Prof Jennie Brand-Miller answers your questions.
What’s wrong with a low carb diet?
Recent studies show that low carb diets can produce faster rates of weight loss than conventional low fat diets. The probable mechanism is lower day-long insulin levels – allowing greater use of fat as the source of fuel – the same mechanism underlying the success of low GI diets.
Low carb diets are relatively safe and effective for weight loss in the short term, but there are potential risks in the long term (longer than six months). One major concern is the potential for high saturated fat intake and the repercussions from that intake. Even a single meal high in saturated fat can have an adverse effect on blood vessels by inhibiting vasodilation, the normal increase in the diameter of blood vessels that occurs after a meal. A short-term and long-term effect of a low carb diet includes an increase in LDL cholesterol. Compounding this, there may be a low intake of miconutrients that are protective against disease. For this reason, a vitamin and mineral supplement is an essential accompaniment to a low carb diet. Low carb diets are often high in protein (although not all high-protein diets are low in carbohydrate). In people with diabetes, higher long-term protein loads (over six months) may accelerate decline in kidney function and increase calcium loss in urine, potentially increasing the risk of osteoporosis and kidney stones.
We believe that low carb diets are unnecessarily restrictive (bread, potato, rice, grains and most fruits are restricted) and may spell trouble in the long term if saturated fat takes the place of carbohydrate. Low GI diets strike a happy medium between low fat and low carb diets – you can have your carbs, but must choose them carefully.
GI testing by an accredited laboratory
Dr Alexandra Jenkins
Glycemic Index Laboratories
20 Victoria Street, Suite 300
Toronto, Ontario M5C 298 Canada
Phone +1 416 861 0506
Research Manager, Sydney University Glycemic Index Research Service (SUGiRS)
Human Nutrition Unit, School of Molecular and Microbial Biosciences
NSW 2006 Australia
Phone + 61 2 9351 6018
Fax: + 61 2 9351 6022