Nieman is a pioneer in the research area of exercise and nutrition immunology and helped establish that

regular moderate exercise lowers upper respiratory tract infection rates while improving immunosurveillance,
heavy exertion increases infection rates while causing transient changes in immune function, and
that carbohydrate and flavonoid ingestion by athletes attenuates exercise-induced inflammation.
Nieman’s current work is centered on investigating unique nutritional products as countermeasures to exercise- and obesity-induced immune dysfunction, inflammation, illness and oxidative stress using a multi-omics approach.

He has received more than $10.9 million in research grants and published more than 370 peer-reviewed publications in journals and books. He is the Editor-in-Chief of the sports nutrition section of the journals Nutrients and Frontiers in Nutrition, and sits on 10 journal editorial boards including Medicine and Science in Sports and Exercise, and the International Journal of Sport Nutrition and Exercise Metabolism.