Osteoporosis affects approximately 54 million Americans, is responsible for 2 million broken bones, and accrues annual costs of $19 billion (NOF, 2015). It is estimated that half of women and a quarter of men 50 years and older will experience an osteoporosis-related bone break. Osteoporosis presents a challenge because many people with the disease do not realize it – osteoporosis generally does not cause pain or discomfort until a bone breaks or the spine compresses.
The Dietary Guidelines for Americans lists calcium among the shortfall nutrients of public health concern for nearly all age groups, and under-consumption of calcium has been linked in the scientific literature to osteoporosis and other adverse health outcomes (USDA, 2015). Close to three-quarters of girls between the ages of 9 and 18 years, women over 50 years of age, and men 71 years and older do not meet the estimated average requirement (EAR) for calcium, the key mineral associated with bone strength and prevention of osteoporosis.
Osteoporosis Impacts the Health of (Older) Adults
Globally, osteoporosis impacts adults as they get older and is a major disease around the world. With poor calcium status to blame, osteoporosis can negatively affect quality of life when it results in fractures that lead to decreased mobility, pain, and other consequences that make life more difficult. According to the International Osteoporosis Foundation, 33 percent of adults who fracture a hip become physically impaired and lose their ability to live independently within one year of the fracture (IOF, 2015). Spinal fractures are particularly debilitating.
Calcium Intake is Important Earlier in Life
In the presence of dietary calcium and other minerals and nutrients, the body builds bone and bone density during childhood and into the mid-20s. Bone mass then decreases throughout adulthood, with an acceleration in demineralization in women after menopause. Building stronger bones during childhood, the teen years, and early adulthood reduces the risk of osteoporosis and bone breaks later in life. Also later in life a sufficient calcium uptake by the body is important to stay healthy.
Boosting Calcium Absorption
Recommended calcium intakes are relatively high because less than one-third of dietary calcium is absorbed. Most absorption takes place in the acidic environment of the duodenum via active transport and under the influence of vitamin D. The alkaline pH in the jejunum and ileum allows primarily passive absorption in small amounts. The colon, so far, was not seen as a significant place for calcium absorption.
Ingestion of non-digestible, fermentable chicory root fiber, particularly a combination of longer-chain (inulin) and shorter-chain (oligofructose) inulin, can change the environment of the large intestine in a way that promotes calcium absorption. Bacterial fermentation of inulin/oligofructose generates short chain fatty acids (SCFAs) that appear to increase calcium absorption in several ways: acidifying the colon, stimulating growth of mucosal cells to increase absorptive surface, increasing intracellular permeability, and indirectly stimulating the synthesis of calcium-binding proteins.
Studies on various animal models support short- and long-term effects of inulin, oligofructose, and inulin/oligofructose on intestinal calcium absorption, bone turnover, and bone mineralization (Scholz-Ahrens and Schrezenmeir, 2007). Higher calcium absorption and bone calcium content following oligofructose supplementation was observed in ovariectomized rats, which serve as a model for postmenopausal osteoporosis in women (Scholz-Ahrens and Schrezenmeir, 2002). In another study on rats, Coudray et al (2003) demonstrated that calcium absorption was highest after consumption of an inulin/oligofructose product, Orafti®Synergy1 (SYN1) (50:50 short chain and longer chain inulin) , followed by inulin, then oligofructose. Absorption was lowest during feeding of a placebo control.
More than a dozen short- and long-term clinical trials on subjects of different ages and ethnicities support the positive effects of SYN1 on intestinal calcium absorption, bone turnover, and bone mineralization in humans. With its unique combination of short- and long-chain inulin, SYN1 has been shown to increase calcium absorption by up to 20 percent in humans by acidifying and extending the absorptive environment of the colon. The specific chain-length distribution of SYN1 fosters fermentation starting in the proximal colon and continuing into the distal colon, with a broad decrease in pH throughout. SYN1 effects have been demonstrated in various food and beverage matrices, do not negatively influence absorption of other minerals, and do not affect vitamin D levels. SYN1 has been shown to be effective in post-menopausal women, the group most susceptible to poor calcium status and bone loss (Holloway et al, 2007). Holloway et al showed that fractional absorption and bone resorption of calcium increased after 6 weeks of supplementation with 5 g SYN1 twice daily, specifically in those women who entered the study with the lowest bone mineral density.
Looking at potential mechanisms and sites of action, Abrams et al (2007) tracked calcium absorption kinetically through the GI tract using labeled calcium in a racially diverse group of young adults. Among those whose calcium absorption increased after 8 weeks of 8 g/day supplementation of SYN1, the absorptive pattern for calcium was consistent with increased absorption in the colon 7-8 hours after ingesting a meal with the labeled calcium.
Boosting Calcium Absorption in Children and Adolescents
Using inulin and oligofructose as a tool to boost calcium absorption in children may help increase bone calcium storage and lower the risk of osteoporosis in adulthood. In one study, a dose of 15 g oligofructose, separated into three 5 g doses taken with meals, improved calcium absorption, as compared to a sucrose control, in a group of 12 male teens (van den Heuvel et al, 1999). A combination of inulin and oligofructose, but not oligofructose alone, was shown to significantly increase calcium absorption, as compared to a placebo control, in a group of 59 adolescent girls receiving 8 g/d of oligofructose, inulin/oligofructose, or sucrose control for a three-week period (Griffin et al, 2002). The subjects in this study also consumed approximately 1,300-1,500 mg/d calcium in fortified orange juice.
The boost in absorption was more pronounced in girls with the lowest levels of intestinal calcium absorption during the placebo period (Griffin et al, 2003). One study, however, did not show an effect on calcium absorption following a 3-week supplementation period with 9 g/d of an oligofructose-enhanced inulin in adolescent girls. The authors postulate that absorption may not have improved because their study subjects were in a developmental period of high calcium absorption (Martin et al, 2010).
Abrams et al (2005), in a study conducted at the USDA Children‘s Nutrition Research Center at the Baylor College of Medicine, examined whether longer term supplementation with SYN1 would have similar positive benefits on calcium metabolism. A group of adolescents (n=100) received 8 g/day SYN1 over a one-year period, with measurements of calcium absorption and bone mineral accretion after 8 weeks and 1 year of supplementation. Compared to a control group, the SYN1 group had significantly greater calcium absorption at 8 weeks and greater bone mineral content density at one year. This is the most tangible demonstration of long-term benefits for the bones.
Based on the balance of the scientific evidence, it can be concluded that chicory root fiber improves calcium absorption in animals and humans, with Orafti®Synergy1 having more pronounced effects. A majority of SYN1 studies also show increased bone mineral density, improved markers of bone turnover, and/or prevention of bone loss. Effects occur independent of food matrix, in all age groups, in various ethnic groups, and both short- and long-term.