RIBOFLAVINE 



in Great Britain during the war of 1939-45 were based on 70 % of the 

 1941 estimates,' whereas the actual consumption of riboflavine was i-6 

 mg. per day during 1939 to 1941, followed by a steady rise during the 

 next two or three years to a maximum of 2-0 mg. in 1944, then by a 

 slight fall in 1945 and another rise in 1946 to 2-0 mg. per day.^ 



Requirements of Rats 



A diet containing 3 fxg. of riboflavine per g. of air-dried food was 

 adequate to support normal activity in adult rats and enabled them 

 to live for a normal life-span.^ It was inadequate to produce the 

 normal growth rate in young rats, however, and for this purpose, the 

 riboflavine content had to be increased to 10 fig. per g. G. J. Mannering 

 and C. A. Elvehjem ^^ found that the food requirement of rats varied 

 with the riboflavine intake. As the latter increased, less and less food 

 was required in order to produce the same increment of growth, 

 whilst rats receiving adequate amounts of riboflavine were able to 

 grow at the same rate as rats on a diet partially deficient in riboflavine, 

 when the food intake of the former group was much lower than that 

 of the latter. This suggests that food was utilised m.ore efficiently 

 when adequate amounts of riboflavine were available. However, the 

 riboflavine-deficient rats fed on a more liberal diet were much more 

 active than the rats with a limited food intake and receiving adequate 

 riboflavine. Riboflavine deficiency in rats led to an increased deposi- 

 tion of body-fat.i^ 



Rats on high protein and high fat diets required at least twice as 

 much riboflavine as did rats on a normal diet in order to maintain 

 an equal level of riboflavine in the organs and urine. ^^ On a low fat 

 diet, the animals required only about half the normal amount of ribo- 

 flavine, which was calculated to be about 7-5 fjig. per day. It was 

 assumed that the different amounts required were due to differences 

 in the amounts of riboflavine synthesised in the intestine in a form 

 available to the organism. 



Requirements of Other Species of Mammals 



The amount of riboflavine required by mice varied according to 

 the strain. 1^ The C57 strain gave maximal growth with 0-4 mg. per 

 100 g. of bodyA\'eight and the A strain with o-6 mg. per 100 g. At a 

 level of 0-2 mg. per 100 g., the C57 mice had a reduced red blood-cell 

 count and a lower muscle and liver riboflavine, whereas the A strain 

 suffered no change. 



Dogs required 15 to 100 /xg. of riboflavine per kg. of bod3rv^'eight 

 per day to maintain normal health,^^ young growing pigs 40 to 66 /xg. 



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