When we were kids, our mothers always told us to eat all of our vegetables so that we could grow big and strong.  But Mom had always heard that vegetables were good for you.  It turns out that may be less true today than it was just fifty years ago.  In a 2009 Time Magazine article₁, researcher Donald R. Davis is quoted as saying that today's vegetables contain anywhere from 5% to 40% fewer nutrients than those of 50 years ago.  

Researchers attribute this decline to several factors:

1. Dilution
2. Shorter growing periods
3. Soil depletion

Dilution

 When I go to the store, I'm not looking for the smallest peach.  Many of us are looking for a bigger and better-looking product.  The genetic manipulation that has produced these big, beautiful crops, has not increased the amount of nutrients they contain. The result is a larger product with a lower nutrient density per unit of food.  A cup of sliced peaches does not contain as much nutritional value as it did when peaches were smaller.  Even more concerning, there is some evidence₂ to suggest that genetic manipulation has actually reduced the total amount of nutrients in some fruits and vegetables.

Shorter Growing Periods

That same tinkering that has led to larger and more attractive fruits and vegetables has also produce crops that reach maturity more quickly.  If you are running a large factory farm, that's great news.  Now you can get two crops in a growing season instead of just one.  If you're a consumer, not so much.  You see, it takes time for a plant to absorb nutrients, whether they be synthetic ones applied to the plants by the grower or natural ones absorbed by the plants from the soil.  The faster a plant is harvested, the less time it has to absorb those nutrients.

Soil Depletion

Continuously farming the same piece of ground for years using intensive cultural practices eventually leads to the decline of the soil quality in that spot.  There are some tricks that a grower can use to get around poor soil quality, but reasearch is begging to show that the results do not measure up to plants grown in quality soil using sustainable cultural practices.  

Finding a Better Product

So how can you find more nutritious produce?  A good place to begin is buying organic.  Researchers have found that organically grown tomatoes can have as much as 30% more phytochemicals (which are very good for you) than their non-organically grown cousins.₃  Another good tip is to look for smaller, more brightly colored fruits and vegetables, as these will likely be higher in phytochemicals and have a higher nutrient density than larger, paler specimens.  Red leaf lettuce is better for you than iceberg.  Duh!

Heirloom variets are often better than modern cultivars as well.  This is because they were bred to thrive without modern chemical fertilizers, pesticides, and herbicides.  If your grocery store doesn't stock these, check out a farmer's market.  You'll find another big advantage there: plants grown in season and picked closer to full ripeness.  Not to mention the fact that a small grower can tell you all about how they farm.  If they are using natural fertilizer instead of synthitic ones, if they rotate crops and let fields lay fallow, if they plant green manuare crops that bind nitrogen in the soil, and lots of other healthy and sustainable practices.  

1 Stephey, M.J. Eating Your Veggies: Not As Good For You? (Time Magazine, 2009.)

2 Davis, Donald R. Declining Fruit and Vegetable Nutrient Composition: What Is The Evidence? (Journal of HortScience, 2009.)

3 Burns, Sarah Nutritional value of fruits, veggies is dwindling (Prevention Magazine, 2010.)