SIBO Center for Digestive Health at NCNM

Meet Our Providers

Steven Sandberg-Lewis, ND, DHANPssl_2013_188

Dr. Steven Sandberg-Lewis has been a practicing naturopathic physician for 36 years, previously on Orcas Island in Washington state and now exclusively at the NCNM Clinic.  Dr. Sandberg-Lewis receives referrals of patients with digestive diseases who desire naturopathic treatment options; often these are conditions that have defied diagnosis by other physicians. He understands the diseases of the gastrointestinal tract, but also can assess function and often find successful treatments to regain normal function of the digestive system.

Allison Siebecker, ND, MSOM, LAc

Dr. Allison Siebecker is a 2005 graduate of National College of Natural Medicine, where she earned both her Naturopathic Doctorate and Masters in Oriental Medicine.  She has worked in the nutritional field since 1988 and taught on the subjects of gastroenterology, endocrinology, nutrition and natural beauty treatments. Since 2009 she has focused her practice on Small Intestine Bacterial Overgrowth (SIBO).  She is the author of an educational website on SIBO, is currently writing a book on SIBO and teaches continuing education to physicians on SIBO and related topics.

Melanie Keller, ND

Dr. Melanie Keller is an NCNM alumna and SIBO Center physician specializing in the treatment of digestive disorders. She currently serves as president of Gastro ANP. Her evidence-based naturopathic approach focuses on addressing the whole person by utilizing functional testing, nutrition, energetic psychology techniques, and visceral and structural manipulation.

While a student at NCNM, Dr. Keller had the privilege of an extensive internship with the renowned Dr. Steven Sandberg-Lewis. His influence during and after this internship greatly enhanced Dr. Keller’s practice philosophy. She has also received post-graduate extended training in Small Intestine Bacterial Overgrowth (SIBO) with Dr. Allison Siebecker. Dr. Keller has applied this training in her functional medicine practice where she has helped many patients to restore their health and vitality.

The SIBO-IBS Center wishes to thank Dr. Siebecker for her contribution of information about SIBO on this site. For more information about SIBO, visit her educational website at