There is no doubt we've seen a significant drop off in nutritional value of crops. We've done some great radio shows on this with renowned soil scientist.
One way of combating this decline is to buy local, organic and real high quality. Also, there's some great supplement and super-food powders that make it easy to whip up high protein, low-fat smoothies.
The paramount answer, which will take more time, is to restore the nutritional value of our food supply.