20th Century Drop in Nutrient Levels of Food

For the past 50 years or so, pushing for higher and higher crop yields without concern for nutrient levels has resulted in a dramatic decrease in the nutrient levels of our food. How do we change this trend?

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As with one of my previous articles, my very health-conscious brother suggested that I look into this issue. Incidentally, I am reading a book right now that mentioned this as well and directed me to a wonderful, comprehensive report on the topic. The bottom-line, general finding is that as we have increased crop yields, nutrient levels of these crops have fallen.

“Government data from both America and the United Kingdom have shown that the concentration of a range of essential nutrients in the food supply has declined in the last few decades, with doubledigit percentage declines of iron, zinc, calcium, selenium and other essential nutrients across a wide range of common foods. As a consequence, the same-size serving of sweet corn or potatoes, or a slice of whole wheat bread, delivers less iron, zinc and calcium,” Brian Halweil reports in Still No Free Lunch: Nutrient levels in U.S. food supply eroded by pursuit of high yields [PDF].

While farmers doubled or tripled the yield of most major grains, fruits and vegetables over the past 50 years or so, nutrient levels steadily decreased as well. This trade-off seems to have occurred across a variety of crops and regions.

“Substantial data show that in corn, wheat and soybeans, the higher the yield, the lower the protein and oil content. The higher tomato yields (in terms of harvest weight), the lower the concentration of vitamin C, levels of lycopene (the key antioxidant that makes tomatoes red), and beta-carotene (a vitamin A precursor). High-production dairy cows produce milk that is less concentrated with fat, protein and other nutrition-enhancing components, and are also more vulnerable to a range of metabolic diseases, infections and reproductive problems.”

Why the Drop in Crop Nutrients?

The reasons for this drop in nutrient value seem clear. Crop breeders primarily focus on increasing yields not nutrient values because this is what farmers, farm commodity markets, federal policies, and agricultural research and extension programs reward. Additionally, the tactics farmers use to increase yields have a negative effect on nutrient uptake.

“Agronomic practices have worked hand-in-hand with plant breeding in setting the stage for this nutrient decline. Together, the tactics farmers use to increase yields—including close plant spacing and the widespread use of chemical fertilizers, irrigation and pesticides—tend to create big plants that grow fast, but do not absorb a comparable quantity of many soil nutrients.”

Why is This a Problem?

You might say, “What is the problem? If we have more food available for a cheaper price, we can get the same amount of nutrients, and we can fortify our diets with vitamins and minerals in other ways as well.” Of course, there are problems with eating more food, fortifying our diets is complicated and not always effective, and there are numerous nutritional issues we are still relatively blind to.

“Further erosion in nutrient density should be avoided for several reasons. Americans need to consume foods that deliver more nutrients per calorie consumed. Science has yet to identify, much less understand, the nutritional benefits linked to thousands of phytochemicals produced by plants. Many epidemiological studies have concluded that there are likely many beneficial nutrients in fruits and vegetables that we do not know about.

Plus, the relative levels, or ratios of nutrients in food, may also play important roles in human nutrition and health promotion. And what we surely do not need are staple crops delivering more sugar and starch per serving, and lower levels of vitamins, minerals and antioxidants.”

Image Credit: *Kicki* via flickr/CC license