A. Micaela Karlsen, a PhD candidate at Tufts Friedman School, replies: The reason many people are interested in eating oat bran is because of its high fiber content, which can aid in satiety and potentially weight loss. Per 100 grams of dry weight (about 3.5 ounces), oat bran contains 15.4 grams total fiber, while oats contain 10.6 grams, and oat bran is also slightly higher in minerals, including magnesium, phosphorus and potassium, as well as vitamins like thiamin, riboflavin, niacin and B6. At the same time, oats provide more energy at 389 calories per 100 grams compared to 246 from oat bran. (Remember, these calories are complex carbohydrates-healthy calories.)
To reframe your question a little bit, in an ideal world we would all be eating plenty of foods that are naturally high in both fiber and other nutrients-whole grains like oats, vegetables, legumes and so on. Remember that everything that is in oat bran is also in oats; the bran is one component of the whole food, but removing only the bran changes the proportions of the nutrients. Comparing oat bran to oats is a bit like comparing your finger to your hand-which is better? A finger can dial a phone, but a hand can dial a phone and also hold a fork.
Adding oat bran to your cereal may be a quick and easy way to add fiber and other nutrients to your diet, and if those are your goals and you like the taste of oat bran, it may be a helpful change to make. At the same time, keep your mind open to exploring ways to consume the original whole food (in this case oats), as there are many components of food whose function or relationships we do not yet understand, and a diet built entirely on whole foods is very likely to contain adequate amounts of fiber and micronutrients anyway.