Organic food starts to prove its worth | Science News for Students

Organic food starts to prove its worth

Scientists are finding benefits for the environment and possibly human health
Aug 21, 2015 — 7:15 am EST
organic veggies

Research is showing that organic farming, which uses fewer pesticides and synthetic fertilizers, can be better for the environment. Whether it’s also better for human health remains uncertain. Some studies show benefits, others don’t.

DOUGBERRY/ iStockphoto

At the supermarket, there are usually two sections in the produce aisle. In one, all the fruits and vegetables, from apples to zucchini, are labeled “organic.” Often these products cost more than ones that look the same but don’t have the organic label.

The big price tag can lead people to assume organic food is better than conventionally grown food. But, in the United States, the label simply means that the food has met guidelines set out by the U.S. Department of Agriculture.

For instance, organic fruits, vegetables and other crops must not have been treated with synthetic fertilizers, certain pesticides or sewage sludge. Meat, eggs and milk must come from animals that have been raised according to specific health and welfare standards. Also, farmers may not treat these animals with antibiotics or growth hormones and must raise them on organic feed. Products with multiple ingredients must contain 95 percent or more organic content.

What benefits the organic label might signify, though, has not always been clear.

For years, scientists have been trying to tease out whether organic foods are themselves different than those grown conventionally. Research is beginning to show organic foods can be better — and not only for the people who eat it. Growing foods organically also can help the environment, new data show.

Pesticides are good travelers

On a farm, pests and weeds can destroy a crop. So most U.S. farmers apply chemicals called pesticides to limit the damage.

crop sprayerConventional farmers can apply any pesticide approved for use in the United States. Organic farmers cannot use all of those same chemicals. That doesn’t mean organic farmers allow insect pests and weeds to live peacefully among their crops. They too can use pesticides and weed killers. They just have a smaller list from which to choose.

But none of these chemicals will necessarily stay put. Some share of them will tend to move off through the soil, air or water. Eventually, these pesticides end up in streams where they can mix, creating a mystery soup.

Scientists have been studying how far and how fast pesticides can move through the environment. These data may then point out which animals are at risk of being exposed to the pollutants.

For instance, researchers recently looked at pesticides commonly used on California farms. They found the pesticides in Pacific chorus frogs living in national parks, forests and other locations high in the Sierra Nevada mountains. In some cases, the frogs lived more than 100 kilometers (62 miles) from the nearest farms that had used the chemicals.

pacific chorus frog“This is the first time we've detected many of these compounds, including fungicides, in these remote locations,” says Kelly Smalling. She's the study’s lead author. She's also a hydrologist with the U.S. Geological Survey (USGS) in Lawrenceville, N.J. A hydrologist studies the movement, distribution and quality of water. Her team published its findings in the July 2014 issue of Environmental Toxicology and Chemistry.

Discovering that pesticides contaminate frogs is bad news. Earlier research had found that pesticide exposure could cause problems for the frog’s immune system. And this could alter how the frogs developed. It might even cause male frogs to adopt some female traits.

Smalling and her colleagues think their study supports the idea that pesticides used in conventional agriculture may play some role in the falling numbers of many species of frogs and toads.

But amphibians aren’t the only animals in decline. Honeybees also are in trouble. A problem called colony collapse disorder causes seemingly healthy bees to suddenly abandon their hives. The queen bee remains. Without the worker bees, though, the hive eventually dies.

bee in flower

A May 2014 study published in the Bulletin of Insectology looked at 18 beehives for almost a year. As they go around collecting pollen, bees may pick up any pesticides that had been sprayed onto the plants they visited.

To probe possible effects of these chemicals, scientists looked at hives whose bees had been exposed to two pesticides: imidacloprid (Ih-MEED-uh-KLOH-prid) and clothianidin (Klo-thee-AN-ih-din). Neither can be used on organic farms. The scientists compared bees in these hives to those in hives free of these chemicals. And they found that even small amounts of the two pesticides triggered a biological change that led to bee deaths.

This suggests the pesticides create unintended problems for growers. Farmers need bees to pollinate many crops, including almonds, cherries and broccoli. If too many bees die, less pollination may occur. And this can shrink farm harvests.

But without using chemicals like these, an influx of pests and diseases also may shrink those harvests. So even organic farms are allowed to use some pesticides. These chemicals just supposed to pose less of a risk to bees and other beneficial wildlife.

