역사 ≫ 진화 ≫ 유기농

유기 농산물

유기농
- 유기농이 더 영양이 높은가?
- 유기농이 더 안전한가?
- 식물은 유기질을 흡수하지 못한다 :  화학비료 vs 퇴비
- 유기농의 진정한 가치는 공생, 착한 소비가 아닐까 ?
- 천연 독이 훨씬 더 많다,  천연 독이 수 백배 강하다
- 천연물 속의 기형발생물질
- 채식 한계 :  유기농 채소가 오히려 독 ?

유기농 식품 전반적인 암 발생 위험 감소시키지 못한다?
농약을 사용하지 않은 유기농 식품을 먹는 것이 여성의 암 발생 위험을 감소시키는 데 별 도움이 되지 않는다는 연구결과가 나왔다. 오히려 연구진은 유기농 식품을 선택한 소비자들에게서 유방암 발생 위험이 약간 더 높은 것을 발견했다고 한다.

연구진은 50세 이상의 여성 60만 명에게 유기농 식품을 먹었는지에 대해 물어보고 그들의 건강을 9년간 추적 확인했다. 이들 여성들 중 약 5만 명이 연구기간 동안 가장 흔한 16가지 암 중 1가지에 걸렸다. 유기농 식품을 전혀 먹지 않은 18만 명의 여성과 유기농 식품을 보통 혹은 항상 선택하는 4만 5천명의 여성을 비교해본 결과 전반적인 암 발생 위험에 별 차이가 없는 것으로 드러났다.

게다가 연구진은 유기농 식품을 먹는 여성들에게서 유방암 발생 위험이 조금 더 높은 것을 발견했다. 그러나 연구진은 이런 연구결과는 다른 요인이나 순전한 우연으로 인해 그럴 수도 있다고 밝혔다. 유기농 식품을 먹는 것이 혈액암의 일종인 비호지킨 림프종의 발생 위험 감소와도 관련이 있는 것으로 드러났지만 이 역시 정말로 연관관계가 있는 것은 아닐 수가 있다고 연구진은 말했다.
K. E. Bradbury et al., "Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom" Br J Cancer. 2014 Mar 27. doi: 10.1038/bjc.2014.148.


전세계 유기 농산물의 절반은 미국이 먹는다.
그래서 건강문제가 해결되었는가?


Is organic better for your health? A look at milk, meat, eggs, produce and fish.

By Tamar Haspel

Organic or conventional? It’s a choice many grocery shoppers are faced with, over and over. The price difference is easy to see; it’s right there on the product. The quality difference is much harder. Is the organic milk better for your kids? Is the conventional lettuce more likely to carry pathogens?
Leave aside for the moment whether organic agriculture is better for the planet and whether organic livestock have better lives, although there’s a strong case for both of those arguments. Leave aside flavor, too, because it’s subjective and variable. What motivates many organic buyers, particularly the parents of small children, is health benefits, and there are two questions: Do organics do us more good (in the form of better nutrition), and do they do us less harm (in the form of fewer contaminants and pathogens)?
Because the risks and the benefits vary by product — meat is different from produce — it’s important to look at each category separately. While every category has the potential to harbor pathogens (such as E. coli in produce and salmonella in chicken), there are some product-specific concerns, including pesticide residue in produce and hormones in milk.
Here’s a rundown of the evidence on nutrition and contamination levels for organic and conventional products in five categories — milk, produce, meat, eggs and fish — to help you decide whether to buy organic or stick with conventional.

Milk

Nutrition: Compared with conventional milk, organic milk has higher levels of omega-3 fats, which protect against heart disease and may decrease the risk of depression, stroke, cancer and other diseases, but the quantities are too small to be very meaningful. (It takes 11 quarts of organic milk to equal the omega-3s in four ounces of salmon.) Milk’s omega-3 content is a function of the cow’s diet, and higher levels reflect more grass. (A few other nutritional differences between organic and conventional milk have been studied, but there isn’t enough research to draw conclusions.)

Contamination: Neither organic nor conventional milk contains antibiotics. By law, every truckload of milk, organic and conventional, is tested for veterinary drugs, including antibiotics, by trained dairy workers. Any load that tests positive is pulled out of the food supply. In 2012, that was one in 6,000 loads. Organic cows aren’t given antibiotics, and conventional ones are given them only for illness, and their milk isn’t used until after a withdrawal period.

