Tuesday, March 15, 2011

Vitamin (C)an't help you much

     I was looking through Facebook this morning and came upon a picture posted by a friend.  It was her breakfast; and it was intended to fight off her cold.  It consisted of:

fast food oatmeal
orange juice
two other random supplements

     If you think the supplement industry has developed a successful model for monetizing the placebo effect, then the cold-remedy arm of this industry should be the flagship.  The common (viral) cold is an elusive malady.  It has a weak seasonal trend, a wide range of signs and symptoms that vary person to person, and has always been particularly difficult to prevent or treat.  As the saying goes, "if you don't treat your cold, it could last as long as 7-10 days.  If you do treat it, you'll get over it in as little as 7-10 days."  Despite the paucity of evidence that any treatment (let alone a supplement) can prevent or reduce the severity of a cold, most people seek a remedy.
     Vitamin C is probably best known for ostensibly treating the common cold, and perhaps the most widely used.  However, according to a 1998 Cochrane Collaboration analysis (and as of 2011, still considered up to date by the group), numerous trials have failed to show that vitamin C can reduce the severity or duration of the common cold when taken at the onset of a cold compared to a placebo.  However, the report did indicate modest reductions in cold duration and severity if vitamin C supplements were taken preventatively or taken by intensely training athletes (Cochrane Vitamin C).  While simply having no benefit would be a waste of money, it is a bigger problem when the supplement (or food) is detrimental.  
     When we are sick, we look for easily prepared and comforting foods.  Sometimes this means chicken noodle soup.  We also try to get some therapeutic benefit from our food.  Again, sometimes this means chicken noodle soup.  However, many times it simply means foods that naturally contain or are fortified with high amounts of vitamin C.  So if we are short on time and want some food-therapy, we end up with something resembling my friend's breakfast.  And please know that I've fallen victim to this for the entirety of the past decade, so I pass no judgement in this post.  But what else are we getting besides vitamin C?
     This meal likely has between 65 and 80 grams of sugar, depending if the oatmeal included the complementary brown sugar, and tens of grams of starch.  The irony is that glucose and vitamin C are taken up by cells in the body via the same mechanism.  Thus, vitamin C and glucose may compete to gain entry into the cells, so that high concentrations of glucose can prevent cellular uptake of vitamin C.  Provisional data suggest that lower tissue concentrations of vitamin C in diabetics is due directly to hyperglycemia, and that a large bolus of glucose can deplete tissue concentrations of normal individuals to that of diabetic's (see Cunningham 1988 for details).  And while it is pure speculation, it would be interesting to see if the benefits of preventative vitamin C supplementation reported in the Cochrane study were at least partially attributable to normalizing low vitamin C secondary to high glucose consumption.  But alas, maybe another post.
     So while it is always tempting to find a quick fix to our ailments, even ones as benign as a cold, there doesn't appear to be one available.  And our attempts can likely put us in nutritional disarray at some of our most vulnerable times.

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