Still, those chemicals approved for use on organic farms are not necessarily harmless. One 2010 study in PLOS ONE, for example, looked at organic pesticides applied to soybeans. These chemicals controlled a type of insect known as an aphid. The study found that organic pesticides were more poisonous to the aphid’s natural enemies than conventional pesticides were. That means these organic pesticides may have a worse overall impact on this environment that will conventional ones.

Dirt poor, dirt rich

Pesticides help growers by poisoning some of the farmers’ worst enemies: insects, weeds and disease. But there’s another family of farm chemicals that also help growers: fertilizers. To grow, plants need nutrients, especially the elements nitrogen and phosphorus. And fertilizers add nutrients to the soil. 

lake erieOrganic farmers cannot use these elements if they come from synthetic (human-made) sources, such as ammonia salts. Instead, the farmers need to find natural fertilizers. For instance, they may plant beans. These plants naturally increase nitrogen levels in the soil. Crops that are planted after the beans are gone can now use that nitrogen.

With rich, healthy soil, crops also may need fewer pesticides or fertilizers, farmers are finding. And because they don’t have to use as much of these chemicals, naturally fertilized soils can cut the amount of pollution linked to the frequent overuse of nitrogen and phosphorus.

“Having nitrogen in a plant form, as compared to a liquid form [used] in more conventional agriculture, tends to be less leaky,” notes Meagan Schipanski. As an agronomist at Colorado State University in Fort Collins, she studies soil and crop production. By “leaky,” she means that liquid nitrogen is easily washed out of the soil and carried off the farm. The reason plant-deposited nitrogen tends to stay put is because it “is attached to carbon molecules,” she explains. “There's a molecular bond there” to hold it in place.

field coverBoth nitrogen and phosphorus can build up in nearby waterways. This is called nutrient pollution. Plants and animals need nutrients to thrive. But when large amounts of these elements end up in lakes and oceans, they can cause large growths of algae. Those growths are called algal blooms. They can kill fish and other aquatic life.

The problem can be made worse by unpredictable rains. This may be happening in the Midwest, says Lisa Nowell. As a chemist with the USGS in Davis, Calif., she studies how pesticides and other chemicals affect water quality. In 2012, the Midwest experienced a drought. The following year it rained. A lot. Rivers overflowed their banks. Towns and fields flooded. All that rain risks washing away fertilizers and other chemicals that had collected in the soil, Nowell says.

Indeed, she says: “Preliminary data show really high concentrations of both nutrients and atrazine and other herbicides in the streams. It was kind of phenomenal. And that can cause real problems downstream.” The atrazine (AT-truh-zeen) she mentioned is one of the most common weed killers used in the United States.

Organic farms tend to produce less of that kind of pollution. One reason: These farms often work to build soil that retains more water and that produces less runoff.

microarthropodOrganic farmers also use compost. This soil-enriching mix is usually made from decomposed plants, food waste and manure. Compost provides nutrients for plants. It also is rich in microscopic life. Research suggests these microbes are important for the health of soils — and plants.

Rick Carr is a compost-production specialist at the Rodale Institute in Kutztown, Pa. He says, “We know that if you have diverse microorganisms in your soil, that's going to lead to better soil health.” Scientists have found evidence that healthy soils help suppress plant diseases. Healthy soils also can help plants take up nutrients and can hold water in the root zone, where plant's most need it.

Carr is researching how microbes in compost can help fight plant diseases. Being full of microbes, “Soil is alive and it's doing things," Carr says. "So we're really relying on the soil. We're taking care of the soil so it can take care of our plants.”

What about us?

Many people buy organic food because they think it's healthier. But whether it is remains an open question — even after years of research and debate. A 2012 study found no real difference between organic and conventional food in terms of nutrition. Its findings appeared in the Annals of Internal Medicine.

tomatoesMore recently, a team of experts in England and elsewhere came to the opposite conclusion. They reviewed all of the research they could find on this question. The team chose 343 studies for its members to analyze. They published their results in the July 2014 British Journal of Nutrition.

Organic crops contain, on average, 17 percent more antioxidants than crops grown conventionally, they found. Antioxidants are compounds in many fruits and vegetables. They are not listed on a product’s Nutrition Facts label. But there is evidence that people who consume foods rich in antioxidants have a lower risk of diseases such as stroke and cancer.

