8 replies to this topic

[osris]

"The combination of vitamin C and grape-seed polyphenols increases blood pressure"

 

https://pubmed.ncbi....h.gov/15662232/

 

Does this apply to all polyphenols or just those in grape seed I wonder?

 

 

Abstract

 

Background: There is growing evidence that oxidative stress contributes to the pathogenesis of hypertension and endothelial dysfunction. Thus, dietary antioxidants may beneficially influence blood pressure (BP) and endothelial function by reducing oxidative stress.

 

Objective: To determine if vitamin C and polyphenols, alone or in combination, can lower BP, improve endothelial function and reduce oxidative stress in hypertensive individuals.

 

Design: A total of 69 treated hypertensive individuals with a mean 24-h ambulatory systolic blood pressure > or = 125 mmHg participated in a randomized, double-blind, placebo-controlled, factorial trial. Following a 3-week washout, participants received 500 mg/day vitamin C, 1000 mg/day grape-seed polyphenols, both vitamin C and polyphenols, or neither for 6 weeks. At baseline and post-intervention, 24-h ambulatory BP, ultrasound-assessed endothelium-dependent and -independent vasodilation of the brachial artery, and markers of oxidative damage, (plasma and urinary F2-isoprostanes, oxidized low-density lipoproteins and plasma tocopherols), were measured.

 

Results: A significant interaction between grape-seed and vitamin C treatments for effects on BP was observed. Vitamin C alone reduced systolic BP versus placebo (-1.8 +/- 0.8 mmHg, P = 0.03), while polyphenols did not (-1.3 +/- 0.8 mmHg, P = 0.12). However, treatment with the combination of vitamin C and polyphenols increased systolic BP (4.8 +/- 0.9 mmHg versus placebo; 6.6 +/- 0.8 mmHg versus vitamin C; 6.1 +/- 0.9 mmHg versus polyphenols mmHg, each P < 0.0001) and diastolic BP (2.7 +/- 0.6 mmHg, P < 0.0001 versus placebo; 1.5 +/- 0.6 mmHg, P = 0.016 versus vitamin C; 3.2 +/- 0.7 mmHg, P < 0.0001 versus polyphenols). Endothelium-dependent and -independent vasodilation, and markers of oxidative damage were not significantly altered.

 

Conclusion: Although the mechanism remains to be elucidated, these results suggest caution for hypertensive subjects taking supplements containing combinations of vitamin C and polyphenols.

[pamojja]

 

Conclusion: Although the mechanism remains to be elucidated, these results suggest caution for hypertensive subjects taking supplements containing combinations of vitamin C and polyphenols.

 

 

I've been taking 25 g/d of ascorbic acid, along with 2.9 g/d of flavonoids and 2.6 g/d of other polyphenols. OPC mainly from Grapeseed extract 330mg, alltogether for the last 14 years. I didn't experience increased blood-pressure. Consistently 109 sys. and 72 dys. in average all the years.

 

 

Does this apply to all polyphenols or just those in grape seed I wonder?

Studies always report averages. Some would experience a raise, some lower, some no change. The average reported always concerns only a small part of a study population.
 

 

[CynthesisToday]

This paper specifically examines people who already have hypertension _and_ take an anti-hypertensive drug to successfully control it. The discussion section of the full paper says an examination of blood parameters related to redox status:

 

"However, in our study, there was no effect of the combination supplement on any of the measured markers of oxidative stress."

 

Also, metabolism of arachidonic acids (a P450 metabolite correlated to hypertension) is not affected with any combination.

 

A key insight from the discussion is: 

 

"The possibility that the combination of vitamin C and grape-seed polyphenols may be interfering with the metabolism of antihypertensive drugs has not been ruled out."

 

Beyond the abstract conclusion, the full paper conclusion is: 

 

"While the mechanism behind this increase in BP following supplementation with the vitamin C and grape-seed polyphenol combination remains to be elucidated, the results indicate that the effect is unlikely to be due to increased oxidative stress or 20-HETE production, but still allow the possibility that it may be related to inflammation or endothelial dysfunction. "

 

So, The headline for this post is incomplete. It needs to say:

 

"The combination of vitamin C and grape-seed polyphenols increases blood pressure for hypertensive individuals successfully managing their BP using anti-hypertensive pharmaceutical drugs."

 

Or, to the question: "Does this apply to all polyphenols or just those in grape seed I wonder?" 

It applies to hypertensive individuals taking anti-hypertensive drugs to successfully control their hypertension. There is no data in this paper to say anything about any other individuals or any other polyphenols.

[Advocatus Diaboli]

Re post #3

 

The study design from post #1 specifically states that there was a 3-week washout:

 

"Following a 3-week washout, participants received 500 mg/day vitamin C, 1000 mg/day grape-seed polyphenols, both vitamin C and polyphenols, or neither for 6 weeks.". (my emphasis)

 

In other words, from the washout hyperlink above:

 

"In clinical trials, a washout period describes the length of time that someone enrolled in a trial must not receive any treatment before receiving the trial’s experimental therapy."

 

You wrote:

 

"So, The headline for this post is incomplete. It needs to say:"

 

""The combination of vitamin C and grape-seed polyphenols increases blood pressure for hypertensive individuals successfully managing their BP using anti-hypertensive pharmaceutical drugs.""

 

Your proposed new "headline" should leave off the "successfully managing their BP using anti-hypertensive pharmaceutical drugs" part. The subjects, although hypertensive, weren't using hypertensive drugs during the 6-week study, which followed the 3-week washout. The phrase "successfully managing" is not mentioned in the study. Full study title is here.

