Why sugar is an antioxidant!

A sugary breakfast.
The same chemical composition as
'table sugar' aka sucrose, but with minerals/fibre!

Sugar (glucose + fructose = sucrose), or more specifically white sugar has been demonised for years and it seems as if the attack on sugar (just like salt and fat) takes place in cycles of 5 or so years. 

Though glucose can actually be viewed as the ultimate antioxidant. We tend to think of antioxidants as compounds that will directly neutralise reactive oxygen species in a test tube, but we actually have a complex endogenous antioxidant system that is ultimately fuelled by glucose.

Through the pentose phosphate pathway, glucose supplies hydrogen ions and electrons, which we could call "reducing power", to NADPH, which is derived from niacin, also known as vitamin B3. The enzyme glutathione reductase uses riboflavin, also known as vitamin B2, to pass this reducing power to glutathione. Glutathione, the master endogenous antioxidant, then uses this reducing power to neutralise hydrogen peroxide to water, to neutralise lipid peroxides to less harmful hydroxy-fatty acids, and to recycle vitamin C, vitamin C recycles vitamin E, the principle component against lipid per oxidation in cellular membranes.

Thus, the multiple roles of gluthathione within the antioxidant defines system, mitigating the accumulation of reactive oxygen species, protecting vulnerable fatty acids within the cellular membranes, and cleaning up any damage that has slipped through the system, are all ultimately supported by the reducing power derived from glucose.

Insulin signalling is also important to the antioxidant defence system because it increases the synthesis of glutathione. One small but fascinating study publish demonstrated the relevance of this point in type two diabetes. Compared with the healthy controls, diabetic patients had poor glutathione status. In fact, their ratio of reduced to oxidised glutathione was cut in half. The investigators then exposed the diabetic patients to a euglycemic hyperinsulinemic clamp. In this approach, both the sugar and insulin are infused into the patients blood at concentrations that keep blood sugar normal and insulin elevated. After being exposed to this condition for two hours, the glutathione status of the diabetics normalised to the levels of healthy controls.  

In principle, what Mr Master John is trying to say, is that glucose is the master antioxidant and insulin is central to the defence against oxidative stress and glycation. But that doesn't mean, more is always better!  

Be Wise.

Beatle