The latest headlines have been fueled by the ill-advised national obesity forum publication ‘Eat fat, cut the carbs and avoid Snacking to reverse obesity and type 2 diabetes” (23rd May) and the findings from diabetes.co.uk survey of its 80,000 diabetic patients undertaking a 10-week low carb programme (31st May).
It is always important to challenge current thinking and explore new research. It is however, highly irresponsible to debate current thinking using studies that have already been discredited for methodological flaws. Add to which, in our opinion, it’s also unhelpful and damaging to design and direct a debate around controversial research findings for the consumer arena. Unless of course, we expect consumers to be totally adept at interpreting research findings into context of public health and able to fully understand and critique statistics and methodologies. This is unlikely when we consider that not all expert health professionals are able to correctly interpret research data into context nor have the skills to grasp appropriate selection criteria, dietary methodologies and limitations of study findings.
Low saturated fat debate – based on the same bad science
It was very disappointing to see the NOF cite the same studies that have been discredited in the past for methodological flaws and study selection bias. Their conclusions that lowering saturated fat intakes has no correlation to cholesterol levels or CVD outcome does not only go against the totality of scientific evidence but demonstrates their experts lack of knowledge in the critiquing of published data. Obvious factors such as the presence of trans fats from polyunsaturated margarines, the overall macronutrient profile of diets and which macronutrient replaced saturated fat reductions in the intervention groups were completely ignored in the studies cited by the NOF. These are very basic and undisputed factors that impact on CVD and serum cholesterol outcomes. An excellent explanation has been published by Dr Nita Forouhi from the University of Cambridge and covered by Prof. Bruce Griffin from University of Surrey during the Alpro Foundation symposium in March this year.
The totality of evidence points to:
• We should be talking about foods and diet and not individual nutrients.
o I.e. saturated fat sources from dairy do not adversely affect serum cholesterol levels compared to saturated fat from processed meat. Therefore, advice to consumers should be to eat less processed meats and not to eat less saturated fats.
• Lowering saturated fat intakes is important for reducing serum cholesterol levels, however, it isn’t enough. Which macronutrient replaces the saturated fat energy is important with polyunsaturated fats proving most effective whilst refined carbohydrates will show no benefit and in some cases negative effect.
• Whole diet approach should be encouraged where higher soluble fibre wholegrains, beans and peas, fruit and veg, oil rich fish and lean proteins are encouraged. It is the nutritional profile of the whole diet that will impact on CVD outcomes.
• Meta-analysis are not full proof and their conclusions should never be taken at face value. It is important to have a full understanding of the selection criteria used and potential contraindications that have been missed.
Low carbohydrate diets and type 2 diabetes
This has been fuelled by the patient led forum at diabetes.co.uk where it encourages its subscribers (over 120,000 patients with diabetes) to embark on a low carb 10-week programme. This has been championed by Dr Unwin, a GP from Southampton, who was frustrated at the lack of weight loss and poor glycaemic control of his type 2 DM patients following traditional dietary advice. He embarked on prescribing the low carb diet and has found that his patients are sticking to the dietary regimen, losing weight and significantly improving their HbA1c readings with significant financial savings to his practice. He has published two papers, one with 19 subjects and the other based on a case study. The low carb diet recommends anything from 0-130g of carbohydrates a day – normally no more than 100g – and a higher vegetable intake with lower fruit intake. To put it into context, 100g carbohydrate equates to 5 thick slices bread, 4½ medium bananas, 4 small servings (30g) of cornflakes OR 1¾ medium jacket potatoes. Carbohydrate calories are replaced, in the main, by unsaturated fats but also from proteins. Studies published on the success of this regimen are often small in number and over a short period of approx. 3 months. However, they are promising and seem to support the high protein satiety theory and better compliance to dietary restrictions. Ultimately, individuals on these regimens do consume significantly fewer calories. Although this dietary regimen can be successful for some patients, so have other regimens been proven to be as successful including higher wholegrain and low fat diets.
The primary goal for type 2 diabetes is weight loss to help optimise glucose control, therefore, dietary regimens should be matched to the individual patient’s needs. Different approaches will work for different individuals.