Sugar, and fructose in particular, is often heavily scrutinised. Sugar has been likened to addictive drugs like cocaine, or deemed ‘evil’ and ‘toxic’. While high intakes of sugar in the diet is associated with obesity, diabetes, hypertension and metabolic syndrome, is there more to the story? Are fruit sugars really as ‘evil’ and ‘toxic’ as we are lead to believe?

Let’s break the story down and focus on the evidence:

The sugar conundrum..

Sucrose, fructose, dextrose, glucose, molassess, hydrolyzed lactose syrup, cane sugar, agave syrup, brown rice syrup, maltodextrine, date syrup, agave syrup, corn syrup, high-fructose corn syrup … have I missed any? There are so many different types of sugar (and ‘alternatives’), that it can be hard to get your head around it all. We often hear, this sugar is better than that, or, replace that sugar with this ‘nourishing’ (and expensive) alternative. Confusing!

Sugars can be classified into two main groups:

A) Naturally occurring sugars – These sugars are found naturally in many healthy whole foods such as fruit (fructose) and dairy (lactose).

B) Refined or added sugars – These sugars are not naturally occurring, they are manufactured and added to a food products in some way. Sugar (aka sucrose) is made from sugar cane or beet. Sucrose is added to foods and beverages like sweet drinks and confectionary foods. Look out on a food label for hidden sources of refined sugars including: rice malt syrup, date syrup, agave, golden syrup and high-fructose corn syrup.

The Bottom Line: Sugar can be classified into two main groups: naturally occurring and added.

What about Fruit Sugars?

Let’s get ‘sciencey’ and break it down with a 101 on fructose …

Fructose is the main naturally occurring sugar in fruit and honey. It is a monosaccharide. Monosaccharides are single units of sugar which cannot broken down any further. The body absorbs these single units and uses them for energy. Monosaccharides are joined together, almost like a necklace, to make more complex carbohydrates.

Although commonly found in fruit, fructose is often manufactured into a calorie dense sweetener called high fructose corn syrup. This sweetener is added to foods and beverages.

The Bottom Line: There are two types of fructose: naturally occurring (aka fruit sugars) and refined (high-fructose corn syrup).

Fructose Metabolism

The hypothesis around why fructose is called ‘evil’ and ‘toxic’ refers to the way fructose is absorbed and processed, or ‘metabolised’. The biochemistry around this hypothesis is complicated – so let’s set the scene first.

When we eat sugars, our body breaks them down in to their simplest form (monosaccharides) so that they can be absorbed and used.

Glucose is absorbed straight from our intestines into blood stream. The hormone insulin comes along and allows glucose to travel from the blood, into the body’s cells where it’s used for energy or stored for later.

However, our body does not metabolise fructose the same way. Instead, fructose travels from intestines to the liver. The liver then changes the fructose into other things like glucose and glycogen.

There is a theory that if there is too much fructose, the liver produces mores triglycerides (fat). Triglycerides can then travel into the bloodstream where they contribute to plaque formation in the walls of arteries and increase body fat. This theory is the basis for avoiding fructose and fruit.

But this theory and is not well supported by evidence. Fructose metabolism in the liver is a very complicated process and only a very small percentage of fructose is converted into triglycerides.  The research doesn’t indicate that high consumption of fruit will raise triglyceride levels in the blood.

The Bottom Line: Fructose from fruit is absorbed differently to other sugars but does not contribute to higher triglyceride levels.

What’s the verdict?

The media often misrepresents and confuses the distinction between fructose in its natural and artificial forms. . If we really take a deeper look into the accusations against fructose, we need to make sure that we are not confusing naturally occurring fructose to foods sweetened with concentrated fructose.

It is important to remember that fruit contains more than just fructose. Fruits contain vitamins, minerals, phytochemicals and fibre. So, in the big scheme of things, the amount of fructose found in fruits is not substantial.

The ‘harmful’ effects of fructose are likely to apply to the artificial sources of fructose. Artificial fructose is added to products like sugary drinks and confectionary food, which are void of nutritional value.  Unlike fruits, artificial sources of fructose, and all refined sugars, provide empty calories without providing vitamins, minerals and fibre.

The Bottom Line: Consuming moderate amounts of fruit sugars (2 servings of fruit per day) is part of a healthy and well balanced diet. There is no need to avoid fruit!

Helpful tips and tricks

  • Look for a product that contains less than 10g per 100g ‘sugar’ on the product’s nutrition panel.
  • Dried fruits and flavours will increase the amount of  ‘Sugar’ on the nutrition label
  • Become more familiar of hidden sources of sugar.
  • Slowly start to reduce the amount of sugar you add to hot beverages (coffee and tea).
  • Sauces, some cereals, muesli and granolas all can contain high amounts of added sugar, along with confectionary, baked goods and sugary drinks.

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References

Nutrition Australia, 2010, Fructose and Sweet Poison

International Food Information Council Foundation, The Science of Sugars

White. J.S. ‘Challenging the Fructose Hypothesis: New Perspectives on Fructose Consumption and Metabolism’, Adv Nutr, 2013, 4;246-256.

Morenga, L.T, Mallard, S, Mann, J. ‘Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies’. BJM, 2013;346

Stanhop, K.L. ‘Sugar consumption, metabolic disease and obesity: The state of the controversy’, Crit Rev Clin Lab Sci, 2015; 52-67

Australian Health Survey, 2011-2012.