Bread enriched with lupin kernel flour at the expense of wheat flour reduced energy intake and increased the feeling of fullness, says new research from Australia that may have important implications for weight management.
"These results suggest that protein and fibre enrichment of bread with lupin kernel flour has the potential to influence appetite and reduce energy intake, at least in the short term," wrote lead author Ya Lee from the University of Western Australia, Perth.
Lupin flour has been earmarked as the next major competitor to soybean as a high protein source.
Lupin (Lupinus angustifolius L.), is the major grain legume grown in Australia and production exceeds 800,000 tons per year. Used mainly for feed, since 2001 in Australia lupin bran and flour have been used as a substitute in food formulations for more expensive traditional cereal grains.
The average protein content of lupin is just over 30 per cent, compared with 44 to 48 per cent in soybeans. In Europe, the flour is already being used in bakery and pasta products because it can replace eggs and butter to enhance colour and additional potential uses of lupins are in crunchy cereals and snacks, baby formula, soups and salads.
In addition to the protein, lupin flour is also said to contain non-starch polysaccharides which act like both soluble (oat fibre) and insoluble (wheat bran) fibre.
It is not the first time that lupin flour has been linked to increased satiety with, for example, Deakin University researchers reporting in 2004 that fibre from lupin-kernels used as fat replacers in sausage patty was associated with reduced energy intake in men (British Journal of Nutrition, Vol. 91, pp. 591-599).
However, lead researcher Jonathan Hodgson told NutraIngredients.com: "Apart from matching energy intake and the higher inclusion rate, our study is the first to assess effects both within and between meals and to look at ghrelin as a factor that might modulate the effect of LKF on satiety."
The new research, published in the November issue of the American Journal of Clinical Nutrition (Vol. 84, pp. 975-980), reports results from two randomized controlled crossover trials. The first study looked at the effects of bread enriched with lupin kernel flour (LKF) on satiety and energy intake compared to standard white bread. The second study looked at the effects of LKF bread or white bread on blood ghrelin levels, a hormone produced in the stomach that stimulates appetite.
In the first study 16 participants (average age 58.6, eight women, average BMI 31.3 kg per sq.m) were assigned to eat the LKF bread or white bread as toast at breakfast and as a sandwich at lunch for four weeks. After one week's washout period the participants were crossed over to the other intervention type. The LKF bread was made by replacing 40 per cent of the wheat flour found in normal white bread with LKF. The finished breads contained the same calorific value at breakfast.
The Australian researchers report that eating the lupin bread breakfast resulted in significantly higher self-reported satiety than the white bread group, and a lower energy intake (488 kJ less) at lunch than the white bread breakfast.
Eating the lupin-enriched bread at lunch also reduced between meal energy intake (1028 kJ less) than the white bread lunch.
"Consistent with the findings for self-reported satiety, the lupin bread breakfast resulted in up to 20 per cent lower energy intake at lunch that did the white bread breakfast," said the researchers.
"These results are supported by previous studies that showed that high-protein diets reduce energy intake at subsequent meals more so than do high-carbohydrate and high-fibre diets reduce energy intake at subsequent meals more so than do low-fibre diets," they said.
In the second study 17 participants (average age 61, six women, average BMI 27.2 kg per sq.m) were fed a lupin toast breakfast or a white bread breakfast and blood levels of ghrelin measured at regular intervals for three hours. The participants returned one week later and ate the other type of toast for breakfast.
Dr. Hodgson and his co-researchers report that the plasma ghrelin concentration was significantly lower in the lupin toast group compared to the white toast group (0.97 versus 1.93 picograms per millilitre of plasma, respectively).
"Thus, LKF is a novel food ingredient that could be incorporated into a range of products that might benefit appetite regulation," concluded the researchers.
Satiety has been called the 'Holy Grail of nutrition' and is seen as a key target in the battle against obesity, with figures from Europe showing that up to 27 percent of men, 38 percent of women, and 3m children are clinically obese in some parts of the bloc.
The retail market for weight management products was estimated by Euromonitor International to be worth US$0.93bn (€0.73) in Europe in 2005 and $3.93bn in the US, indicating that call to slim down or face the health consequences is being heeded by a slice of the overweight population at least.
Foods marketed for satiety enhance feelings of fullness after eating, acting as a boost to a person's will-power and helping them avoid a reversion to old habits in a bid to stave off hunger pangs, or 'grazing' in between meals.
Dr. Hodgson added a note of caution regarding any potential link between lupin flour and obesity, however: "Longer-term studies need to be conducted to determine whether these acute effects translate into reduced energy intake and weight loss longer-term in overweight individuals," he said.