Cannabis oil comes in many forms with different benefits. It can be injected into cooking oil, which the user can squirt under the tongue, or mixed into food. Its vapor can also be inhaled. Marijuana products are illegal under federal law, although several states have enacted laws legalizing their medical use.

Evidence: While commercially available cannabis compounds are FDA-approved to reduce side effects associated with cancer treatment, such as nausea and vomiting, and improve appetite, no clinical trials have shown that cannabis products can treat cancer.

The claim that cannabis oil cures cancer is anecdotal and largely unsupported, based on very few studies in mice and laboratories. Side effects may include memory and concentration loss. Perhaps most importantly, there is evidence that cannabis compounds may inhibit enzymes that patients need to metabolize other cancer drugs, thereby increasing their toxicity or reducing their effectiveness.

The verdict: "So far, no human studies have shown that cannabis oil can be used to treat cancer," Dr. Yang said. "Patients who use cannabis, or any form of cannabis, should let their doctors know so they can give you appropriate advice."

Laetrile

The hype: Laetrile, first promoted as a cancer treatment in Russia and the United States more than a century ago, is the trade name for a purified form of amygdalin, an extract from apricot pits and some nuts and plants. Intestinal enzymes break down Laetrile to produce cyanide, which proponents claim kills cancer cells and leaves normal tissue unharmed. Some also claim that lysine is actually a vitamin called B-17, a deficiency of which has been linked to certain cancers. Laetrile is banned in the United States and is also available in oral form in other countries.

The evidence is clear: Laetrile does break down into cyanide, but the poison not only selectively attacks cancer cells, it can also make patients sick or die. Clinical studies conducted in the 1970s and 1980s, including those sponsored by the National Institutes of Health, showed that Laetrile did not reduce the size or growth of malignancies, but some patients experienced cyanide poisoning

The verdict: "Laetrile has not been shown to be effective against cancer and may even be dangerous for some patients," Dr. Young said. "If amygdalin ends up being used as one of natural cures for cancer, it would have to be used in a different form because the oral form is toxic and too dangerous to use."