The regulation of blood sugar is an important part of your health from a functional perspective. We know that having high blood sugar is unhealthy. The extreme form of high blood sugar is called diabetes and is clearly associated with a variety of serious health risks including increased risk of cardiovascular disease, stroke, and overall morbidity and mortality.

The increased awareness of blood sugar problems and diabetes has led to the widespread belief that if blood sugar is bad, then dietary sugar is bad. The conventional nutritional advice for management of blood sugar dysfunction is to consume a low-carbohydrate diet, and those carbohydrates that are consumed should be “complex” carbohydrates, which are carbohydrates that break down more slowly in the digestive tract.

Let’s examine the evidence for some of the basic assumptions behind this theory.

Firstly, let us look at something called the glycemic index. The glycemic index is a measure of the effect of a food taken in isolation on blood sugar. For reference, pure glucose administration is defined as 100, and the lower the value the lower the blood sugar rise associated with that food.

Orange: 45

Apple: 36

Orange juice (unsweetened): 50

Apple juice (unsweetened): 41

Wonder bread: 73

Whole wheat bread: 69

As you can see, the glycemic effect of fruit and fruit juice (which are generally considered to be “simple” or “unhealthy” sugars) is actually lower then regular or whole wheat bread.

There have been studies that show that “sugar-sweetened juice” is associated with type 2 diabetes; however, these types of drinks are highly processed and are likely similar to soda in their nutritional value. However, review of the medical literature has consistently shown that consumption of 100% fruit juice is not associated with diabetes. (see Intake of fruit juice and incidence of type 2 diabetes: a systematic review and meta-analysis)

A study in 1993 by Bantle et al, compared two groups of people with type 2 diabetics eating the same amount of calories and total carbohydrates; however, one group consumed 19% of their calories from sucrose and the other group consumed <3% of calories from sucrose with most of the carbohydrate energy coming from starch. There was no difference in blood sugar at 28 days between the two groups. (see Metabolic effects of dietary sucrose in type II diabetic subjects). A similar study was done with fructose, which actually showed serum glucose was 12.5% lower in the fructose-diet group compared to the starch-diet group. (see Metabolic effects of dietary fructose in diabetic subjects). A meta-analysis in 2012 by Cosma et al also showed that isocaloric exchange of fructose for other carbohydrates resulted in a decrease of the average blood sugar (hemoglobin A1c) (see Effect of fructose on glycemic control in diabetes: a systematic review and meta-analysis of controlled feeding trials).

The truth is that the blood sugar story is more complicated than “dietary sugar = blood sugar.” High blood sugar is likely not a “sugar toxicity” issue, but rather a “sugar utilization” issue. While there may be some efficacy of a low-carbohydrate diet in terms of a short-term reduction of weight and/or blood sugar, these effects are likely minimal and not sustainable in the long-term due to the metabolic damage induced by such low-carbohydrate diets. In our practice, we routinely see diabetics who have maintained a low-carbohydrate intake for years; however, continue to have elevated blood sugars.

In fact, low carbohydrate diets are associated with the following:

  • Decreased thyroid output

  • Increased cortisol output (increased activation of the stress response)

  • Hormonal dysfunction (low testosterone, low progesterone)

  • Decreased anti-stress hormones (DHEA, pregnenolone)

  • Protein catabolism (breakdown of muscle and organs to be used as energy)

  • Decreased overall metabolic rate (as assessed by pulse, temperature, carbon dioxide, lactate, etc)

Instead, a better strategy for dealing with blood sugar dysregulation is to deal with the underlying metabolic issue. The efficient uptake of sugar into the cell and the efficiency with which it is utilized in aerobic respiration within the mitochondria are the primary concerns. A variety of issues contribute to sluggish metabolism, including calorie/carbohydrate restriction, vitamin/mineral deficiencies, elevated polyunsaturated fatty acids (PUFA), gastrointestinal dysfunction, adrenal fatigue (stress dysregulation), and hypothyroidism. See How to Heal Your Metabolism.