Dr. Wesley Boyd, the letter's lead author, says insurance companies have over $4 billion in tobacco company investments.

Dr. Boyd says the U.S.-based Prudential Financial company, which provides life insurance and long-term disability coverage has total tobacco holdings over $264 million.

He says the U.K.-based Prudential, which offers life, health, disability and long-term care insurance has a nearly $1.4 billion stake in tobacco.

Standard Life, another UK-based company with Canadian operations, is said to own nearly $950 million in tobacco stock.

Canada’s own Sun Life, which offers life, health, disability and long-term care insurance, is charged as owning over $1 billion in tobacco stock.

Dr. Boyd said that although investing in tobacco while selling life or health insurance may seem self-defeating, insurance firms have figured out ways to profit from both. Insurers exclude smokers from coverage or, more commonly, charge them higher premiums. Insurers profit — and smokers lose — twice over.