Diabetes is a growing epidemic. Approximately 425 million adults are living with diabetes, across the world, today; in India, the figure is 70 million.
Picture this: the estimated prevalence of diabetes, worldwide, in 2025, is slotted to rise to over 500 million, with India slotted to be ‘home’ to 100 million individuals with the disorder.
The cornerstone of therapy, apart from appropriate medical and supportive treatment, for diabetes is a lifestyle that centres on diet — this may be supplemented by oral anti-diabetic agents, or insulin. It should, however, be emphasised that modification of dietary practices cannot work effectively in isolation. It has to be combined with appropriate individualised, or bespoke, lifestyle changes and augmentation of physical activity.
First things, first. Being overweight, or obese, may slowly lead to a state of insulin resistance and compensatory hyperinsulinaemia [excess levels of insulin in the blood relative to the level of glucose]. This, in turn, leads to frank glucose intolerance, or diabetes. Hence, individuals with a family history of diabetes and obesity should be assessed routinely for the presence of carbohydrate intolerance and encouraged to maintain desirable body weight. Approximately 80 per cent of patients, for instance, with non-insulin dependent diabetes [NIDDM], or type-2 diabetes, are overweight. Hence, suitable dietary programmes ought to be directed to achieve suitable caloric reduction.
This is primarily because blood glucose usually returns to normal as weight loss occurs in the obese diabetic patient. Weight loss improves high blood pressure [hypertension], hypertriglyceridaemia [high triglycerides] and hypercholesteraemia [high cholesterol] too. In genetically susceptible individuals, clinical data suggest that the degree of obesity, duration of obesity and specific distribution of excess body fat are often associated with the development of NIDDM, or type-2 diabetes.
DIET FOR DIABETICS
To cut a long story short. The American Diabetes Association suggests that there is no one ‘diabetic’ diet. The recommended diet, it avers, can only be defined as a dietary prescription based on nutritional assessment and treatment goals. Medical nutrition therapy for people with diabetes is, therefore, the best option, because it provides individualised programmes with consideration given to eating habits and other lifestyle factors. Flexibility in use of ordinary foods is just as important for patients and their families.
The first decision in prescribing a diabetic diet is the caloric content of the diet, based on individual needs to gain, or maintain current weight, or, most universally, lose weight. The caloric recommendations from the Food and Nutrition Board, for adults carrying out average activity, is about 36Kcal/kg for men and 34Kcal/kg for women. Also, moderate caloric restriction of 500-1,000Kcal below daily requirements, it says, may be optimal in producing a gradual, also sustained, weight loss.
The minimal protein requirement for good nutrition is about 0.9gm/kg body weight/day; the acceptable range is 1.0-1.5gm/kg/day [12-20 per cent of total calories]. The intake of proteins should be primarily in the form of vegetables, proteins [dal, legumes], and a small quantity of animal protein [skimmed milk, yoghurt, fish etc.,]. In patients with diabetic nephropathy, the protein content should be limited to 0.8gm/kg/day, i.e., about 10 per cent of the total calories, as it may slow down the progression of nephropathy. Vegetable proteins are anionic; they tend to reduce albuminuria; they are also useful in cases of diabetic nephropathy.
REDUCTION OF FATS
A restricted fat diet is usually recommended, if weight loss is desired, because of the high energy content of fats relative to proteins and carbohydrates. The average recommendation for non-obese patients and diabetic individuals without hyperlipidaemia is that fats should make up 30 per cent, or less, of total calories, with less than 10 per cent of them being saturated fat. In hypercholesteraemic subjects, saturated fat should be lowered to less than 7 per cent of calories; cholesterol levels should be below 180mg/dl.
Saturated fat and n-6 polyunsaturated fat activate the production of arachidonic acid and subsequently cytokines, which are potent vasoconstrictors and platelet aggregators. Excess of n-6 polyunsaturates are highly thrombogenic [coagulation of the blood, leading to clot], immunogenic [capable of producing immune response] and proinflammatory. Metabolism of n-3 fats, on the other hand, leads to metabolites such as prostacyclin. The n-6/n-3 ratio of 4:1 also prevents the tonic effects of n-6 polyunsaturated fat. Hence, the use of n-3 fat is desirable in a diabetic diet.
Fish oils are a rich source of n-3 fat. They have a salutory effect on lipid profile. They reduce LDL [bad] cholesterol, triglycerides and VLDL cholesterol. Animal fats, like dairy products, butter, ghee, and hydrogenated fats [vanaspati] are about 50 per cent saturated. They should be discreetly avoided, when consumed in excess.
Virgin coconut oil is reported to be beneficial for diabetics.
Trans-unsaturated fatty acids have been demonstrated to cause a ‘hike’ in total cholesterol, LDL cholesterol, and a fall in HDL [‘good’] cholesterol levels. Natural sources of trans-fatty acids are primarily milk, butter, ghee and animal fats [beef and pork] which contain about five per cent trans-fatty acids. Much larger amounts of trans-fatty acids are found in manufactured products, such as margarine, partially hydrogenated oils and fats used for deep frying and shortening. Deep frying increases the percentage of transmonosaturated fat. This provides the rationale for avoiding hydrogenated oils [vanaspati], excess ghee, butter, red meat and fried foods.
After appropriate proteins and fats are chosen, the remaining calories are assigned to carbohydrates. The use of sucrose as a taste additive in mixed meals in a small quantity [up to five per cent of carbohydrate calorie intake] is acceptable in patients who are lean and/or do not have carbohydrate-aggravated hyperlipidaemia [high cholesterol, or triglycerides]. Increasing the fibre content of the diet is a good idea. This could be made available from whole grains, pulses, green vegetables and fruits. However, the use of purified fibre supplements is not recommended.
Oxidative stress [imbalance between free radicals and antioxidants in the body] is implicated in the causation of diabetes and the genesis of its complications, like diabetic retinopathy and glomerulopathy. It has also been implicated in causing peripheral insulin resistance in type-2 diabetes. Free radicals oxidise LDL and oxidised LDL is a potent atherogenic [tending to promote the formation of fatty deposits in the arteries] substance — it is linked to accelerated macroangiopathy. Hence, foods like fruits, vegetables, spices and condiments, green tea and sprouts which are abundant sources of antioxidants must be included in a diabetic diet. Vegetables, such as carrots, tomatoes, pumpkin and fruits, like papaya, are rich sources of beta-carotene. Sprouts are rich in vitamin E. Vitamin C is abundant in citrus fruits and guava. Minerals dissolve in cooking water; hence, vegetables should be steamed, or cooked, in microwave, instead of boiling. The absorption of iron in legumes, whole grains and green vegetables is better when food rich in vitamin C [i.e., orange juice; or, nutritional supplements] is taken at the same time.
DISTRIBUTION OF CALORIES
The distribution of calories in the day is also important, especially if hypoglycaemia has to be avoided in type-1, or insulin-dependent patients. A typical pattern might include 20 per cent of the total for breakfast, 35 per cent for lunch, 30 per cent for dinner, and 15 per cent as a late evening feed. Often a mild morning and mid-afternoon snack are necessary as well. Vigorous adherence to diet is required in patients of NIDDM, or type-2 diabetes — more so, in individuals who have not been treated with exogenous insulin [since their endogenous insulin reserve is limited], because they may not respond to increased demands produced by excess calories.
EXERCISE & DIABETES
The American Association of Clinical Endocrinologists [AACE] strongly advocates regular exercise along with appropriate diet in diabetic patients. Its bottom line is — good healthy diet and physical activity not only add quality years to a diabetic’s life, but also good quality of life to their years.