Saturday, November 8, 2008

Low-Carb Diet Lowers Insulin Levels


While not all dietary approaches are applicable or beneficial to everyone, there are some, I think, that generally hold true. Here’s one: If you want a long, healthy life, do what you can to ensure stability of blood sugar and insulin levels.

What this usually means in practice is the regular eating of foods that tend not to disrupt blood sugar (and therefore insulin) levels, such as meat, fish, eggs, green vegetables, certain fruits (for example, apples, berries), beans, lentils, nuts, and seeds.

What this diet is generally devoid of, you may notice, is foods containing refined sugar and starchy carbs such as bread, potatoes, rice, pasta, and breakfast cereals. The primal diet above is often dubbed a low-carb diet on the basis that it contains considerably less carbohydrate compared to the starch-rich diet so often advocated (and eaten) these days. Some people even recommend such a starch-rich diet for diabetics, even though carbohydrate is the specific dietary element that diabetics have difficulty handling.

Part of the rationale for a carb-controlled diet in diabetics comes from the fact that the less carbohydrates one eats, the lower the blood sugar level will tend to be. And at the risk of stating the obvious, this is of clear merit for diabetics whose prime ambition might be to keep blood sugar levels under control.

However, another important part of the rationale for eating a low or lower carbohydrate diet is that it demands less insulin to be secreted by the body’s pancreas. Generally speaking, the less insulin someone secretes, the less likely they are to suffer from insulin resistance (when the body’s ability to respond to insulin’s blood sugar lowering effects is blunted). Also, less insulin means less likelihood that the cells in the pancreas responsible for secreting insulin—the beta cells—will become exhausted.

Basically, the more insulin someone secretes over time, the more likely they are to suffer from a lack of insulin or an inability to respond to it appropriately. This is a situation many type 2 diabetics can find themselves in, particularly, logic dictates, if they eat a diet replete with carbohydrates, including starchy ones.

Of course this concept of controlling carb intake is not just relevant for diabetics, but also for those who would prefer not to develop diabetes. I was therefore interested to read a recent study that tested the effects of low-carb and low fat (and higher-carb) diets in a group of obese adolescents aged 12 to 18. This 12-week long study showed that these diets performed similarly well with regard to changes in measures such as body mass index and body fat percentage.

On the other hand, the low carbohydrate diet out-performed the low fat one in two critical areas. Firstly, insulin levels were lower in those eating a lower-carb diet. The researchers also used an assessment known as the homeostatic model assessment (HOMA), which is used to measure the extent to which an individual is suffering from insulin resistance and beta-cell exhaustion. Here too, the low-carbers faired better.

In short, after just three months on a lower-carb diet, adolescents saw improvements in their biochemistry, which would, generally speaking, put them at reduced risk of developing type 2 diabetes over time. This evidence is in line with other research that has found that the consumption of blood sugar-disruptive carbohydrate is associated with an increased risk of diabetes.

References:

Demol S, et al. Low-carbohydrate (low and high-fat) versus high-carbohydrate, low-fat diets in the treatment of obesity in adolescents. Acta Paediatrica. 2008 Sep 29. [Epub ahead of print]

Dr. John Briffa is a London-based physician and author with an interest in nutrition and natural medicine. Dr. Briffa's Web site

Last Updated Oct 29, 2008

Low GI Diet Protects Eyes


Age-related macular degeneration (AMD) is the most common cause of loss of vision in adults.

Last year, I wrote about a study that found a link between eating a diet relatively disruptive for blood sugar levels (a high-glycemic index diet) and increased risk of AMD. The authors of this study concluded that eating a low-glycemic index (GI) diet would perhaps eliminate 20 percent of cases of AMD.

I was interested to read a recent study that has replicated this finding. This particular research, conducted in Australia, assessed the relationship between dietary GI and risk of AMD over 10 years in a group of almost 2,000 people [1].

The results of this research showed that compared to individuals consuming lower-GI diets, those consuming the highest-GI diets were at a 77 percent increased risk of developing AMD. These findings are very much in line with those reported in the study from last year.

Eating a low-GI diet means eating a diet mainly of meat, fish, eggs, nuts, seeds, green vegetables, beans, lentils, and certain fruits such as apples and berries. My advice would be to limit grains, most bread, and many breakfast cereals. They are particularly disruptive to blood sugar and insulin levels when eaten in quantity.

This recent Australian research also looked at the relationship between cereal fiber intake and AMD risk. As the intake of these foodstuffs went up, risk of AMD generally went down. However, even in the individuals eating the most, the risk of AMD was not significantly lower statistically than those eating the least.

This should not be too surprising given that many grains can be quite disruptive to glucose and insulin levels, including some that are quite high in fiber (for example, whole-grain bread).

There are plenty of good reasons for eating a diet of relatively low-GI foods, including, most likely, a reduced risk of weight gain, type 2 diabetes, cardiovascular disease, and maybe some forms of cancer too. We now have evidence that suggests a lower-GI diet may help to protect against AMD and preserve vision as we age.

References:

1. Kaushik S, et al. Dietary glycemic index and the risk of age-related macular degeneration. American Journal of Clinical Nutrition 2008; 88(4): 1104–1110

Dr. John Briffa is a London-based physician and author with an interest in nutrition and natural medicine. Dr. Briffa's Web site

Last Updated
Nov 6, 2008