Soy protein does not improve bone mineral density

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Soy protein does not improve bone mineral density

Rheumawire

Jul 6, 2004

Nainggolan

Utrecht, the Netherlands - Soy protein supplements do not improve bone

mineral density (BMD) in postmenopausal women, a new study has found

[1].

Nor do they have any impact on cognitive function or plasma lipids, Dr

Sanne Kreijkamp-Kaspers (University Medical Center, Utrecht, the

Netherlands) and colleagues report in JAMA this week.

They explain that the sudden decline in estrogen levels after menopause

coincides with acceleration of several aging processeson average, BMD

decreases and cognitive function declines, whereas total cholesterol and

low-density lipoprotein cholesterol (LDL-C) increase.

Hormone-replacement therapy has been used to counteract some of these

changes, but increasingly it has been shown to have short- and long-term

risks, and so many women have turned to alternatives perceived to have

fewer side effects, such as phytoestrogenscompounds naturally occurring

in plant foods such as soy.

However, Kreijkamp-Kaspers told rheumawire that the reason they found no

effect of soy on BMD could be because the women in this study were too

old. " There is evidence that it's easier to prevent bone loss

immediately after the menopause, " she said.

Kreijkamp-Kaspers et al studied 202 healthy postmenopausal women aged 60

to 75 years between April 2000 and September 2001 in the Netherlands.

They were randomly assigned to receive 25.6 g of soy protein containing

99 mg of isoflavones or placebo, a total milk protein as a powder, each

of which could be mixed with food or beverages on a daily basis for 12

months.

Cognitive testing was performed at baseline and at the final visit, 1

year later, using several standardized tests. BMD was measured at

baseline and 12 months using dual-energy x-ray absorptiometry (DEXA)

scans, and plasma lipid levels also were assessed at baseline and 12

months. Adherence to therapy was good, as evidenced by plasma genistein

levels, which were markedly different between the intervention and

placebo groups, the researchers report. Adverse effects did not differ

between the soy and placebo groups, they note.

" In this longer-term, relatively large, double-blind,

placebo-controlled, randomized trial, we did not find any effect of soy

protein supplementation, which naturally contains large amounts of

isoflavones, on cognitive function, BMD, or plasma lipids in the

relevant population of aging women, " the authors state.

Kreijkamp-Kaspers et al say that for BMD, although " several studies have

indicated encouraging effects of isoflavones on osteoporosis, " other

clinical-trial results are less consistent. In this study, both groups

showed a decrease in BMD after a yearat most sites, there were no

differences between the groups, with the exception of the

intertrochanter region of the hip, which showed a mean increase in the

soy group.

One important factor may be timing of the supplementation, they note.

" In our trial women were, on average, 18 years menopausal. With respect

to bone it has been suggested that it is easier to prevent changes or

losses after menopause than reverse them when they have already taken

place. "

So they also did a subgroup analysis by the number of postmenopausal

years, which showed that those in the lowest tertile-ie, those who had

the most recent start of menopause, had better results after a year of

soy intervention, while women in the highest tertile did slightly worse

compared with the placebo group. " This was the case for both hip and

lumbar spine, but the interaction . . . did not reach statistical

significance, " they note.

Kreijkamp-Kaspers told rheumawirethat what is needed is a study of soy

on BMD in perimenopausal womenthose who are around 50 years of agethe

average age of onset of menopause. She said experiments in rats indicate

that if soy is given immediately after ovariectomy, it is very effective

in preventing loss of BMD, but if the soy is not given for 20 to 40 days

after the ovariectomy, there is no effect. She said her group hopes to

do a study of this kind in perimenopausal women and is trying to get

funding.

Source

Kreijkamp-Kaspers S, Kok L, Grobbee DE et al. Effect

of soy protein containing isoflavones on cognitive function, bone

mineral density and plasma lipids in postmenopausal women. A randomised

controlled trial. JAMA 2004; 292:65-74.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org