Simplify the following text for a Grade 9 native English-speaking person.
Original: 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 . They are thought to have made up for this by regularly eating thiamine-rich soba .
Simplified: It was discovered that beri beri could be prevented by regularly eating thiamine-rich soba .