Original: This tradition originates from the Tokugawa period when the population of Edo ( Tokyo ) , being considerably wealthier than the rural poor , were more susceptible to beri beri due to their high consumption of white rice , which is low in thiamine .
Simplified: At that time , the population of Edo ( Tokyo ) was considerably wealthier than the rural poor , were more susceptible to beri beri because of their high consumption of white rice which is low in thiamine .