I grew up in the 50s and 60s. My mother was a big gardener. By the time I was in my teens she was providing our family of four with fruits and vegetables year round. When I left home and started eating store bought vegetables, I immediately noticed the difference in the way I felt and in my energy levels. By age 20, I was taking vitamins to make up for the lack of nutrients.
Time passes. In my mid 60s I started my own garden and am now growing almost enough fruit--I still buy some apples--and more than enough vegetables to keep me and a friend supplied year round. And again, once eating fruits and vegetables from my own garden, the improvement in my health and energy levels was noticeable. I still take vitamins, but it's no big deal if I miss a day or two. In the past, it would have been.
I read some years back that we were getting about 20% of the nutrition from store bought vegetables that people got 100 years ago. Some fruits, like watermelon, are pumped full of water to make them grow faster. And, yes, this is done at the cost of flavour. If you can manage any kind of garden to supplement your vegetable and fruit supply, I highly recommend doing so.