GL evidence – Cardiovascular health
Two groups of overweight or obese people followed either a low GL diet or a low-fat low-calorie diet for two years. After each person had lost ten per cent of their body weight, other measures of their health were taken. Those on the low GL diet had greater improvements in insulin resistance (blood sugar control), triglycerides (fat circulating in the blood), inflammation and blood pressure compared with those on the conventional low-fat, low-calorie diet. The researchers concluded that a reduction in glycemic load may aid in the prevention or treatment of obesity, cardiovascular disease, and diabetes mellitus.
One group of people followed a low GL diet while another group followed a conventional low-fat, low-calorie diet (Canada’s Food Guide to Healthy Eating). Those following the low GL diet, not only lost more weight, they also had greater improvements in HDL cholesterol, triglycerides and fasting glucose compared to those on the conventional low-fat, low-cal diet after six months. These health gains were sustained or improved upon after twelve months. The researchers concluded that ‘implementation of a low GL diet is associated with substantial and sustained improvements in abdominal obesity, cholesterol and blood sugar control’.
A study published in the Lancet in 2004 in which two groups of mice were fed either a low-GL diet or a high GL diet and their health compared. Besides being leaner, the low-GL group had better blood sugar control, lower blood fats and did not suffer the pancreatic disruption of the high-GL group.
A study of 574 adults in Massachusetts between 1994 and 1997, found that higher total carbohydrate intake, percentage of calories from carbohydrate and glycemic index/glycemic load were related to lower levels of beneficial HDL cholesterol and higher blood triglyceride levels. These results show an unfavourable effect of increased intake of highly processed carbohydrate on fat profile, which may have implications for metabolic syndrome, diabetes and coronary heart disease.
Participants in this study were assigned to either a low-fat diet or 1 of 2 Mediterranean diets. Those in the Mediterranean diet groups received nutritional education plus either free virgin olive oil (1 litre per week) or free nuts (30g per day). Changes were evaluated after 3 months.Compared with the low-fat diet, the Mediterranean diet produced more beneficial changes in blood sugar levels, blood pressure and good HDL cholesterol. The Mediterranean diet with olive oil also reduced levels of the dangerous C-reactive protein, associated with heart disease. These results show that a Mediterranean-style diet, which promotes low GL carbohydrates and increased monounsaturated fat intake, is more beneficial than a low fat diet.
Twelve men with type two diabetes followed a low GL or high GL for 4 weeks. Blood sugar levels after a meal were significantly lower in people following the low GL diet than those in the high GL diet. Insulin levels and ‘bad’ LDL cholesterol were also lower in the low GL group.
Another study, this time from Italy, called the EPICOR trial, which involved more than 47,000 people, compared diet with cardiovascular risk over almost eight years. Those women in the top quarter of glycemic load (GL) diets, eg eating the most carbs in the form of fast-releasing sugar and refined foods, had double the risk of coronary heart disease than those in the lowest quarter. This study didn’t find the same association with men. There is no clear reason for the sex differences however it may be that women are more sensitive to the hormonal changes that accompany high GL diets.
There’s a quandary in the diet world. Evidence shows that a low-carb, high protein diet, aka Atkins, does work for weight loss, but, on the other hand, a high meat/milk intake fails to lower bad ‘LDL’ cholesterol and is associated with increased cancer risk. But what happens if you eat a lower carb diet, with more protein instead from vegetable sources, such as beans, nuts, seeds, soya, all foods associated with lowering cholesterol and cancer risk? A study published in the Archives ......
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