PubMed Food Problem – Olive Oil

By Eric Rumsey and Janna Lawrence

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Olive oil as a healthy food is a highly popular topic among consumers. It’s also popular among researchers, as shown in a list of the 100 most popular research articles of 2013, by the Altmetric site, in which the number two ranking article is a comparison of olive oil and nuts for prevention of cardiovascular disease, in NEJM. This article shows a major problem with the MeSH indexing of olive oil. Even with its trending popularity, olive oil does not have its own MeSH term. In the NEJM article, and in most articles on olive oil, the only MeSH term that corresponds with olive oil is Plant Oils. This is a problem because Plant Oils is not in any food-diet-nutrition (FDN) explosion, and is therefore not retrieved by broad searches for FDN.

Fortunately, articles on olive oil are often picked up by broad FDN searches because they have other FDN-related MeSH terms. But in many cases, they are not. Here are some examples of articles with olive oil in the title that are not retrieved using our broad FDN hedge because they contain no MeSH terms or text words relating to food, diet or nutrition:

As we’ve discussed previously, most plant-based foods are difficult to search in PubMed because the MeSH terms for them are in the Plants explosion and not in any FDN explosion. Notably, olive oil has a different problem. It’s like other plant-based foods in not having a MeSH term that’s in an FDN explosion. But instead of being in Plants, its MeSH term, Plant Oils, is in the Chemicals and Drugs explosion.

There’s another baffling quirk in the MeSH indexing of olive oil. Although it doesn’t have its own MeSH term, there are MeSH terms for several other dietary oils in the Dietary Fats explosion (which, of course, is retrieved in broad FDN searches). These other dietary fats are Cod Liver Oil, Corn Oil, Cottonseed Oil, Safflower Oil, Sesame Oil, and Soybean Oil. None of these has close to the number of citations as there are on olive oil. We searched for each of these oils as a phrase in the title, and compared this with olive oil, and found, remarkably, that the total of all of these other oils combined is about the same as the number for olive oil by itself. So why is there not a MeSH term for olive oil?!