Charles Benbrook is an agricultural economist at Washington State University in Pullman. He also was an author of the British Journal of Nutrition study. And he is quick to point out that his team’s analysis does not mean all organic foods are more nutritious. “Every study reports dozens of results involving different nutrients. For some nutrients, organic might be higher. For other nutrients, conventional might be higher. And for a lot, there are no [real] differences,” Benbrook says.

The study did not identify specific  fruits or vegetables where the organic or the conventional variety was more nutritious. However, farming practices can have the biggest impact on nutritionally dense foods, Benbrook notes. “There are only modest differences in the nutrient profile of organic versus conventional cucumbers or lettuce,” he says. But, “there are big differences between conventional and organic berries, apples, tomatoes and other nutrient-dense produce.”

His group’s study also found that conventionally grown farm crops are four times more likely than organic crops to contain pesticide residues. For many people, that's enough reason to buy organic.

kid in grassIn 2012, the American Academy of Pediatrics advised parents to reduce their children's exposure to pesticides. Developing fetuses, babies and children are most vulnerable to potential harm, they noted. That’s mainly because their bodies are still developing.

The key concern in the advisory was with direct exposure to pesticides. In places like farms and lawns, people may come into direct contact with these chemicals after they have been sprayed.

What kind of harm might they pose?

Autism is one worry. A2014 study found that when pregnant women lived near fields treated with pesticides, their children were more likely to develop autism. Published in Environmental Health Perspectives, this study surveyed 970 pregnant women. One-third lived less than 1.6 kilometers (1 mile) from a site where pesticides had been applied. Women had a 60-percent higher risk of having a child with an autism spectrum disorder if they had lived closest to sites using insect killing chemicals known as organophosphates (Or-GAN-oh-FOSS-fates). These include diazinon (Dy-AZ-uh-nahn) and chlorpyrifos  (Klor-PY-rih-foss). Neither can be used in organic agriculture.

Organophosphates work by interfering with the insect brain and nervous system. They may have the same effect on animals, including people, some studies suggest. These chemicals can still be used on many farms.

The American Academy of Pediatrics (AAP) advisory did not make a statement about whether organic food is a better choice for children than is conventionally grown food. The group’s president said that remains an open question.

“Organic foods do have lower levels of pesticides,” said AAP president Thomas McInerny in a statement. Although kids can be more vulnerable to toxic substances, he notes, when it comes to these chemicals “we simply don’t have the scientific evidence to know if the difference will affect a person’s health over a lifetime.”

appleOverall, the AAP emphasized that what’s most important is eating a diet rich in fruits and vegetables — whether they’re organic or not.

What does this all mean when you go the grocery store? There can be benefits for the environment and for the people who grow organic food. There also may be some advantage to people dining on organic foods. For families who can afford them, organic foods might be worth the higher price. Where money is tight, people can buy targeted organic foods. They might choose an organic apple, for instance, since the skin of that fruit will get eaten. But you can buy the conventionally grown avocado since its skin — and any pesticides on it — will be discarded.

But no one should be deterred from buying fruits or vegetables. An apple is always going to be a healthier snack choice than a bag of chips — no matter how the piece of fruit was grown.

Power Words

(for more about Power Words, click here)

agronomy The science of soil health and crop production.

algae    Single-celled organisms, once considered plants (they aren’t). As aquatic organisms, they grow in water. Like green plants, they depend on sunlight to make their food.

ammonia A colorless gas with a nasty smell. Ammonia is a compound made from the elements nitrogen and hydrogen. It is used to make food and applied to farm fields as a fertilizer. Secreted by the kidneys, ammonia gives urine its characteristic odor. The chemical also occurs in the atmosphere and throughout the universe.

amphibians  A group of animals that includes frogs, salamanders and caecilians. Amphibians have backbones and can breathe through their skin. Unlike reptiles, birds and mammals, unborn or unhatched amphibians do not develop in a special protective sac called an amniotic sac.

antibiotic  A germ-killing substance prescribed as a medicine (or sometimes as a feed additive to promote the growth of livestock). It does not work against viruses.

antioxidant  Any of many chemicals that can shut down oxidation — a biologically damaging reaction. They do this by donating an electron to a free radical (a reactive molecular fragment) without becoming unstable. Many plant-based foods are good sources of natural antioxidants, including vitamins C and E.

