1270.pdf

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Scientific Opinion on the substantiation of health claims related to soy isoflavones and maintenance of bone mineral density (ID 1655) pursuant to Article 13(1) of Regulation (EC) No 1924/2006[sup]1[/sup] EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2 European Food Safety Authority (EFSA), Parma, Italy
Słowa kluczowe: Soy isoflavones   bone mineral density   daidzein   genistein   glycitein   health claims   post-menopausal women   soybean protein isolates  
ID:    1655  
Produkty: Izoflawony sojowe  

1. Charakterystyka żywności / składnika

The food constituents that are the subject of the health claim are soy isoflavones. Soy isoflavones constitute a wide range of compounds of plant origin, which mainly comprise genistein, daidzein, and glycitein, among others (Ma et al., 2008a and 2008b). Soy isoflavones could be consumed as soybean- protein isolates (SPI), as whole-soybean foods or extracts, as supplements or as pure compounds (Cassidy et al., 2006).
The Panel considers that the food constituent, soy isoflavones, which is the subject of the health claim is sufficiently characterised.

2. Znaczenie oświadczenia dla zdrowia człowieka

The claimed effect is “bone health”. The Panel assumes that the target population is post-menopausal women.
Bone health relates to bone mass, bone mineral density (BMD) and bone structure, which all contribute to bone strength. Whereas bone structure and bone strength are not usually measured in vivo, BMD is a good indicator of bone health in the general population.
After menopause, an increased rate of bone loss and bone remodelling, and a decrease in BMD, are observed. These changes have been associated with an increased risk of bone fractures. Bone metabolism can be measured by assessing biochemical markers of bone turnover. BMD, a relevant factor for the assessment of bone health, can also be measured by established methods.
The Panel considers that maintaining bone mineral density is beneficial to the health of post- menopausal women.

3. Naukowe uzasadnienia wpływu na zdrowie człowieka - Utrzymanie prawidłowej gęstości mineralnej kości u kobiet po menopauzie

Publications on the health effects of phytoestrogens in general, or on the effects of soy isoflavones on health outcomes unrelated to bone status, were not considered pertinent to the evaluation of this claim.
Two meta-analyses and one systematic review were presented investigating the effects of soy isoflavones on bone parameters in post-menopausal women (Cassidy et al., 2006; Ma et al., 2008a and 2008b). These studies deal with the effect of soy isoflavones on BMD and/or on biochemical markers of bone turnover. All the individual studies presented have been considered in these publications.
The systematic review only included placebo-controlled double-blind randomised clinical trials (RCTs) conducted in healthy women >1 year post-menopausal with a duration from six months up to one year (Cassidy et al., 2006). Six studies investigating the effects of soybean phyto-oestrogens on BMD, bone turnover, or both, met the inclusion criteria. Three of these studies used pure compounds or extracts and three studies provided foods containing soybean protein or SPI (Gallagher et al., 2004; Potter et al., 1998; Kreijkamp-Kaspers et al., 2004). Of the three studies that used soybean isoflavone extracts or pure genistein, two are suggestive of an effect on BMD at doses ranging from 35 to 54 mg/d aglycone equivalents (Clifton-Bligh et al., 2001; Morabito et al., 2002). Only one of the three studies performed with SPI showed an effect on BMD at a dose of 56 mg/d aglycone equivalents (Potter et al., 1998), while the two other studies show no effect with doses ranging from 4 to 103 mg/d aglycone equivalents (Gallagher et al, 2004; Kreijkamp-Kaspers et al, 2004). Only three of the studies included biomarkers of bone formation or bone resorption. One study using SPI (Gallagher et al, 2004) and one study using red clover extract (Clifton-Bligh et al., 2001), showed no effect of the intervention on markers of bone turnover, whereas the study using genistein (54 mg/d) showed an increase in bone formation and a reduction in bone resorption biomarkers (Morabito et al., 2002).
The first meta-analysis (search dates 1966 – April 2006) selected nine RCTs including 432 peri- (two studies, total of 66 subjects) and post-menopausal women and investigating the effects of soy isoflavones on markers of bone turnover (Ma et al., 2008a). The duration of the intervention varied widely among studies (from 4 to 48 weeks), with only three of them lasting longer than 12 weeks. Soy isoflavone intake varied between 37 and 118 mg/d in the various intervention groups. Soy isoflavone intake was associated with a significant increase in bone-specific alkaline phosphatase (a marker of bone formation) and with a significant decrease in urinary deoxypyridinoline (a marker of bone resorption) compared to placebo. Differences between intervention and control groups were not significant when only the three RCTs lasting >12 weeks were taken into account. The Panel notes that meaningful changes in bone resorption and bone formation markers in response to an intervention can only be expected after 12 and 24 weeks, respectively (Prentice et al., 2003). The Panel also notes these markers alone cannot be considered as primary indicators of bone health.
The second meta-analysis (search dates 1966 – September 2006) selected 10 RCTs including 608 peri- (two studies, total of 66 subjects) and post-menopausal women and investigating the effects of soy isoflavones on BMD (Ma et al., 2008b). The duration of the intervention varied widely among studies (from 3 to 24 months), with only four of them lasting longer than one year. Soy isoflavone intake varied between 4.4 and 150 mg/d in the various intervention groups. When all the studies were combined, soy isoflavone intake significantly increased spine BMD compared to placebo. However,
these results were not significant when the analysis was restricted to the four studies with at least one year of duration. The Panel notes that at least 6–12 months are needed to evaluate the short-term impact of an intervention on BMD, and that 2–3 years are necessary to evaluate the long-term effects.
In weighing the evidence the Panel took into account that, although statistically significant effects on markers of bone turnover and/or on spine BMD have been described in some short-term RCTs (up to 12 weeks and up to 12 months, respectively) in relation to the dietary intake of soy isoflavones, longer-term interventions do not support a sustained effect of soy isoflavone intake on markers of bone health (Ma et al., 2008a and 2008b). The Panel also took into account the lack of a clear dose- response relationship between the dietary intake of soy isoflavones and the claimed effect, and the different results obtained depending on the source and nature of the isoflavones used (Cassidy et al., 2006; Weaver and Cheong, 2005).
The Panel concludes that the evidence provided is not sufficient to establish a cause and effect relationship between the consumption of soy isoflavones and the maintenance of bone mineral density in post-menopausal women.

Wnioski

On the basis of the data presented, the Panel concludes that:
The food constituent, soy isoflavones, which is the subject of the health claim, is sufficiently characterised.
The claimed effect is “bone health”. The target population is assumed to be post-menopausal women. Maintenance of bone mineral density is beneficial to the health of post-menopausal women.
The evidence provided is not sufficient to establish a cause and effect relationship between the consumption of soy isoflavones and the maintenance of bone mineral density in post-menopausal women.