High intakes ov vitamin C let a low absorve fracction (< 30%) With low doses the fraction absorved is near 90-100% so it is not a very usefull thing taking several grams a day and can lead to gastrinstinal problems due to a big fracction excrete via rectal. But anyway there is a lot of controverse with that. Several authors advocate about the high intakes if vitamin C in the ilness. Who knows?