The use of low carbohydrate diets in the management of Type 2 diabetes

Changes in Diabetes Dietary Guidelines Nutrient1930’s1970’s1980’s1990’s2000’s CHO % of Energy 15%40%>50%50-55%60-70% With MUFA Protein % of Energy 17%45%15%10-15% Fat % of Energy 68%15%<35%30-35%<35% Added Sucrose None A little mixed diet <25g/day<10%

Current Recommendations Little evidence for the ideal macronutrient composition in the management of hyperglycaemia Great flexibility and consumption of macronutrients based on RI for healthy eating is encouraged Looking at different diets (low CHO, low fat) small and inconsistent differences regarding weight loss. Adherence is the important factor.

Casting Doubt on Carbohydrate Feinman et al 2014 Restriction of CHO decreases blood glucose levels reducing hyperglycaemia During increase in obesity and T2 DM, calories have increased due to CHO intakes See benefits of reducing CHO without requiring wt loss Adherence to low carb diets is as good as other diet interventions Replacement of CHO with protein is beneficial Total and sat fat do not correlate with CVD Feinman et al, Dietary Carbohydrate Restriction as the first approach in diabetes management. Nutrition and Metabolism, /

Feinman et al 2014 cont’d Plasma sat fatty acids are controlled by CHO more than diet lipids Best predictor of Microvascular and to smaller degree macrovascular in T2 DM is glycaemic control Restricting CHO is the most effective method of reducing TG and increasing HDL Patients with T2 DM on CHO restricted diets reduce and eliminate medication. T1 DM require less insulin Intensive glucose lowering by CHO restriction has no side affects comparable to medication

How much Carbohydrate? Moderate carbohydrate: 130 to 225g of carbs (26 – 45% of Energy) Low carbohydrate: under 130g of carbs (<26% of Energy) Very low carbohydrate: under 30g of carbs (<10% of Energy)

Evidence for Low Carb diets Trudi Deakin Current recommendations do not control epidemic of diabetes, 50% of calories from CHO is not beneficial Failure of low fat diets to improve obesity, cardiovascular risk or general health Side affects of commonly prescribed medication Evidence that low carb diets are successful without side affects Carbohydrate requirements differ based on individual preference, body weight, diabetes control, insulin resistance and physical activity levels; People need carbohydrate awareness education so that they can assess their carbohydrate intake and set goals to meet their individual needs.

Does a low fat diet help? Diet- Heart theory has never been proven. 2/3 rds people admitted to hospital with MI have normal cholesterol Current evidence does not support high consumption of PUFA and low SFA Small dense particles of LDL – increase risk of CHD. Excess consumption of CHO leads to small dense LDL (de novo lipogenesis) Low fat diet decreases blood lipids but concern reduces large LDL cholesterol and HDL not small dense LDL Low fat diet have not decreased prevalence of obesity and T2 DM Eating unprocessed foods containing SFA, MUFA and Omega 3 from fish but avoid trans fat, PUFA and excessive high GI foods has been shown to help health status

Example of very low carb diet Breakfast: 1 fried egg, 2 rashers of bacon, grilled tomato, fried mushrooms in butter Coffee/tea with milk allowance Lunch: Mackerel fillets, salad, 1 tbsp mayo, almonds Evening meal: ¼ roast chicken, broccoli and carrots. Gravy from meat juices Sugar free jelly with whipped cream and fruit Supper: glass of red wine, 50g cheese Milk in drinks: 200mls full fat 1875 kcals, Fat: 135g (65%), CHO: 36g (8%)

Evidence against Low carb diets Carla Gianfrancesco Reducing carbohydrate reduced healthy CHO which have been shown to protect against heart disease A restricted carbohydrate diet results in an unbalanced diet Low carb diets leads to the production of Ketones - ? Long term effect Brain prefers glucose as a fuel, needs 130g per day No conclusive evidence that low carb diets are better - ? Adherence Teaching carb awareness is beneficial help people enjoy a variety of CHO

Diabetes UK response Use an individualised approach People need to understand what foods contain CHO, how to estimate CHO portions, monitor effects on BG Aim to obtain CHO from vegetables, fruit, wholegrains and dairy

What does BHF advise? Whilst the latest study didn’t show saturated fat is associated with cardiovascular disease, it also didn’t show that eating more of it is better for your heart health. Eating a diet rich in fruit and vegetables, pulses, beans, wholegrains, unsaturated oils and fish means there is less room for the foods high in saturated fat and salt like fatty or processed meats and sweet treats. We need to think about the overall balance of the food and nutrients

Dietary fat consumption in the management of type 2 diabetes (Diabetes UK and DMEG) Replacing SFA with PUFA and MUFA reduces the risk of CVD in general populations and in high-risk populations including people with type 2 diabetes. When saturated fat intake is replaced by wholegrain/unrefined carbohydrates there is evidence for cardiovascular benefit. Refined carbohydrates appears to increase cardiovascular risk. No evidence suggesting increasing SFA intake is beneficial in reducing risk of CVD. Evidence suggests that Mediterranean-type (MUFA-rich) diets are effective for improving glycaemic control and CVD risk in people with type 2 diabetes. Low carbohydrate diets, which are not high in SFA, and other diets that are evidence-based options for the management of type 2 diabetes can continue to be recommended for weight loss under appropriate dietetic or medical supervision on an individual basis.

Conclusion Researchers can’t agree - ? Will policy change Use an individualised approach with patients. Focus on food rather than single nutrient Review patient’s CHO intake and if obese/ poor glycaemic control then makes sense to reduce CHO intake Patient choice of going on a low carb diet – ensure that they are aware of the side affects Promote unprocessed foods - Mediterranean style diet