New values for nutrients reveal more about health benefits

Related tags Dietary fibre Nutrition

Knowing a food's dietary fibre content says nothing about how it
will impact the body, says a New Zealand researcher, who is calling
for an alternative evaluation of nutrients that will give consumers
more information about their real benefit to health.

The new values, which describe the physical effect of a nutritional component on the body, could also offer more reliable support for health claims, which the food industry is increasingly turning to to add value to their products.

Dr John Monro from the New Zealand Institute for Crop and Food Research believes that if people are going to choose foods that could avert health problems, they need to know about properties that cannot be represented in currently used nutrient information panels.

"Such properties include the ability of a food to provide faecal bulk, which depends on more than just the amount of dietary fibre, and the glycaemic impact of a food, which depends on more than just its content of available carbohydrate,"​ he writes in the Journal of the Science of Food and Agriculture​ this month.

Like traditional nutritional information, virtual food components (VFCs) - coined by Monro last year - are presented as weights. They provide information about the functional efficiency of a food, by comparing the effect of that food with a suitable reference material of known activity.

The first VFC developed by Monro is the glycaemic glucose equivalent (GGE), a measure of the glucose-raising potential of a food, compared to glucose.

The activity of the test food is deduced as a percentage of the activity of an equal amount of the reference food. Thus a food with a GGE of 15 would impose the same blood glucose level as 15g of glucose.

The GCE is in fact already incorporated in the 'Net Atkins Count' used by followers of the Atkins diet.

But Dr Monro believes this system should be extended to a whole variety of foods.

"Important though nutrient values are, they can be hopelessly inadequate for communicating the benefits of foods."

Public food and health bodies around the world have repeatedly underlined that consumers find nutritional labeling confusing and fail to interpret the key information relevant to their health. This has been attributed as one of the factors behind the slow uptake on healthier eating.

Whether the VFCs will be any easier to implement or understand remains to be seen but they could gain favour from companies developing healthy foods and seeking to demonstrate an edge over numerous other foods making similar claims.

One of the most commonly used claims today is a 'high fibre' content. But Monro says that dietary fibre is a completely unreliable guide to the effect of fibre on the body, given that some fibres are actually destroyed by fermentation in the colon, and thus do not contribute bulk.

The second VFC developed by Dr Monro, described by the researcher and colleague Eva Martinet from the Institut National Superieur de Formation Agroalimentaire in France in the JSFA paper - concerns wheat bran equivalents for faecal bulk (WBEfb).

Colonic bulk provides significant protection against a range of bowel disorders. Rates of colorectal cancer, (among the four most common cancers in the UK and US), soar as faecal bulk drops below 150-200 g per day, shows research.

"Faecal bulking is an important property that should be possessed by products for which a claim of healthiness is to be made,"​ write the authors.

However in an analysis of 28 Australasian breakfast cereals carried out by Dr Monro in 2002, "it was concluded that most did not contribute to faecal bulk as well as one would expect from their associated nutrient claim".

In the new paper, the authors describe a study done on rats to determine the accuracy with which the WBEfb content of ingredients typically used in cereal bars would predict the overall effect on faecal bulking.

They found that the faecal bulking efficacy of all fibre sources in a sample bar - oats, pysllium and wheat bran - was not closely related to the amount of dietary fibre that they contained.

The use of the WBEfb however accounts for the physiological properties of complex sugars, such as the hydration properties of psyllium. These are not taken into account in dietary fibre analysis yet fibre's effects on faecal bulking are influenced by water retention capacity, note the authors.

The study therefore shows how an effective food product for bowel regularity could be designed from knowledge of the VFC content of its ingredients but not from its dietary fibre content.

"We now intend to build up the data so they can be used across a wider range of foods,"​ said Monro.

"The time is right for virtual food components to play a role in food choice and development…An ageing population, a high incidence of diseases related to poor food choices, the growing interest in self care…and the inadequacy and mistrust of health claims are all likely to make objective measures of the functional efficacy of foods highly acceptable,"​ claim the authors.

Related topics Research

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