 

Edited by Advocatus Diaboli, 08 March 2023 - 11:47 AM.

[Advocatus Diaboli]

In post #4

 

"The subjects, although hypertensive, weren't using hypertensive drugs during the 6-week study, which followed the 3-week washout."

 

should read:

 

The subjects, although hypertensive, weren't using anti-hypertensive drugs during the 6-week study, which followed the 3-week washout.

[Harkijn]

I have not read this study, I would be much more interested in what taking this combination would do to those with average blood pressure.

[CynthesisToday]

If I click on the link in the original post, I get the abstract. When I click on the link provided by Advocatus Diaboli, I get the same abstract. Both provide the following DOI:

 

doi: 10.1097/00004872-200502000-00026

 

I don't know what the policy about providing sci-hub links here might be but if you put that DOI into sci-hub, you get the full article. I tried searching in that full article for the phrase Advocatus Diaboli included above ("The subjects, although hypertensive, weren't using anti-hypertensive drugs") but it doesn't find that phrase. I very carefully read through the full article looking for this phrase but never saw it. What I did see is this set of sentences:

 

"All volunteers ceased any vitamin,

fish oil or antioxidant supplements for at least 3 weeks
prior to study entry. All usual medication was taken as
prescribed on the morning of each visit and maintained
for the duration of the trial."

 

These two sentences started at the 3rd line down in the right hand column of page 428. Could you give me the specifics of where the sentence saying the participants stopped using anti-hypertensives during the washout? I can't find it by reading or by using the search function in my PDF reader. I suspect we're not looking at the same paper.

 

If LongeCity policy allows for the posting of sci-hub links to full papers, please advise and I'll provide the sci-hub link to the full paper that results with the use of doi: 10.1097/00004872-200502000-00026

 

 

And, you're correct about the study doesn't say specifically "successfully managing". My apologies for that mistake.

[CynthesisToday]

I have not read this study, I would be much more interested in what taking this combination would do to those with average blood pressure.

 

 

I found this paper: https://www.heimat-l..._Toxicology.pdf  (full text). It includes in its review of grapeseed extract a study (section 2.3.7) in normotensive rats. It does not include a combination with Vitamin C.

 

I am normotensive. I take vitamin C and grapeseedextract (GSE) within the same day and continue to maintain my normotensive status. N=1. I take them for different reasons but do take them within the same day. Vitamin C for adrenal health along with meals. GSE along with l-tryptophan on an empty stomach first thing in the morning to increase NAD (as part of my overall NAD protocol) in a circadian supporting manner via mechanisms described in this paper:

 

https://www.nature.c...icles/srep24977 "Dietary proanthocyanidins boost hepatic NAD+ metabolism and SIRT1 expression and activity in a dose-dependent manner in healthy rats" (full text) The materials and methods section describes the proanthocyanidin (PAC) composition of the grape seed PAC extract used in the study.

Edited by CynthesisToday, 08 March 2023 - 09:24 PM.

[Advocatus Diaboli]

Re: post #7

You wrote:

"If I click on the link in the original post, I get the abstract. When I click on the link
provided by Advocatus Diaboli, I get the same abstract. Both provide the following

DOI:

 doi: 10.1097/00004872-200502000-00026"

My intent in providing that redundant link was to get the readers to notice that the title
osris assigned to the thread was incomplete--assuming that it was his/her aim to
present the study title as the thread title.

You wrote:

"I don't know what the policy about providing sci-hub links here might be but if you
put that DOI into sci-hub, you get the full article. I tried searching in that full article for
the phrase Advocatus Diaboli included above ("The subjects, although hypertensive,
weren't using anti-hypertensive drugs") but it doesn't find that phrase. I very carefully
read through the full article looking for this phrase but never saw it."

My phrase wasn't presented as being a suggested revision to the headline title

(or study title?), as was your phrase. With a change in study title, for example, there is an
expectation to see that change reflected in the text of the study. You didn't find my
phrase because I didn't present it as being something that might be found in the study
text--it was merely a consequent of ratiocination.

You wrote:

"What I did see is this set of sentences:

"All volunteers ceased any vitamin, fish oil or antioxidant supplements for at least 3
weeks prior to study entry. All usual medication was taken as prescribed on the
morning of each visit and maintained for the duration of the trial.""

These two sentences started at the 3rd line down in the right hand column of page
428. Could you give me the specifics of where the sentence saying the participants
stopped using anti-hypertensives during the washout? I can't find it by reading or by
using the search function in my PDF reader. I suspect we're not looking at the same
paper."

The conclusion that the subjects weren't taking anti-hypertensives can be logically
deduced from the fact that the authors essentially claimed a washout, along with the

fact that the study objective was "To determine if vitamin C and polyphenols, alone or in
combination, can lower BP, improve endothelial function and reduce oxidative stress
in hypertensive individuals.".

Only ceasing "any vitamin, fish oil or antioxidant supplements for at least 3 weeks
prior to study entry" doesn't constitute a washout, if that's what the authors were trying

to imply. A washout for the study would be to cease the aforementioned supplements,

as well as any drugs, specifically anti-hypertensives, that might conflict with, or interfere

with, the study objective. In much the same way that researchers conducting a study

evaluating the efficacy of a new cancer-treatment drug would direct their subjects to not

take other cancer-treatment drugs during washout, and during the course of the study.

If the authors didn't washout anti-hypertensive drugs, then their study is essentially
worthless. Giving the authors the benefit of doubt, via Hanlon's razor, I assumed that
they actually did include anti-hypertensives in the washout--and hence my reasoned,
and reasonable, assertion.