Organic vs non-organic

I am guessing a lot of tortoise keepers are told to buy organic greens, and most do, even if they do not buy organic for even themselves. I personally do not fixate on buying organic greens, but instead pick out the freshest produce and try to aim for the most variety (which means I sometimes buy organic). Also being a scientist, who’s research revolves around plants and our agricultural systems, I figured it would be a good idea to do some unbiased research to explore the potential benefits of an organic-only tortoise diet. Most of the research presented here are exerts from:

Winter, C.K. and Davis, S.F. (2006) Organic Foods. Journal of Food Science. Vol. 71, No. 9, pp. R117-R124.

Organic production can be defined as a production system that promotes and enhances biodiversity, biological cycles, and soil biological activity. It is based on minimal use of off‐farm inputs and on management practices that restore, maintain, and enhance ecological harmony. U.S. regulations require that organic foods are grown without synthetic pesticides, growth hormones, antibiotics, modern genetic engineering techniques (including genetically modified crops), chemical fertilizers, or sewage sludge.

One of the major reasons consumers purchase organic foods over conventional is to avoid pesticides (Whole Foods Market, 2005). The USDA’s pesticide data program (PDP) sampled 26893 foods for pesticide residues from 1994 to 1999. Results showed that nearly 73% of the conventionally produced samples contained detectable residues of pesticides. Those samples produced by organic methods still had pesticide residues present in 23% of these samples. Almost 50% of the residues encountered in organic foods were environmentally persistent chlorinated hydrocarbon insecticides that have been banned for use for several decades but are still present in small amounts in many agricultural fields and can result in food residues. Despite these results, we have not discussed the levels of pesticide residues found in each. A study from 1991 indicated that pesticide residue exposure, even in the conventional foods, was over 10,000 times lower than the levels that just begin to show toxicological effects. From a practical standpoint, this means that the marginal benefits of reducing exposure to pesticides in the diet through increased consumption of organic produce appear to be insignificant.

This does not mean that pesticides are safe, nonetheless. Direct (occupational) exposure to pesticides presents a much greater health risk than consumer exposure to pesticides.  This presents a major threat to tortoises living in outdoor enclosures 24-7, especially in residential areas. Do not spray tortoise enclosures with pesticides, for any reason. Owners are encouraged to ask their neighbors to inform them when they apply pesticides so that their tortoises can be removed to a safer area (Boyer, 1994).

So, we have ruled out the risk of harmful “chemicals” being present on conventional greens, but are there any other benefits to choosing organic?Studies have shown that organic foods can sometimes be more nutritious than non-organic. Davis et al. (2004), confirmed that conventional crops did show a decline for 6 nutrients (protein, calcium, potassium, iron, riboflavin, and ascorbic acid). Davis also noted, however, that these declines were attributed the cultivars (plant varieties) used. They argue that cultivars are selected for their yield characteristics, growth rate, and pest resistance but are not chosen because of their nutrient content.  Therefore, any increase in nutritional content is not due to management practices (organic practices). Nonetheless, whatever the cause may be, organic does tend to be slightly higher in nutritional content. On the other hand, this doesn’t mean conventional is not healthy.

So, if anything, select organic for the freshness or the marginal increase in nutrition. At the same time, be aware that conventional greens will not harm your tortoise, and if you need to buy conventional greens – it’ll be just fine!


Boyer, D.M. and Boyer, T.H. (1994) Tortoise Care. ARAV, Vol. 4, No. 1.

Davis DR, Epp MD, Riordan HD. 2004. Changes in USDA food composition data for 43 garden crops, 1950 to 1999. J Am Coll Nutr 23:669–82.

Whole Foods Market. 2005. 2005 Whole Foods Market organic trend tracker. Austin , Tex. : Whole Foods Market. Winter, C.K. and Davis, S.F. (2006) Organic Foods. Journal of Food Science. Vol. 71, No. 9, pp. R117-R124.