Health benefits of organic foods are unproven

DEAR DOCTOR K: Many of my friends buy only organic foods. But are they really healthier than non-organic?

DEAR READER: Organic crops are grown without most synthetic fertilizers and pesticides. Organic animal products are free of antibiotics and hormones. Many people believe these foods are better for them. But we really don't know that they are.

The U.S. Department of Agriculture (USDA) regulates the organic industry with strict standards. The soil where crops are grown must be inspected and shown to be free of most manmade pesticides and fertilizers. The crops cannot be genetically modified. Animals raised on organic farms receive no antibiotics or growth hormones. They are given feed that has been grown organically. And they are able to roam around outside. Processed organic foods cannot contain synthetic additives. Only foods that are 95 percent organic are certified with a "USDA Organic" seal.

There have been several studies comparing the nutritional content of organic and non-organic foods. They have found that foods grown either way are quite similar in terms of vitamins, minerals and carbohydrates.

According to the USDA, organic foods have fewer pesticide residues than conventionally grown foods. But the amounts of pesticide residues in non-organic food fall within the level for safe consumption.

Similarly, we don't have enough information yet for a verdict on animal products. Does the lack of hormones and antibiotics in organic animal products make them healthier? We don't know.

I spoke with registered dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital. She noted that organic foods usually have a higher price tag than conventional foods.

If you do want to go organic, McManus suggests starting with produce. Try buying organic versions of foods on the "Dirty Dozen" list. This annual list reveals which conventionally grown foods are most likely to contain pesticide residues. This year's list includes apples, celery, cherry tomatoes, cucumbers, grapes, nectarines, peaches, potatoes, snap peas, spinach, strawberries and sweet bell peppers. All of these fruits and vegetables should be washed before you consume them, even if they are organically grown.

Fruits and vegetables that typically do not appear on the Dirty Dozen list are those that have a thick skin that is usually removed before eating. By removing the skin or peel, you're also removing most of the pesticide residue. As a result, it's less important that it be organic. Examples of the "Clean 15" include bananas, avocados, grapefruit and eggplant.

Why don't we know if organic foods are healthier? Such a study would be very hard to conduct. The research team would have to recruit thousands of people. Those people would be assigned at random to either eat organic foods or not. They would have to follow their assignment every day, for many years. The research team would need a way to be sure that participants followed their assignments. That's all very hard to pull off.

Then there's the expense. Such a study would cost tens of millions of dollars. And, in my opinion, the U.S. government already is not providing sufficient funding for medical research.

So I would recommend choosing organic foods if they taste better to you. It is hard to argue with certainty that they have health benefits.