Does it or doesn’t it? That is, does soy relieve menopausal hot flashes or not?
The evidence has been less than definitive however, researchers now say that trials examining the benefits or lack thereof of soy in attenuating symptoms may have been negatively affected by significant limitations, such as failing to recognize treatment timing and duration on effectiveness, small numbers of women in the studies and wide variations in how much hot flashes were reduced with treatment. And so, they took another look at the data using a new model, one that allows scientists to actually compare different treatments and evaluate the effectiveness of different factors, including dose, duration of treatment and formulations. This is an important method of analysis and one that could truly be considered a game changer. They say that their findings, published online in the British Journal of Pharmacology, will provide “information for deeper understanding of the efficacy of soy isoflavones on menopausal hot flashes.”
I am going to skip over the science mumbo jumbo and get right to the meat of how they came to their ultimately conclusions:
Findings were based on an analysis if 16 studies published between 1998 and 2012 enrolling over 1700 subjects.
In terms of duration, the effect of soy isoflavones were studied for anywhere from 4 weeks to two years, with a median of 12 weeks.
In these studies and vis a vis modeling, soy isoflavones were compared to both placebo and estradiol, the latter in terms of how long it takes to reach effectiveness. This last point is important.
And now, the result.
While the effect of isoflavones on hot flashes was superior to placebo, the researchers still observed a relatively strong placebo effect at play. Importantly, however, the placebo effect at play was even higher in trials examining estradiol and hot flashes. The reason? Apparently, women might have lower expectations when it comes to alternative therapies like soy. Yet, there was still another important finding that was teased out by this new modeling:
Soy isoflavones require at least 13.4 weeks to reach at least half of their full level of activity in the body. In comparison, estradiol only needs about 4 weeks. So, when you do the math, at four weeks (which is the usual length of most clinical trials of this nature), estradiol has reached 80% of its peak activity level and soy isoflavones, only 47%. By 48 weeks, soy isoflavones catch up.
Additionally, as I’ve written time and again, there are different components of soy with differing levels of effectiveness. Genestein is the strongest and yet, only three studies specifically looked at soy agents that contained genestein only. So, there was no way for the researchers to break down the findings by components.
Overall, the key takeaway is that it takes longer for soy to reach maximum effectiveness than it does estrogen. So, if we are going to quantify value moving forward, it’s important to account for this significant distinction.
When it comes to soy, it may simply be that slow and steady wins the race.
I’ve long been intrigued by the replacement of hormone replacement therapy with soy isoflavones. Yet, studies looking at their effectiveness for alleviating hot flashes and other vasomotor symptoms have been mixed. The reasons for this are multiple, and point to such factors as dose and actual composition of the supplements used, severity of hot flashes and how often women are taking isoflavones over the course of the day. Researchers have also discovered that only 20% to 30% of Westerners produce equol, (there’s even a dispute over this stat) a component of the potent isoflavone dadzein that has an affinity for estrogen and appears to be slowly cleared from the body;(note that both of these factors contribute to its beneficial effect against flashes.
Despite these challenges, what would happen is you simply upped the dose and/or frequency? Would it change the’ iso what’ or ‘who’ to an actual ‘iso yes!?’
That’s exactly what researchers sought to learn when they recruited 130 peri- and post-menopausal women with severe hot flashes (i.e. five or more a day). Women who produced equol and those who did not were separated and then randomly asked to take placebo, low dose (33 to 66 mg/day) or high dose (110-200 mg/day) equol or placebo capsule (s) and take them once daily or two to three times daily. They also kept daily hot flash diaries, assessing each hot flash by its intensity, daytime or nighttime occurrence and how bothersome they were. They met with the research team face to face twice — 9 weeks in, and 3 weeks after the study completed.
The findings made it quite clear that dose and frequency are almost as important as whether or not a person is able to produce equol. In fact, when women took higher doses of isoflavones more frequently, they had 2.4 per day fewer hot flashes than women taking the lower doses just once a day. And, the flashes were significantly less severe. What’s more, most of these benefits were realized during the night, when, as most of us know, flashes and sweats are especially disruptive. Moreover, there was not much of a difference between women who are able to produce equol and those who are not; while these women did experience greater declines (as much as 10%) in both how intense their flashes were and how frequently they occurred, the difference was apparently not statistically significant.
So, let’s cut through the scientific clutter:
Higher doses of isoflavones tend to have a greater effect than lower doses
More frequent dosing (two to three times a day) appears to be more beneficial than once a day dosing.
Greater benefits are likely to be seen in women who naturally produce equol, especially when it comes to hot flash intensity
Both perimenopausal and menopausal women may potentially benefit from higher, more frequent dosing.
This type of research is just beginning and the findings need to be teased out in larger numbers of women. It’s also unclear if spreading the lower dose out throughout the day would make a difference. Still, what these findings do bring to light is an evolution of thinking and that’s what makes me most excited. Rather than determining that isoflavones are useless, researchers are finally starting to treat them as though they were pharmaceutical agents, using them in randomized clinical trials, varying doses, frequency and patient populations and truly, thinking outside the box.
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