Vitamin C and Recovery

Vitamin C and Blood Pressure

G. Douglas Andersen, DC, DACBSP, CCN

If you ask the average adult what vitamin C is used for, the most common reply will involve the common cold. Over the years I have found that when a person does not have a cold, the vitamin C often sits on a shelf. Of course, vitamin C has many other functions including the reduction of inflammation and help with wound healing which the typical DC treats on a daily basis. Recently vitamin C was in the headlines regarding blood pressure.

Here is a sample:
Vitamin C has a modest effect on lowering BP
Vitamin C is associated with significant reductions in BP
Vitamin C may lower BP
Vitamin C regulates BP

It only took a couple of minutes to confirm that the various headlines concerned the same study. Once I retrieved the whole paper I only had to read a few lines before it became apparent that none of the people who wrote articles about this study in the popular press read anything more than the abstract or a press release.

The Study:
Researchers from Johns-Hopkins did a meta-analysis of vitamin C trials and blood pressure. 29 studies between 1982 and 2010 met the inclusion criteria and ranged from 10 to 120 subjects. The average length of intervention was 2 months. The doses of vitamin C in use were as follows:
10 studies used 500 mg/d
7 studies used 1000 mg/d
2 studies used 2000mg/d
2 studies used 400 mg/d
The remaining 8 studies used 4000, 3000, 1500, 1250, 515, 300, 200 and 6o mg/d respectively.

RESULTS - Systolic
22/29 studies lowered systolic BP to varying degrees.
3/29 had no change in using 1000, 500 and 500 mg/d doses
4/29 studies showed elevation of systolic BP. Their respective doses were 4000, 2000, 1500 and 1000 mg/d.

RESULTS - Diastolic
18/29 studies lowered diastolic BP to varying degrees.
5/29 had no change. The doses they used were 1500, 1000,1000, 500 and 500 mg/d.
6/29 studies that showed elevation of diastolic BP. Their doses were 4000, 2000, 1000, 500, 500 and 300 mg/d.

COMMENT
Analyzing the actual data was interesting for a number of reasons. Although every summery article and commentary about this paper in the popular press called 500 mg of vitamin C a 'high dose,' when we look at the amount of vitamin C used in each study, we see that higher doses were not necessarily better. In fact, the study that used the highest dose (4000 mg/d), and one of the two studies that used the third highest dose (2000 mg/d) raised both systolic and diastolic blood pressure. Conversely, the second highest dose used (3000 mg/d) and the second 2000 mg/d study lowered blood pressure. What was most ironic was that after reading the entire meta-analysis, rather than answering the questions raised from the press release based articles, I was left with even more questions (as I am sure anyone who reads this article is) which future studies will hopefully answer.

In the meantime, I will stick to my general vitamin C recommendation of 5 mg per pound of bodyweight which, for the average person, comes out to around 500 mg/d.

Juraschek, SP., Guallar, E., Appel LJ., Miller, ER. Effects of Vitamin C Supplementation on Blood Pressure: A Meta-Analysis of Randomized Controlled Trials. ACJN 2012; (95) 5; 1079-1088

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