Does Resveratrol Improve Blood Sugar Control?

Written by Dr. Steve Chaney on . Posted in Food and Health, Issues, Supplements and Health

Is The Promise of Resveratrol True?

Author: Dr. Stephen Chaney

blood sugar testIt was just a few years ago that resveratrol was the latest “miracle nutrient”. It was featured on Dr. Oz and on 60 Minutes. It was hot! Today you see dueling headlines. The headlines one week proclaim the benefits of resveratrol. Next week’s headlines say that it’s all hype. What’s a person to believe?

Let me take you behind the headlines to look at the actual studies and answer some important questions.

1)    What do we actually know about the benefits of resveratrol?

2)    Is the evidence for beneficial effects of resveratrol where it should be considering the number of clinical studies that have been published?

3)    What additional studies need to be done before we can be sure that resveratrol is beneficial?

4)    Should you wait until we are absolutely certain resveratrol is beneficial, before you start using it? This is perhaps the most important question of all.

To answer those questions, let’s examine the study behind one of the latest headlines, namely: “Resveratrol Improves Blood Sugar Control in Diabetics”. One of the promises of resveratrol has been that it might help diabetics and pre-diabetics who struggle with blood sugar control. However, this promise was based on animal studies. The study that generated the headlines in question was a meta-analysis of recently published human clinical trials in this area (Liu et al, Am. J. Clin. Nut., 2014, doi: 10.3945/ajcn.113.082024).

Does Resveratrol Improve Blood Sugar Control?

The meta-analysis included 11 published placebo controlled double blind clinical studies looking at the effects of resveratrol supplementation on fasting blood sugar levels, insulin levels, hemoglobin A1c (a measure of blood sugar control) and insulin resistance (a measure closely associated with type 2 diabetes).

A strength of this meta-analysis is the fact that it included 11 clinical studies. However, a weakness of this analysis is that these studies utilized a wide variety of resveratrol doses (10 mg/day to 1 gram/day), a wide variety of end points and both diabetic and non-diabetic patients. That means that there were only a few studies with common population groups, resveratrol doses, and end points.

The conclusions of the study (and the headlines you may have seen) were that:

•    Resveratrol appeared to improve blood sugar control (based on improvements in fasting blood sugar levels, insulin levels, hemoglobin A1c and insulin resistance) in diabetics.

•    No consistent effect of resveratrol on blood sugar control was seen in non-diabetics.

How Good Are These Studies?

While these studies are very promising, they are bot definitive.  There were only 3 published clinical studies in diabetics. While all 3 of the studies showed a positive effect of resveratrol supplementation:

•    The doses used were different in each study (ranging from 10 mg/day to 1 gram/day)

•    Each study measured different end points (one measured blood glucose, insulin levels, hemoglobin A1c and insulin resistance, one measured blood glucose and hemoglobin A1c and the third measured insulin resistance).

As a research scientist I would like to see more studies done at comparable doses and measuring the same end points – we scientists always want more studies.

Similarly, there was not enough consistency in the studies with non-diabetics to draw a firm conclusion. (3 were with obese patients, 3 were with patients with cardiovascular disease, 1 was with patients with metabolic syndrome and 1 was with perfectly healthy subjects.)

If you really wanted to see if something like resveratrol helps non-diabetics with blood sugar control, you would want to start with people who are already experiencing some difficulties with blood sugar control (pre-diabetics or patients with metabolic syndrome) and follow them for a couple of years to see if resveratrol reduces the number of them who become diabetic.

Are The Headlines Just Hype?

Newspaper HeadlinesDoes that mean that the blood sugar benefits of resveratrol are just hype? The answer is no. There is a difference between “very promising, but not yet definitive” and “hype”. We shouldn’t be surprised that human studies on the health benefits of resveratrol are not yet definitive. Science moves slowly. It often takes decades of scientific research before promising concepts are widely accepted by the scientific community.

When a research area is as young as this one, we sometimes need to go beyond the clinical studies and look at the totality of evidence. In this case:

•    In mice resveratrol exerts its beneficial effects by turning on a specific anti-aging gene called SIRT1 (Cell Metabolism, 15: 675-690, 2012). In humans, resveratrol appears to activate the same genetic pathways as in mice (Journal of Clinical Endocrinology & Metabolism, 96: 1409-1414, 2011).

•    In obese mice resveratrol improves markers of blood sugar control (Nature, 444: 337-342, 2006). Published clinical studies in diabetic humans also show improvements in blood sugar control (Journal of Clinical Nutrition, 2014, doi: 10.3945/ajcn.113.082024).

So while more and better clinical studies are needed to be absolutely certain that resveratrol helps improve blood sugar control, the evidence supporting that effect is substantial.

What Should You Do?

The ONLY important question for each of you is probably: “Should I wait a decade or two until we are absolutely sure about the health benefits of resveratrol before I take a resveratrol supplement?” That question is ultimately yours to answer. It’s all about benefits and risk.

Benefits – In animal studies resveratrol clearly improves blood sugar control. The human clinical studies published to date are consistent with the animal studies.

Risk – Current data suggest that resveratrol appears to be safe, even at high doses. For example, one recent study indicated that up to 5 gm/day is safe (Cancer Epidemiology BioMarkers & Prevention, volume 16:1246-1262, 2007), but I wouldn’t personally recommend exceeding 100-200 mg/day.

The Bottom Line:

1)     Don’t get too excited about the headlines suggesting that resveratrol might help improve blood sugar control in diabetics. The few human clinical studies that have been published to date are consistent with previous animal studies. That is very promising, but more studies are needed before we can be absolutely confident that resveratrol supplementation is beneficial for diabetics.

2)     Similarly, don’t be discouraged by the headlines suggesting that resveratrol does not help with blood sugar control in non-diabetics. Those results are preliminary as well.

3)     That doesn’t mean that the headlines are just hype. It takes decades to accumulate definitive proof that any kind of food or nutrient offers proven benefits, and the bulk of human clinical research on reveratrol has occurred in the last couple of years. We are exactly where we should expect to be at this point in time.

4)     With something as promising as resveratrol, the real question becomes whether you can afford to wait a decade or two until you know whether the potential benefits have been definitely proven. That question is up to you. On the plus side, current data suggest that resveratrol is highly promising for blood sugar control. In addition, resveratrol appears to be safe, even at high doses, but I wouldn’t personally recommend exceeding 100-200 mg/day.

5)     We already know that weight control, exercise and a healthy diet improve blood sugar control. You should think of resveratrol as something you may wish to add to a healthy lifestyle, not as a substitute for a healthy lifestyle.

6)     If you are diabetic and decide to try a resveratrol supplement, be sure to work with your physician so they can modify your dose of insulin or blood sugar medication as necessary.

7)     Finally, you may be asking whether resveratrol supplements are even necessary. Can’t you just get all the resveratrol you need from a glass or two of red wine? Stay tuned. I’ll have the answer to that question in a couple of weeks.

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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