Study suggests that low-carb diets can bring long term benefits for type 2 diabetics

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The body likes to keep its internal environment quite stable, and this includes the amount of sugar circulating in the bloodstream. The chief blood sugar lowering hormone is insulin. In diabetes, there can be a problem here leading for blood sugar levels to be higher than is healthy. Diabetics either don’t have enough insulin, or it’s not working particularly well, or both. As a result, blood sugar levels tend to be high, and this in the long term can lead to a variety of issues including eye disease, kidney disease, nerve damage, heart disease and premature death.

The fundamental source of sugar in the body is foods that contain sugar and/or starch (carbohydrates). So, common sense dictates that if diabetics are looking to keep their blood sugar levels under control, they may naturally look to a diet relatively low in carbohydrate. Even without any nutritional knowledge whatsoever, I suspect you’ll still be with me so far. The problem with this area is, I think, that many individuals who profess to have nutritional knowledge often claim that it’s important for diabetics to eat carbohydrate such as bread, potatoes, rice and pasta with every meal.

My experience is that diabetics that act on this advice have a generally hard time in regulating their blood sugar levels. It’s not just my experience that causes me to question the conventional dietary advice given to diabetics, its also what is to be found in the scientific literature. There has amassed to date a considerable body of evidence which shows that diets lower in carbohydrate produce better results in terms of blood sugar control than diets higher in carbohydrate

So, why is this advice dished out so frequently? Well, one ‘defence’ of the ‘diabetics need starchy carbs’ line of thinking is that the long-term effects of carbohydrate restriction are unknown. The suggestion here is that a lower-carb diet is one that is likely to be high in fat that is going to put diabetics at risk of heart disease. First of all, low-carb diets are not necessarily high in fat. And even if they are, fats found naturally in the diet don’t have a strong link with heart disease. And even if they did, any increased risk here may be more than offset by eating a diet that reduces the impact diabetes has in the body, which would likely reduce the risk of heart disease.

Bearing in mind the reticence some still have to suggesting a carb-controlled diet for diabetics because of lack long-term data, I was interested to read a study that has recently been published on-line in the journal Nutrition and Metabolism [1]. This study was actually a continuation of an original piece of research which pitted a low carbohydrate diet (20 per cent carb) against a higher carb diet (55 per cent carb) in a group of obese type 2 diabetics over a 6 month period [2] .

The results of this original study showed that the lower carbohydrate diet led to significant improvements in body weight and blood sugar control (glycaemic control) compared to the higher carbohydrate diet. After the initial study was over, the researchers assessed these individuals again in another 16 months (a total of 22 months), and discovered that the benefits seen after 6 months had been broadly maintained [3].

In this latest study, individuals who were originally put on the lower-carb diet were assessed again, this time a total of 44 months after the initial trial started (and more than 3 years after the initial trial ended).

Compared to how they were at the start of the original study, these individuals were found to have:

Significantly lower body weight ” an average reduction of 7.5 kg or 16.5 lbs

Significantly lower levels of HbA1c (which gives a measure of blood sugar control over the preceding 2-3 months) ” the reduction was from an average of 8.0 per cent to an average of 6.8 per cent.

Significantly higher levels of high density lipoprotein (HDL) cholesterol ” believed to be a marker of reduced risk of cardiovascular disease

Significantly lower total cholesterol: HDL ratio ” which would also generally be taken as a sign of reduced risk of cardiovascular disease

The study also reports on the fact that many individuals were able to reduce or even stop their diabetic medication as a result of the lower-carbohydrate diet.

The current study is hampered by its relatively small size (only 16 individuals started the lower carb diet at the very beginning). Also, the ‘control group’ (those eating a higher carb diet) were only properly in place up until the 6 months stage, after which most of them converted to the low-carb diet (the results that I’ve presented above exclude these individuals).

All-in-all, though, this study I think provides support for the idea that carbohydrate control is effective for the management of diabetes in the long term. It also provides no evidence at all that such a diet is anything but safe as far as cardiovascular disease (heart attacks and strokes) is concerned.

Guidance for those wishing to comment on this blog post:

This blog post is about the use of low-carbohydrate diets in the long-term management of type 2 diabetes, and some of the evidence that supports this approach. If you have a comment to make, please make sure it’s about this subject specifically. In particular, if you disagree with the views I express here, then I encourage you to debate this using science.


1. Nielsen JV, et al. Low-carbohydrate diet in type 2 diabetes: stable improvement of bodyweight and glycemic control during 44 months follow-up. Nutr Metab (Lond). 22 May 2008 [Epub ahead of print]

2: Nielsen JV, et al. Lasting improvements of hyperglycemia and bodyweight: low carbohydrate diet in type 2 diabetes. Ups J Med Sci 2005;110(2):179-83

3 Nielsen JV, et al. Low-carbohydrate diet in type 2 diabetes. Stable improvement of bodyweight and glycemic control during 22 months follow-up. Nutr Metab (Lond). 2006;14;3:22.

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