We’ve all seen plenty of evidence suggesting that components of red wine possess many health benefits, including (but certainly not limited to) cardiovascular benefits. Specifically, polyphenols in red wine have been shown to decrease the risk of many different cardiovascular diseases by increasing the production of nitric oxide and endothelium-derived hyperpolarizing factor, both which play important roles in the cardiovascular health of humans.
One cardiovascular health benefit in particular which studies have found associated with moderate red wine consumption is improved vascular function. In the rat model, studies have shown that blood pressure is reduced after consumption of red wine polyphenols in normotensive and hypertensive animals. In humans, the results of similar studies have been inconsistent for a variety of reasons. Based on the evidence of improved blood pressure in rats, it could be hypothesized that the intake of red wine polyphenols would decreases blood pressure in hypertensive patients. The paper presented today sought to explore this hypothesis by examining the effect of a dairy beverage containing red wine polyphenols on blood pressure in patients with high-normal blood pressure and grade 1 hypertension.
Male and female subjects between the ages of 35 and 70 with mildly elevated blood pressure and normal values of general health markers and that were not on blood pressure medications that had similar pathways to red wine polyphenols were eligible for this study. Blood pressure measurements were taken during two separate screening visits one week apart. Three consecutive blood pressure measurements were taken at two minute intervals for 15 minutes (in a seated position).
In order to be included in the study, blood pressure measurements were required to be between 130 and 179mmHg systolic and less than 100mmHg diastolic. If the blood pressure was within these limits for both screening visits, height and body weight were measured and blood and urine samples were taken. Those with a 10 year risk of cardiovascular disease greater than 10% were excluded. Subjects were also excluded if they had any of the following: history of metabolic diseases, chronic gastrointestinal disorders, cardiovascular or renal disease, medically prescribed diet, engaging in intense sporting activities, using blood pressure medication or any medication that may affect red wine polyphenol availability, use of systemic antibiotics 3 months prior to the study, intolerance/allergy to dairy, pregnancy or lactating, 10% or more weight change in the 6 months prior to the study, eating meat or fish less than twice per week, smoking cigarettes within the last year prior to the study, or an irregular pulse.
The study was a double-blind, placebo-controlled randomized full-crossover design with three treatments. Treatments were randomly assigned to study participants. Study participants were asked to consume a dairy drink with or directly after breakfast that contained either 1) a placebo (no red wine polyphenols added); 2) 280mg red wine polyphenols; or 3) 560mg red wine polyphenols. These levels were chosen because they were in line with the levels of polyphenols one would consume at a moderate level (560mg red wine polyphenols is roughly equivalent to 2-3 glasses of red wine). Placebo and red wine polyphenol dairy beverages were the same in respect to taste.
The study lasted a total of 14 weeks consisting of three 4 week intervention periods separated by 1 week washout periods. The active ingredient in the red wine polyphenols was Provinols. Red wine polyphenols were dissolved in the dairy beverage in order to hide the bitterness of the polyphenols.
Throughout the study, subjects were required to maintain their usual diets and lifestyles. They were required to refrain from supplements 4 weeks before and during the study and also not to drink more than two alcoholic beverages per day. On the day before study visits, subjects were asked to refrain from drinking any alcoholic beverages, red grape juice, and engaging in strenuous exercise. Day one required the study subjects to record the contents of their breakfast in detail. Breakfast was consumed 2.5 to 3.5 hours before the office visits.
24-hr ambulatory blood pressure was measured at the start and end of the intervention periods of the study. Blood pressure was measured every 20 minutes during the day and every hour during the night for 24 hours. Blood pressure was measured in the office on two consecutive days at both the beginning and the end of the intervention period and 3 hours after consumption of the treatment beverages. Subjects sat for 15 minutes while 6 blood pressure measurements were taken.
The following were also measured or calculated: central hemodynamic measurements (finger blood pressure), mean arterial pressure, brachial blood pressure, central systolic and diastolic blood pressure, augmentation index (AIx), and reflection index. For laboratory analysis, blood was collected after an overnight fast. Urine samples were also collected for analysis. For the blood samples, glucose and lipids were measured, and in the urine, sodium, potassium, creatinine, and albumin were measured.