The U.S. Department of Agriculture tests for pesticide levels and has found them to be “very low.” The main culprit is DDE, a remnant of the agricultural pesticide DDT.
DDT was banned years ago, but the USDA said it “is very persisten[t] and remains in many cropland soils. It is also in the body fat of all Americans and most farm animals and wildlife. Conventional and organic farmers can do little to avoid the DDE residues in milk. Over the next thirty to fifty years these residues will gradually decline below limits of detection.”
Pasteurization fails some of the time, allowing milk contaminated with bacteria to get into the food supply, but there are no reports comparing illnesses caused by organic vs. conventional milk.

Hormones: The issue with milk is that many conventionally raised dairy cows, unlike organic ones, are injected with bovine growth hormone (BGH, the synthetic version of which is called either recombinant bovine growth hormone, rBGH, or recombinant bovine somatotropin, rBST) to increase their milk production. The problem isn’t the hormone itself — it’s unlikely to survive pasteurization or human digestion and, even if it did, its mechanism doesn’t work in humans — but rather a compound called insulin-like growth factor (IGF-I).

Both organic and conventional cows have IGF-I in their milk, but cows that get hormone treatment may have more of it. Humans also produce IGF-I, and a recent review of many studies concluded that milk drinkers generally have higher IGF-I levels. But it may not be because of IGF-I in milk. Eating animal and soy protein can also increase IGF-I levels in our bodies. It’s not the IGF-I in foods, but how the body responds to other compounds, that increases human levels.

Some research has linked IGF-I to cancer. The American Cancer Society found that “some early studies found a relationship between blood levels of IGF-I and the development of prostate, breast, colorectal and other cancers, but later studies have failed to confirm these reports or have found weaker relationships.” The organization concluded in 2011 that “the evidence for potential harm to humans is inconclusive.” A 2009 FDA report says that IGF-I levels in rBGH milk are safe

The use of rBGH has fueled concerns among some parents about giving milk to children, but the FDA report concluded that “consumption by infants and children of milk and edible products from rBGH-treated cows is safe.”

Bottom line: Organic milk has higher omega-3 fat levels, but probably not enough to make a difference. Exposure to pesticides, contaminants or hormones is not a significant risk in either organic or conventional milk.

Produce

Nutrition: Many studies have compared the vitamins, minerals, macronutrients and other compounds in organic and conventional produce, and a 2012 review concluded that the results were all over the map. The one exception was that the phosphorus content of organic produce is higher, although the review, done by Stanford University scientists, calls that finding “not clinically significant.” Along with calcium, phosphorus helps build strong bones and teeth.

Contamination: There are two issues for foods that grow in the ground: pesticides and pathogens. There is widespread agreement that organic produce, while not pesticide-free, has lower residue levels and fewer pesticides. A study using USDA data found that 73 percent of conventional produce sampled had residue from at least one pesticide, compared with 23 percent of organic, though that study is more than 10 years old. There also isn’t agreement about whether that’s meaningful for human consumption.

Carl Winter, a toxicologist at the University of California at Davis, says that the Environmental Protection Agency, working from animal research and factoring in the special sensitivities of human subgroups such as babies and children, has found that lifetime risk of adverse health effects due to low-level exposure to pesticide residue through consumption of produce is “far below even minimal health concerns, even over a lifetime.”

Dana Barr, a research professor at Emory University’s Rollins School of Public Health, has less faith in the EPA standards. She points to one particular pesticide class, organophosphates, and notes evidence — including a 2013 review she co-authored — correlating exposure to possible neurological problems such as ADHD and lower IQ in children, which she says the EPA standards don’t adequately consider.

But another review last year by a different group of scientists found “the epidemiologic studies did not strongly implicate any particular pesticide as being causally related to adverse neurodevelopmental outcomes in infants and children.” As of December 2013, the position of the Centers for Disease Control and Prevention was that high levels of organophosphate exposure were associated with some neurobehavioral problems in farm communities with exposure higher than that in the general population.

An American Academy of Pediatrics 2012 report noted the correlation between organophosphate exposure and neurological issues that had been found in some studies but concluded that it was still “unclear” that reducing exposure by eating organic would be “clinically relevant.”

