Dear EarthTalk: What’s the nutritional difference between the carrot I ate in 1970 and one I eat today? I’ve heard that that there’s very little nutrition left. Is that true? -- Esther G., Newark, NJ
It would be overkill to say that the carrot you eat today has very little nutrition in it—especially compared to some of the other less healthy foods you likely also eat—but it is true that fruits and vegetables grown decades ago were much richer in vitamins and minerals than the varieties most of us get today. The main culprit in this disturbing nutritional trend is soil depletion: Modern intensive agricultural methods have stripped increasing amounts of nutrients from the soil in which the food we eat grows. Sadly, each successive generation of fast-growing, pest-resistant carrot is truly less good for you than the one before.
|Although fruits and vegetables are
still our best source of nutrients,
those grown decades ago were much
richer in vitamins and minerals than
the varieties most of us get today.
The main culprit in this disturbing
nutritional trend is soil depletion.
Credit: Martin Poole,
A landmark study on the topic by Donald Davis and his team of researchers from the University of Texas (UT) at Austin’s Department of Chemistry and Biochemistry was published in December 2004 in the Journal of the American College of Nutrition. They studied U.S. Department of Agriculture nutritional data from both 1950 and 1999 for 43 different vegetables and fruits, finding “reliable declines” in the amount of protein, calcium, phosphorus, iron, riboflavin (vitamin B2) and vitamin C over the past half century. Davis and his colleagues chalk up this declining nutritional content to the preponderance of agricultural practices designed to improve traits (size, growth rate, pest resistance) other than nutrition.
“Efforts to breed new varieties of crops that provide greater yield, pest resistance and climate adaptability have allowed crops to grow bigger and more rapidly,” reported Davis, “but their ability to manufacture or uptake nutrients has not kept pace with their rapid growth.” There have likely been declines in other nutrients, too, he said, such as magnesium, zinc and vitamins B-6 and E, but they were not studied in 1950 and more research is needed to find out how much less we are getting of these key vitamins and minerals.
The Organic Consumers Association cites several other studies with similar findings: A Kushi Institute analysis of nutrient data from 1975 to 1997 found that average calcium levels in 12 fresh vegetables dropped 27 percent; iron levels 37 percent; vitamin A levels 21 percent, and vitamin C levels 30 percent. A similar study of British nutrient data from 1930 to 1980, published in the British Food Journal, found that in 20 vegetables the average calcium content had declined 19 percent; iron 22 percent; and potassium 14 percent. Yet another study concluded that one would have to eat eight oranges today to derive the same amount of Vitamin A as our grandparents would have gotten from one.
What can be done? The key to healthier produce is healthier soil. Alternating fields between growing seasons to give land time to restore would be one important step. Also, foregoing pesticides and fertilizers in favor of organic growing methods is good for the soil, the produce and its consumers. Those who want to get the most nutritious fruits and vegetables should buy regularly from local organic farmers.
UT’s Davis warns that just because fruits and vegetables aren’t as healthy as they used to be doesn’t mean we should avoid them. “Vegetables are extraordinarily rich in nutrients and beneficial phytochemicals,” he reported. “They are still there, and vegetables and fruits are our best sources for these.”
Dear EarthTalk: I read a heart-wrenching story of a polar bear that swam 400 miles with its cub on its back in search of an ice floe to rest on. It survived but its cub did not. What can be done to save these magnificent creatures? Is it too late? -- Jerry Bresnehan, Des Moines, IA
It’s sad but true that life is getting harder for polar bears due to global warming. Polar bears live within the Arctic Circle and feed primarily on ringed seals. The bears’ feeding strategy involves swimming from the mainland to and between offshore ice floes, poaching seals as they come up to breathe at holes in the ice.
But climate change is heating up the atmosphere and substantial amounts of offshore sea ice are melting. The result is that bears must swim further and further out to sea in search of ice floes; some expend all of their energy in doing so and end up drowning. Scientists first noticed this deadly phenomenon in 2004 when they noticed four drowned polar bears in the Beaufort Sea off Alaska’s North Slope.
More recently, researchers from the United States Geological Survey (USGS) fitted several Alaskan polar bears with tracking collars to find out the extent of their travels and document how much trouble they are having hunting in a warmer Arctic. One of the bears, a mother with a yearling cub on her back, made what researchers are calling an “epic journey in search of food” during September-October 2008. “This bear swam continuously for 232 hours and 687 km and through waters that were 2-6 degrees C,” reports USGS research zoologist George M. Durner. “We are in awe that an animal that spends most of its time on the surface of sea ice could swim constantly for so long in water so cold." During the rest of the two-month tracking period, the bear
Climate change is causing substantial amounts of
intermittently swam and walked on ice floes for another 1,200 miles.
But while the mama bear survived the ordeal, she lost 22 percent of her body fat during a crucial time of year for fattening up before a long winter’s hibernation. And her cub was not so fortunate. “It was simply more energetically costly for the yearling than the adult to make this long distance swim,” said Durner, whose findings were published in the January 2011 edition of Polar Biology. The case of this one polar bear and the failure of her offspring to survive in the new environmental conditions of the Arctic doesn’t bode well for the future of the species, especially as Arctic sea ice continues to retreat at a record pace.
The International Union for the Conservation of Nature (IUCN), which maintains the international “Red List” of threatened species, considers the polar bear “vulnerable” due to climate change-induced retreating sea ice. For its part, the U.S. government listed polar bears as “threatened” in 2008 under the Endangered Species Act. The IUCN website also points out that, while the polar bear has come to symbolize the impact of global warming on wildlife, many other species are similarly affected, including the ringed seal and well-known species like the beluga whale, arctic fox, koala and emperor penguin.
Some argue that, since it is illegal to engage in activities that could harm or kill threatened or endangered species, Americans should be forced to cut their greenhouse gas emissions to preserve polar bear habitat. While such a notion hasn’t forced many of us to voluntarily drive fewer miles or turn down our heat, it might be just what it will take the world’s largest land carnivore from going the way of the dodo.
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