The fibres are most commonly used as fat and sugar replacers, and have increasingly been linked to gut health benefits due to their action as prebiotics to promote the growth of beneficial intestinal microflora populations.
But an increasing body of science is emerging linking the ingredients to help control blood sugar levels, reduce cholesterol, and boost bone strength, with inulin maker Orafti highly active in this area.
The new review, by Douwina Bosscher and colleagues from Orafti and published in the September 2006 issue of the International Dairy Journal (Vol. 16, pp. 1092-1097), draws together the current science linking these prebiotics to bone health.
The review is a timely summary of the state-of-play for an ingredient that could be seen by food makers as a way to offer products to consumers that are increasingly aware of the threat of osteoporosis.
Osteoporosis is estimated to affect about 75m people in Europe, the USA and Japan. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is €31.7bn in Europe, and 17.5bn in the US (2002 figure). The total annual cost of osteoporosis in the UK alone is over £1.7bn (€2.5bn), equivalent to £5m (€7.3m) each day.
There are two approaches to prevent osteoporosis, said the Orafti reviewers. First, optimise bone mass acquisition during adolescence, and secondly, minimise bone loss after the menopause.
The majority of work with inulin and oligofructose in both animals and humans has focussed on the first approach, according to the review, although some data from animals in available regarding prevention of bone loss post-menopause.
Animals studies have "repeatedly shown… over the last 10 years" that inulin/ oligofructose supplementation to a diet results in more absorption of calcium, accumulation of bone mineral and improved trabecular network structure (J. Nutrition, Vol. 132, pp. 3599-3602; Br. J. Nutr., Vol. 88, pp. 365-377).
In human adolescents, short-term supplementation with the so-called synergistically active mixture of oligofructose and long-chain inulin (SYN1) is reported to have a higher calcium absorption (38 per cent), than the placebo group (32 per cent).
"This finding is important as these girls might be most likely to benefit from SYN1 supplementation to their daily diet," wrote Bosscher.
These increases in calcium absorption were subsequently repeated by long-term supplementation studies of up to a year in length.
Indeed, one study reported that girls and boys aged between 9 and 12 supplemented with SYN1 had an additional net accretion of calcium of 30 milligrams per day, compared to the controls who received a placebo (American Journal of Clinical Nutrition, 2005, Vol. 82, pp. 471-476).
"It appears that increased true calcium absorption with eight grams per day of SYN1 during pubertal growth enhances bone mineralisation probably resulting in increased peak bone mass during adolescence," wrote the Orafti scientists.
Dr. Bosscher and colleagues said that these results had "implications for future preventative strategies for osteoporosis."
The prebiotic is thought to work by changing the flora in the colon, with the more slowly fermented inulin acting as a selective 'fuel' for this modified flora, which is kept metabolically active further in the gut.
This selective fermentation pattern results in the production of short chain fatty acids, which decrease the pH within the colon, improving the solubility of the calcium present. The calcium is then better absorbed into the body.
The data from the short and longer-term studies with adolescents is strong and highly positive, and more research continues to strengthen these results.
In terms of reduction of bone resorption post-menopausal, data is already mounting from animal models of increased bone balance and calcium absorption, said the reviewers.
"These data show promising results on the role inulin and oligofructose can play in positively modulating bone mineral metabolism during post-menopausal age and need to be confirmed in human intervention trials which are currently ongoing," wrote the reviewers.
A spokesperson from the National Osteoporosis Society (NOS) told NutraIngredients.com that the preliminary data from animal and experimental studies on calcium absorption were promising, but said the findings needed confirmation by more science.
"Randomised control trials in humans across the age span are needed before any links with improvements in bone health or reductions in osteoporosis risk can be claimed and, at present, there are too few available," she said.