Not a day goes by without a well-meaning somebody reminding us that we don't eat enough fruit and vegetables. The nagging of the nutritionists rivals that of my grandmother who used to force her famous "borscht" down my throat. The limp and tasteless bits of cabbage would stick to the roof of my mouth making me gag and my shaking hand would invariably spill the red liquid on her white tablecloth, resulting in an extra serving of beetroot goodness. I am obviously still deeply scarred.
The bright images of squeaky clean green apples and shiny red capsicums are often displayed in contrast to the pictures of insipid and suspicious-looking burgers with visible grease glistening on the meat patty, with horror movie music theme in the background. You have to be a moron not to realise which one is better for you, right?
Is it any wonder that a word "fructose", which we immediately associate with "fruit", sounds so wholesome? Fructose is indeed the predominant sugar in fruit. But it is a little more than that.
For something that sounds so healthy, fructose has been implicated in several nutritional crimes of late. Several studies have found that excess fructose consumption can cause insulin resistance in the liver, NAFLD (non-alcoholic fatty liver disease), gout, hypertension and abdominal obesity, colloquially known as a "spare tyre". Does it make sense from physiological point of view?
Simple science
Actually, it does. While fructose is a simple sugar (=monosaccharide) just like glucose, it is actually processed in the body quite differently. After being absorbed from your intestine, it goes directly to the liver. The liver is like your body's own Border Control. It receives raw materials, a.k.a. nutrients, from the gut, examines them for suitability (is it poison? is it a building block?) and then packages the good stuff up, loads them onto specialised freight trucks (transport molecules) and sends them via blood to customers, the cells in your tissues.
As you already know, the liver helps the pancreas keep the blood glucose on a tight leash, either by releasing more of it or by diverting extra glucose to fat stores. However, unlike glucose, fructose is too toxic to be floating around your body. Like a conscientious customs officer, your liver recognises the danger and neutralises it by converting ALL fructose into triglycerides (fat). Triglycerides can be sent to the safe heaven of your fat tissues in their own trucks called LDLs (did you just have a little "Eureka" moment?), or they can be stored in the liver itself. Not good either way. Nobody likes love handles or their liver resembling fois gras.
Incidentally, do you know what else is processed in a similar way by the liver? Alcohol. So what would happen from a love match between alcohol and fructose? Bacardi Breezer, anyone?
Back to reality
Hang on, you ask, are you saying that fruit will make me fat and diabetic? No. The concentration of fructose in fruit is unlikely to harm you. In a manner of a true toxin, fructose has a dose-response relationship: the more you have, the worse it is.
The real question is: what other foods contain fructose? You are probably familiar with HFCS, high fructose corn syrup, a ubiquitous sweetener in the land of stars and stripes. HFCS is a product of industrial engineering genius: it is cheap, subsidised by the government (yay for corn subsidies) and is sweeter than sucrose, table sugar. It has been justly vilified and we often think we are lucky that it never took off in Oz.
However, your humble sucrose is not much better. HFCS normally used in soft drinks has 55%/45% fructose/glucose content. The white stuff that you put in your coffee is 50/50. Let's say you don't use sugar in your coffee and you don't drink Coke, does it let you off the fructose hook? Sorry, no. Fructose is used in pretty much every processed and packaged product, whether on its own or as part of sugar. Fortunately for manufacturers, they don't have to put fructose on nutrition labels. But you can estimate fructose content of foods yourself by dividing the amount of sugar on the label in half. (Be careful, it doesn't work with dairy products, as their main sugar is lactose, not sucrose).
Here is a little table I prepared earlier.
| | Sugar content (g) | Estimated fructose content (g) |
Apple green,
small | 9.6 | 4.8 |
Apple juice,
250mL | 26 | 13 |
Banana bread,
57g piece | 14.7 | 7.4 |
| Lipton Iced Tea, 375mL bottle | 22.1 | 11.1 |
Nutrigrain
cereal, 40g | 12.8 | 6.4 |
Coca Cola,
600mL bottle | 63.6 | 31.8 |
As you can see, you have to have a hell of a lot of apples to come close to the level of fructose an average Australian/American consumes daily in the course of their processed food addiction.
What about fruit juice? Not too long ago fruit had to be squeezed by hand. Homemade juice sans the electrical juicer can be used as a babysitting tool: it will keep your kids busy for hours as they diligently work up a sweat trying to earn one glass of precious sugary orange liquid. If you want to be really mean, tell them to make apple juice by hand. Nobody in their right mind will eat 6 to 8 oranges in one sitting, but apparently a glass of juice, made from the same amount of fruit, is a healthy addition to our diet with breakfast, lunch and dinner.
Due to its current love affair with GI, Diabetes Australia tells diabetics that
"a healthy eating plan for diabetes can include some sugar". Glucose has a GI of 100, but table sugar, with only 50% of glucose, is 65. But the other 50%, fructose, is the real killer. Unfortunately, the very thing which makes the GI of sugar lower is the reason NOT to give it to diabetics. Its effects on the liver make it a ticking time bomb: you can't see the blood glucose rise but your liver is developing insulin resistance with every bite of that low-fat banana bread.
So what do you do?
1. Whenever you drink soft drinks, juices, sports drinks, it is not just
the calorie load and fat-storing effects of insulin you have to worry about. It
is the direct toxicity to the liver. So don't.
2. Avoid sweets and cakes with high load of sugar.
3. Avoid processed pre-packaged foods, bars, biscuits, as they have a lot
of hidden sugar.
4. If your goal is to lose fat, limit your fruit consumption to 2 a day.
5. If you have a diagnosed fatty liver, temporarily avoid fruit. It has
nothing that you can't find in vegetables.
More information:
1. A must to see: "Sugar: the Bitter Truth"
Robert H. Lustig, MD, UCSF Professor of Pediatrics in the Division of Endocrinology, explores the damage caused by sugary foods. He argues that fructose (too much) and fiber (not enough) appear to be cornerstones of the obesity epidemic through their effects on insulin. Series: UCSF Mini Medical School for the Public [7/2009] [Health and Medicine] [Show ID: 16717]
2. Dr Eades on sugar vs HFCS
3. Double danger of HFCS
4. Fructose content in popular beverages differs from data labels
5. Review: Fructose, weight gain and the insulin resistance syndrome
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