(Not So) Scary Things About Peanut Butter

Photograph by Piccolo Namek, made available via Wikimedia Commons under a GNU Free Documentation License.

Back in December, I wrote about using peanut butter, straight from the jar, as a winter food for birds. Someone then asked about the possibility that sugar or preservatives in commercial peanut butter might be harmful to birds. I decided to do some investigating, and this is what I learned:

As far as I have been able to find out without checking the ingredients of every brand, commercial peanut butters contain salt, sometimes sugar, and what are known as stabilizers, which prevent the oil and solids from separating.

You can leave it on the shelf (for a while anyway)

Preservatives are not generally found in peanut butter because peanut butter has such a low moisture content that it does not support the growth of bacteria—at least, that’s what is claimed by leading peanutbutterologists.

That’s why people are able to keep opened peanut butter on the shelf rather than refrigerate it. However, the oils in peanut butter can go rancid, especially in heat. That jar on your shelf will eventually start to smell off if you leave it long enough, and should be thrown out at that point.

A fungus among us?

Peanuts, hence peanut butter, are also susceptible to an Aspergillus mold (A. flavus, to be exact) that produces the potential liver carcinogen called aflatoxin. Both commercial and “natural” peanut butters are equally subject to this problem as Aspergillus occurs naturally on peanuts as well as on a number of other food products. Amounts of aflatoxin in human food are closely regulated in North America, and most authorities seem to agree that risk from aflatoxin in foods in the industrial world is vanishingly low.

That being said, the risk of aflatoxin contamination is apparently lowest when the peanuts are ground soon after picking and immediately placed in an airtight container. As a result, this may be one of those cases (and they do occur) where buying the big supermarket brand is a safe choice. About 5-10 years ago when the Consumers Union in the United States tested various brands of peanut butter for their aflatoxin content, the highest levels were found in peanut butter “ground fresh” in health food stores, whereas the lowest levels were found in the big supermarket brands.

Trans-fat free?

Another possible reason to be afraid of peanut butter is the stabilizers used to keep peanut butter from separating. Generally these are fats of some type; they used to use hydrogenated vegetable oils but these are being phased out. I don’t have information on what’s being used to replace them. However, in the United States at least (and I suspect in Canada as well), peanut butter must be at least 90% peanuts. The quantity of stabilizers of any type to be found in peanut butter is relatively small.

Our friend, the peanut

Peanuts themselves convey quite a few health benefits, incidentally. According to the Wikipedia, they contain high levels of monounsaturated fats and Resveratrol (a phytoalexin also found in the skin of red grapes), various nutrients, and an antioxidant called p-coumaric acid. The American Peanut Council is even touting a study in which peanuts were found to be so nutritional and satiating that they might be used as a method of weight control.

But that's a possible benefit to me, not a bird. When all is said and done, I've concluded that peanut butter is not very scary at all. I certainly have not been able to find any evidence that birds are placed in any danger by consuming the relatively small amounts of sugar, stabilizers, or salt found in commercial peanut butter.

This item originated as a posting to the NSNature e-list.