) said that the main risk factors for osteoporotic hip fracture in Hong Kong Chinese are a low calcium intake, lack of load bearing activities and hormonal deficiency. Pun K.K., Chan L.W.L., Chung V. of University of Hong Kong, (June 1989) had the opinion that the calcium intake of the Chinese population in Hong Kong is much lower than the recommended daily intake and this deficiency may have an important role in predisposing to negative calcium balance and bone loss. The clinical dietitian negotiates with the patient to ensure the milk allowance is acceptable and he/she is willing to consume the quantity as prescribed in one form or another. Diarrhoea due to lactose intolerance can be treated by using lactose reduced milk. It is the responsibility of the dietitian to ensure the planned diet is balanced and help patients who may have problems tolerating milk with enzyme predigested low lactose products. If the patient dislikes milk, he/she can have some local foods or non-diary foods with high calcium content including fortified ready-to-eat cereals, soy beverage (calcium fortified), sardine (Atlantic, in oil, drained), tofu (firm, prepared with nigan), pink salmon (canned with bones), spinach (cooked from frozen), soybeans (green, cooked) instead. (Source: Dietary Guidelines for Americans 2005) There are 12g of carbohydrates in a cup (250ml) of milk. Protein in diabetes In the U.S. protein intake accounts for 15-20% of average energy intake. This is fairly consistent across all ages from infancy to old age, and appears to be similar in people with diabetes.23 For people with diabetes, there is no evidence to suggest that usual protein intake (15 to 20% of total daily energy) should be modified if renal function is normal (American Diabetes Association, Position Statement, 2004). Protein in foods such as meat, eggs and full-cream dairy products are usually associated with saturated fat and cholesterol; proper evaluation of protein intake levels should be made by a dietitian to maximize the safety for all concerned. Dietary fat in diabetes The primary goal in persons with diabetes is to limit saturated fat and dietary cholesterol intake. Professor Collin Campell and his China-Oxford-Cornell Study team investigated the Chinese diet in rural districts for over twenty years in China. His conclusion and recommendations to reduce animal fat (saturated fat) and use a low cholesterol "plant based" diet similar to the traditional Chinese diet are solid evidence supporting the value of reducing dietary fat and cholesterol for people with or without diabetes.24 The "Mediterranean diet" shows that not all fats and oils are harmful to our health. Healthy fats are found in such foods as olive oil (monounsaturated), avocados, nuts and fish.25 Dietary fiber in diabetes Based on my clinical observation and investigations, most Hong Kong people do not eat enough fruit and vegetables - a major recommended source of dietary fiber. The National Nutrition Survey (Australia, 2000) finds 65% of 40 years old women do not eat enough fiber.14 Researchers on both sides of the Atlantic report a high-fiber diet reduces the risk of colon cancer.26 Current evidence suggests that a high-fiber diet, especially one which includes both soluble and insoluble types may offer some improvement in carbohydrate metabolism, lower total cholesterol and low-density lipoprotein (LDL) cholesterol, and have other beneficial effects in patients with non-insulin-dependent diabetes mellitus (NIDDM). A practical goal would be to establish the present level of fiber intake (15-30 g/day) and to increase it gradually. An intake of up to 40g of fiber per day or 25g/1000 kcal of food intake appears beneficial.27 Alcohol use in diabetics According to Emanuele, N.V., Swade, T.E. and Emanuele, M.A., (Department of Medicine, Division of Research on Drugs Abuse, Loyola University Stritch School of Medicine, USA, 1998), occasional participation in alcohol consumption does not worsen blood sugar control in people with diabetes. Some benefits may even be derived from its regular use in small, even moderate quantities (two to four drinks per day). More than two drinks should be consumed over extended periods, but not at the same time. Heavy drinking in diabetics can cause the accumulation of certain acids in the blood resulting in serious health consequences. Alcohol consumption can also worsen diabetes-related complications such as disturbance in fat metabolism, nerve damage and eye disease. Non-nutritive sweeteners The U.S. Food and Drug Administration has approved four non-nutritive sweeteners for general use: saccharin, aspartame, Acesulfame-K and sucarlose. Moderation in use is recommended. Nutritional deficiencies and nutritional supplements It is claimed that vitamin and mineral deficiencies affect a third of the world's people - debilitating minds, bodies, energies and the economic prospects of nations.28 The Australian Nutrition Survey, 2000 has revealed that the intake of three nutrients, Calcium, Zinc