There's a great book, Gardening for Maximum Nutrition,that was written in the early '80's. I have taken it out of the library several times in the past few years and this fall I needed to refer to it again for some articles I was working on. But when I went back to the library I discovered it was no longer in their collection. I guess it was just too old. The library I go to has a fantastic collection of materials and is constantly adding to it, but the drawback is that they have to purge the older books (even the high quality ones) to make way for the new.
I checked on the sale shelf down it the lobby, hoping it would still be there, but had no luck. Eventually I decided I would have to order my own copy from Amazon. I found the bookseller who was closest to me, Atheneum in Denver, and ordered a used copy for $1.70 plus shipping. The description stated it was a used library copy, and I just had a funny feeling it was going to be the copy from my library. When it got here, that was the first thing I checked. Sure enough it was! I guess that book was just destined to be mine.
The thing I really love about the book is that the author, Jerry Minnich, evaluates the nutritional qualities of foods in a number of different ways. He has a list of the the most calcium-rich crops, protein-rich crops, Vitamin C-rich crops, and so on. And then a list of the top ten most nutritious crops and a list of the top twelve most versatile crops (those that contain the greatest number of different vitamins and minerals, plus protein). To gather his data, Minnich analyzed the USDA's Agriculture Handbook No. 456, Nutritive Value of American Foods in Common Units. In order to make the data most useful, he compared foods by typical serving sizes rather than by an equal weight of food. This makes a great deal of sense to me, since we will commonly eat a half-pound potato, but not a half a pound of asparagus in one sitting. Other studies list asparagus to be more nutritious on a pound-for-pound basis, but that is simply not the way we eat. When compared in terms of typical serving sizes, the potato wins.
So, what were his findings? The top ten most nutritious foods he listed were: leaf amaranth, sunflower seeds, broccoli, soybeans, almonds, collards, navy beans, cowpeas, potatoes, dandelion greens, and peanuts. His twelve most versatile foods were: broccoli, leaf amaranth, lima beans, cowpeas, watermelons, almonds, collards, peas, potatoes, soybeans, sunflower seeds and the twelfth spot was a tie among five items, which he unfortunately didn't list.
I love these sorts of lists, but of course they're only useful up to a point. Minnich's lists evaluate the 89 most common fruits and veggies, but certainly there are highly nutritious crops that were excluded simply because they weren't part of the typical American diet. Also grains weren't included, nor were herbs and most seed crops (sunflower seeds notwithstanding).
Again, when it comes to growing foods for maximum nutrition, I believe that variety is key. The more diverse our diets are, the more likely we will be getting the full range of nutrients necessary for optimal health. If you're planning next year's garden, certainly focus on the nutritional powerhouses, but also plant a diverse range of fruits, veggies, beans, nuts, seeds, grains and herbs, as space allows.