GI News Briefs

The vegan advantage
For over a hundred years, people with diabetes have been given advice on what to eat. It was not until the 1970s that carbohydrate was considered to be a valuable part of the diabetic diet. Researchers found that not only did the nutritional status of patients improve with a higher carbohydrate intake, but their insulin sensitivity improved as well. Now a US and Canadian research team led by Dr Neal Barnard suggests that a high carbohydrate (favouring low GI carbs), low fat vegan diet treats type 2 diabetes more effectively than a diet based on American Diabetes Association (ADA) guidelines – especially in reducing the need for diabetes medications.

Neal D Barnard, MD

In the randomised, controlled pilot trial, 49 people with type 2 diabetes followed a low-fat vegan diet consisting of about 10% of daily calories from fat, 15% from protein, and 75% from carbohydrates. They avoided animal products and added fats and favoured low GI foods like beans and green vegetables. Portion sizes and total daily calories or food intake were unrestricted and they took a B12 supplement because people on a vegan diet are at risk for vitamin B12 deficiency.

The other 50 participants followed a low-fat diet based on ADA guidelines – 15%–20% protein, 60%–70% carbohydrates and monounsaturated fats (such as olive oil), and less than 7% saturated fats (such as animal fats and butter). Total cholesterol was also limited to 200 milligrams or less per day. Overweight participants in this group were also advised to reduce daily calorie intake by 500–1,000 calories per day.

Participants on both diets significantly improved their glycemic control and reduced unhealthy cholesterol levels; but the changes were even greater in the vegan group.

• 43% of those on the vegan diet reduced their need to take drugs to manage their diabetes compared with 26% of the ADA group.
• Weight loss averaged more than 14 pounds in the vegan group; it was less than 7 pounds in the ADA group.
• LDL ‘bad’ cholesterol dropped by an average of 21% in the vegan group compared with 11% of those in the ADA group who did not change their cholesterol drug use.

It’s early days, as the research team acknowledges concluding that ‘further research is necessary to establish longer term diet effect and sustainability.’ However, in a news release, Dr Barnard makes the point that: ‘The diet appears remarkably effective, and all the side effects are good ones – especially weight loss and lower cholesterol. I hope this study will rekindle interest in using diet changes first, rather than prescription drugs.’
– Diabetes Care 29:1777-1783, 2006

Photo: Ian Hofstetter

Want to try some delicious veg-based recipes? Check out The Low GI Vegetarian Cookbook reviewed in this issue – it features 80 vegetarian and vegan recipes along with 7-day menu plans for vegetarian and vegan adults, teenagers and children.

High blood glucose linked to dementia
A four-year study of post-menopausal women has found that chronically elevated blood glucose (glycated hemoglobin or HbA1c levels of 7% or higher) is linked with an increased risk of developing mild cognitive impairment or dementia. ‘We already know there’s a connection between diabetes and cognitive problems,’ says the study’s lead author Dr Kristine Yaffe of the University of California, San Francisco. ‘We were interested in what this measurement would tell us about a group of women with and without diabetes who were followed for four years. Nobody has really looked at that before.’

The four-year prospective study looked at 1,983 women whose HbA1c levels were tested at the beginning of the study. Over the course of the study, 86 women developed mild cognitive impairment or dementia – for every 1% increase in HbA1c, the women had a greater age-adjusted likelihood of developing mild cognitive impairment or dementia. Women with a HbA1c of 7% or higher at baseline were four times more likely to develop mild cognitive impairment or dementia than women who tested at less than 7%. Even when the researchers excluded the 53 women known at the outset to have diabetes, there was still a statistically significant association between elevated HbA1c and cognitive risk.

‘Type 2 diabetes is a very common and growing problem,’ says Yaffe. ‘The point is that now you can identify people who are at risk for mild cognitive impairment or dementia and monitor them closely … I think we need to take these people who are at risk and see whether we can target them for trials or interventions for better blood glucose control.’
– Journal of Nutrition, Health, and Aging (10) 4.

What’s glycated hemoglobin?
Glycated hemoglobin, also known as HbA1c or simply A1c, measures the percentage of hemoglobin – the oxygen-bearing protein in red blood cells – that is bound to glucose. A result of 4 to 6% is normal. In people with diabetes, 7% or less indicates good long-term blood glucose control. Unlike a standard blood glucose test that measures your blood glucose at the moment of testing, HbA1c gives an indication of your blood glucose levels over the 2–4 months preceding the test.