The EPA expects to have a new assessment of organophosphates in 2016. In the meantime, the agency has determined that certain foods —snap beans, watermelon, tomatoes and potatoes — are likely to have higher residues of the pesticide than other produce. If you’re pregnant or feeding small children, you may want to consider organic versions of those foods.

As for pathogens, the 2012 Stanford review found that E. coli contamination is slightly more likely in organic than conventional produce.

The best strategy to reduce risk from produce isn’t to buy either organic or conventional. Rather, it’s to cook your food. A CDC review notes that leafy vegetables, led by lettuce and spinach, are the No. 1 cause of food-borne illnesses, responsible for 22 percent of food-borne illnesses.

Bottom line: While there may be no significant nutritional difference between organic and conventional produce, organic does have lower levels of pesticide residue. However, there isn’t universal agreement on the risk those residues pose.

Meat

Nutrition: As with milk, the main issue here is omega-3 fats. Some organic meat and poultry have more of them than conventional products do. The reason is diet: Animals that eat more grass have lower fat levels overall and higher omega-3 levels than animals fed more grain.

Although measurements of omega-3 fats in beef vary, the numbers are low and substantially below what can be found in a serving of salmon.

Contaminants: The USDA randomly tests carcasses for residues of pesticides, contaminants and veterinary drugs including antibiotics. In 2011, it screened for 128 chemicals, and 99 percent of the tested carcasses were free of all of them.

It found a few with residue violations and a similar small number with residue within legal limits (mostly of arsenic and antibiotics). Although the USDA doesn’t report organic and conventional separately, contaminant risk overall is extremely low.

The bigger concern is pathogens. Studies of bacterial contamination levels of organic and conventional meat show widely varying results. These findings suggest that organic meat may be slightly more likely to be contaminated, possibly because no antibiotics are used. But conventional meat is more likely to be contaminated with antibiotic-resistant bacteria. The 2012 Stanford review found that slightly more organic chicken samples were contaminated with Campylobacter than conventional samples and that organic pork was more likely than conventional to harbor E. coli. But the risk in meat overall was essentially the same. And whether meat is conventional or organic, the solution is adequate cooking.

Bottom line: There doesn’t seem to be much difference, health-wise, between organic or conventional meats. Grass-fed beef has a slight edge over grain-fed because of higher omega-3 levels, but the amounts are probably too small to affect human health.

Eggs

Nutrition: As with milk and meat, the omega-3 levels of eggs are affected by the hens’ diet and can be increased by pasturing or diet supplementation for either organic or conventional hens. Eggs high in omega-3s are generally labeled.

Contaminants: There’s very little research on contaminants in eggs. The USDA’s 2011 National Residue Program tested 497 egg samples and found no residues of pesticides, contaminants or veterinary drugs, including antibiotics. This isn’t surprising because, according to Pat Curtis, a poultry scientist at Auburn University, laying hens aren’t routinely given antibiotics, and there is a mandated withdrawal period after they do get the drugs (to treat illness) before their eggs can be sold. The 2012 Stanford review concluded that there is “no difference” in contamination risk between conventional and organic eggs.

Bottom line: There are no significant differences affecting health between organic and conventional eggs.

Fish

The USDA has not issued any organic standards for farmed fish or shellfish, but several overseas organizations have. (Because there’s no way to control the diet of wild fish, “organic” doesn’t apply.) Canadian standards prohibit antibiotics and hormones, restrict pesticides and set criteria for acceptable feed. There’s not enough research comparing organic and conventional fish to draw any conclusions about their health benefits.

유기농이 내성균을 키우는 원인  

H 자연에 존재하는 많은 세균들은 일부 곰팡이나 다른 세균이 생성하는 천연 항생물질에 대한 대응으로, 저절로 항생제 내성 유전자를 보유하게 된다. 한편 실험실에서 만들어진 항생제는 인간과 동물의 감염증을 치료하거나 가축의 성장을 촉진할 목적으로 투여되는데, "소(牛)나 기타 가축에게 항생제를 투여한 다음, 그들로부터 나온 퇴비를 토양에 뿌리면 항생제 내성 세균의 증식을 초래할 수 있다"는 것은 잘 알려진 사실이다.

