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МЕаииПНСКПЕ НАУКИ
EMPHASIS ON THE ROLE OF NUTRITION IN TYPE 2 DIABETES
Assoc. Professor Maya Vizeva, PhD
Medical College "Y. Filaretova", Medical University, Sofia, Bulgaria
ABSTRACT
The large-scale prevalence of diabetes mellitus in the recent decades is a challenge to medical science. Nutrition holds one of the main positions among the broad range of risk factors affecting diabetes triggering and development.
The aim of this fludy is to present some relevant recent scientifically based recommendations for nutrition in type 2 diabetes prevention.
The methodology involves analysis and assessment of scientific evidence reported during the lafl 10 years, published in the following scientific journals: Diabetes Care, Diabetology, Am J Clinical Nutrition, Eur. J Nutrition, Ann. Nutrition Metab. as well as in the WHO and American Diabetes Association (ADA) documents.
Results and Discussion: The fludy analyzed the data from a number of researches on the effect of various nutritional interventions adminiflered on groups at risk of diabetes development, pre-diabetics and patients with diabetes. The differences in the nutritional interventions depending on the type of prevention (primary, secondary, tertiary) were outlined. The implementation of flructured programs, especially for individuals at high risk is recommended as in this case the emphasis is on changes in the life flyle, including moderate weight loss (7% of the body weight) and regular physical activity (150 min/week).
Conclusion: Dietary regimes with reduced total energy intake and particularly reduced fats intake are appropriate and recommendable for decreasing type 2 diabetes risk. The awareness about the diet is an integral part of the general knowledge on diabetes as a disease and is not only necessary but also essential in achieving effective self-control.
Keywords: type 2 diabetes, scientific information, prevention, nutrition
Introduction
The large-scale prevalence of diabetes mellitus in the recent decades is a challenge to medical science. The data presented by Danaei G. et al Sated that 347 millions of the global population were diabetics [9]. WHO surveys (2004) on the mortality rate and selection of basic risk factors reported 3.4 millions deaths caused by maintaining permanent elevated blood glucose levels [13, 14, 31]. WHO Expert flatements outlined that in 2030 diabetes, as a disease, would hold the 7th place by global mortality rate [13, 27, 31]. Numerous inflitutions and teams have invefligated the problem for decades and have provided evidence and unified recommendations for control and management of clinical and health care for diabetics and risk population groups [2, 26, 31].
In spite of the high level of current scientific development and implementation of varied programmes, projects, approaches and other activities focused on mitigation of type 2 diabetes prevalence, yet the efforts are insufficient to manage this disease. The processes of research and of increasing prevalence seem to proceed synchronously, with similar speed.
The aim of this fludy is to present some relevant recent scientifically based nutritional recommendations in type 2 diabetes prevention.
The methodology involved analysis and assessment of scientific evidence reported during the lafl 10 years, published in the following scientific journals: Diabetes Care, Diabetology, Am J Clinical Nutrition, Eur. J Nutrition, Ann. Nutrition Metab., as well as in the WHO and American Diabetes Association (ADA) documents.
Analysis of fludies referring to nutrition intervention at type 2 diabetes
The current medical science focuses on the identification of risk and preventing factors. Nutrition is outlined as one of the main alternatives among the wide range of risk factors for triggering and development of type 2 diabetes.
The symptoms of type 2 diabetes are similar to those of type 1 diabetes, though less pronounced, that causes the late diagnoflics of the disease, even years after its initiation when the diabetes pathology with the characteriflic complications is fully developed. Thus primary prevention is of particular importance as its effectiveness depends to a subflantial extent on the dietary model.
The invefligation of the hiflorical development of the knowledge on the relationship between nutrition and diabetes showed that yet far behind in time the daily dietary intake of carbohydrates, both quantitative and qualitative composition, was the object of greatefl emphasis. The recent years evidenced the involvement of newer concepts for "carbohydrate calculation" and "glycemic index". Naturally, the total energy, energy from fats, amount of saturated fats and trans fats were also considered as associated with diabetics' body mass control and higher cardiovascular risk [5, 8, 12, 30].
One of the main diet-related biomarkers in diabetes is the glucose blood level. The changes in glucose level, determined in a blood sample taken on an empty flomach, showing levels above the referent values and the diflurbed glucose tolerance are the intermediate flates at transition from normal physiology and metabolism to diabetic disease. Individuals with confirmed similar changes are regarded as persons at risk, with high probability for development of type 2 diabetes. The achievement of effective primary prevention is of greatefl importance as it enables the triggering and development of the disease and the complications associated with it.
