Soy and Hot Flashes

Written by Dr. Steve Chaney on . Posted in current health articles, Health Current Events, Nutritiion

Will Soy Put Out The Fire?

Author: Dr. Stephen Chaney

 

soy and hot flashesThere has been a lot of controversy in recent years about soy and hot flashes. The question is whether soy isoflavones reduce the hot flashes associated with menopause.

And this is an important question! Because of concerns about increase heart attack risk with hormone replacement therapy (HRT) many women have been looking for natural alternatives to HRT for reducing hot flashes and other symptoms of menopause. They’ve been asking whether soy isoflavones are effective, and the answers that they’ve been getting have been confusing.

For example, you can still find many experts and health professionals who will tell you that soy isoflavones have no proven effect on menopause symptoms.

That is somewhat surprising since two recent meta-analyses (Howes et al, Maturitas, 55: 203-211, 2006; Williamson-Hughes, Menopause, 55: 203-211, 2006) and a 2010 expert panel of The North American Menopause Society have all concluded that soy isoflavones alleviate hot flashes.

Will Soy Put Out The Fire?

However, clear guidance in this area was sorely needed, so Taku et al (Menopause, DOI: soy10.1097/gme.0b013e3182410159, 2012) performed an even larger meta-analysis that included 19 published clinical trials – some of which had been published after the previous two meta-analyses were performed.

I’ve talked about meta-analyses before, so you probably already know that they are very powerful because they combine the results of many individual clinical trials into a single data analysis.

But you also may remember me telling you that meta-analyses can be misleading if they introduce bias because of the kinds of clinical studies that they exclude from their analysis.

So I examined the design of this meta-analysis very carefully. It excluded clinical trials that:

  • were not double blind, placebo controlled and designed in such a manner that the placebo was indistinguishable from the soy isoflavone preparation.
  • contained other substances in addition to the soy isoflavones (The presence of other substances in the preparation might have influenced the response).

There were several other well justified reasons for excluding some studies from the meta-analysis, but they were technical in nature. In my opinion this was a very well designed study.

And the results were clear cut. An average of 54 mg of soy isoflavones (some studies used a little less, some a little more) was sufficient to reduce:

  • the frequency of hot flashes by 21% – and –
  • the severity of hot flashes by 26%

Soy and Hot Flashes: What This Study Mean For You?

The results of this study were highly statistically significant. So if you are suffering from hot flashes and are wondering whether soy isoflavones will put out the fire, the answer appears to be YES.

That’s the good news.

The bad news is that 21-26% is not a huge effect.

And, if you look at the individual clinical studies it is apparent that the response is highly variable. Some women experience major relief from hot flashes and other menopause symptoms, while other women experience little or no relief.

The reason for this variability is not known, but it is likely that the effectiveness of soy isoflavones on reducing hot flashes is modified by other components of the diet and by lifestyle factors such as obesity, exercise and stress.

Soy and hot flashes; the bottom line.

My take on this is that soy isoflavones should not be thought of as a “magic bullet” that will make hot flashes go away by themselves, but rather as a proven part of a holistic approach that encompasses a healthy diet, exercise, weight control and stress reduction

The Bottom Line

  • A recent meta-analysis of 19 published clinical studies showed that soy isoflavones reduced the frequency of hot flashes by 21% and the severity of hot flashes by 26%.
  • The results were highly statistically significant, but 21-26% reduction in symptoms is not a huge effect.
  • When they looked at the individual clinical studies it was apparent that the response is highly variable. Some women experienced major relief from hot flashes and other menopause symptoms, while other women experienced little or no relief.
  • My take on this is that soy isoflavones should not be thought of as a “magic bullet” that will make hot flashes go away by themselves, but rather as a proven part of a holistic approach that encompasses a healthy diet, exercise, weight control and stress reduction

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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