Red Blood Cells

Not chubby by choice
The energy equation says energy intake and energy expenditure need to be in balance if you are to maintain a healthy weight. Simple isn’t it. So if you are overweight or obese you eat too much or exercise too little. And it is your fault. No, says Dr Robert Lustwig, professor of clinical pediatrics at UCSF Children’s Hospital. It’s not like that. Certainly not when it comes to children. They should not be blamed or expected to take personal responsibility for their diets when they are offered foods full of sugar and devoid of fibre. ‘The concept of personal responsibility is not tenable in children. No child chooses to be obese,’ he says.

In a comprehensive (and passionate) review of obesity research published in the August edition of Nature Clinical Practice Endocrinology & Metabolism, he concludes that changes in manufacturing processes over the past 30 years have made food ‘toxic’ and ‘addictive’, leading to obesity. ‘Our current Western food environment has become highly insulinogenic (elevates insulin levels),’ says Dr Robert Lustig, ‘as demonstrated by its increased energy density, high-fat content, high glycemic index, increased fructose composition, decreased fibre, and decreased dairy content.’ This upsets the balance of two hormones, which regulate how much we eat – leptin and insulin.

Here’s how it works. Insulin encourages eating in two ways. It blocks the signals that travel from the body’s fat stores to the brain by suppressing the effectiveness of leptin – and this leads to increased eating and decreased activity. It also promotes the signal carried by the chemical dopamine that seeks the reward of eating. So we want to eat for that pleasurable dopamine ‘rush’ – and this is the addictive bit.

Calorie/kilojoule intake and expenditure are normally regulated by leptin. When leptin is doing its job it ‘increases physical activity, decreases appetite, and increases feelings of well-being.’ When it is not, activity levels decrease, appetite increases and you get ‘leptin resistance’. Prof Lustig suggests that two factors which are promoting insulin production and making foods addictive are adding sugar to foods that never used to have it, and removing fibre in the processing.
– Nature Clinical Practice Endocrinology & Metabolism (2006) 2: 447–458

Robert H Lustig, MD

The chromium question
Chromium is an essential mineral that plays an important role in how our bodies metabolise carbohydrate, fat and protein. Current research suggests that it helps insulin work more effectively in the cells of the body, which in turn will help the body manage blood glucose levels better. So, if you have type 2 diabetes, will taking extra chromium as a supplement improve your blood glucose levels. To date studies have yielded conflicting results. A new, small double blind study by Julie Martin from the University of Vermont published in Diabetes Care in August found that ‘chromium picolinate supplementation in subjects with type 2 diabetes who are taking sulfonylurea agents significantly improves insulin sensitivity and glucose control’. The researchers tested whether chromium supplements were useful in combination with a sulfonylurea medication – an older class of diabetes drugs that often spur weight gain. They randomly assigned 29 diabetic adults to take either the medication plus 1,000 micrograms of chromium picolinate per day or the drug plus a placebo (sugar pill) for 6 months. In the end, study participants who took the supplement showed greater improvements in insulin sensitivity and blood glucose control. They also gained less weight and body fat than those on the medication alone.
– Diabetes Care 29: 1826-1832, 2006

GI Group: A word of caution about this interesting result – the researchers did not monitor the participants’ food or physical activity before or during the study. So it is not possible to say conclusively that the improvements were due to the chromium picolinate alone.

In addition, the body loses many vitamins and minerals (including chromium) in urine, and when urination increases, as it does with poorly managed diabetes, losses can be excessive and lead to a deficiency. Most people with type 2 diabetes can reverse this deficiency within a few months by achieving and maintaining optimal blood glucose levels. During this initial period, it may be useful to take a multivitamin supplement to boost the replenishment process. But once an individual is managing blood glucose levels and eating a healthy diet this should no longer be necessary. As for chromium, the body only needs only a minute amount – around 25 micrograms a day for women and 35 micrograms a day for men. And it is found in many foods. Good sources are bran-based breakfast cereals and wholegrain breads and cereals; brewers yeast; cheese; fruits such as apple, oranges and pineapple; vegetables such as broccoli, mushrooms, potatoes with their skin on, tomatoes; liver; peanuts; and some spices.