Yeah, if you consume 1,000 Calories of soda and add vitamins you won't get as good absorption as if you got it from whole food sources. All vitamins are actually groups of compounds that can be used for the same role, but not everything in the group is as bioavailable (efficient) as everything else in the same group.  For example, take "vitamin A".  You can either get it from meat (in the form of retinol) or plants (in the form of alpha-, beta-, and gamma-carotene, and beta-cryptoxanthin.  Each of these is absorbed at a different rate by the body.  Take a look at this table, taken from here.    Substance and chemical environment μg of retinol equivalent per μg of substance     retinol 1   beta-carotene, dissolved in oil 1/2   beta-carotene, common dietary 1/12   alpha-carotene, common dietary 1/24   gamma-carotene, common dietary 1/24   beta-cryptoxanthin, common dietary 1/24    The problem is these are often simply classified as "vitamin A" on nutrition labels, so you may think you're getting 3 grams of vitamin A, but in reality you're getting 3 x 1/24 = 0.125 grams of useable vitamin A, because the food only contained gamma-carotene. The other vitamin families behave similarly, and there are other nutrients that might work like this, too.  You're better off drinking 300 Calories of milk than drinking 300 Calories of Pepsi and adding supplements of all the good things you're missing out on (Calcium, vitamin A, vitamin D, protein, B2, B12, and so on and so on.