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Unnecessary avoidance of natural sugars

Have you heard of people avoiding fruit because it’s “full of sugar”? This alarming scenario is troubling, and we explain why.

Natural sugars

The main foods containing natural sugars are fruit (containing mostly fructose) and milk products (containing mostly lactose). Increasingly however, fruit concentrates are being added to processed foods as a more ‘natural’ way to sweeten them.

While lactose has remained neutral in current public debate about sugar, sucrose and fructose have been painted as dietary villains. Current anti-sugar messages specifically target fructose as harmful, and warn against consumption of sucrose (because it is 50% fructose) and high fructose foods including high fructose corn syrup (HFCS), fruit juices, dried fruit and more than 2 pieces of fruit daily.

NOTE: Australian foods and beverages contain very little HFCS because of the availability and economy of locally grown cane sugar.

Natural vs’ added sugars

Natural and added sugars from any source are chemically identical; the fructose in fruit is identical to the fructose in HFCS. Regardless of their source, sugars provide the same amount of energy (17kJ/g). The differences between natural and added sugars are usually in their amount, or concentration and the food context (see examples below). For example, fructose in whole fruit comes along with moisture, fibre and micronutrients.

Total sugars content of apple and apple products (from NUTTAB)

Unsweetened apple juice 7.3g/100ml

25% apple juice drink 10.2g/100ml

Red delicious apple 12.4g/100g

Dried apple 62g/100g

Apple juice concentrate (syrup) 71g/100g

Glycemic impact

Sugars vary in their glycemic impact, and fructose and lactose both have a low GI (Glycemic index). However the physical form of the food can affect the glycemic impact of sugars in foods. Consuming concentrated sources of fruit increases the glycemic load (GL) of a serving of that food, even if the GI is low. For example the GL of 250ml orange juice (12) is higher than the GL of a 120g whole fresh orange (6) when they have the same or very similar GI. Research conducted by SRAS member John Monro from Plant and Food research New Zealand, found whole kiwi fruit elicits a lower glycemic response than the equivalent amount and type of kiwi fruit sugars, demonstrating the glycemic advantages of whole fruits.

non cho components of kiwifruit.png

Sourced from: Mishra S, Monro J. Diabetes Research and Clinical Practice 2016;120S1: s38 

Is fructose a problem?

The evidence supporting a particular health risk from fructose is unconvincing. Most studies showing adverse effects are in animals given extremely high doses of fructose that bear no resemblance to the way we eat fructose in the diet. Human studies using realistic amounts show it does not cause any more or less weight gain than any carbohydrates, or any harm above that of other sources of excess dietary kilojoules. It’s the excess energy consumption that is the problem rather than any metabolic effect.

Epidemiological evidence

When it comes to eating fruit, all evidence is positive for health- not surprising considering fruit is a core food recommended to be consumed daily.  A tenet of the traditional Mediterranean diet is ‘no day without fruit’. Eating fruit regularly appears to reduce all-cause mortality risk of heart disease, stroke and type 2 diabetes. Alarmingly, research conducted in Western Sydney Australia has identified cases of scurvy in people with diabetes with poorly healing foot ulcers, which they suggest might be due to diabetics avoiding fruit due to its sugar content.

Even drinking fruit juice appears to be protective against metabolic disease  and the protective mechanisms described. Drinking fruit juice is not associated with weight gain, even in the highest consumer groups: children and teenagers.  Research using data from the Australian Health survey shows people with higher intakes of fruit were 12% less likely to be obese than those who ate little fruit.

A large study of half a million adults from across China shows that rather than fresh fruit being a problem, consuming fresh fruit was associated with significantly lower risk of diabetes, and lower risks of death and major vascular complications in people who already have diabetes. A new systematic review and meta-analysis of fructose found the evidence does not support the idea that fructose containing sugars are associated with type 2 diabetes.

Practical implications

Fruit products are a source of natural sugars including fructose and these provide kilojoules. Evidence for usual amounts of fructose causing metabolic disease is lacking, and there is no evidence that eating fresh fruit is harmful in any way. It makes sense to limit (not avoid) concentrated sources of fruit such as dried fruit, juice and processed concentrated fruit products as dietary balance and kilojoules permit.

NEXT: Sugar and addiction: a review of the evidence  

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