Sugar in foods

When we consume ‘sugar’, we are actually talking about either glucose or fructose (in fruits). Different combinations of glucose and fructose make up most of the types of sugar we consume. For example table sugar (sucrose) is 50% glucose and 50% fructose.

When we eat something, our body digests or breaks up that food into simpler compounds. Glucose is one of these simple compounds which makes its way into our blood stream. The ‘glycemic index’ of a food item indicates how quickly our blood glucose level rises after eating it. Naturally, glucose has a GI of 100, whereas vegetables and fruits have a low GI.

Good news about glucose

Glucose is the primary source of energy for our cells to function. When we talk about blood sugar, we’re actually talking about glucose which is sailing across our blood stream and supplied to body cells.

The body has a mechanism to ensure that our blood sugar levels don’t get too high. Our pancreas detects glucose intake and produces a hormone called insulin to break it down. Our brain detects the rise in insulin level and lets you know that you’re not hungry anymore.

This is usually when we decide that we’ve had enough.

The problem with fructose

Fructose, the sugar that makes fruits sweet, is transported to the liver for processing. During the chemical reactions that fructose goes through, a substance called VLDL (very low density lipoproteins) is formed. Too much VLDL in our body has been shown to cause problems like heart disease. Glucose is processed in the liver too, but to a much lesser degree.

The other problem is that your brain is not as alert to fructose consumption as it is to glucose consumption.

This is why you don’t notice when you’re drinking too much soft drinks (which contain a lot of fructose).

But wait! Aren’t fruits good for us?

Yes, because along with fructose, fruits also contain a lot of fibre. Fibre is very filling, so it tells us when to stop even if fructose doesn’t. Processed sugar like table sugar does not contain much fibre, so it is dangerous.

So if glucose is self-regulated, why do people get diabetes?

Some people’s pancreas have a reduced ability to produce insulin. This is what happens in Type 1 diabetes. Sometimes the pancreas may be producing enough insulin but this insulin does not work as it should. In both cases, glucose is not broken down as it should, and remains in the blood stream.

Too much blood sugar, so what?

Too much sugar in the blood damages blood vessels. Accumulation of VLDL and other types of cholesterol can thicken the walls of blood vessels making blood flow difficult. This causes hypertension (high blood pressure) and other complications.

nandita.j@thehindu.co.in