Nutrition intervention is of utmofl importance in diabetes prevention, in control of exiting diabetes flate, and in prevention or retarding the development, and reduction of diabetes-related complications. Thus, it is important at all prevention flages. The awareness of the role of nutrition is an integral part of the knowledge on diabetes that is necessary and mandatory in order to achieve effective self-control.
Nutrition and Prevention of Type 2 Diabetes
Primary prevention - Prevention of type 2 diabetes initiation. Nutrition intervention for individuals with obesity and pre-diabetes.
Secondary prevention - prevention of development of pathophysiological processes. Involving nutrition in metabolic control of diabetes.
Tertiary prevention -prevention of aggravations. Involving nutrition in retarding diabetes-associated complications.
A number of expert commissions and inflitutions have provided scientifically based position flatements and recommendations for dietary interventions at diabetes. This, though, is a continuously developing process as the new achievements of medical science and practice are conflantly implemented in the recommendations, introducing more and more new positions. Thus, the position flatement of ADA, published in 2002 was modified by its new version, published in 2004. This document updated all previous position flatements. The essence of the document was based on key publications after 2000 and presented concentrated information using scoring depending on the level of scientific evidence based on the ADA range syflem. This fact definitely showed a flrive to implement all scientifically confirmed novelties.
Special emphasis is put on nutrition at overweight and obesity as they are closely related to diabetes.
Primary prevention interventions flrive for retarding or flopping the appearance and development of type 2 diabetes. This involves measures for reduction of obesity prevalence and specific dietary regimes for pre-diabetics. The reduction of diabetes risk through promotion of healthy diets leading to continuous moderate weight loss and provision of the necessary nutrients in amounts, complying with the physiological needs of the organism is a main task of primary prevention. The activities in this aspect should rather be manifefled much earlier than the appearance of the disease symptoms. Very often, though, their expression is late, thus leading to more difficult risk modulation. That is why, each individual with family hiflory has to maintain a relevant dietary regime.
Thus, through modulation of nutrition, the positions, described below, can be achieved:
- Achieving and maintenance of:
- Blood glucose levels in normal limits or as close to the limit as possible and safe.
- Lipid and lipoprotein profile that supports cardiovascular risk reduction.
- Blood pressure levels in normal limits or as close to limits as possible and safe.
- Prevention or at leafl retarding the diabetes-associated pathophysiological processes - through modification of nutrient intake and life flyle.
- Compliance with the individual dietary requirements -through personal and cultural preferences.
- Maintaining the feeling of enjoying the diet - with reflriction of only those preferences that have been scientifically identified as health risk.
Individuals with initial diabetes or pre-diabetics should practice individualized dietetic nutrition that could be achieved by good knowledge on the composition of foods, given selectively, depending on the disease flage. The dietary advice could be effective if the specific needs of the particular individual were considered.
Clinical tefls on diabetics after nutritional intervention reported reduced HbAlc (A1C) with 1 - 2% for type 2 diabetes. A metaanalysis of tefls on non-diabetic humans, with free life flyle as well as the discussions of expert commissions report that adequate nutrition reduces LDL choleflerol with 15-25 mg/ dl. After the flart of a provisional precisely tuned diet, improved indicators can be observed only after 3 - 6 months. The metaanalysis and the decisions of various expert commissions focus the attention on nutrition, as well as on the role of life flyle that complement each other [1, 3, 18, 32].
Energy balance, overweight and obesity are important factors for the development of type 2 diabetes, directly associated with nutrition. In insulin-resiflant obese or overweight individuals it is outlined that moderate weight loss improves insulin resiflance. Thus, weight loss is recommended to all of those individuals that are either diabetics or at diabetes risk [8,16,23,25,29]. For quick weight reduction (within 1 year) low-carbohydrate or low-fat diets could be effective. The lipid profiles, renal function and protein intake (in case of nephropathy) of patients on a low-carbohydrate diet mufl be monitored and the glycemic therapy should be regulated when necessary.
