Buck the fizz

There’s an ongoing debate in nutrition circles about the effect of sugar-sweetened drinks (non-diet fizzy drinks) on body weight.

The issue first came to prominence in the US, where the marked rise in obesity rates over recent decades coincided with a rise in consumption of soft drinks from the 1960s onwards.

Of course, lots of other things have changed since the days of free love and moon landings, so even though this research suggested an association between obesity and sugared-drink consumption, it wasn’t really possible to prove a causal link between the two. And that’s how things stood until relatively recently.

Over the past five to 10 years, we’ve begun to get information from studies tracking large numbers of people over many years to assess how the behaviour of those who become obese differs from that of their lean counterparts. And one of the top predictors of obesity? You guessed it... high intake of sugar-sweetened drinks.

What’s even more compelling is that science is now beginning to discover how over-consumption of these drinks damages the human body.

There’s no question they are high in calories (roughly 200 per 500ml bottle), but it now seems much of the harmful effect relates to the intake of a sugar called fructose, which is a natural component of the sucrose used to sweeten these beverages. When we take large amounts of sucrose (a fizzy drink, for example) in isolation over a short space of time, this sucrose is snapped in half into its constituent glucose and fructose components and these are then rapidly absorbed from the gut.

The first place that they’re sent is the liver, but thereafter they’re handled in very different ways. In essence, once the liver has taken in sufficient glucose, it has the ability to “shut the door” to further entry of this sugar. However, with fructose, we go on piling it in until the liver gets overloaded with it. And it’s at this point that things go wallop, because now we start converting the excess fructose to fat, with disastrous consequences all round.

The most obvious of these damaging effects is that this new fat gets deposited as body fat, especially around the abdominal organs, causing us to expand around the middle. But it doesn’t stop there, because apart from weight gain around the belly, this fat also clogs up the liver increasing our likelihood of getting diabetes, as well as leaking out into the blood where it can block up our arteries and increase the risk of high blood pressure, heart disease and stroke.

Where does Ireland stand in terms of fizzy drink consumption? Well encouragingly, between 2000 and 2011, the percentage of adults consuming these sugary drinks dropped significantly among men and women in all age groups.

Now for the bad news: the level of intake among those still consuming these beverages has rocketed upwards over the same period, more than doubling among men and women in the older age groups.

This greater intensity of fizzy drink consumption has coincided with a 30% jump in obesity rates over the same 10-year period. While it’s difficult to definitively apportion blame for the Irish obesity epidemic to fizzy drink intake, it’s plausible if not highly probable, that it’s been a contributory factor in our inexorable march towards a fatter future.

So what do we do as consumers? The answer here is simple: minimise intake of these sugary drinks, and if we must take them, do so along with other food to slow the rush of fructose from the gut into the liver. In terms of replacement beverages, milk intake has been consistently associated with better weight control, and particularly with the avoidance of weight gain around the tummy.

So, if slimming’s your aim, replace the fizz with low-fat milk - your waistline (and your bones) will thank you for it.

¦ Dr Daniel McCartney is a lecturer in DIT and INDI PRO