aquatic  An adjective that refers to water.

atrazine   A common weed killer used on many farms in the United States.

autism (also known as autism spectrum disorders)   A set of developmental disorders that interfere with how certain parts of the brain develop. Affected regions of the brain control how people behave, interact and communicate with others and the world around them. Autism disorders can range from very mild to very severe. And even a fairly mild form can limit an individual’s ability to interact socially or communicate effectively.

bloom      (in microbiology) The rapid and largely uncontrolled growth of a species, such as algae in waterways enriched with nutrients.

bond  (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.

cancer   Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.

carbon  The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

chemical     A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O.

chemistry   The field of science that deals with the composition, structure and properties of substances and how they interact with one another. Chemists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances.

colony collapse disorder  A phenomenon in which worker bees abandon their hive, leaving behind their queen.

compost    The end product in the breakdown, or decomposition, of leaves, plants, vegetables, manure and other once-living material. Compost is used to enrich garden soil, and earthworms sometimes aid this process.

conventional agriculture  A method of farming, often done on a large scale, where chemicals may be used to enrich the soil and to control insects and weeds.

conventional   An adjective meaning something that reflects or upholds standard or usual practices, ideas or expectations.

economics   The social science that deals with the production, distribution and consumption of goods and services and with the theory and management of economies or economic systems. A person who studies economics is an economist.

element   (in chemistry) Each of more than one hundred substances for which the smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon, lithium and uranium.

environment    The sum of all of the things that exist around some organism or the process and the condition those things create for that organism or process. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature, humidity and placement of components in some electronics system or product.

epidemiologist  Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.

fertilizer   Nitrogen and other plant nutrients added to soil, water or foliage to boost crop growth or to replenish nutrients that removed earlier by plant roots or leaves.

fetus  (Adj.fetal) The term for a mammal during its later-stages of development in the womb. For humans, this term is usually applied after the eighth week of development.

fungicide   A type of pesticide that kills fungi, such as molds and yeasts.

herbicide   A weed killer. Some herbicides kill all types of plants, but others are “selective.” That means they are designed to kill certain unwanted plants (considered weeds) but leave desirable plants, such as lawn grasses or crops, untouched.

hormone   (in zoology and medicine)  A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.

hydrology  The scientific study of water, often in relation to land. Experts in this field are known as hydrologists.

immune system The collection of cells and their responses that help the body fight off infections and deal with foreign substances that may provoke allergies.

microbe    Short for microorganism.  A living thing that is too small to see with the unaided eye, including bacteria, some fungi and many other organisms such as amoebas. Most consist of a single cell.

microscopic   An adjective for things too small to be seen by the unaided eye. It takes a microscope to view such tiny objects, such as bacteria or other one-celled organisms.

molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nervous system The network of nerve cells and fibers that transmits signals between parts of the body.

nitrogen    A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn.

nutrients   Vitamins, minerals, fats, carbohydrates and proteins needed by organisms to live, and which are extracted through the diet.

organic   (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms. (in agriculture) Farm products grown without the use of non-natural and potentially toxic chemicals, such as pesticides.

organophosphates   A family of pesticides that disrupt the brains and nervous systems of insects. They also can have severe health impacts on people and animals, and prove deadly if consumed in high amounts.

pediatrics   A field of medicine that has to do with children and especially child health. A doctor who works in this field is known as a pediatrician.

pesticide   A chemical or mix of compounds used to kill insects, rodents or other organisms harmful to cultivated plants, pet or livestock, or unwanted organisms that infest homes, offices, farm buildings and other protected structures.

phosphorus   A highly reactive, nonmetallic element occurring naturally in phosphates. Its scientific symbol is P.

pollinate  To transport male reproductive cells — pollen — to female parts of a flower. This allows fertilization, the first step in plant reproduction.

pollutant   A substance that taints something — such as the air, water, our bodies or products. Some pollutants are chemicals, such as pesticides. Others may be radiation, including excess heat or light. Even weeds and other invasive species can be considered a type of biological pollution.

population  A group of individuals from the same species that lives in the same area.

runoff    The water that runs off of land into rivers, lakes and the seas. As that water travels over land, it picks up bits of soil and chemicals that it will later deposit as pollutants in the water.

