Prof Jennie Brand-Miller on how low should a low GI diet go?
‘The GI was introduced back in 1981 to rate the glycemic character of the carbohydrate in individual foods like bread, breakfast cereal, rice, pasta, apples etc.,’ says Prof Jennie Brand-Miller. ‘The purpose was to exchange one carbohydrate source with another for snacks and in your meals (e.g. replacing a high GI breakfast cereal like corn flakes with a low one like natural muesli). The decision behind the cut-offs for rating high GI (70 or higher) and low GI (55 or less) foods, was based on the scatter of GI values among the single foods that had been GI tested.
Increasingly we are asked about the GI of mixed meals and the effect of extra protein and fat in the food on GI and blood glucose response. Eaten alone, protein and fat have little effect on blood glucose levels, but that’s not to say they don’t affect your blood glucose response when they are combined with a carb-rich food. Protein will stimulate additional insulin secretion, resulting in lower blood glucose levels. Protein and fat both tend to delay stomach emptying, thereby slowing the rate at which carbohydrate can be digested and absorbed. So a high fat meal will have a lower glycemic effect than a low fat meal even if they both contain the same amount and type of carbohydrate.
We believe there’s a real need to define the difference between a low GI diet and/or meal and a low GI food. Because a low GI food is defined as 55 or less, people have made the reasonable assumption that a whole diet that averages less than 55 is low enough. In fact the average Australian and American diets already has a GI of 56 to 58 because we all eat low GI fruits and dairy products and of course sugar has a medium GI (65). To reduce the risk of chronic disease, we believe that a low GI eating pattern/diet must have much lower number.
We would propose that a GI of 45 or less is a reasonable definition of a low GI diet or meal. This is because what we now know from numerous observational cohort studies around the world is that the daily average GI of the diet of people in the lowest quintile (20% of the population) is about 40–50. Similarly, in a meta-analysis we published in Diabetes Care of 15 experimental studies investigating the role of low GI diets in managing diabetes, the daily 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.’
Why we can’t afford to be so dependent on so few crops.
Graziano da Silva
From the peaks of the Andes to the Asian steppes, from the Arctic coasts to the African savannah, roughly 30,000 edible crops have been identified throughout the world. At December 2012’s international Crops for the 21st Century seminar José Graziano da Silva reminded us that while some 7000 species of plants according to FAO estimates have been cultivated or consumed as food throughout human history, many of these species are disappearing today. ‘If we lose these unique and irreplaceable resources, it will be more difficult for us to adapt to climate change and ensure a healthy and diversified nutrition for all,’ he said. ‘Globalisation has created an abundance of food in some parts of the world, but has failed to end the chronic shortages that exist elsewhere. It has also created a homogeneity of products, accompanied by a loss of different culinary traditions and agricultural biodiversity.’
According to FAO, the caloric intake of most people on the planet is based today on only four crops: rice, maize, wheat and potatoes. ‘Our dependence on a few crops has negative consequences for ecosystems, food diversity and our health. The food monotony increases the risk of micronutrient deficiency,’ he said. ‘We are slowly forgetting how to identify, cultivate, cook and conserve hundreds of local varieties that have adapted over time to the climactic conditions and the characteristics of every kind of land. We are losing a precious fountain of knowledge that has been accumulated over generations to find in local nature a response to our needs.’
To address these challenges, the FAO has called for the sustainable intensification of agricultural production via a food production model it calls Save and Grow, that also preserves and enhances natural resources. In calling for increased research on under-utilised crops, Graziano da Silva stresses that such species ‘play a crucial role in the fight against hunger and are a key resource for agriculture and rural development’.
He also underlined the importance of sustainable diets. ‘While almost 870 million people go hungry, an even greater number are overweight or obese. And even as inadequate access to food causes suffering in poor countries, every year consumers in industrialised countries waste 220 million tons of food, an amount equivalent to sub-Saharan Africa’s total annual food production,’ he said.