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White bread is a no-no

Eating a diet containing too many easily-digestible carbohydrates and not enough fibre – like in white bread – increases the risk of obesity and diabetes. The same is true for pigs that are useful models for studies of the effects of diet on the metabolism in humans.

[Translate to English:] Grise reagerer ofte på samme måde som mennesker, når det drejer sig om ernæring, og er derfor gode at bruge som modeller. Foto: Janne Hansen

We spend too much time sitting on our backsides and eating the wrong foods! This can lead to obesity, diabetes and other lifestyle diseases. All this we have probably heard before, but how are these things connected when looking at it from the metabolism angle? And can we do anything to prevent it? These questions have been studied by scientists at Aarhus University by using the pig as a model.


The results showed that the types and quantities of fibre in bread affected the metabolism to different degrees. It also turned out that pigs are excellent models for this type of investigation, but that there was surprising variation between cloned animals that are genetically identical.


Rye bread and white bread

- The diet in the Western world is rich in easily-digestible carbohydrates but generally contains too little dietary fibre. This leads to sharp fluctuations  in blood sugar and insulin levels several times during a day. These fluctuations and a sedentary lifestyle is one of the main causes of the rise in lifestyle diseases like overweight, obesity and diabetes, says PhD student Kirstine Lykke Nielsen from Aarhus University.


In the first part of her PhD project she investigated how different types and contents of dietary fibre affected the metabolism. She did this by feeding the pigs either dark rye bread with or without whole rye grain or white wheat bread to which either wheat fibre (arabinoxylan) or oat fibre (?-glucan) had been added. An ordinary white wheaten loaf with a low fibre content was used as control.


The effect on the metabolism could be measured as soon as it happened as the pigs had been catheterised. This meant that blood samples could be taken directly from the digestive system without anaesthetising or stressing the pigs.


The results showed that dark rye bread and white wheat bread with arabinoxylan had the largest effects on the metabolism by lowering the acute glucose and insulin response compared with the normal white bread.


Pigs and humans are alike

In the PhD project Kirstine Lykke Nielsen also examined whether pigs and humans are completely comparable when it comes to nutritional experiments.


- Pigs are often used as models for humans in experiments on nutrition, but the question is whether the two species react the same to a diet intervention and whether the effects found in pigs can be transferred to humans, she says.


To clarify this, a human test panel ate the same types of bread as the pigs and had blood samples taken at the same intervals as the pigs. The results were generally fully comparable for pigs and humans, which support the fact that the pig is a good model for predicting the nutritional effects in humans.


In a third experiment the pigs were fed either ad libitum or a restricted amount of a diet corresponding to the white bread diet. The purpose of the ad libitum group, which was given free access to a low-fibre, high-calorie wheat diet over a longer period, was to examine whether the pigs would develop the same lifestyle diseases as in humans. The ordinary slaughter pigs did not do so, but the pigs fed the diet restricted in white bread were healthier and leaner according to the blood sample analyses.


Cloned pigs are not identical

Cloned pigs were used for some of the investigations, since they have the same genetic make-up and therefore ought to be identical. But cloned pigs were not the expected exact copies – quite the reverse. Their individual response to different treatments varies just as much as for ordinary pigs and cloned pigs are apparently even more sensitive to a diet that can lead to lifestyle diseases.


The large variation in the group of cloned pigs despite their identical genetic composition shows that there are other factors at large, for example that epigenetics and/or gut microflora may cause variability to develop.


- The results from the experiments give a closer insight into how the metabolism is affected by different carbohydrates. They show that both concentrated arabinoxylan and wholegrain bread can be used to prevent and treat lifestyle diseases and that it is good for health to reduce the calorie intake, says Kirstine Lykke Nielsen.


Further information: PhD Kirstine Lykke Nielsen, Department of Animal Science, e-mail: kirstinel.christensen@agrsci.dk, telephone: +45 8715 4259, mobile: +45 2275 1684