Many people buy organic foods thinking they're better for them than their conventional cousins. Yet findings from a new study – the most comprehensive analysis to date – casts doubt on this notion.

There's no nutritional or safety differences between organic and conventional foods, dispelling the belief that organic food is always healthier and more nutritious, according to the report published in the Annals of Internal Medicine.

Organic foods are grown and harvested without the use of synthetic pesticides and fertilizers, growth hormones, antibiotics, genetically modified organisms, irradiation and artificial additives. Organic livestock are fed organic feed and are given access to the outdoors, fresh air and sunlight.

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The term organic is not synonymous with natural. So-called "natural" foods should not be significantly altered from their natural state nor should they contain any added nutrient, artificial flavouring or food additive.

Researchers at Stanford University Medical Center in California reviewed 237 studies – 17 human studies and 223 studies that compared nutrient and contaminant levels (bacterial, fungal and pesticide) in foods grown organically and conventionally.

There were no consistent differences in the vitamin content between organic and conventional produce. Only one nutrient – phosphorus – was higher in organic versus conventional produce. But because a phosphorus deficiency is rare in North America, this finding is unlikely to be clinically important.

There was also no difference in the fat and protein content between organic and conventional milk.

The analysis did, however, turn up weak evidence that organic produce contains higher levels of phenols, phytochemicals thought to have numerous health benefits. The review suggested that organic chicken and milk may contain more omega-3 fatty acids than conventional products. (However, most milk studies examined raw, not pasteurized, milk.)

The researchers found meagre evidence that conventional foods posed greater health risks than their organic cousins. While organic produce was 30 per cent less likely to be contaminated with pesticides than conventional produce, 7 per cent of organic food samples contained pesticide residues. The pesticide levels of both types of foods, however, fell within allowable safety limits, set by government regulators.

Synthetic pesticide residues that end up on organic produce can come from pesticides used in the past now cycling in the soil or water as well as spray drift from non-organic farms.

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While two studies in the review found lower pesticide levels in the urine of children fed organic versus conventional diets, levels of urinary pesticides in both groups of children were below safety thresholds.

There was no difference in bacterial contamination between organic and conventional foods – both were commonly contaminated with Salmonella and Campylobacter. In fact, the results suggested that organic produce is more likely to be contaminated with E. coli. Research has found that produce from organic farms using manure for fertilization is much more likely to contain E. coli than produce from organic farms not using animal waste.

Conventional chicken and pork had a higher risk of contamination with bacteria resistant to antibiotics. However, the extent to which antibiotic use for livestock contributes to antibiotic-resistant bacteria in people is debated.

These findings don't mean you should stop eating organic foods. There are reasons to choose organic over conventional that go beyond health. Many people find organic food tastes better. Others are concerned about the effect of conventional farming on the environment and animal welfare.

And not everyone needs proof that organic foods are healthier for you. When it comes to synthetic chemical residues in foods – pesticides, hormones or antibiotics – many people feel it's better to be safe than sorry. Some people don't want to wait around to find out if long-term exposure to pesticide residues does, in fact, increase the risk of health problems.

That's especially true for many women and parents of young children. Some scientists and watchdog groups worry that pregnant and breastfeeding women, infants and young children may be more vulnerable to the harmful effects of pesticide residues, especially during critical periods of development.

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Clearly, buying organic food is a personal choice based on availability, price, taste and personal values.

In Canada, all foods labelled organic must follow strict organic production standards and be certified by an accredited certification body. Only foods that contain at least 95-per-cent organic ingredients can be labelled as "organic" and/or bear the Canada Organic logo.

A diet plentiful in fruits and vegetables – organic or conventional – is one that delivers more fibre, vitamins, minerals and phytochemicals. The key is to include seven to 10 servings in your daily diet. (One serving is equivalent to one medium fruit, one cup chopped fruit, ½ cup raw or cooked vegetables, and one cup of salad greens.)

And whether you eat organic or conventional foods, it's important to take steps to handle foods safely. Wash and rinse all produce – conventional and organic – with running water (not soap) to reduce the amount of pesticide residues, bacteria and dirt. Peel fruits and vegetables, remove and discard outer leaves of lettuce, leafy greens and cabbage. Scrub thick-skinned produce like potatoes, carrots and parsnips.

Eat a wide variety of fruits and vegetables each day to minimize your exposure to a particular pesticide residue.

Remove visible fat from meat and skin from poultry and fish before cooking since some pesticides store in animal fat.

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If you're considering adding a few organic foods to your shopping cart, focus on foods your family eats the most such as fruits, vegetables, meat and dairy. Keep in mind that "organic" potato chips, cookies and candy typically have just as much salt and sugar and just as many calories as their conventional counterparts.

Leslie Beck, a registered dietitian, is the national director of nutrition at BodyScience Medical. She can be seen every Thursday at noon on CTV News Channel's Direct (www.bodysciencemedical.com).