- 58 participants completed the study.
- Mean age of participants was 61 +/-8 years old.
- Participants were slightly overweight (BMI of 27+/-3kg/m2).
- 78% of participants were male, 22% were female.
- Average office blood pressure at baseline was 135 +/-9 /82+/-8mmHg.
- Average 24 hour blood pressure was 145 +/-12 / 86+/-8mmHg.
- Plasma and glucose levels were within normal reference values.
- Office blood pressure was not significantly affected by either red wine polyphenol treatment.
- There was no effect of 280mg red wine polyphenols on 24 hour blood pressure.
- There was a slightly significant difference between the three treatment periods, but neither of the two red wine polyphenol treatments was different from the placebo.
- Ambulatory day time blood pressure was higher than office blood pressure.
- There were no significant differences between the three treatments in central blood pressure, aortic AIx, or reflection index.
- Red wine polyphenols had no effect on plasma glucose or levels of total, high-density lipoprotein or low-density lipoprotein cholesterol or trigylcerides.
- 24 hour urinary sodium, potassium, sodium/potassium ratio, albumin, and creatinine were not significantly different among the different treatments.
According to the results of this study, there was no effect of red wine polyphenols on 24 hour ambulatory and office blood pressures compared to placebo controls after 4 weeks of treatment in patients with high-normal blood pressure or grade 1 hypertension. Results also showed that there was no effect of these treatments on central hemodynamic parameters.
According to the authors, this is the first human intervention study to examine the effects of red wine polyphenols on blood pressure. From the results, it is clear that there is no effect and red wine polyphenols do not appear to help (or hurt) blood pressure in humans. The authors address several limitations which may make interpretation of the results difficult, including too brief of a study (only 4 weeks per intervention period), not being able to extrapolate the results to different blood pressure groups/categories and also the bioavailability of the red wine polyphenols in the body. Personally, I think the sample size could stand to be larger as well, and perhaps only then would we potentially see more significant results.
Even though this study showed that red wine polyphenols do not improve blood pressure (and thereby vascular function) in humans, the results aren’t necessarily a bad thing. Sure, no additional health benefit was found in regards to blood pressure; however, at least red wine polyphenol consumption didn’t hurt/damage the vasculature of the study subject. Since there are so many other health benefits to red wine, some of which are blood-pressure-independent, the results of this study should not discourage anyone from consuming their favorite libations of the grape variety. However, if one were simply drinking the red wine for the sole purpose of reducing blood pressure that may not be the best solution.
I would have also liked to see if there were any differences in response when comparing the two sexes, and also comparing different ages. Since 78% of the study subjects were men in this study, can we really extrapolate the results to women as well (my answer is no).
Finally, I’m not convinced the results of this study can be extrapolated to red wine in general. This study looked at red wine polyphenols only; however there may be some synergistic effect between red wine polyphenols and other components of wine that were not present in the simplified dairy+polyphenol beverage of this study that could potentially alter the results. Perhaps these polyphenols act in concert with other compounds to reduce blood pressure, which one does not see when simply examining the polyphenols alone. Certainly more research needs to be done.
I’d love to hear what you all think about this topic! Do you agree with the methods and analysis of the results? Would you like to have seen the authors take a different approach to the question? If so, what would you like to have seen done?
Please leave your comments/questions below! (Reminder: all unapproved HTML solicitations will be promptly removed).
Source: Botden, I.P.G., Draijer, R., Westerhof, B.E., Rutten, J.H.W., Langendonk, J.G., Sijbrands, E.J.G., Jan Danser, A.H., Zock, P.L., and van den Meiracker, A.H. 2012. Red wine polyphenols do not lower peripheral or central blood pressure in high normal blood pressure and hypertension. American Journal of Hypertension 25(6): 718-723.
I am not a health professional, nor do I pretend to be. Please consult your doctor before altering your alcohol consumption habits. Do not consume alcohol if you are under the age of 21. Do not drink and drive. Enjoy responsibly!