Why low GI foods make you feel full
Researchers at the Department of Nutrition and Dietetics at King’s College London report that low GI meals increased the levels of GLP-1 gut hormone levels, leading to the suppression of appetite and the feeling of fullness in a paper presented at the annual society for endocrinology BES meeting in the UK in March 2009.
Dr Tony Leeds, and Reza Norouzy looked at the effects of a single low versus high GI meal on gut hormone levels in 12 healthy volunteers. Each participant ate an identical moderate GI meal for dinner, fasted overnight, and was given either a low GI (46) or high GI (66) meal for breakfast. Blood samples were then taken every 30 minutes for 150 minutes, and levels of the gut hormone GLP-1 and insulin measured. GLP-1 is a hormone produced by the gut that has been shown to cause a feeling of fullness and suppression of appetite. Volunteers who ate a low GI breakfast had 20% higher blood plasma levels of GLP-1 and 38% lower levels of insulin compared to those who had consumed a high GI breakfast.
Researcher Dr Reza Norouzy said: ‘Our results suggest that low GI meals lead to a feeling of fullness because of increased levels of GLP-1 in the bloodstream. We now need to expand the findings of this preliminary study and look at the effects of low versus high GI meals in a larger group of people.’
– Kings College London press release.
Low GI diet halved number of women with gestational diabetes needing to use insulin
Women with gestational diabetes can halve their chances of needing insulin by following a low GI diet, according to a new Australian study. Sixty-three women (aged 18–40, all non smokers) followed either a low GI diet or a conventional high fibre (and higher GI) diet. Women on the low GI diet consumed foods such as whole grain pasta and breads, and unprocessed, high fibre breakfast cereals. The control group was advised to eat a high fibre, low sugar diet with no specific guidelines with respect to GI. Both diets met current dietary recommendations for pregnant women.
The results published in Diabetes Care, show that 29% of the women on the low GI diet required insulin, while 59% on the higher GI diet needed insulin. Of the 19 women in the control group who met the criteria for starting insulin, 9 were able to avoid insulin use by switching to a low GI diet.
Gestational diabetes is the type of diabetes that women can develop during pregnancy. In any pregnancy, some insulin resistance develops as a pregnant woman’s insulin needs are 2–3 times her normal needs. But, if you are overweight at the same time, it’s worse. And if your body can’t produce enough insulin to overcome the insulin resistance, your blood glucose levels increase above normal. If gestational diabetes is undetected and untreated, the baby is at risk of growing too big in the womb, which can make the birth difficult. The baby is also at risk of other complications and is more likely to be overweight as a child and develop health problems such as high blood pressure, heart disease and diabetes later in life.
About 5%, or one in every 20 pregnant women, will develop gestational diabetes, and those numbers are increasing. Most women can manage their gestational diabetes with healthy eating, exercise and regular blood glucose monitoring. Here are dietitian Kaye Foster-Powell's healthy eating tips for women with gestational diabetes.
- Eat regular meals and mid-meal snacks, and avoid getting overly hungry.
- Limit sugary foods and drinks including soft drinks, cordials, confectionery and desserts.
- Limit fatty foods, especially foods high in saturated fats such as crisps, pastries, take-aways, butter and cream, biscuits and cakes.
- Include low GI (slow release) carbohydrate foods at each meal and snack.
- Eat a wide variety of nutritious foods
Great discoveries in nutrition, and the challenges we face
The past 30 years have yielded major new discoveries in nutrition and health. At a one-day symposium at Wageningen University the audience voted on the greatest discoveries in nutrition since 1976 – and on the greatest nutrition and health challenges ahead. The results have now been published in the European Journal of Clinical Nutrition. The participants chose ‘Folic acid prevents birth defects’ as the greatest discovery in nutrition science since 1976. GI (‘Interaction of carbohydrate/glycemic load with insulin resistance’ – Jenkins) came in at #12 and GI News’ Prof Trim (aka Prof Garry Egger with Prof Boyd Swinburn) at #7 with ‘Obesity is a normal response to an abnormal environment’. ‘Controlling obesity and insulin resistance through activity and diet’ was voted as being the biggest challenge we face with ‘Can diet delay cognitive decline’ coming in as the #2 challenge for the years ahead.