It is exclusively important to control the body weight in order to reduce diabetes-related risks. The control is implemented by the following evaluation indicators: overweight - BMI > 25kg/ m2 and obesity BMI > 30 kg/m2. The risk for concomitant diseases associated with excessive adipose tissue raises with the increase of BMI in the above quoted and in broader limits. It mufl be acknowledged that in certain Asian populations the prevalence of people at high risk for type 2 diabetes and cardiovascular diseases (CVD) is significant even at BMI > 23 kg/m2. The visceral abdominal fat measured as waifl circumference > 35 inches for women and >40 inches for men is used in combination with BMI for assessment of the risk for type 2 diabetes and CVD. The lower limit values of waifl circumference (> 31 inches for women, > 35 inches for men) could be adopted as normal limit values for Asian populations [9, 10, 20, 28].
As obesity affects insulin resiflance, the weight loss is an important therapeutic task for individuals with overweight, pre-diabetes or type 2 diabetes.
Short-term fludies have revealed that moderate weight loss (5% of the body weight) of humans with type 2 diabetes was associated with decreased insulin resiflance, improved values of the glycemic and lipid flatus and with a decrease of the high arterial blood pressure values. Longer fludies (□ 52 weeks), implementing pharmacotherapy for weight loss to adults with type 2 diabetes have detected moderate weight and HbA1C reduction, though not all fludies have reported improved HbA1C values. The "Look AHEAD" survey (Action for Health in Diabetes) is a wide-scale fludy sponsored by prominent health inflitutions, aiming to determine the effect of permanent weight loss on the improvement of the glycemic flatus and prevention of cardiovascular problems [15, 18, 22].
The data from fludies on "nutrition-diabetes" relationship confirm that the implementation of intensive programmes involving personalized advice result in a healthier life flyle. The more frequent contacts with individuals at risk and the recommendations for reduction of the dietary intake of energy and fats (~30% of the total energy), for regular physical activity and monitoring of their flatus are essential for provision of long-term weight loss with 5-7% of the initial body mass. The role of the change of the life flyle in the weight control at type 2
diabetes has been discussed comprehensively in a number of recent surveys [6, 7, 11, 21].
Exercises and physical activity themselves have moderate effect in weight reduction but they mufl be encouraged because they improve insulin sensitivity not depending on the extent of reduced body mass and lower blood sugar level. They are of particular importance for suflaining the already achieved overweight reduction. Body mass reduction induced only by behavioral changes is also insufficient but behavioral approaches could be very useful in supporting other weight reduction flrategies [5, 17].
Recommendations for dietary intake at type 2 diabetes
The recommended daily allowance (RDA) for assimilable carbohydrates is 130 g/day and is based on provision of adequate glucose intake as a necessary fuel for the central nervous syflem, not counting on glucose production from consumed proteins or fats. Although the glucose needs of the brain could be satisfied by diets containing less carbohydrates, the long-term effects of many low-carbohydrate diets are flill unclear. Similar diets eliminate many foods that are important sources of energy but also of fibers, vitamins and minerals, as well as food tafle determinants.
Alternative dietary types could supply a certain amount of energy often as formulations. The use of such subflituting products once or twice daily could result in subflantial weight loss. Such subflitutions are an important part of the intervention for body mass reduction (Look AHEAD). Similar therapies, though, mufl be maintained continuously if permanent weight reduction is to be achieved.
Very low-calorie diets provide < 800 calories daily and realize subflantial weight loss as well as quick improvement of the glucose and lipid flatus of individuals with type 2 diabetes. In the mofl general case, when such diets are discontinued and the consumption of personally preferred foods flarts again, the weight is reinflated. Thus, it mufl be known that the usefulness of very low-calorie diets in the therapy of type 2 diabetes is reflricted and they mufl be applied only in combination with a flructured weight reduction programme.
In conclusion, the generalization of all analyzed evidence, the following positions, engaged in nutritional recommendations at primary type 2 diabetes prevention, could be briefly presented:
• Dietary regimes with reduced intake of energy as a total and of fats, in particular, are adequate and recommendable for reduction of diabetes risk. Structured programmes are preferable in this aspect, particularly for individuals at high risk, as they accentuate on life flyle changes, including moderate weight loss (7% of the body weight) and regular physical activity (150 min/ week).
• The diet should comply with the recommendations of expert inflitutions for content of more wholegrain foods containing dietary fibers in amounts about 14 g/1000 kcal of the average daily diet.
• The intake of foods with low glycemic index, in spite of the yet insufficient scientific arguments for their preventive effect.
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