June 25, 2013

Why Homegrown Food Is More Nutritious

When you walk through a typical grocery store produce section, the foods you see might appear impressive: shiny apples, bright red tomatoes, large, uniform-looking bell peppers without the slightest blemish. But a deeper look into these foods reveals one of the industrial food system’s biggest secrets: Most fruits and vegetables today are far less nutritious than they ever were before.

A basket of homegrown apples

More people are joining the exciting movement of growing backyard gardens and choosing local, seasonal foods grown on a small scale without chemicals — and the reasons for doing so are diverse. Local, organically grown foods are better for the environment; they are free of the pesticide residues on typical grocery-store produce; homegrown food almost always tastes better; growing backyard vegetables is fun and can save a family money; and buying produce from farmers nearby helps build a vibrant local economy. These arguments make sense, and they’re gaining traction. Now, thanks to research done on the nutritional content of vegetables and fruits over time, there’s another important reason to ditch industrially grown produce: Homegrown food is just plain better for you, providing more of the nutrients you need.

What the Research Shows


The way most food is grown today — using limited cultivars on large monocultures with heavy inputs of fertilizers and pesticides — is so different than it was 50 or 100 years ago that researchers began asking questions, investigating how seed breeding and growing methods might be affecting the foods themselves.

Baby spinach growing in a gardenSome of the most comprehensive research on the nutrient decline of industrial fruits and vegetables was conducted by Donald Davis and colleagues at the University of Texas Biochemical Institute. The team analyzed nutrient data over a 50-year period for 43 common crops, from broccoli, spinach and tomatoes to strawberries, sweet corn and melons. The results were jaw-dropping. Among the findings were a 16 percent overall decline in calcium, a 9 percent decline in phosphorus, a 15 percent drop in iron, a 20 percent decline in vitamin C and a 38 percent drop in riboflavin. Almost all of the nutrients they tested for had fallen.

A different research study published in the British Food Journal showed a dramatic fall in the nutrient content of spinach over time. Its potassium content dropped by 53 percent, its phosphorus by 70 percent, its iron by 60 percent and its copper by 96 percent. The same study explained that a person would have to eat three apples in 1991 to receive the same iron content as they would have gotten by eating one apple in 1940.

Other studies show a similar trend: We are a growing the bulk of our food — including staple crops such as wheat and corn — in a way that makes it less nutritious.

Why Are Industrial Foods Declining in Nutrients?


The reasons for nutrient decline in mainstream foods are many. One main reason is continual breeding for high yields. The key breeding goals of Big Ag are growing more food per acre and producing larger fruits. Any consideration for nutritional content is typically not a part of the equation. Breeders have developed plants that devote much energy to producing large fruits and less energy to absorbing micronutrients. Davis’ research team explains that “cultivars selected for yield, rapid growth or other non-nutrient characteristics may suffer resource limitations in their abilities to extract soil minerals or transport them within the plant, or in their abilities to synthesize proteins, vitamins and other nutrients.”

When plants put a lot of energy into making big fruits, the fruits — even though they are bigger — are more watery and less nutrient-dense. A study of broccoli done at the U.S. Vegetable Laboratory found a strong negative correlation between the weight of a head of broccoli and its calcium and magnesium content. The bigger the broccoli, the lower the concentration of nutrients.

A field of golden wheatThe root systems of crops grown with typical industrial techniques also have a lot to do with the resulting nutrients in the foods. In a large-scale agricultural setting using modern industrial methods, plant roots don’t have to work very hard, or grow very deep. This is because they receive a steady input of water and commercial fertilizer at the soil surface, which in turn leads to small, weak root systems on each plant. Because the plant has no need to grow deep roots to access water deeper down in the soil, it doesn’t (plants only work as hard as they need to). A plant’s root system is where nutrient uptake happens, and a small, weak root system generally equals nutritionally weak fruits. Plus, many plants grown in such a system have root disease, which further inhibits nutrient uptake. Using slow-release fertilizers such as manure and compost leads to much stronger root systems, but such soil amendments are not common in a large-scale setting.