The Joy of Cooking … too much
Eating out is often blamed as being one of the key culprits for gaining weight, but a letter published in the Annals of Internal Medicine, suggests that what we do in our own homes may be just as bad. In the study, the researchers found recipes for four, that would have served around seven people in 1936.
Examining 18 ‘classic’ recipes found in seven editions of the ‘classic’ The Joy of Cooking since it was first published in 1936 until the 2006 update, Dr Brian Wansink and Dr Collin Payne found that the average calories per serving jumped 63% in 70 years in 17 of the 18 recipes. In calories that's from about 268 calories (1125 kJ) per serving in 1936 to about 436 calories (1831 kJ) in 2006.
In analysing just the calorie density of the recipes – the total amount of calories, regardless of serving size – the foods in the 2006 edition had 37% more calories than the 18 recipes did in the 1936 edition. Similar increases were found in other classics such as the Better Homes and Gardens Cook Book.
Speaking to Susan Lang of Cornell Chronicle Wansink said: ‘This jump in calories was influenced by both changes in ingredients – usually increases in fat and sugar – and changes in serving size. Family size has gotten smaller, but calorie content and portion sizes have gotten bigger’. The researchers cite beef stroganoff as an example. In the 1997 edition, the recipe called for three tablespoons of sour cream (that’s less than ¼ cup). The 2006 edition calls for 1 whole cup. The study also found that some of the added calories came from substituting ingredients, such as extra meat instead of vegetables.
Meat and mortality – the real risks
High intake of red and processed meats is associated with increased risk for death in older adults, while white meat may have a protective effect are the findings of a study published in Archives of Internal Medicine.
More than a half million adults aged 50 to 71 completed food-frequency questionnaires and then were followed for 10 years. The study relied on people’s memory of what they ate, which can be faulty. In the analysis, the researchers took into account risk factors such as smoking, family history of cancer and high BMI.
Over 10 years, eating the equivalent of a quarter-pound hamburger daily gave men in the study a 22% higher risk of dying of cancer and a 27% higher risk of dying of heart disease. That's compared to those who ate the least red meat, just 5 ounces (150 g) per week. Women who ate large amounts of red meat had a 20% higher risk of dying of cancer and a 50% higher risk of dying of heart disease than women who ate less. High intake of processed meat was also associated with increased mortality risks. Conversely, consumption of white meat (poultry and fish) was associated with significantly decreased risks for total and cancer-related mortality.
In an accompanying editorial, Prof Barry Popkin, director of the Interdisciplinary Obesity Center at the University of North Carolina at Chapel Hill, wrote that reducing meat intake would have benefits beyond improved health. Livestock increase greenhouse gas emissions, contributing to global warming, he wrote, and nations should reevaluate farm subsidies that distort prices and encourage meat-based diets. ‘We’ve promoted a diet that has added excessively to global warming,’ Popkin said in an interview. Successfully shifting away from red meat can be as easy as increasing fruits and vegetables in the diet, said Elisabetta Politi of the Duke Diet and Fitness Center in Durham, N.C.
www.foodwatch.com.au has had a facelift
Catherine Saxelby’s website is a one-stop information shop on all things food and nutrition. It’s just had a facelift and now offers product reviews (goji berries, vitamin waters), free fact sheets on topics like fibre, salt and portion caution, expert articles, and delicious recipes to try. You can sign up for Catherine’s free monthly newsletter, take part in one of her regular polls on nutrition and food hot topics, or post your own comments on her blog: Catherine’s News, Chews and Reviews!
Interested in controlling your cholesterol and looking after your heart? Check out Nicole Senior’s website where you’ll find the latest research, news you can use, fascinating facts about heart-friendly food, food myths, frequently asked questions, and the recipe of the month. Nicole presents the scientific facts in a way that’s easy to understand and, importantly, to put into practice. “It’s all about food that’s good to eat and good for you”, says Nicole.