The nutrient levels in fruits, vegetables, fish, and grains are declining. Find out why, and how it affects your diet
Your parents taught you that vegetables are the healthiest foods, but your greens are probably not actually as nutritious as theirs were 25 years ago. Mineral levels in fruits and vegetables have actually declined up to 40 percent from 1959 to 2009, according to a study in HortScience. (Check out the 7 Ingredients That Are Robbing You of Nutrients, too.)
And in the eight years since that study, it’s pretty safe to say nutrient levels haven’t returned to what they once were, says study author Donald Davis, Ph.D., research associate at the Center for Sustaining Agriculture and Natural Resources at Washington State University at Pullman. An earlier study of Davis’ found that for 43 different fruits and vegetables, there were significant declines in the amount of protein, calcium, phosphorus, iron, riboflavin (vitamin B2), and vitamin C over the past half century.
What’s up with the fading nutrition? It’s the dilution effect, says Davis: Fertilizers and irrigation methods in modern farming yield a bigger vegetable, but the nutrient level doesn’t increase at the same rate. In fact, "because the size of the fruit and vegetables is bigger, there’s less nutrient per square inch of the crop,” he explains.
Same goes for grains: Levels of phosphorus, manganese, sulfur, calcium, zinc, copper, and magnesium all significantly declined in wheat crops after 1968, the year most farmers began pairing fertilizers and crops, according to a 2011 study analysis in Breeding for Fruit Quality.
It’s Not Just Crops
One piece of farmed salmon may contain as little as half the amount of omega-3s as it did 10 years ago, according to the International Fishmeal and Fish Oil Organization (IFFO), a trade group that sells farmers omega-3-rich feed for salmon. But take that stat with a grain of salt. After all, the IFFO profits if people believe omega-3 levels are low: Farmers buy more of their nutrient-boosting product. But there's also truth to the decline: Junk fish like menhaden and sardines—less desirable to serve people but still high in omega-3s—are still expensive in terms of feed options, says Davis. Plus, environmentalists have been steadily pressuring the farmed salmon industry to become more eco-friendly, which means further reducing the quantity of salmon's only omega-3 source, the junk fish. (Should you be eating wild anyway? Ask the Diet Doctor: Farm-Raised vs. Wild Salmon.)
How Should This Affect Your Habits?
Despite all this, salmon is still one of the best sources of omega-3s, just possibly less robust than a decade ago, says Eric Decker, Ph.D., professor at the University of Massachusetts Amherst and expert in food lipids like omega-3s. The lower levels just mean you have to fill up more often: Eating salmon a few times a week will provide you with more than enough of the nutrient, Decker adds.
Same goes for fruits and vegetables: Even though each thing on your plate may be less of a superfood than it was for your grandparents, the nutrients vegetables and fruit offer—especially per calorie—still blow other processed food options out of the water, Davis explains. (Try The 10 Best Leafy Greens.) The depleted level of nutrients in fish, fruits, and vegetables just means you need to eat more of what you already know is good, he adds. If you aren't as strict about a fresh, vitamin-packed diet, you should consider supplements (like a multi-vitamin and fish oil), Davis says—although a whole-food approach is always ideal for the thousands of phytochemicals that can't be packed into a capsule. (Find your perfect supplement at GNC Live Well.)