U.S. District Judge Robert Timilin also ordered Dr. Christine Daniel to forfeit $1,277,083.
Daniel, 58, was found guilty of 11 counts, including wire fraud, tax evasion and witness tampering in September 2011.
She enticed patients to take her herbal product and charged them as much as $100,000 for a six-month treatment program that she claimed could cure cancer, diabetes and multiple sclerosis, authorities said.
Some of her patients, however, died from complications of cancer within three to six months after taking the supplement. In one case, prosecutors contend a 22-year-old woman who had a highly curable form of neck lymphoma died because she relied on Daniel's recommendation to avoid radiation or chemotherapy treatments.
"The scope of Daniel's fraud was breathtaking," U.S. Attorney Andre Birotte Jr. said in a statement after Daniel was sentenced. "Daniel robbed victims of more than money — she also stole their hopes and dreams for a cure. Daniel is responsible for a shockingly cold-hearted fraud that has brought her a richly deserved federal prison sentence."
Prosecutors sought a 27-year prison term, while Daniel's attorney argued that nearly six years behind bars was more appropriate.
In all, authorities believe Daniel siphoned about $1.1 million from dozens of families between 2001 and 2004.
Some patients also endured additional pain and suffering because they took the herbal tonic provided by Daniel.
At trial, experts called by federal prosecutors said chemical tests of the product showed it contained beef extract flavouring and a sunscreen preservative, among other ingredients.
"I live with the guilt that I should have seen that none of what she was going through was helping her, but instead was hurting her," Debra Harris wrote in a letter submitted to the court about her sister Barbara Davis, who was one of Daniel's patients and who later died. Harris said Daniel's patients were not only convinced they could be cured, but so were family members who "wanted to believe it just as bad."
Paula Middlebrooks also put her faith in Daniel, who billed her nearly $60,000 over a five-month period to help treat her terminal breast cancer. Eventually, Daniel pronounced Middlebrooks free of cancer and threw her a party. But in reality, the cancer was spreading and Middlebrooks died shortly after she returned to her home in Georgia.
Federal prosecutors said Daniel preyed upon people in their most vulnerable state.
Daniel "repeatedly demonstrated a merciless and callous indifference to the suffering of her patients and their family members," Assistant U.S. Attorney Joseph Johns wrote in court documents. "It is unlikely that our federal criminal justice system will see the like of defendant Christine Daniel again."