It all depends on what is meant by "large amounts". Vitamin A is toxic in large amounts, as is also B12, aspirin, morphine, nicotine, alcohol, and thousands of other substances. The Supersize Me movie showed that large amounts of what some consider food is also not without ill effects. What's a large amount for Sallyl, might not be a large amount for Peter. That's why the MD's have come up with their loading test.