Vitamin A deficiency has been associated with a number of prevalent diseases, including childhood asthma, 43,44 kidney stones formed spontaneously from calcium phosphate, 9 and fatty liver disease.45 Vitamin A in doses above those needed to prevent deficiency protects against oxidative stress, 46 kidney stones formed
from dietary oxalate, 28 and exposure to environmental toxins.47
For normal people both of those risks
from oxalates are relatively low; in healthy people only 5 % of
dietary oxalates are absorbed, versus 50 % in those with compromised gut function.