Nutrition for health
and performance

PROFESSOR DAVID ROWLANDS - School of Sport, Exercise and Nutrition, College of Health

Professor David Rowlands of Massey University’s School of Sport, Exercise and Nutrition is interested in both human health and performance nutrition, carrying out diverse research in each of these arenas.

One project involves investigating using keratin protein derived from wool as a new dietary protein for people with Type-2 diabetes. Protein, and protein supplements, are widely used to enhance recovery in athletes, and in diabetics they could help improve the metabolic health of muscle. There is growing evidence that different proteins have different effects on the body, and keratin has the potential to be particularly useful. ‘A lot of protein sources carry other minerals and micronutrients,’ explains Professor Rowlands. ‘For example, in New Zealand, most people are deficient in zinc, which is important for immune health. So, protein sources that are enriched in zinc may be a useful addition to the diet.’

In order for it to be edible, keratin must first be processed. ‘Keratin contains disulphide double bonds which are very strong, making it indigestible in the human gut,’ Professor Rowlands says. ‘Animals can digest it, because they have the right microflora, but our gut doesn’t, so it has to be chemically processed.’

So far, a clinical trial of baked goods containing processed keratin has been carried out. The work was funded by a grant from The Ministry of Business, Innovation and Employment’s Smart Ideas fund, and is a collaboration between Massey University and Professor George Dias from the University of Otago. ‘We’ve got very good results, and the next step is to finish the analysis and find another industry partner to work towards commercialisation,’ says Professor Rowlands. ‘But certainly, right now it could be used as a protein in the diet.’

Another benefit is that the protein can be produced cheaply, with coarse-grade wool turned into edible protein for just $10 per kilo. ‘It’s also environmentally friendly, because you can grow sheep on almost anything, and the technique can be transferable to llamas, goats and camels, which live in quite harsh, arid climates.’

Choosing the correct blend and form of carbohydrate can be the difference between minutes and seconds off your time.


As well as his work in human health, Professor Rowlands is also interested in nutrition for high-performance athletes. During prolonged, intense exercise, muscle requires a ready source of carbohydrate, and there is strong evidence that with adequate carbohydrate availability athletes perform better. However, as Professor Rowlands explains, the mixture of carbohydrates that athletes choose is important. ‘Choosing the correct blend and form of carbohydrate can be the difference between minutes and seconds off your time.’

Laboratory research has suggested that for performance athletes, a fructose-maltodextrin (glucose-polymer) blend would significantly outperform a glucose blend, because the combination of fructose and glucose is transported across the gut wall at a faster rate than glucose alone, meaning more carbohydrate can get into the bloodstream, and therefore to muscles. ‘The effect is most pronounced when a lot of carbohydrate is ingested, because the glucose, when ingested at higher rates, just accumulates in the gut lumen. It’s reached saturation point, and the gut can’t absorb any more. Whereas at these higher rates of ingestion, the fructose and the glucose combined can be absorbed at a faster rate. We took this into the field to ask the question: Does a fructose blend perform the best when it’s ingested in the food sources that athletes use during long distance exercise?’

In the largest sports nutrition study ever conducted, 74 male triathletes were divided into two groups in a crossover: one who took the fructose-maltodextrin mix and the other a glucose-maltodextrin mix. The sugars were at a concentration previously shown to maximise performance, which, importantly, is only two-thirds of that used in the majority of laboratory studies.

Contrary to the lab results, the results showed only a small benefit of the fructose blend, giving half a per cent improvement in performance. ‘For an athlete this is still worthwhile, but it’s nowhere near as impressive as the two to eight per cent enhancements we were seeing in the lab,’ says Professor Rowlands. ‘The problem is, they never looked at what happens when it is taken at a lower dose, which is necessary in real conditions, otherwise athletes experience gastrointestinal distress as glucose accumulates in the gut, leading to stomach cramps, nausea, and a drop in performance.

‘This is the danger of extrapolating from laboratory results to real life too quickly. People have a tendency to reductionism. We take a small piece of information on a complex question, and make inferences on it, and it doesn’t translate. We need to ask the question when we begin research: How translational is this study going to be?’

Project details

Dates 2015–2017; 2013–2014
Funders The Ministry of Business, Innovation and Employment; Nestec Ltd, Switzerland