The best way to determine if organic foods are more nutritious than conventionally grown foods is to compare the same varieties of fruits and vegetables grown in similar locations. For example, compare the same cultivar of tomato grown organically and non-organically in similar soils and climate. When this type of comparison is done, 60% of the studies show organic foods to be higher in nutrients than conventionally grown foods. 30-35% of the time there is no statistical difference and 5-10% of the time nutrient levels are higher in conventionally grown foods.
A recent Stanford University review claimed that organic produce is not more nutritious than non-organic however, only half of the studies reviewed employed the method of comparing like to like in variety and similar growing conditions.
Generally organic produce has about 5-15% higher nutrient levels. However, in a two year study of tomatoes purchased in Barcelona markets, organic tomatoes had twice the level of some polyphenols as conventionally grown tomatoes. Polyphenols are antioxidants that may be the main reason tomatoes reduce our risk of heart disease.
It is thought that organics have higher nutrient levels because of two reasons. One is that when produce is grown without pesticide use, the plants have to fend off a range of insects so their natural defense mechanisms are stronger. The same compounds that protect them also keep us healthier. Another reason might be one of dilution. Apples that are grown with a lot of nitrogen fertilizer are larger and sweeter. The higher water and sugar content makes a larger apple that has a lower concentration of vitamins, minerals, and phytonutrients.
Producers are beginning to find another advantage of organics, an extended shelf life. For example, organic apples have a higher concentration of antibacterial phenolic acids right under the skin which retards mold and bacterial growth thus extending shelf life.
Most people choose organic produce to reduce their exposure to pesticides. And studies support the fact that organics have lower levels of pesticide residues than do traditionally grown foods. But as we develop agricultural methods that support a growing world population, we must also consider the impact of nitrogen fertilizer use leaching nitrates into ground water and potential health risks of pesticide residues to our children. Organic farming systems are developing a new form of agriculture that supports rather than degrades the health of ecosystems. This transformation in agriculture is more sustainable and healthy for us all.
Remember to keep this in context. The most important change for health that anyone can make is to eat more fruits and vegetables, less harmful fats, and fewer sweets. Next, we have to maintain daily activity to remain healthy. Then comes the decision to buy organic or not. And that decision is up to the consumer.
Tim Scallon is a registered dietitian and Director of Clinical Nutrition and the HC Polk Education Center at Memorial Health System in Lufkin. The Polk Center provides individual and group education on diabetes, heart disease and stroke; monthly classes on healthy cooking; and monthly support groups in Lufkin and Livingston. In cooperation with Sodexo Food Service and the City of Lufkin, the Polk Center produces the nationally viewed TV series Memorial Cooking Innovations where dietitian Tim Scallon teams up with Chef Mani Marini to demonstrate how healthy eating can taste great. The show can be seen on cable in 46 cities and on the Memorial web site at http://www.memorialhealth.org.
By Tim Scallon, M.S. R.D. L.D., Director of the Horace C. Polk Jr. Regional Diabetes Center and Department of Clinical Nutrition at Memorial Health System of East Texas