It seems like everyone has a bit of a cough or sore throat today. That common cold is a bit annoying but luckily, there's a million claims about any number of vitamin/mineral/herb supplements that can help your immune system out! What holds up to the science? What can you tell your patients/friends/family? Here's a quick breakdown of the evidence for/against the popular ones:
1. Vitamin C - Go into any drug store in the winter and you're bombarded by Emergen- C and Airborne as soon as you enter. Their box covers usually advertise that they've got 1000mg of vitamin C - yay!! right? The clinical trials are actually pretty dim regarding Vitamin C's ability to prevent or treat the common cold. The latest Cochrane review (1) on vitamin C supplementation showed a very small benefit for regular supplementation with Vitamin C (generally over 1g/day), and no effect for therapeutic use (started at beginning of onset). The only individuals that Vitamin C may be beneficial for are athletes performing strenuous activity. I'm not totally against vitamin C consumption from foods though - there's evidence to suggest that other components of the food matrix may work in concert with vitamin C to reduce cold symptoms (2). This lends further support to the associations that regular consumption of fruits and vegetables can improve immune function (3). Ditch the supplements and eat an orange - it's been shown your body can do anything with excess vitamin C beyond consumption of 200mg/day anyway (5).
2. Zinc - I've started to see zinc losenges and zinc added to vitamin C supplements - is it worth it? The data is very mixed, but it seems that zinc supplementation is most prudent if started within a day of seeing symptoms (6). Significant reductions are seen in the duration of colds with intakes >75mg - it's important to only use this for a bit as high zinc intake can negatively impact other mineral metabolism. It's also important to note that many of the studies don't measure zinc status of the participants at the beginning of the trial (there isn't a great way to do this). Zinc is important for the maturation of T lymphocytes into B/T-cells - if you're zinc intake is low, a supplement may benefit you more. If you notice some cold symptoms, there's no major danger to taking a zinc supplement or two over the next day, and it may just help reduce the severity of that cold. However, you've got to weigh those benefits against the potential for nausea.
4. Probiotics - I hear the saying "70% of your immune system is in your gut" from a lot of medical practitioners but can't find a source for that... either way, probiotics seem to be doing some good for your immune function (11) and preventing the common cold (12). Modest benefits have been seen from probiotic supplementation, for greater than 3 months - though the most beneficial strains are hard to tie down - in my opinion, stick to Lactobacilli and Bifidobacterium. Regular consumption of fermented foods and prebiotics (fibers) can help to maintain your healthy flora .
5. Green Tea - as i've blogged before, green tea gets over-exaggerated constantly on the internet - a quick google search of common cold and green shows up tons of promises about green tea and immune function. I drink multiple cups of green tea daily and I'd certainly drink it if I were sick (but I don't expect anything magical from it). However, going out and buying green tea supplements lacks enough evidence to recommend it - One study used its own specific green tea formulation to show a reduction in symptoms and duration of sickness. The other clinical trial I could find showed a benefit to the elderly who supplemented with both green tea catechins and theanine (the amounts in multiple cups of green tea) (19)
6. Mushrooms - consumption of mushrooms, oddly enough, has a number of documented immune boosting effects, through a number of potential mechanism (13, 14). however, there aren't any well controlled trials that I can find showing an effect on the common cold symptoms or duration. Their immune system effects seem to be more appropriately applied to the list of anti-cancer benefits, as our 'favorite' alternative health practitioner Dr. Mercola adequately cites (15) - however, he makes the jump after listing this that mushrooms then must help with the common cold. I don't see the evidence as of yet.
7. Echinacea - There's a lot of mixed data surrounding Echinacea - some find it to reduce duration of colds (16), and others of similar design find no effect (17). Larger studies find that Echinacea had no effect on number of colds, with regular supplementation over a period of four months, but did reduce duration of colds - however, this study has been critiqued due to the authors not releasing their funders, which turned out to be an herbal supplement company (18). Take that for what you will, even if you do choose to consume echinacea, it would appear that you need a longer duration of supplementation, and that treatment upon noticing symptoms has no appreciable effect.
And don't forget exercise - your lymph won't move itself (No, seriously, it won't)
1. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000980.pub4/abstract
2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3023145/
3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808435/
4. http://ajcn.nutrition.org/content/96/6/1429.full
5. http://jama.jamanetwork.com/article.aspx?articleid=189536
6. http://www.ncbi.nlm.nih.gov/pubmed/23775705
7. http://archinte.jamanetwork.com/article.aspx?articleid=414815
8. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
9. http://www.ncbi.nlm.nih.gov/pubmed/23246640
10. http://www.ncbi.nlm.nih.gov/pubmed/18767337
11. http://www.ncbi.nlm.nih.gov/pubmed/19442167
12. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3560336/
13. USDA/Agricultural Research Service (2008, July 1). Shiitake Mushrooms May Improve Human Immune Function, Especially If Grown On Old Oak Logs
14. http://jn.nutrition.org/content/138/3/544.abstract
15. http://articles.mercola.com/sites/articles/archive/2011/12/31/organic-mushrooms-for-immune-support.aspx
16. http://www.ncbi.nlm.nih.gov/pubmed/11505787
17. http://www.ncbi.nlm.nih.gov/pubmed/21173411
18. http://www.nhs.uk/news/2012/10October/Pages/Herbal-remedy-echinacea-does-protect-against-colds.aspx
19. http://www.ncbi.nlm.nih.gov/pubmed/21338496
1. Vitamin C - Go into any drug store in the winter and you're bombarded by Emergen- C and Airborne as soon as you enter. Their box covers usually advertise that they've got 1000mg of vitamin C - yay!! right? The clinical trials are actually pretty dim regarding Vitamin C's ability to prevent or treat the common cold. The latest Cochrane review (1) on vitamin C supplementation showed a very small benefit for regular supplementation with Vitamin C (generally over 1g/day), and no effect for therapeutic use (started at beginning of onset). The only individuals that Vitamin C may be beneficial for are athletes performing strenuous activity. I'm not totally against vitamin C consumption from foods though - there's evidence to suggest that other components of the food matrix may work in concert with vitamin C to reduce cold symptoms (2). This lends further support to the associations that regular consumption of fruits and vegetables can improve immune function (3). Ditch the supplements and eat an orange - it's been shown your body can do anything with excess vitamin C beyond consumption of 200mg/day anyway (5).