그러나 새로 발표된 연구결과에 의하면, "설사 가축에게 항생제를 투여하지 않았더라도, 퇴비 자체가 항생제 내성에 기여할 수 있다"고 한다. 퇴비가 항생제 내성을 초래하는 메커니즘은 아직 확실히 밝혀지지 않았지만, PNAS 10월 6일호에 실린 이번 논문은 "농업에서의 항생제 사용과 항생제 내성 세균 간의 복잡한 관계"를 암시하고 있다(참고 1).

퇴비는 토양 속에 서식하는 세균총의 구성을 변화시키므로, 예일 대학교의 조 한델스만 교수(미생물학)가 이끄는 연구진은 퇴비가 토양 속 세균의 약물 저항성에도 영향을 미치는지를 알아보기 위해 이번 연구를 실시했다. 연구진은 토양 샘플을 질소비료와 (항생제를 일절 투여하지 않은 소에게서 나온) 퇴비 중 하나로 처리했다. 연구진은 비료나 퇴비를 사용하기 전후에 토양세균의 구성을 검사하여, 베타락타마제(β-lactamases: 페니실린 계열의 항생제를 파괴하는 효소)를 코딩하는 유전자를 포함하고 있는지 확인했다.

2주 후, 퇴비를 뿌린 토양에서는 질소비료를 뿌린 토양에서보다 훨씬 더 많은 베타락타마제 생성세균이 검출되었다. 그런데 항생재 내성세균의 유전적 표지를 추적한 결과, 이 세균들은 퇴비가 아닌 토양에서 유래한 것으로 판명되었다. 이는 "퇴비가 세균에게 영양분을 공급하거나 경쟁세균을 제거해 줌으로써, 토양 세균의 증식을 도왔다"는 것을 시사한다. 퇴비는 특히 슈도모나스(Pseudomonas)종에게 유익한 것으로 나타났다.

그러나 이번 연구에서 퇴비가 항생제 내성세균의 증식에 유리한 환경을 조성하는 과정은 밝혀지지 않았다. 연구진은 "퇴비 속에 포함된 특정 영양소나 중금속이 항생제 내성세균의 증식을 초래했을 것"이라고 추측하고 있다. 왜냐하면 베타락타마제를 보유한 세균은 금속에 저항성을 띠는 경향이 있기 때문이다(참고 2). 연구진은 조만간 이 가설을 검증할 계획을 갖고 있다. "이번 연구결과는 `인간의 모든 행동은 자연생태계나 공중보건에 예기치 않은 영향을 미칠 수 있다`는 주장에 힘을 실어 준다"라고 워싱턴 대학교의 가우탐 단타스 교수(미생물학)는 논평했다.

가축에 대한 항생제 과잉사용이 임상적인 항생제 내성에 얼마나 영향을 미치는지에 대해서는 아직 논란이 많다. 미국 정부는 지난 9월에 발표한 보고서를 통해, "보다 많은 연구가 필요하다"고 전제하면서, 의학적으로 중요한 항생제를 가축들에게 사용하지 말라고 권고하지는 않았다(http://www.nature.com/doifinder/10.1038/nature.2014.15962). 그러나 퇴비로 인해 세균구성이 바뀐 토양에 항생제를 쏟아부을 경우, 항생제 내성을 악화시킬 것은 불을 보듯 뻔한 일이다. "이번 연구는 농민들이 항생제 사용에 신중을 기해야 함을 일깨워 줬다"라고 단타스 교수는 말했다.

한편 이번 연구는 질소비료 대신 퇴비를 사용하는 유기농 기법에 대한 재검토가 필요함을 시사한다. "어쩌면 우리는 지금껏 유기농이라는 이름 하에 항생제 내성세균을 키워 왔는지도 모른다. `질소비료는 무조건 나쁘고 퇴비는 무조건 좋다`고 말하기 전에, 각각의 장단점을 신중히 따져 볼 필요가 있다"라고 단타스 교수는 말했다.

※ 참고문헌
1. Udikovic-Kolic, N. et al., "Bloom of resident antibiotic-resistant bacteria in soil following manure fertilization", Proc. Natl Acad. Sci. USA http://dx.doi.org/10.1073/pnas.1409836111 (2014).
2. Knapp, C. W. et al., "Antibiotic Resistance Gene Abundances Correlate with Metal and Geochemical Conditions in Archived Scottish Soils", PLoS ONE 6, e27300 (2011).