Farming can deplete soil of valuable nutrients. What’s the effect on your health?
Why the Levels of Nutrients in Fruits and Vegetables Differs
The authors of both studies are very candid that most of the differences are probably explained by factors other than nutrient depletion of the soil—and it’s not at all clear that these changes pose a problem. For example, the dramatic decline in copper levels in vegetables from 1960 to 1990 is probably because copper-based pesticides, which were widely used then, are not as commonly used now.
When you actually read the studies, it becomes clear that a lot of the differences are most likely the result of changes in sampling methods and measurement techniques, geographical variation, and the random variation in nutrient values from one pepper or strawberry to the next—which is much more significant than most people realize.
Can We Grow More Nutritious Fruits and Vegetables?
But the biggest factor of all appears to be that we simply grow different varieties than we used to. Vegetables have been intensively bred to increase yield, decrease time to harvest, and have greater resistance to pests and disease—but not to improve nutrient content. That, by the way, is changing fast. As consumers become more focused on nutrition, they’re now concentrating on breeding fruits and vegetables that boast higher nutritional value.
There’s also been a big resurgence in heirloom varieties, lately—people are returning to strains that may be more similar to those we were growing back in the 1950s and 60s. And, finally, as concerns about mineral depletion have been raised, many organic and biodynamic farmers and gardeners are taking steps to replenish the soil with mineral-rich amendments like rock dust, in addition to the regular organic fertilizers. See also Are Organic Vegetables Healthier? and Are Organic Foods Worth the Cost?
My point is that there are a lot of factors that influence the nutritional value of fruits and vegetables—and I think many of them are actually trending in a positive direction. In the meantime, even if some vegetables are a little lower in certain minerals, I don’t think this is as big a deal as some people think. In my opinion, skimping on your veggies poses a far more present danger to your nutritional well-being than nutrient-depleted soil. As long as you’re eating a healthy diet with nice variety of fresh fruits and vegetables, you should still have your bases covered. See also my article How to Get More Vegetables in Your Diet.
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Have a great week and remember to eat something good for me!
Historical changes in the mineral content of fruits and vegetables
Mayer, Anne-Marie. British Food Journal. Vol 99, No 6, 207 (1997)
Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999 Donald R. Davis, PhD, FACN, Melvin D. Epp, PhD and Hugh D. Riordan, MD. Journal of the American College of Nutrition Vol. 23, No. 6, 669-682 (2004)