A potentially deadly, purported cancer cure dismissed as ineffective by the scientific community two decades ago, laetrile continues to attract the attention of some despairing patients as well as regulatory authorities.

Cancer experts and health-fraud watchdogs are concerned about the risks of taking this substance and patients being duped. There is little or no evidence in support of laetrile's proposed anti-cancer properties, and considerable evidence of its dangers. Even so, glowing testimonials fill supporters' Web sites.

"The primary risk of using any unproven treatment for cancer is the patient forgoes traditional treatment that could help them," says oncologist Clarence Brown, MD. He is president/CEO of the M.D. Anderson Cancer Center Orlando (Florida). "Secondly, they may be taking something that's harmful to them. It could interact with other medications. Or they could have a bad reaction. And they're spending, often times, big dollars to take a treatment that has absolutely no benefit."

What Is Laetrile?

Laetrile is a pure form of the chemical amygdalin. This compound occurs naturally in many fruit pits and nuts. French chemists first identified it in 1830. They found that when amygdalin breaks down, it produces the poison cyanide.

Vitamin B17 and apricot kernels are other names for laetrile. It is not a vitamin. Some advocates believe cancer results from a vitamin deficiency that laetrile can presumably correct. Opponents think the term was coined to avoid federal drug safety and efficacy requirements.

Theories on Laetrile

During the 1800s, doctors tried using amygdalin to treat cancer. It proved too toxic. In the 1950s, a semi-synthetic form, called laetrile, was produced and promoted as a cancer cure. Several theories exist about its anticancer action. In addition to the "vitamin" theory, some supporters believe an enzyme found primarily in cancer cells, but lacking in healthy cells, breaks down amygdalin. The amygdalin is broken down to cyanide, which then kills the cancer.

"Every cancer cell has a prodigious quantity of beta-glucosidase, or the unlocking enzyme," says G. Edward Griffin, who maintains that laetrile works. He wrote World Without Cancer: The Story of Vitamin B17 . He adds, "It's a beautiful mechanism of nature that couldn't have been accidental."

None of these theories has held up well under scientific scrutiny.


Laetrile gained notoriety during the 1970s, a time when doctors had fewer effective cancer treatments in their arsenal. Chemotherapy side effects were hard to control. Patients began looking for other options. More than 70,000 Americans had tried laetrile by 1978. That year, the National Cancer Institute (NCI) reviewed cases submitted by doctors touting its benefits. Only two of 67 patients had a complete response. Tumors got smaller in four others.

The NCI then sponsored research to evaluate laetrile. Two of the six patients in the first study died of cyanide poisoning after eating almonds. During the second study, patients received an infusion of amygdalin, followed by laetrile pills. Some patients reported feeling better while taking the drug. But cancer progressed in all 175 patients by the end of treatment. The agency decided not to investigate further. The American Cancer Society concluded laetrile had no role in cancer care.

Current Use of Laetrile

The U.S. Food and Drug Administration (FDA) has not approved the use of laetrile and has taken action against U.S. companies to halt Internet laetrile sales. It is illegal to bring it into the country for personal use.

"This product has not been found to be safe and effective, so they're in violation of U.S. drug laws," says FDA spokesperson Susan Cruzan, of organizations that sell laetrile.

Mexican doctors still give laetrile to patients, despite the lack of scientific evidence. Oasis of Hope Hospital spokesman Alex Phillips said his Tijuana facility has treated 100,000 patients with laetrile during the past 38 years. He says, "It's not a magic bullet, but it seems to help many people."

Patients initially receive laetrile through a vein. Then they take laetrile tablets—sometimes for the rest of their lives.


Adverse reactions to laetrile are similar to those that occur with cyanide poisoning. Eating raw almonds or some fruits and vegetables when taking laetrile increases the risk of having an adverse reaction. Side effects tend to be more severe when laetrile is ingested, and some patients have died from laetrile treatment.

Adverse effects of laetrile include:

  • Nausea
  • Vomiting
  • Headache
  • Dizziness
  • Bluish skin color
  • Droopy eyelids
  • Trouble walking
  • Fever
  • Confusion

General Advice

Many cancer patients want to try alternative therapies. Talk with your doctor if you are considering laetrile or other therapies. Herbal remedies can interfere with drugs ordered by your doctor.

"Some people choose to go the alternative route. Other people do both," Dr. Brown concludes. "Openly discuss with your doctor the value or lack thereof of these treatments. Don't be afraid to tell us."