I am taking a nutrition course this semester and my professor mentioned that the RDA is doubled what is actually required for a few reasons, one being to ensure there are no deficiencies and the other because some vitamin supplement manufacturers lobbied to keep it high, so we will purchase their product.
Her second reason intrigued me. Do you know if this is true?
The RDA’s are based on scientific research of both humans and animals and are set at levels to provide for 98% of all healthy people living in the US. There is a cushion built in so that if you get 67% of the RDA for a nutrient, you should be getting a minimum amount as an average person.
Remember that the RDA’s are based on preventing deficiency symptoms specific to each vitamin and mineral. Some people think that the RDA values of some nutrients, in particular, antioxidants, are set too low and recommend much higher levels.
I cannot comment on whether the vitamin supplement manufacturers lobby has been effective in keeping the RDA’s high, but I doubt that this is true since the Food and Nutrition Board who meet to discuss changes every 5 years or so. These nutrition scientists base their recommendations on nutrition research.
The nutritional and health problems in the US today have less to do with preventing nutritional deficiencies and more to do with eating a healthy diet composed of real foods. Remember that the human body absorbs only about 10 – 15% of a vitamin pill and excretes the rest in urine and feces. Pretty expensive urine for some!