Some thoughts on fructose
I’ve been asked a lot of questions recently about fructose. The comments and threads have been overwhelmingly negative. While the questions vary, they all centre around the same core issue – is fructose bad for you?
In short the answer is an annoyingly cryptic – probably yes, but not really at the moment . . . as is ever the case with nutrition.
Problems with the research
Fructose is a type of sugar. It’s a very simple sugar, called a mono-saccharide and there’s a fair amount of research showing fructose is bad for you.
However there’s an issue with much of this research: it’s based on people being fed extremely high intakes of fructose, higher than we regularly consume. This type of research is really effective at showing us biochemical pathways and how a food or substance is metabolised by the body. However it doesn’t reflect how you consume fructose in real life, therefore it’s not telling us much about the effects of the fructose you are eating.
As an example, figures in the US show that about 8.5% of daily kilojoules come from fructose. Whereas in much of the research fructose is fed to participants at levels of 30% or more of daily energy intake. A significant difference.
How do we consume fructose?
Fructose is a common substance – it’s found in a whole lot of different foods, from fruit and vegetables, through to honey, normal table sugar, alcohol, bread and biscuits. It’s also found in the sweetener high fructose corn syrup (HFCS). To get an idea of all the different foods that contain fructose, look at the list in the FSANZ database.
While fructose is contained in all these foods, it’s almost always found with at least one other mono-saccharide – glucose – although the ratio between these two varies a lot.
Even within one food group the ratio of fructose to glucose varies between different foods. For example all fruit contains fructose and glucose. However, while apricots have three times as much glucose as fructose in nectarines the levels are about even.
Therefore we rarely consume fructose at the levels found in much of the research. And it’s pretty much always found together with other simple sugars, like glucose.
What about high fructose corn syrup (HFCS)?
Even in HFCS fructose is matched up with glucose. In fact, while HFCS is high in fructose for corn syrup, it has similar fructose levels to other sweeteners.
- HFCS contains 55% fructose and 45% glucose.
- This is not very different from normal table sugar, which is 50% fructose and 50% glucose
- Honey is about 50% fructose and 40% glucose (and 10% other saccharides)
As you can see there’s little difference between the levels of fructose and glucose in HFCS and table sugar. However there is a difference in the form in which they’re found. In table sugar the fructose and glucose molecules are bound together to form di-saccharides. In contrast they are unbound and free in HFCS. It has been suggested this may lead to differences in metabolism, but it appears not to be the case. The di-saccharide bond in table sugar is quickly and easily broken. This job is partly done by enzymes in the saliva in your mouth and partly in your small intestines. In studies which compare sugar consumption with HFCS consumption, there is little consistent difference in the health effects of the two.
But what about the obesity epidemic?
HFCS is promoted as one of the big culprits of the obesity epidemic in the US. HFCS has been part of the US food supply since the 1970s. It’s relatively cheap and easy to use, when compared with sugar – which makes it attractive to manufacturers.
This use of HFCS corresponds with the period when obesity has been on the rise. Leading many people to suggest it’s the cause.
However, while fructose consumption has increased in the US since 1970s, so has overall kilojoule consumption. Between 1970 and 2005 the daily kilojoule consumption per capita increased by 24%. During that time the use of sugars, as a proportion of total energy consumption has stayed about the same. The obesity problem is not just because people are eating more HFCS, it’s because they’re eating more of everything.
HFCS are an issue, but they are not the only problem. The cheapness of HFCS, combined with our love of the sweet flavour means they can be easily added to food, to make them more attractive. But it’s misleading to say they are responsible for obesity in the US.
On another note, HFCS are virtually unknown here in Australia. They are not a large part of our food supply at the moment. However, we have as much of an obesity problem as the US does. We’re managing to gain weight, without the help of HFCS – because people are eating too much and doing too little.
To sum up
- Yes there are health issues with fructose. On it’s own and in high doses it stimulates and encourages problems. It’s not a good food to be eating a lot of.
- But it’s a furphy to say that fructose is the only problem. We are eating too much of the sweet stuff in general, whatever the source. In fact many people are eating too much of the wrong foods in general.
- Don’t specifically worry about HFCS, be aware of all sweeteners. Watch what you’re adding to your coffee, how many soft drinks you’re consuming and take a look at what’s in the ready meals and canned foods you’re buying.
- Eat more fruit and vegetables. These foods do contain fructose, but you need them in your diet. They are low in kilojoules, contain good fibre and are full of the vitamins, minerals and antioxidants your body needs. Make sure you’re getting your five serves of vegies and at least two of fruit.
- Watch your portions in general and make sure you move – at least 3.5 hours of exercise per week.