Friday, June 26, 2015
Are you one of them who know their sugars and consider fructose to be much better over glucose? Numerous studies do show that fructose does not increase blood glucose and insulin levels. However, digging down to the gene level, a recent study found that fructose may not be all that benevolent. Excessive ingestion of fructose could lead to cardiac enlargement and heart failure by a relatively unknown mechanism.
Previous research has noted that fructose is readily taken up by the liver and converted to fat. Thus, a high fructose diet could lead to development of hypertension, dyslipidaemia and other conditions comprising the metabolic syndrome. The new research, published in the journal Nature, found this hitherto unknown side effect of fructose by analysing mouse models and biological samples from patients with heart enlargement.
Hypertension may cause the heart muscle to grow to facilitate efficient pumping of blood. However, the growing heart muscle requires considerable oxygen supply, failing which it will resort to an alternate energy source (anaerobic glycolysis). According to the researchers, if during this phase, the heart muscle gets access to fructose in addition to glucose, then it may set off a fatal chain reaction.
The study elaborated the following mechanism for poor heart health due to fructose metabolism:
- Lack of oxygen causes the release of the hypoxia inducible factor (HIF) molecule which is synthesised during disease processes such as cardiac enlargement or cancer
- HIF causes the heart muscle to produce ketohexokinase – C (KHK-C), an enzyme involved in fructose metabolism
- This enzyme has high affinity for fructose and metabolises it quickly. Since fructose metabolism is not regulated by any negative feedback, it initiates a vicious cycle ultimately leading to heart failure.
- This mechanism was corroborated when the researchers found the presence of HIF and KHK-C molecules in the heart samples of patients with heart enlargement.
Ironically, KHK-C is produced abundantly in the liver whereas other organs produce ketohexokinase – A (KHK-A), a genetically similar but milder enzyme. According to the researchers, stress may cause the HIF molecule to splice KHK-A to produce the much active KHK-C in the heart muscle.
Fructose, a common fruit sugar, has increasingly found its way in processed foods. Keeping in mind the findings of this study, staying away from foods with added fructose would be good for heart health. Does it mean cutting down on fruits too? No say researchers because they provide vitamins, minerals, and fibre too! So make a wise choice at the supermarket next time.
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