From: hrubin@stat.purdue.edu   
      
   In article ,   
   Henry Spencer  wrote:   
   >In article ,   
   >Herman Rubin  wrote:   
   >>There is another problem, which is much more serious than   
   >>it might appear.  If we reduce the food supply to those   
   >>nutrients about which we know, we may end up missing   
   >>something important over moderately long periods.   
      
   >Except, of course, that's not what anyone is proposing.  The only way you   
   >*could* do that would be chemical synthesis of food, which is out of the   
   >question.  Realistic proposals all involve preserved normal foods, and the   
   >only significant question is whether absolutely everything of importance   
   >survives preservation.   
      
   >And as has already been noted, anything that will survive freezing *will*   
   >survive essentially indefinitely in cryogenic refrigeration.  So there   
   >should be no difficulty with anything that's needed only in trace amounts,   
   >given a modest amount of frozen whole food as a supplement to dehydrated   
   >stuff.   
      
   You are underestimating the nature of the problem.  If a   
   large enough variety of foods, from enough regions, are   
   used, this might not be a problem.  One nutrient which I   
   mentioned, selenium, is a problem in both directions; one   
   needs enough, and not too much, and where food is grown can   
   make a large difference.   
      
   >People have lived on such diets -- in fact, on diets considerably inferior   
   >to that -- for periods of a year or more in places like the polar regions.   
   >Extending this to Mars-mission durations would require some confirming   
   >experiments to be absolutely certain, but major trouble is most unlikely.   
      
   The polar regions might not be the worst.  The American   
   Midwest was known as the "goiter belt" because of a   
   shortage of iodine.  In this case, the danger of too much   
   is not that great, but I do not know what the effect would   
   be if too much accumulates in recycled water.   
      
   There can be some problems which cannot occur on earth;   
   in these cases, our ignorance is immense.  We have no   
   idea about the need, if any, for aluminum and silicon,   
   and as soil is mainly composed of aluminum silicates,   
   a shortage is not a problem.  I know an excess of   
   aluminum can be toxic, and is difficult to test for.   
      
   --   
   This address is for information only.  I do not claim that these views   
   are those of the Statistics Department or of Purdue University.   
   Herman Rubin, Department of Statistics, Purdue University   
   hrubin@stat.purdue.edu         Phone: (765)494-6054   FAX: (765)494-0558   
      
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