Canned foods: appropriate in trace element studies?

This study was conducted to help decrease the variability of metabolic diets. The effects of production lot and storage time on the trace element content of canned food products were compared. Various production lots of peaches, green beans, and tomatoes, canned in tinplate, were purchased and opened at three different times, spaced at 6-month periods. Storage time contributed more to the variability of tomatoes and green beans than production lot. Production lot was the more important factor in peaches. The following guidelines may be useful for metabolic studies lasting more than a few weeks: Use only frozen foods or foods canned in glass, maintaining constant production lots when possible. If only tin-canned products are available, remove the product from the can and freeze when appropriate. When products are retained in the can, maintain storeroom at a low temperature above freezing. In all cases, purchase specifications should require products to be from the most recent canning season, and kitchen procedures should be constant.