Dr. Daniel S. Bernstein, whose devoted care to patients and colleagues made him one of the most respected figures in health care in the greater Boston area, died early Wednesday morning, July 25 at Brigham and Women's Hospital after a courageous struggle with lung cancer. He was 80 and lived in Cambridge and Chilmark.

Born in Baltimore in 1927, he joined the Navy at age 17, near the end of World War II. He subsequently attended Haverford College, majoring in English and pitching for his school's baseball team. Although no Cy Young, his enthusiasm was contagious. He then put himself through Johns Hopkins Medical School and did medical residencies at Boston City Hospital and the Peter Bent Brigham Hospital in Boston. In 1954, he married Marjorie R. Hiatt of Worcester. They first lived in Cambridge and then moved to London, England when Dr. Bernstein was awarded a fellowship in endocrinology at the university hospital there.

He began his research and clinical careers in 1956 in Durham, N.C. When he returned to Boston to assume a research position at the Robert Breck Brigham Hospital and later the Harvard School of Public Health, he studied bone metabolism and parathyroid hormone, publishing a number of articles. His work on fluoride's effects on bone and teeth was groundbreaking. After some years, he was recruited to Boston University School of Medicine as associate dean, clinician and professor of medicine where he redirected his focus to teaching and mentoring students. He also oversaw admissions where he especially enjoyed interviewing prospective students. He volunteered for many years at the Cambridgeport Clinic one evening a week providing free care to homeless young people. His strong political convictions led him to take an active role in opposing the Viet Nam War and nuclear proliferation. His outspoken advocacy caused him to be blacklisted by the Nixon administration. Throughout, he maintained a private practice and saw patients in his Brookline office on Longwood Avenue. Dr. Bernstein provided medical care to all, regardless of whether a patient could pay. Many showed their appreciation with a variety of homemade gifts ranging from mittens to fruitcakes.

After he retired from his academic roles in the 1990s, Dr. Bernstein returned to practicing medicine full time at Brigham & Women's Hospital. His patients implored him not to retire, and he continued to practice medicine until just one month ago when he took a medical leave, hoping to return after the summer and the conclusion of his own treatments. "I intend to practice medicine," he said, "for my whole life." And that is precisely what he did.

His family was his greatest love. He had three children, Jeffrey of Newton, Carolyn of Newton, also a physician, and Andrew of Brookline; five grandchildren, Benjamin, 18, Ally, 16, Jemma, 16, Samantha, 4 and William, 17 months. He was never too busy to help a family member with an exam or a paper. He loved to play tennis and to ski the mountains of New England and the Rockies. He was an avid reader, chess player and Red Sox fan. He was rarely separated from the apple of his eye, his devoted wife, Marge. They loved to travel the world, from Russia to London, Mexico to Alaska, but his favorite spot was the deck of his house on the Vineyard, where he would watch the boats heading toward the Elizabeth Islands, sipping a glass of wine with his family.

In lieu of gifts, contributions may be made to the Daniel S. Bernstein Internship Fund for the Center for Peace and Global Citizenship and sent to Haverford College, Institutional Advancement Department, 370 Lancaster Avenue, Haverford PA 19041. Students are chosen to participate in domestic or international summer internships that are committed to social justice and creating a more peaceful world, an abiding commitment of Dr. Bernstein's. See haverford.edu/CPGC/about/missionfor more information.

There will be a celebration commemorating his life on Sunday, Sept. 16 at 4 p.m. at a location to be announced later. Details may be obtained by e-mailing jbernstein@hurricanelodge.com or contacting Dawn at 617-244-9500.