Modern, high-intensity farming is charged with causing food to lose some of its goodness. Could organic food offer an alternative?
This is a controversial question. Antioxidant levels are higher in organically grown plants, according to a meta-analysis of existing studies published last year. However, in 2012 researchers at Stanford University in California found no strong evidence that organic foods are more nutritious.
“In general, for minerals, the differences [between organic and inorganic] are pretty small,” says biochemist Donald Davis. One reason for the nutrient declines seen in some of today’s vegetables is down to breeding – making broccoli heads larger, for example – and organic growers tend to plant the same varieties as non-organic growers, he says.
Another complication is that it is difficult to make a direct comparison of organic and non-organic crops. “You have to take enough samples to grow on a very controlled patch, and expose them to exactly the same treatment,” says Paul Finglas of the UK’s Institute of Food Research in Norwich. “There may well be some evidence that some organic foods are different – such as in vitamin C – but it’s not going to make a big nutritional impact.”
Things look better for organic milk. Recent UK and US studies found that organic milk from cows reared outdoors had higher amounts of antioxidants and omega-3s. The difference is down to diet. “Cattle on organic farms are provided much more access to pasture and fed a much higher proportion of forage-based feeds,” says Charles Benbrook, who showed in 2013 that organic milk produced in the US contains a healthier ratio of omega-3 to omega-6 fatty acids than non-organic milk. “Grass and legume forages are the building blocks for omega-3 fatty acids, while corn – which plays an important role on conventional farms – is the basis for omega-6.”
One area of concern is the low intake of omega-3s. These essential fatty acids, particularly long-chain omega-3s found in oily fish and shellfish, are vital for growth and development. The average intake among adults in the US and UK falls far short of the recommended amount, largely due to the fact that many people eat little or no seafood. “Omega-3 is probably one nutrient that [Western] people have a deficiency in – at least, they’re not at the optimum level,” says Eric Decker, a food scientist at the University of Massachusetts. Meanwhile, people are consuming more omega-6 acids, found in vegetable oils. These are important too, but in excess amounts they can trigger the body’s inflammatory response.
What’s worrying some is that changes in farming methods are making some foods lower in omega-3s and higher in omega-6s. This has been shown most clearly in fish. Half of all fish consumed globally now come from aquaculture, and farmed fish have a different nutritional profile to wild-caught varieties. Wild salmon, for example, is an excellent source of omega-3s, because it feeds on smaller fish that have eaten omega-3 rich algae. But farmed fish are increasingly fed vegetable oil, boosting their omega-6 levels.
Last year, a study of salmon sold in the UK found that farmed salmon had twice the amount of fat as wild salmon, a lower proportion of omega-3s and significantly more omega-6 fatty acids – although the authors stress that farmed salmon is still a good source of omega-3s. Similar trends have been seen in organic and non-organic milk and beef , though these contain far less omega-3 than fish.
Fortification is one way to tackle this problem – hence the array of omega-3 enriched products, such as juice and yogurt, now on the market. (adapted from an original article by Chloe Lambert in the New Scientist).