GI News Briefs
The biggest losers go low GI
Not only is it hard to lose weight, there’s not a lot of consensus about the best way to do it other than ‘eat less and exercise more’. But that piece of advice on its own doesn’t seem to be able to deliver the necessary results for most of us – if we can stick to it.
A team of Cochrane researchers in Australia analysed six carefully conducted randomised controlled trials running from 5 weeks to 6 months and involving 202 participants. They found that overweight and obese people lost more weight (on average 1 kilogram or 2.2 pounds more) on low GI diets than on similar energy high GI or other conventional energy-restricted weight loss diets. Not only that, the low GI diet had heart health benefits, too. ‘Low GI diets appear to be particularly effective for people who are obese,’ says lead author Dr Diana Thomas, who is the Scientific Director of the Centre for Evidence Based Pediatrics, Gastroenterology and Nutrition. She went on to comment that this may be because it’s easier for people to stick to low GI diets as there’s less need to restrict food so long as the carbs have a low GI. Their systematic review appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic. Check out the online review.
‘The (US) farm bill helps determine what sort of food your children will have for lunch in school tomorrow’ says Michael Pollan
‘A public-health researcher from Mars might legitimately wonder why a nation faced with what its surgeon general has called “an epidemic” of obesity would at the same time be in the business of subsidizing the production of high-fructose corn syrup. But such is the perversity of the farm bill: the nation’s agricultural policies operate at cross-purposes with its public-health objectives. And the subsidies are only part of the problem. The farm bill helps determine what sort of food your children will have for lunch in school tomorrow. The school-lunch program began at a time when the public-health problem of America’s children was undernourishment, so feeding surplus agricultural commodities to kids seemed like a win-win strategy. Today the problem is overnutrition, but a school lunch lady trying to prepare healthful fresh food is apt to get dinged by USDA inspectors for failing to serve enough calories; if she dishes up a lunch that includes chicken nuggets and Tater Tots, however, the inspector smiles and the reimbursements flow. The farm bill essentially treats our children as a human Disposall for all the unhealthful calories that the farm bill has encouraged American farmers to overproduce.’
– ‘You Are What You Grow’, The New York Times Magazine, 22 April 2007. Michael Pollan is author of the best-selling The Omnivore’s Dilemma.
Five great things about dark chocolate apart from the obvious
Like so many good things in life, a little goes a long way – remember it’s high in calories and saturated fat and rather more-ish. But a square or two (just 6 grams, 30 calories/126 kilojoules) is a delicious treat that can do you some good. Here’s how writes dietitan Alan Barclay.
- Chocolates don’t have a big impact on your blood glucose levels. In fact the average GI is around 45 because their high fat content slows the rate that the sugars are released from the stomach into the intestine, and absorbed into the blood.
- Chocolates are energy dense – you get a lot of kilojoules (calories) in a little piece. This is good if you are trying to gain weight, travel long-distances with limited storage space, or participate in an endurance sport where it is an advantage to be able to carry around a concentrated and highly palatable source of carbohydrate and energy.
- In real chocolate, cocoa butter (which is rich in a particular kind of saturated fat called stearic acid) is the main source of fat. Stearic acid raises the ‘bad’ LDL cholesterol much less than other saturated fats. It also raises the ‘good’ HDL cholesterol, so the net effect on your total blood cholesterol levels is not too bad at all.
- Chocolate (along with tea, berries, cabbage and wine) is one of nature’s richest sources of a powerful group of antioxidants, known as flavonoids. It’s believed that these antioxidants may benefit people with diabetes or pre-diabetes by helping to prevent cholesterol sticking to the walls of blood vessels, relaxing major blood vessels, and maybe even reducing the ability of the blood to form too many clots.
- Just one square of dark chocolate a day reduces blood pressure by a few mm Hg in healthy people with above-optimum blood pressure according to a new study published in the Journal of the American Medical Association. The researchers found that from baseline (the starting point) to 18 weeks, dark chocolate intake (just one little square – 30 calories/126 kilojoules) reduced average systolic blood pressure by about 3 mm Hg and diastolic BP by about 2 mm Hg without changes in body weight, plasma levels of lipids or glucose. Hypertension prevalence declined from 86% to 68%. ‘This study provides enough evidence to suggest that low amounts of polyphenol-rich dark chocolate as an addition to a healthy diet caused progressive reductions of systolic and diastolic blood pressure in older subjects with pre-hypertension without inducing weight gain or other adverse effects,’ said lead author Dr Dirk Taubert from the University Hospital of Cologne.
JAMA. 2007;298(1):49–60; JAMA News Release
Low GI carbs a key to healthy eyes as you age
Age-related macular degeneration (AMD) is one is the most common causes of blindness in the over-50s in the Western world. In ‘Food for Thought’ (May 2006) we reported on research suggesting that the quality of the carbohydrates you eat may help to bring it on – or hold it off. A new study published in the American Journal of Clinical Nutrition confirms that it would be a good idea to make a low GI diet part of any AMD prevention plan along with foods you already know about such as dark green leafy vegetables, a variety of fruits (all different colours) and fish. Dr Allen Taylor, director of the Tufts Laboratory for Nutrition and Vision Research, says the study shows that men and women who consume diets with a higher GI than average for their gender and age-group are at greater risk of developing advanced age-related macular degeneration.
The researchers analysed data from 4099 men and women participating in the Age-Related Eye Disease Study in the US. ‘Our findings suggest that 20% of the cases of advanced age-related macular degeneration might have been prevented if those individuals had consumed a diet with a GI below the average for their age and gender. Our results support our hypothesis that dietary GI, which has been related to the risk of diabetes, is also associated with the risk and severity of age-related macular degeneration.’ Taylor speculates that carbohydrates that comprise a high-GI diet may provide eye tissue with too much glucose too quickly, and overwhelm the ability of the eye cells to use the carbohydrate properly. ‘It is possible that the type of damage produced by poor quality carbohydrates on eye tissue is similar in both diabetic eye disease and age-related macular degeneration.’
– American Journal of Clinical Nutrition July 2007 Volume 8, Number 1; Nutraingredients- usa.com