and Fiber have fallen below recommended dietary intake levels in 40 years old women group.14 Some revolutionary and fashionable diets recommend high protein and low carbohydrate food choices. At the same time, the diet advocates claim that their diet regimens are "balanced". The term "balanced" simply means that a diet adequately meets one's nutritional needs while not providing individual nutrient in excess. It provides optimal protein, complex carbohydrates while containing only moderate amounts of sodium, fats and simple sugars. Nutrition experts have emphasized the importance of achieving balance in both diets for people with diabetes and weight problems as recommended by the American Diabetes Association. Is there any scope for supplementation? Although difficult to ascertain, if deficiencies of vitamins and mineral are identified, supplementation of these can be beneficial. Selected populations, such as the elderly, pregnant or lactating women, strict vegetarians, and those on calorie-restricted diets, may benefit from supplementation with a multivitamin preparation.28 One of the goals in designing MNT is to produce a balanced diet. However a planned programme of less than 1200 calories is likely to be deficient in a number of nutrients. An expert review group, headed by Franz M. J. supports the use of vitamin supplements where nutritional deficiencies become apparent, as in the elderly individuals, or individuals on calorie restricted diets.28 People over age 50 A key recommendation by U.S. Department of Health and Human Services and U.S. Department of Agriculture in their new Dietary Guideline for Americans 2005 states "People over the age 50: Consume vitamin B12 in its crystalline form (i.e. fortified foods or supplements).15 There is no clear evidence of benefit from vitamin or mineral supplementation in people with diabetes who do not have underlying deficiencies. It is important for clinicians to consider that people over the age of 50 who have reduced intake or malabsorption of Vitamin B12 would benefit from food fortification or supplementation. Functional foods These are foods that provide health benefits beyond basic nutrition. The appeal of functional foods lies in their potential to lower the incidence of diet-related diseases, particularly those occurring in later life.29 The consumption of phytochemicals (plant chemicals) in a variety of foods such as fruits, vegetables, grains, legumes, nuts, seeds, herbs, spices and tea has shown to keep the cells in the body healthy and stable in many ways. Active components are also found in animal sources (zoochemicals) such as the omega-3 fatty acids in some fishes which have been found to reduce the risk of heart disease.30 Researchers at the University of Western Australia have demonstrated that a weight-loss diet combined with daily fish consumption is "highly effective" in reducing blood pressure, lowering triglyceride levels while increasing "good" (HDL) cholesterol levels and in improving glucose tolerance.31,32 Dr Anna Arnold, Professor of Food Chemistry, University of Milan emphasizes the importance of diet in the prevention of cardiovascular disease and diabetes in her new reference on functional foods.33 Implementation suggestions The referring physician, leader of the multi-disciplinarian team should communicate the patient's background and clinical information to the dietitian and other members of the team. The dietitian should be delegated to determine the levels of calorie and other nutrients based on the patients needs through various assessments. Clinical data such as the record of self monitored blood glucose levels should be easily assessable to team members as they provide feedback of MNT and other forms of treatment. Conclusion Many clinical trials have produced evidence beyond doubt the effectiveness and cost-saving benefits of this nutritional intervention approach. MNT begins with individual assessment, setting of goals, patient and dietitian interaction - food plan development with practical implementation strategies including food preparation and appropriate recipes. Monitoring of metabolic process including blood glucose, HbA1c, blood lipids, blood pressure, body weight, renal function, when appropriate, as well as the quality of life is essential to assess the need for changes in therapy and to ensure successful outcome. Evaluation and developing new and improved strategies in diabetes management should be an on going process (ADA 2004).34 To achieve a successful outcome, the multi-disciplinary intervention programme needs the patient's compliance and cooperation. As leader of the treatment team, the physician understands that most clinical dietitians are trained in how to get compliance from patients.35 Key messages
Robert Y Chan, MA, MDAA(Aust)
Dietitian / Nutritionist, Correspondence to : Mr Robert Y Chan, 3, Brookside Villa, Ko Tong Village, Sai Kung Country Park, N.T., Hong Kong.
References
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