Some thoughts on fructose
Posted by kathryn in Nutrition and Myths
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.
30 September, 2009
Comments
Great review Kathryn.
Great post, Kathryn. Thanks for clearing up some of the confusion. I’d be curious to know your thoughts about agave nectar, which is high in fructose, yet low glycemic (and used by many Type II diabetics). Because of the high fructose levels, some studies are suggesting it’s not healthy. What’s your take on it?
This is why I think you’re great Kathryn. Sense in the cosmos of misleading info and misdirected fears.
Interesting. This is pretty much the same conclusion I had reached Kathryn – fructose isn’t particularly ‘worse’ than any other calorie containing sweetener.
I’ve been pondering the Agave Nectar question a lot recently so I hope you don’t mind me sharing my thoughts Ricki (I’m sure Kathryn will chip in with her own thoughts on the matter too). All of Kathryn’s excellent points regarding other foods with a high fructose content apply to agave nectar far as I can see. Yes it is also low GI, but for a person with diabetes (and for anyone else for that matter) the downside to the low impact on blood glucose levels is that your body is instead busy metabolising fructose. There’s reasonably good evidence that increasing the fructose in your diet can increase your blood triglyceride levels, which in turn can increase cardiovascular disease risk. So it’s perhaps not a better option, just a ‘different’ option, particularly for folks with type 2 diabetes who are at higher risk of heart problems anyway. Another vote for variety being the best policy I guess!
p.s Kathryn, what is a furphy???
Excellent post, Kathryn. I really appreciate your intelligent. practical “to sum up” tips.
Ricki, I am pretty much in agreement with Sophie about agave nectar. I suspect it’s not as evil as some sites are making out, but the high levels of fructose (up to 90% in some products) are a concern.
I think at the moment we don’t know the effects of agave and even the research on high fructose is somewhat contradictory. Buuut high intakes of fructose do seem to increase the risk of abdominal obesity, worsen insulin resisance and increase blood triglycerides – all of which are bad news to diabetics.
I’m not saying don’t eat it, but as with all sweeteners, agave is not a problem free food. Reducing your intake of all sweeteners is a good idea. As is varying around what you are doing.
And Sophie – a furphy is an untrue story, or an improbable rumour. I just looked it up to see the origin and hadn’t realised it was Australian slang.
great post kathryn
I totally agree that you can’t blame HFCS and fructose in general as the cause of the obesity epidemic.
interestingly when I was working for a cereal company and we would try and make american products in australia we generally replaced the HFCS with glucose syrup with no issues
That interesting Jules – much of the research I’ve been reading has commented on HFCS’s ease of use, compared to other added sweeteners. And this being part of the reason they’re so attractive to US manufacturers. They do also make the point HFCS are cheap to use – so that must be the primary reason.
I totally agree with your take home message that we need to reduce all sugars across the board. But the other part of the story is that fructose is metabolised differently to the other sugars and that’s why it has its own bundle of added problems.
The link in your previous fructose post to the excellent Health Report (oh boy do I have a love/hate relationship with Norman Swan!) interview with Robert Lustig in 2007 reiterates that fructose can only be metabolised in the liver and has flow on effects not just to type 2 diabetes, increased cholesterol problems and hypertension that Sophie mentioned but also non-alcohol related fatty liver.
I know diet is all about balance and nothing positive tends to come from demonizing particular foods but the more I learn about fructose the more questions I have about it.
A few points in response, since I’ve been looking closely at fructose consumption for quite a while now:
- Studies exploring the effects of fructose have to be in extreme amounts in order to remove variables = be conclusive. The study which compared a 100% glucose-sweetened beverage diet to a 100% fructose-sweetened beverage diet showed conclusively that fructose is associated with accumulation of dangerous visceral body fat. The ingested amounts were modeled on the average American sugar intake – 25% of calories (which makes me sick just thinking about it). So even if you balance the extremes back to a 50/50 glucose/fructose ratio, like you would usually find in soft drinks and fruit juices, you could logically expect the results for the average sugar-sweetened beverage to be the average between the two groups – half the amount of visceral fat gain, same amount of weight gain since each group gained the same amount, etc. The average American consumed 13% of their calories from fructose. I would hope that in a mostly HFCS-free environment, the Aussie score would be much lower. But you cannot claim that the research is out of proportion and therefore misleading or irrelevant – we might be consuming half as much fructose as the test group, but even half of the ill-effects are devastating. Here is an accessible breakdown of the study, linking to a more sophisticated breakdown by Dr. Stephan Guyenet: http://freetheanimal.com/2009/10/fatty-liver-reversal.html
- As Gil pointed out above, one of the key dangers of fructose consumption is non-alcohol related fatty liver disease. Robert H. Lustid, MD, presents a highly detailed, intellectually stimulating lecture on sugar, zeroing in on what fructose does to the human body, as well as looking at other sugars. The video can be found on YouTube: http://www.youtube.com/watch?v=dBnniua6-oM
You state:
“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.”
Actually, we’re not eating more of everything. Since the Lipid Hypothesis (“sat fat is bad”) was constructed and fed through the government and media ad infinitum (despite the fact that it had not, and still has not, been supported by any conclusive evidence, with many hundreds of studies pointing to opposing findings), we have been consuming less and less fat, meat, and animal products in general. What have we been consuming, in ever-increasing amounts? Carbohydrates – specifically, grains. As grain consumption, along with sugar consumption, has increased, so has obesity rates, heart disease, cancer, diabetes, Alzheimer’s, dental problems, and most other diseases considered ‘lifestyle’ or ‘civilisation’ disorders. These findings have been reported almost everywhere, but since I’ve already mentioned Dr. Stephan Guyenet, I’ll link to his post responding to the then-recent finding that Americans have indeed increased their caloric consumption, with those extra calories coming almost exclusively from refined grains: http://wholehealthsource.blogspot.com/2008/08/hyperphagy.html
For me, I think about the limited access, during our 2.5million years of evolution, humans would have had to fruit for at least half of the year. Some, such as the Inuit, would have consumed practically zero fructose. Other would have had access to the tiny, tart berries that are believed to exist for the majority of human evolution, before we started breeding fruits to be bigger and sweeter. Some fruits are highly nutritious to be sure, but logically, we simply have not evolved to cope with consuming fruits, let alone processed, extracted fructose, in high amounts.
I would never have known how to spell furphy, which is funny, because I wouldn’t have raised an eyebrow if it came up verbally. Nice to see an unusual word in action. Thanks for the review too. It’s lovely to have a comprehensive summary rather than bits and pieces.
hi kathryn, a few minutes ago, i received a test result stating that i’ve fructose malabsorption. i’ve looked at the FSANZ database and am a bit confused. what do i benchmark against; when i’m looking at the fructose per 100g, what is considered high and what isn’t?
thanks kathryn
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