2. Zinc - I've started to see zinc losenges and zinc added to vitamin C supplements - is it worth it? The data is very mixed, but it seems that zinc supplementation is most prudent if started within a day of seeing symptoms (6). Significant reductions are seen in the duration of colds with intakes >75mg - it's important to only use this for a bit as high zinc intake can negatively impact other mineral metabolism. It's also important to note that many of the studies don't measure zinc status of the participants at the beginning of the trial (there isn't a great way to do this). Zinc is important for the maturation of T lymphocytes into B/T-cells - if you're zinc intake is low, a supplement may benefit you more. If you notice some cold symptoms, there's no major danger to taking a zinc supplement or two over the next day, and it may just help reduce the severity of that cold. However, you've got to weigh those benefits against the potential for nausea.
3. Vitamin D - this is less a therapeutic avenue (aka don't get sick and start taking Vitamin D expecting miracles) - but ensuring normal vitamin D (25OHD) levels may protect against sickness and the common cold (7).
It's currently only an association but many argue that itrests on plausible mechanisms
regarding Vitamin D's ability to regulate the innate and adaptive immune
system (8). Supplementation is especially important for obese
individuals (9), and those living at norther latitudes who don't
synthesize Vitamin D from the sun during the winter (10). The current recommendations are set around bone health outcomes, and are population measures, not individual clinical values. It's a good idea to still consume several hundred IUs of vitamin D per day, but those who recommend mega-doses to prevent colds are not using an evidence-based approach.
 |
| Credit: Nature.com |
5. Green Tea - as i've blogged before, green tea gets over-exaggerated constantly on the internet - a quick google search of common cold and green shows up tons of promises about green tea and immune function. I drink multiple cups of green tea daily and I'd certainly drink it if I were sick (but I don't expect anything magical from it). However, going out and buying green tea supplements lacks enough evidence to recommend it - One study used its own specific green tea formulation to show a reduction in symptoms and duration of sickness. The other clinical trial I could find showed a benefit to the elderly who supplemented with both green tea catechins and theanine (the amounts in multiple cups of green tea) (19)
6. Mushrooms - consumption of mushrooms, oddly enough, has a number of documented immune boosting effects, through a number of potential mechanism (13, 14). however, there aren't any well controlled trials that I can find showing an effect on the common cold symptoms or duration. Their immune system effects seem to be more appropriately applied to the list of anti-cancer benefits, as our 'favorite' alternative health practitioner Dr. Mercola adequately cites (15) - however, he makes the jump after listing this that mushrooms then must help with the common cold. I don't see the evidence as of yet.
7. Echinacea - There's a lot of mixed data surrounding Echinacea - some find it to reduce duration of colds (16), and others of similar design find no effect (17). Larger studies find that Echinacea had no effect on number of colds, with regular supplementation over a period of four months, but did reduce duration of colds - however, this study has been critiqued due to the authors not releasing their funders, which turned out to be an herbal supplement company (18). Take that for what you will, even if you do choose to consume echinacea, it would appear that you need a longer duration of supplementation, and that treatment upon noticing symptoms has no appreciable effect.
And don't forget exercise - your lymph won't move itself (No, seriously, it won't)
1. http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD000980.pub4/abstract
2. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3023145/
3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2808435/
4. http://ajcn.nutrition.org/content/96/6/1429.full
5. http://jama.jamanetwork.com/article.aspx?articleid=189536
6. http://www.ncbi.nlm.nih.gov/pubmed/23775705
7. http://archinte.jamanetwork.com/article.aspx?articleid=414815
8. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
9. http://www.ncbi.nlm.nih.gov/pubmed/23246640
10. http://www.ncbi.nlm.nih.gov/pubmed/18767337
11. http://www.ncbi.nlm.nih.gov/pubmed/19442167
12. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3560336/
13. USDA/Agricultural Research Service (2008, July 1). Shiitake Mushrooms May Improve Human Immune Function, Especially If Grown On Old Oak Logs
14. http://jn.nutrition.org/content/138/3/544.abstract
15. http://articles.mercola.com/sites/articles/archive/2011/12/31/organic-mushrooms-for-immune-support.aspx
16. http://www.ncbi.nlm.nih.gov/pubmed/11505787
17. http://www.ncbi.nlm.nih.gov/pubmed/21173411
18. http://www.nhs.uk/news/2012/10October/Pages/Herbal-remedy-echinacea-does-protect-against-colds.aspx
19. http://www.ncbi.nlm.nih.gov/pubmed/21338496
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