These days, it’s one of the most persistent messages we get from the healthfood side of the spectrum. Avoid canned food. Avoid processed food. Eat fresh food. It would be a lot easier to accept this as true if they weren’t simultaneously trying to hawk their very expensive alternative foods and ingredients.
So what’s the truth? Are canned foods really bad for you? Or is this an overblown scare campaign attempting to sell more expensive food?
Accusation 1: Canned Foods Contain Bisphenol A (BPA) and That’s Bad
It’s true that BPA is a potentially toxic chemical. It has been linked with estrogen-like effects, leading to stimulation of mammary gland development (and possible breast cancer linkage), decreased testosterone, prostate size increase, alterations in immune function, and neurobehavioral effects. All of these were recognized when Canada called BPA a “dangerous substance.” It has also been linked to possible increases in migraines.
The main problem with the accusation is that we don’t know how well the results in animal models reflects what is likely to be seen in humans. In addition, recent studies suggest that negative effects may not be seen unless we are exposed to millions of times the normal exposure level.
Some of the inflammatory reports seem to confuse the reported safety levels of BPA. For example, there is concern that the levels of BPA found in canned food reach as much as 1,140 parts per billion, whereas the safe level is supposedly 50 parts per billion. However, the safety level refers to the daily intake at 50 μg/kg of body weight, which is different from 50 μg/kg of canned food. So, let’s say a 160 pound person is eating a 16 ounce can of green beans at that 1,140 ppb rate. In order to reach the 50 μg/kg level, a person would have to eat 7 cans of green beans every day, including drinking the liquid. So we’re still at loose ends on this point. So far, most governments and their agencies believe the compound is safe at current exposure levels.
Accusation 2: Canned Foods Contain Excess Sodium
Another potential problem with canned food is that it contains excess sodium. While this is true, it’s a lot less true than it used to be. As we have become more aware of the risks of excess sodium in our diets, canned food processing has reduced its sodium content. These days, canned food contains 40% less sodium than it used to, and in many cases there are options for getting even lower sodium content in your canned food.
In this case, canned food is better for you if you make informed decisions, as are most food products.
Accusation 3: Sulfites
Sulfites are a preservative that are used in canned foods that can cause a serious allergic reaction in some people. If you have a known sulfite allergy, avoid cans with labels that show sulfur compounds. Again, being a smart consumer means reading the labels.
Accusation 4: Nutrient Loss
Some people accuse canned foods of having fewer nutrients or being of lower food quality than fresh or frozen foods. One of the most comprehensive studies of this question, performed by the University of Illinois, shows that, for the most part, important nutrients are retained in canned food, and in some cases canned food has more nutrients. There are chemical changes in the canned food, however. For example, tomatoes are more acidic in the can than when fresh. It’s worth noting, however, that the U of I study was performed for the Steel Packaging Council.
Accusation 5: Aluminum Leakage
Some people accuse canned foods of being packaged in aluminum because it’s cheaper. First of all, aluminum isn’t necessarily cheaper, and secondly, most foods are canned in steel cans, and many are galvanized (coated with zinc–you can see this if you look at the can and it’s got a shiny, multifaceted surface). Want to know whether a can is made of aluminum or steel? Take a magnet with you to the grocery store. If the magnet sticks, the can is steel.
Some Unanswered Questions, Some Baseless Accusations
Looking at the science, most of the accusations leveled at canned food don’t seem to hold up. The biggest remaining open question–the toxicity of BPA–suggests that we should limit the amount of canned food we eat, but doesn’t make it seem urgent to stop eating it altogether until more is known.
Dr. Matthew B. Candelaria (PhD, U of Kansas 2006) is a freelance writer whose educational background includes not only English, but chemistry, biology, physics, and material science. He focuses most of his writing on medical topics including dentistry, weight loss, and primary care issues.
