Fructose won’t really make your elbows dissolve. Don’t worry. It was just a ‘typical blog headline’.
And I don’t have 47 reasons either. So if that’s what you were expecting, click away now. If, on the other hand, you’re interested in whether fructose is a positive or negative element in your diet, then read on…
In my last blog I mentioned how fructose doesn’t trigger the normal satiation signalling, so humans are prone to gorge on fruit, which might be an evolutionary mechanism that would help us, and other mammals, put on fat over autumn in order to survive winter – ‘scheduled obesity’.
Now that fruit is available in unlimited quantities and at all times, the amount of fructose coursing through our systems is far greater than our liver’s capacity to deal with it. But guess what – the food available to humans today is different from 40,000 years ago. So if you were around then, ate some fruit and got the munchies, you’d eat…some more of the fruit. Today, in the same situation, you might eat some fruit, stay hungry, and you might eat…biscuits, cereal bars, chocolate bars, as well as more fruit. It’s like a gateway drug!
The crucial difference between fructose and glucose, the other common sugar, is that fructose has to go via the liver to be metabolised, while glucose hops straight into the bloodstream to give us a bit of energy. In small quantities, this is not an issue – we’ve evolved to be ok with relatively small amounts of fructose. In large quantities, though, as consumed in modern society, it causes problems.
This is where they may be some confusion – is it fructose that is bad, or excess fructose? This poor sugar has recently been demonised, mainly because of HFCS, high-fructose corn syrup, at whose door the decline of western civilisation has been laid. HFCS isn’t much worse than pure fructose – it’s basically a liquid form of fructose that works well in the food industry. Ah, the food industry. Gigantic faceless factories churning out food-related items to be sold in supermarkets and featured in clever ads. Mainly aimed at our kids. So although per se HFCS isn’t too bad, in the hands of the food industry and the steamrollering advertising machine, beguiling us to eat large amounts of the stuff it can be problematic. And while the fructose in fruit is bound to pectin, a soluble fibre that slows its absorption down, the F in HFCS is ‘free’ and gets on with its evil deeds more quickly.
What are those evil deeds? It is thought that chronically high fructose intake can lead to: fatty liver; global inflammation, gout, leptin resistance, ie less signalling for satiety, hence a tendency to overeat, hypertension and of course the scourge of modern metabolisms, insulin resistance, which in turn helps cause obesity and metabolic syndrome, and diseases like Alzheimer’s.
It’s thought that the human liver is used to dealing with around 25g of fructose per day, maybe more, and in terms of fruit that could be three bananas, for example. Adding any HFCS-laden products to that level of fructose from fruit, then, takes you into risky territory. But let’s not forget the extra added bonus – the leptin-suppressing effect, which has a tendency to keep you wanting to nibble. Over weeks, months and years, this has a compound effect on your health.
From the all-important evolutionary perspective, our digestive system is set up for meat, primarily, from which we get all the nutrients we need, and which we digest easily and efficiently with enzymes and acid, and then non-animal foods as Plan B. We can derive nutrients from fruit, but there can be a price to pay. I just don’t bother eating fruit.
Next up, I’ll put vegetables under the Zero-a-day microscope. Have a steak.