Barley and rye are two whole grains that have been a part of the human diet for centuries. Knowing the nutritional profiles of barley and rye can help you make informed dietary choices. Here's a look at the key differences and similarities between barley and rye, from fiber content to vitamin levels. #1 Fiber content comparison Barley is famous for its high fiber content, especially beta-glucans, which are known to help reduce cholesterol levels. Barley has more niacin than rye, while rye is richer in thiamine.