Organic is healthier: Kiwis prove that green is good. Also: Grapefruit lowers risk of heart disease

The research is reported in the SCI’s magazine Chemistry & Industry. The debate over the relative health benefits of organic versus conventional food has raged for years, with UK environment secretary David Miliband declaring in January that buying organic is just a lifestyle choice.

The Davis scientists, led by Drs. Maria Amodio and Adel Kader, showed that organically grown kiwifruit had significantly increased levels of polyphenols, the healthy compounds found in red wine and coloured berries. They also had a higher overall antioxidant activity, as well as higher levels of ascorbic acid (vitamin C) and important minerals compared with their conventionally grown counterparts (Journal of the Science of Food and Agriculture DOI 10.1002/jsfa.2820). Their work differed to previously inconclusive studies, as they were able to compare like-for-like with kiwis grown next to each other on the same farm at the same time, in the same environmental conditions. Kader added: “[previous] studies did not include phenolic compounds in the comparison.”

The two categories of kiwifruit showed other differences which Kadel believes are most likely due to the fruits having to be able to survive against pests in the absence of pesticides. For example, organic kiwis had thicker skins, which could help the fruits resist insects, and higher antioxidant activity which is thought to be a natural by-product of stress.

However, some people are still unsure about the potential benefits of antioxidants and other compounds elevated in organic farm produce. Carl Winter, director of the FoodSafe Program at UC Davies, asks whether these increases in nutrients and antioxidants are of any appreciable health perspective. He is also concerned about any unknown negative effects on the health. “The authors also did not look for any plant secondary metabolites of potential toxicological impact.”

According to the Soil Association, organic food sales in the UK increased by 30% to £1.6bn in 2006. The world market for certified organic foods was estimated to be worth US $23-25 billion in 2003 and is growing approximately 19% every year, making these products the fastest-growing sector of the global food industry.

Also of interest in C&I issue 6 2007:

Grapefruit diet has hearty perks

Compounds in grapefruit and oranges have been shown to lower cholesterol levels in the blood. Two flavanones, hesperidin and naringin, were extracted from citrus fruits and fed to rats split into groups with some receiving high levels of cholesterol in their diet. Shela Gorinstein of The Hebrew University in Jerusalem found that after 30 days cholesterol levels in rats' blood reduced by around 20-25% in those fed a cholesterol-rich diet (Journal of the Science of Food and Agriculture DOI: 10.1002/jsfa.2834).

David Bender, Sub-dean at the Royal Free and University College Medical School, London, believes that the results show a significant reduction in the increase in plasma lipids caused by cholesterol feeding. “This is potentially beneficial to health with regards to heart disease”, he added.

Casey Gauthier reports on this story in Chemistry & Industry.