Hi Mouse,
I don't think it is a question of preventing nutrient loss but more in the way of "sufficient intake of nutrition", and what some cynics would sarcastically refer to as "expensive urine"!!
Any blood work in a couple of years to see if you are deficient in anything, will depend on how any deficiency is measured I suppose.
You just cannot rely on current RDA's as these are only sufficient to mask the appearance of disease.
I am really talking about "Optimum Nutrition" and not "Malnutrition".
I am not a fan of red-meat either.
I found this as evidence of the real Science you are perhaps looking for....................
In PDF Format........but you have to pay for a subscription before access..............
Declining Fruit and Vegetable Nutrient Composition: What Is the Evidence?
Davis HortScience.2009; 44: 15-19 http://hortsci.ashspublications.org/cgi/reprint/44/1/15?ijkey=RfqpDkPqP6D3rR