Fructose is a simple Sugar naturally found in Fruits and Vegetables

Fructose is one of the major culprits behind the “unhealthiness” of modern world’s processed foods. It is a simple sugar or monosaccharide that is naturally found in fruits and vegetables, usually attached to Glucose, sometimes on its own, and often in polymerised form. It is also one of the sweetest amongst all natural sweeteners.

On a commercial scale it is mass produced for food industry, where it finds its end use in commonly available packed foods and beverages. Natural sources of this mischievous ingredient contain multiple other nutrients such as antioxidants, fibre, vitamins, and minerals that aid in the processing and hence assimilation of fructose in our body. However, commercially produced Fructose can contain up to 90% concentrated forms that will severely hamper the functioning of the body in the long run.

Picture Credit: Cut your Sugar by NYSACHO

How Fructose is Digested / Metabolised in the Body!

Fructose when ingested is primarily processed by liver and passively digested by our intestines. It is metabolised at a much faster rate than Glucose in our body as it does not require insulin. When taken in small amounts, Fructose can actually be beneficial and help manage the Glycogen reserves in the body. However, when consumed regularly and in large amounts (as is the case with modern food products), it overloads and stresses out our Liver (the primary organ where it is metabolised).

Figure below explains what happens in case of Fructose(F) overload to our gut or digestive system. As shown below, majority (~ 75%) of it is sent to the liver, which further processes it into:

Pyruvate – during normal consumption or non-fasting conditions
Glycogen (only during fasting conditions, starvation, or during strenuous physical activity), where it is beneficial and hence given to athletes.
and Uric Acid as a by-product along with Pyruvate – Excess Uric Acid can further promote Hypertension.

When converted to Pyruvate, it can promote synthesis of fatty acids, hence promoting obesity, diabetes, and fatty liver disease. In modern times non-fasting conditions are pretty much the usual way of consumption of sugar sweetened beverages and foods that are loaded with either Fructose(F) or Sucrose which essentially contains both Glucose(G) and Fructose(F) elements of the sugar.

In fact, it has been observed that when Fructose(F) is consumed along with Glucose(G) , the production of fatty acids is promoted by three times as compared to consumption of Fructose(F) alone.

Source: Refined Sugars in Retinal Disease

Fructose leads to Obesity and Obesity further increases one’s response to pleasure from sugary foods

In several studies, Fructose(F) was found to induce an activity spike in the pleasure or reward regions of the brain. In fact, Fructose(F) rich diets can suppress satiety (feeling full) hormone Leptin and also reduce our ability to suppress the hunger inducing hormone Ghrelin. Hence, even after we have had enough of the food we will still feel hungry.

Fructose(F) has been observed to reduce the activity of the Pre-frontal Cortex or executive region (responsible for logic and control) of the brain over long term. This effect was observed to be higher in people who are obese or overweight, resulting in a vicious cycle of metabolic syndrome.

As one of the sweetest sugar components, Fructose(F) is deliberately added to packaged foods and drinks to enhance their palatability. An increase in taste profile and hence the reward action inside our brain further induces us to consume more of such products, hence increasing our risk for obesity.

High Fructose Diet can lead to Diabetes Type 2, Hypertension, and Metabolic Syndrome

Unlike Glucose, Fructose(F) does not need insulin for metabolism. At low doses, it can have a low Glycemic Index effect and over doses of Fructose(F) can result in insulin-resistance in the body. High concentration of Fructose(F) on regular basis trigger Metabolic Syndrome and as a result lifestyle disorders such as Diabetes, Hypertension, and Obesity. Metabolic Syndrome is observed to be the state, where a vicious cycle is initiated resulting in:

Raised blood glucose levels – hyperglycaemia
Lower HDL levels
High blood pressure
Central Obesity

Adverse effects of Fructose can be managed by Exercise

Physical activity has plethora of positive effects that go beyond body and to the mind. Exercise increases blood circulation throughout the body and brain. Increased blood flow helps to flush the undesired substances such as toxins and in this case Fructose and Glucose from the blood stream. Additionally, exercise has been observed to increase oxidation of Fructose(F) and reduce its storage levels. Regular physical activity increases insulin response, glucose transport, and utilisation of fatty acids in the body. These effects are more pronounced when physical activity is performed immediately after consumption of fructose-sweetened products.