Another reason for an overall decline in nutrients is that fruits and vegetables don’t reach their full nutrient potential until they’re ripe. In our mainstream system of picking produce unripe so that it can be shipped great distances to end up in a grocery store, the food simply doesn’t have the chance to acquire the nutrients that it would have developed during natural ripening. A study published in the journal Horticulture and Human Health showed that apricots and apples picked before ripening had no vitamin C, but they had high concentrations of vitamin C when picked ripe. Furthermore, the development of some nutrients, such as anthocyanins (an antioxidant), is sunshine-related. A study in the Journal of Food Chemistry showed that blackberries picked when still green contained less than a fourth of the anthocyanins as the same berries picked ripe.

Writer, gardener and food researcher Jo Robinson recently wrote a hard-hitting New York Times article about how we are unwittingly breeding the nutrition out of our food. The associated infographic showing nutritional weaklings in the supermarket will make you forever look at the produce section differently.

Why Should We Care?  


The average person in an industrialized nation such as the United States eats plenty of food but is undernourished. (Learn more in Overfed and Undernourished: Nutrient Deficiency in Our Modern Diet.) About 30 percent of the U.S. population ingests inadequate levels of magnesium, vitamin C and vitamin A — all nutrients we get from plants. About 97 percent of adult women in the United States consume an inadequate amount of vitamin E. Being deficient in certain vitamins and minerals has a huge host of effects, from higher risk of heart disease and cancer to anxiety and tiredness. It can also affect child development and how well kids can learn.

Of course, a large reason for nutrient deficiency is the high level of processed foods in the typical diet, but this issue of declining nutrient values in many foods is certainly not helping. When reaching for a healthy food such as an apple or a spinach salad, it would be great if those foods actually provided the nutrition of which they are well capable. Comparing apples to apples doesn’t even work anymore, as one apple could be quite different from another depending on the variety, how it was grown, and when it was harvested.

Taking nutritional supplements is a common answer to try to overcome deficiencies, but research shows that the body may not be able to utilize nutrients presented through supplements in the same way that it benefits from nutrients in whole foods.

A Better Way


One of the best ways to get back to more nutrient-rich fruits and vegetables is to seek local produce from plants that grew in rich soil and had the opportunity to develop strong, healthy roots. You can ask three main questions of any fruit or vegetable to help determine whether it likely contains more nutrients than its counterpart at the grocery store: 1) Was it picked ripe? 2) Was it grown organically in healthy soil? 3) Is it a variety other than a common commercial variety that’s been bred for exceptionally high yields?

Relying more (or wholly) on homegrown foods will make it far easier to answer “yes” to these questions with confidence. When I say “homegrown foods,” I don’t necessarily mean those grown in only your yard, but a combination of foods grown in your own plot, in a community garden or by local farmers whose growing methods you trust. And when I say “organically grown,” I don’t necessarily mean Certified Organic food from a large retailer. As I touch on in my post Fresh Food Reflections, some Certified Organic operations these days are getting bigger and bigger, and adopting many of the practices of non-organic industrial farming, including using high-yielding modern varieties and picking foods when not ripe and shipping them a long way. Think small-scale and local.

Growing and seeking out heirloom varieties can also help you in your quest to eat the most nutritious foods available. Researchers studying nutrient decline recommend considering older, lower-yielding varieties of fruits and vegetables, as they may be more nutrient-dense. There are no guarantees, as exact growing conditions and the variety used will play a part in the nutritional value of the harvest. But your best bet is growing a diverse selection of older varieties.

Many of you know that it’s easier to rely on homegrown, nutritious foods in the peak of the growing season. But instead of resorting to nutrient-deficient supermarket produce in the off-season, preserve extra fruits and vegetables by canning and freezing them when they’re readily available.

Several jars of home canned tomatoes on a table

And don’t stop there. Share your gardening love with friends and family. Help someone who wants to learn about growing food to plan his or her first garden. And when given a chance, tell people — in a spirit of caring and inspiration — what you know about the value of homegrown foods.

Spinach photo from Flickr/dogteaknit; all other photos from stock.xchng

17 comments:

  1. Great article, Shelley. The fact about the 3-to-1 apple ratio really surprised me. (Shouldn't have, I know.) I hope this gains momentum and we're nutritionally back where we started within our lifetimes.

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  2. Love the article. It should not be surprising that soil which is not fully replenished with compost, but only the limited content of manufactured fertilizers would result in nutrient deficient foods! I would love to see the citations for the studies though; it always helps to have complete data when teaching new people.

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