Searching Nutrition In PubMed & Embase: The Winner Is…

By Eric Rumsey and Janna Lawrence

As we’ve discussed, the big problem in searching for food-diet-nutrition subjects in PubMed is that the subjects are not together in a convenient bundle, as most subject groupings are in PubMed. To get a list of articles that includes food, diet and nutrition, it’s necessary to search each of these areas separately and then bundle them together into one search set.

When we first wrote about the difficulty of searching food-diet-nutrition in PubMed in 2013, we stated clearly that much of problem is caused by the fragmentation of the the relevant MeSH terms. So, jump forward a year. About two months ago, our library got institutional access to Embase.com, sometimes called the “European MEDLINE.” Embase includes all of the articles in MEDLINE, as well as many other articles, and uses its own subject heading system. Because we’ve long been aware that food-diet-nutrition subjects are generally given more attention in Europe than in the US, we thought that the subject might get better treatment in Embase than it does in PubMed. We weren’t disappointed…

A Nutrition explosion that includes Food and Diet

Embase uses explosions to bundle related subjects together, much like PubMed, and, as we were hoping, it does indeed bring food, diet and nutrition subjects together in a convenient bundle – Nutrition. So in the search box, just type in Nutrition/exp to get the nutrition explosion, that will retrieve everything on food and diet as well as nutrition. This is a great advance over PubMed. It becomes easy to combine a subject of interest with food-diet-nutrition, in one simple step. For example, using Embase.com format:

‘Heart disease’/exp AND Nutrition/exp
Neoplasm/exp AND Nutrition/exp
‘Mental function’/exp AND Nutrition/exp

To do equivalent searches in PubMed, it’s necessary to do a hedge/filter search, such we have developed, or to search food-diet-nutrition terms separately and combine these with the subject of interest.

Better treatment of “Food” in Embase

Certainly having the inclusive food-diet-nutrition explosion is the biggest advantage in Embase. But there are other problems in PubMed, especially in the way the Food explosion is treated. In both Embase and PubMed, Food is the largest food-diet-nutrition explosion. There are several difficulties with this explosion in PubMed. An overall complication is that Food and Beverages have a confusing relationship. They are together in one explosion Food and beverages, which is made up of two separate explosions, one for each of the terms. If the user knows enough to search Food and beverages, he/she will get both terms. But if the user searches “Food,” the search will not include beverages. In Embase, beverage is an explosion that’s included in the food explosion, so searching “food” will retrieve articles on beverages.

Several other problems with the Food explosion in PubMed are caused by a lack of detail, in comparison with Embase. Some examples:

  • In PubMed, Fruit is not an explosion, although there are individual fruits included in the Plants explosion, usually under their Latin plant name. In Embase, the fruit explosion has 43 terms under it, 6 of which are themselves explosions.
  • In PubMed, Spices is an explosion with one term under it – Black Pepper. In Embase, the spice explosion has 31 terms listed under it, 4 of which are themselves explosions.
  • In PubMed, specific kinds of red meat, e.g. beef and pork, do not have their own MeSH terms; instead, they’re indexed under the general term Meat. In Embase, the meat explosion contains a red meat explosion, which has 7 terms, including beef and pork.

Related to the lack of detail in the Food explosion in PubMed is that many foods, especially plant-based foods, are not retrieved in a search for “food” because they don’t have specific terms in the Food explosion. We have written some “case studies” of this on chocolate, cranberries, and olive oil, all of which are in the Food explosion in Embase, but not in PubMed. We have also written an article on red meat being difficult to search in PubMed because there is no MeSH term for it; as mentioned above, Embase does have a term for it.

Looking at articles in Embase and PubMed that mention specific foods in the article abstract, it’s almost always the case that Embase’s detailed indexing will include descriptor terms for the specific foods, and PubMed usually will not. Comparison of article indexing is easy to do because Embase provides a “Source” filter, that makes it possible to limit to articles that are included in both Embase and PubMed. Each of the articles retrieved using this filter has a direct link to the citation in PubMed.

PubMed Advantages

The biggest advantage of PubMed, of course, is that it’s free to world. Embase, on the other hand, is an Elsevier product and is only available at institutions that have a subscription.

Another PubMed advantage is its simple Google-like interface, which is certainly more comfortable to most people. Embase uses an older style of interface that may appeal to librarians more than to most users. For anyone with a serious interest in food-diet-nutrition, though, we would say it’s definitely worth learning.