sewage   Wastes — primarily urine and feces — that are mixed with water and flushed away from homes through a system of pipes for disposal in the environment (sometimes after being treated in a big water-treatment plant).

sewage sludge   Nutrient-rich solid materials pulled out of sewage and other waste waters that have been treated at municipal water-treatment plants.

stroke   (in biology and medicine) A condition where blood stops flowing to part of the brain or leaks in the brain.

synthetic   An adjective that describes something that did not arise naturally, but was instead created by people. Many have been developed to stand in for natural materials, such as synthetic rubber, synthetic diamond or a synthetic hormone. Some may even have a chemical makeup and structure identical to the original.

toxicology  The branch of science that probes poisons and how they disrupt the health of people and other organisms. Scientists who work in this field are called toxicologists.

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Further Reading

S. Milius. “Pesticides offer bees a risky allure.” Science News for Students. May 19, 2015.

K. Kowalski. “Ditching farm pollution — literally.” Science News for Students. April 17, 2015.

S. Zielinski. “Will water woes leave Americans thirsty?Science News for Students. October 30, 2014.

K. Kowalski. “Recycling the dead.” Science News for Students. September 27, 2014.

J. Raloff. “Explainer: What are endocrine disruptors?Science News for Students. August 1, 2014.

S. Ornes. “Bug killer linked to decline in birds.”Science News for Students. July 29, 2014.

J. Raloff. “Your food choices affect Earth’s climate.”Science News for Students. July 11, 2014.

B. Nelson. “Explainer: What is autism?Science News for Students. April 3, 2014.

A. Stevens. “How to limit the need for pesticides.” Science News for Students. January 10, 2014.

A. Stevens. “Why are bees vanishing?Science News for Students. January 10, 2014.

J. Raloff. “Explainer: What are antioxidants?Science News for Students. March 19, 2008.

E. Sohn. “How super are superfruits?Science News for Students. March 19, 2008.

Original Journal Source: J.F. Shelton et al. Neurodevelopmental disorders and prenatal residential proximity to agricultural pesticides: The CHARGE study. Environmental Health Perspectives. Vol. 122, October 2014, p. 1103. doi: 10.1289/ehp.1307044.

Original Journal Source: M. Barański et al. Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses. British Journal of Nutrition. Vol. 112, September 2014, p. 794. doi: http://dx.doi.org/10.1017/S0007114514001366.

Original Journal Source: C. Lu et al. Sub-lethal exposure to neonicotinoids impaired honey bees winterization before proceeding to colony collapse disorder. Bulletin of Insectology. May 9, 2014.

Original Journal Source: L.H. Nowell et al. Pesticide Toxicity Index — a tool for assessing potential toxicity of pesticide mixtures to freshwater aquatic organisms. Science of the Total Environment. April 1, 2014. doi: 10.1016/j.scitotenv.2013.12.088.

Original Journal Source: K. Smalling et al. Accumulation of pesticides in pacific chorus frogs (Pseudacris regilla) from California's Sierra Nevada Mountains, USA. Environmental Toxicology. July 25, 2013. doi: 10.1002/etc.2308.

Original Journal Source: M.J. Adams et al. Trends in amphibian occupancy in the United States. PLOS ONE, Vol. 8, May 22, 2013, p. e64347. doi: 10.1371/journal.pone.0064347.

Original Report Source: J.R. Roberts and C.J. Karr. Technical Report: Pesticide exposure in children. Pediatrics. Vol. 130, December 6, 2012, p. e1765. doi: 10.1542/peds.2012-2758.

Original Journal Source: C. Smith-Spangler et al. Are organic foods safer or healthier than conventional alternatives? A systematic review. Annals of Internal Medicine. September 4, 2012. doi:10.7326/0003-4819-157-5-201209040-00007.

Original Journal Source: C.A. Bahlai et al. Choosing organic pesticides over synthetic pesticides may not effectively mitigate environmental risk in soybeans. PLOS ONE. Vol. 5, June 22, 2010, p. e11250. doi: 10.1371/journal.pone.0011250.

Original Journal Source: A. Albert et al. Dietary exposure to low pesticide doses causes long-term immunosuppression in the leopard frog (Rana pipiens). Environmental Toxicology & Chemistry. Vol. 26, June 2007, p. 1179. doi: 10.1897/05-622R.1.

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