For someone who consumes a lot of vitamins, it's easy to have excess Vitamin A in the body because it's fat-soluble. I've read in a lot of credible places that Vitamin A over-consumption is dangerous, but I haven't found any quantitative figures.
For example, if someone consistently eats twice the RDI of Vitamin A by eating two large carrots a day, will he/she likely (in the long-term) suffer under adverse health effects from it?