Dr. Ken Redcross, MD, author of, “Bond: The 4 Cornerstones of a Lasting and Caring Relationship with Your Doctor,” says vitamin D has been in the spotlight during 2020 because of how it reduces COVID symptoms and deaths, however he says this inexpensive, simple vitamin solution has been his secret weapon of his for improving many other health concerns for patients, including depression, viral respiratory infection, premature births, sleep deprivation and Type 2 diabetes..