Low carb diets should be considered for diabetes management

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DiabetesFollowing a reduced carbohydrate diet can help to lower blood glucose levels, providing a safe and effective strategy for managing diabetes, a London Metropolitan University systematic review suggests.

The authors conducted a systematic review of previous intervention studies, analysing changes to participant’s glycated haemoglobin levels following a switch to a lower carbohydrate diet. Glycated haemoglobin forms when haemoglobin, a protein in red blood cells, combines with glucose and is used to measure long-term blood glucose levels.

The review found that individual’s glycated haemoglobin levels fell when following a reduced carbohydrate diet (up to 120g per day) with the greatest reduction of 2.2% observed in those consuming under 30g per day.

Lead author Michelle McKenzie from London Met’s School of Human Sciences, said: “Our findings suggest that a reduced carbohydrate diet can be an effective technique for managing diabetes and new guidelines that promote lower carbohydrate intakes for both the general population, and those with diabetes, should seriously be considered.

“More long-term studies are required to ensure that the results can be confidently translated into clinical practice, however, the science at this point in time is compelling and should not be ignored.”

Participants following a reduced carbohydrate diet reported a significant decrease in body weight, losing a median of 4.7kg over a two-year period compared to 2.9kg lost by those consuming a low fat diet. A low carbohydrate diet was also associated with a decrease in the psychological stress associated with diabetes management and a reduction in negative moods between meals.

Co-author Sarah Illingworth said: “It’s important to consider which food groups should be used to replace carbohydrates when altering diet. Previous research has shown that diets high in fat, particularly saturated fat, carry risks for people with Type 2 diabetes.

“Clinical guidelines should be reviewed to consider including low carbohydrate diets as a diabetes management strategy but this does not mean that it will suitable, or beneficial, for everyone. Changes to diet should only be undertaken after consulting with a qualified dietitian and taking into account individual medical needs.”

The current dietary recommendations for diabetics are not significantly different from that of the general population; a high carbohydrate, low fat diet. Glycaemic fluctuations are unavoidable when consuming even moderate intakes of carbohydrates, exacerbating hyperglycaemia and dyslipidemia both of which are associated with the development of diabetic complications. The aim was to carry out a literature review to evaluate if restricting carbohydrate intakes was a safe and effective management strategy for diabetes.
A literature review was conducted using primary electronic databases to identify randomised control trials and intervention studies published between 2001–2015. Inclusion criteria were studies that were conducted in adults with diabetes and assessed the impact of restricted carbohydrate intakes on metabolic outcomes. They also specified the amount of carbohydrates in grams per day or percentage of total daily energy intake (TEI). Primary outcomes were changes in glycated haemoglobin levels and weight from baseline. Secondary outcomes were changes in lipoproteins, glycaemic variability and adjustments in medication.
There were significant reductions in glycated haemoglobin levels reported across the literature with the greatest reduction −2·2 % (p < 0·001) correlating with the lowest carbohydrate intakes (30gm/d) ( 1 ) . A decrease of −0·7 % (p < 0·001) was reported at 4 years for those consuming ≤75gm/d ( 2 ) , −1·1 % (p < 0·001) at 22 months for those following 80–90gm/d ( 3 ) and −0·9 % (p < 0·05) at 2 years when consuming up to 120gm/d ( 4 ) . Decreases in bodyweight ranged from −8·6 kg( 3 ) to −0·9 kg( 2 ) with greater reductions reported at 2 years in subjects following the low carbohydrate diet (−4·7 kg) compared to the low fat diet (−2·9 kg)( 4 ). Effects on fasting blood glucose were immediate dropping from 11·7 mmol/l to 7·0 mmol/l requiring an immediate reduction in medication( 3 ). 52 % of subjects consuming 14 % (TEI) from carbohydrates reduced their medication (p = 0·01) compared to 21 % following a diet of 53 % (TEI)( 5 ). A reduction or elimination of medication lead to a decrease in hypoglycaemic events( 1 ) with a two-fold greater decrease in glycaemic variability (p = 0·09) and greater periods in euglycaemic ranges (p = 0·07)( 5 ). There were significant improvements in lipoprotein profiles observed despite increases in dietary fat. When comparing intakes of 58 % fat and 14 % carbohydrates (TEI) (35 % MUFA, 13 % PUFA, 10 % SFA) to 30 % fat and 53 % carbohydrate (TEI) the low carbohydrate group significantly decreased triglyceride levels (p = 0·001) and increased high density lipoprotein levels (p = 0·007)( 6 ). It was also reported that there was a significant decrease in the psychological stress associated with diabetes management alongside a reduction in negative moods between meals( 7 ).
A carbohydrate restricted diet can provide a safe and effective solution for improving diabetes management and should have a place within the diabetic guidelines. The diet was effective in reducing postprandial hyperglycemia and glycaemic variability resulting in low levels of glycaemia without the risk of hypoglycaemia. The ability of the diet to reduce the symptoms of dyslipidemia is of particular importance and when compared to the traditional low fat diet for weight loss, the low carbohydrate diet was comparable and in some instances better. There were significant reductions or cessation of diabetic medication reported throughout the literature alongside a reduction in the psychological aspects of living with a long-term disease. It is possible that the current dietary advice may actually accelerate beta cell exhaustion with elevated blood glucose diminishing the islet cells ability to produce insulin.

MR McKenzie, S Illingworth

London Metropolitan University material
Proceedings of the Nutrition Society abstract

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