Everything we consume in life has a toxicity level, even water. When we eat a nutrient dense diet that includes a variety of whole foods, we tend to end up in a optimal place where vitamin toxicities and deficiencies are not as likely. The standard american diet is the diet that I see most people eating and, if anything, is more prone to vitamin and mineral deficiencies.

Here is an article by Chris Kresser that speaks to Vitamin A toxicity/deficiency. He also explains the interplay between Vitamins A and D and talks about cod liver oil vs organ meats. He points out that you would need to eat 22 ounces of beef liver or 5 tablespoons of cod liver oil each day to create a vitamin A toxicity. I only eat liver occasionally and take 1 teaspoon of green pastures fermented cod liver oil each day because I think it is a reasonable approach.

http://chriskresser.com/9-steps-to-p...lement-wisely/

I'd also recommend reading anything by Chris Masterjohn PhD on this topic; he is a expert in fat soluble vitamins.

This is interesting and caused me to do a little reading on Arctic explorers and their diets. This is not relevant for the average person. Not many of us will ever eat or have access to polar bear livers.

Fruits and vegetables are not sources of Vitamin A, they are sources of beta-carotene. Beta-carotene is the inactive/precursor form of rentinol (Vitamin A). Healthy adults only convert 3% of beta-carotene into Vitamin A and about 45% of the population can not convert beta-carotene into Vitamin A at all; this is due to genetic, disease, infection, or food allergy factors.

The short term vitamin supplements that your brother has been prescribed seem very reasonable to me, provided that he is avoiding seal or polar bear livers in his diet.