Harvard professor John Kenneth Galbraith, the renowned economist whose influence stretched from presidents, as adviser and diplomat, to Main Street, as a prolific best-selling author and TV host, has died at age 97.

Galbraith died Saturday of natural causes at Mount Auburn Hospital in Cambridge, about two weeks after he had been admitted, his son, Alan Galbraith said. "His mind was wonderful, right up until the end," the son said.

The Canadian-born Galbraith became one of America's best-known liberals, and was outspoken in his support of government action to solve social problems. He served as adviser to Democratic presidents from Franklin D. Roosevelt to Bill Clinton, and was John F. Kennedy's ambassador to India.

His 1958 book, "The Affluent Society," caused the country to reconsider its values and helped propel him into the international spotlight.

It argued that the American economy was producing individual wealth but hadn't adequately addressed public needs such as schools and highways. U.S. economists and politicians were still using the assumptions of the world of the past, where scarcity and poverty were near-universal, he said.

"As a result, we are guided, in part, by ideas that are relevant to another world," he wrote. "We do many things that are unnecessary, some that are unwise, and a few that are insane."

In 1999, a panel of judges organized by the Modern Library, a book publisher, picked "The Affluent Society" as No. 46 on its list of the century's 100 best English-language works of nonfiction.

Galbraith also was known for his theories on countervailing forces in the economy, where groups such as labor unions were needed to strike a political and social balance.

Richard Neustadt, a Harvard colleague and fellow aide to presidents Kennedy and Truman, said Galbraith demonstrated how "you have to empower people directly before they could fight for themselves."

Galbraith, greeted by the Great Depression when he graduated from college, also had "much more confidence in the ability to work out of economic difficulties and do so with the help of government," Neustadt said.

After his 1975 retirement from Harvard, Galbraith hosted the British-made television series, "The Age of Uncertainty." His book under the same title was a best-seller, as was "Almost Everyone's Guide to Economics."

Among his other books were "The Great Crash," 1955, and "The Culture of Contentment," 1992. He returned to the theme of the crash of 1929 in a January 1987 Atlantic Monthly article that correctly predicted that year's market plunge by citing the parallels of the two eras.

A globe trotter, Galbraith also wrote a factual account of his India years and a novel, "The Triumph," concerning what he called "an uncontrollably funny institution," the U.S. State Department.

Galbraith was born Oct. 15, 1908, in Iona Station, Ontario, Canada.

After graduating from the University of Toronto in 1931, he moved to the United States where he earned his Ph.D. in economics from the University of California. He taught at Harvard from 1934 to 1939 and at Princeton University from 1939 to 1942, then worked in the federal Office of Price Administration during the war.

Galbraith returned to Harvard in 1948, remaining active on the faculty until his retirement, and served a term as president of the American Economic Association.

He was the recipient of the Medal of Freedom, awarded by Truman in 1946, and another from President Clinton in 2000.

Galbraith was married in 1937 to Catherine Atwater. They had three sons, Alan, Peter and James.