Low GI diet significantly helps people improve blood glucose control
The aim of diabetes management is to keep blood glucose levels as close as possible to the normal range (4–8 mmol/L, which translates to 65–110 mg/dL), to improve quality of life (and life expectancy) and reduce the risk of complications, heart attack and stroke.
A recent Cochrane systematic review that analysed 11 randomised controlled trials of either low GI or low glycemic load (GL) diets finds that following a low GI diet significantly helps people with type 1 and type 2 diabetes to improve their blood glucose control. In fact, the researchers found that HbA1c levels decreased by 0.5% with a low GI diet, and point out that the findings are significant both statistically and clinically. (HbA1c stands for glycated hemoglobin A1c, a measure which gives a picture of a person's blood glucose control over several weeks or months.)
Lead review author, Dr Diana Thomas, from the Center for Evidence-Based Pediatrics, Gastroenterology and Nutrition at the Children's Hospital at Westmead says: ‘The 402 participants were adults in most studies; however, there were two studies in children, all of whom had type 1 diabetes. So, the results are relevant to both adults and children, with either type 1 or type 2 diabetes.’
‘Now that the principles of eating low GI foods are clear,’ she said, ‘this way of eating should be incorporated into daily living.’ The point ‘is to lower the GI or GL of the diet, rather than to follow specific diet plans, which over the longer term can be very difficult to maintain,’ Thomas said.
What are Cochrane systematic reviews? The Cochrane Collaboration is an international not-for-profit organisation providing up-to-date information about the effects of health care. It was set up to collect and collate healthcare data independently and create transparent, systematic, unbiased reviews of the published medical literature on everything from drugs, through surgery, to dietary and community interventions. At the online Cochrane Library you will find its free plain language summaries and abstracts.
A growing concern: more gestational diabetes, more bigger babies
The percentage of babies born heavier than 4 kg (8.8 lbs) has risen from 10.9% in 1990 to 12.1% in 2005 in New South Wales (Australia), according to data collected from midwives and published in annual Mothers And Babies reports. Having a big baby can lead to delivery complications, increased likelihood of having a caesarian, and the baby is more likely to be overweight as a child and develop health problems such as high blood pressure, heart disease, diabetes and fatty liver disease.
A major cause of bigger babies is gestational diabetes which affects almost 5% of pregnant women in ANZ, the US and the UK and is on the rise – it increased by 45% in New South Wales between 1995 and 2005. The main reason for the increase is maternal overweight/obesity. In any pregnancy, insulin resistance develops naturally as a pregnant woman’s insulin needs are 2–3 times her normal needs. If a woman is overweight during pregnancy, it’s worse. If her body cannot produce enough insulin to overcome the insulin resistance, her blood glucose levels increase above normal, placing the baby at risk of growing too big in the womb.
To provide simple dietary solutions that will help reduce the risk of ongoing health problems for mothers with gestational diabetes and their babies, an Australian research team including endocrinologist Dr Tania Markovic and Prof Jennie Brand-Miller have launched a 2-year study where they will monitor women with diabetes on low GI diets and measure their babies’ body fat as well as health.
Low-carb diets better at controlling type 2 diabetes said the headlines.
Dig a bit deeper …
In a six-month comparison (funded by the Atkin’s Foundation) between a low-carb diet (based on Dr Robert Atkins’ books) and a low GI diet (based on Rick Gallop’s GI books), ‘patients who followed the no-glycemic diet (Atkins) experienced more frequent reductions, and in some cases elimination, of their need for medication to control type 2 diabetes,’ according to lead author Eric Westman, MD, of Duke University Medical Center. The findings are published online in Nutrition and Metabolism. ‘Low glycemic diets are good, he said. ‘but our work shows a no-glycemic diet is even better at improving blood sugar control,’ he says.
In the study, 84 volunteers with type 2 diabetes were randomly assigned to either a low-carb ketogenic diet (less than 20 grams of carbs per day) or a high carb (55%), low-glycemic, reduced calorie diet. Both groups attended group meetings, had nutritional supplementation and an exercise regimen. The low-carbers were instructed to eat: ‘unlimited amounts of animal foods (meat, chicken, turkey, other fowl, fish, shellfish) and eggs; limited amounts of hard cheese (cheddar or Swiss, 4 ounces per day), fresh cheese (cottage or ricotta, 2 ounces per day), salad vegetables (2 cupfuls per day), and non-starchy vegetables (1 cupful per day). Participants were encouraged to drink at least 6 glasses of permitted fluids daily.’
According to the findings, of those who completed the study, the volunteers in the low-carb diet group had greater improvements in hemoglobin A1c. Diabetes medications were reduced or eliminated in 95% of the low-carbohydrate volunteers, compared to 62% in the low-glycemic group. The low-carb diet also resulted in a greater reduction in weight.
This is the story that hit the headlines around the world. If you read the paper itself (and don't just rely on the selected findings and quotes from the press release as many journalists did), you'll find that although it’s a dietary study, there's virtually no information on the low GI diet at all. Many health professionals incorrectly assume that all high fibre foods are low GI food. In this study, the researchers don't say what the average GI was.
‘That’s a vital piece of missing information,’ says Dr Alan Barclay, Chief Scientific Officer of GI Limited. ‘A GI of 45 or less is a reasonable definition of a low GI diet or meal,’ he says. ‘This is because what we now know from numerous observational cohort studies around the world is that the average GI of the diet of people in the lowest quintile (20% of the population) is about 40–50. Similarly, in a recent meta-analysis of 15 experimental studies investigating the role of low GI diets in managing diabetes, the average GI was 45. Since this average GI has been proven to have significant health benefits in people with existing diabetes and in reducing the risk of chronic diseases like heart disease and diabetes, and importantly, people can and do achieve it in real life, we believe a GI of 45 or less is what we all need to be aiming for.’
It wasn't all good news for the low carbers in the study either. ‘Bad’ LDL cholesterol went down in the low GI diet and rose on the Atkins diet and side effects like headaches, constipation and diarrhea were greater for the no-carbers. It had a significantly greater dropout rate too.
GI Group: Our position remains the same, whether the low carb option works for you and managing your blood glucose, or if you really enjoy your carbs (in sensible portions of course), you need to make sure it’s the smart, low GI ones you include in your meals and for snacks.