Just when you thought you had your nutrition covered, you hear about yet another vitamin you're probably not getting enough of. But don't worry — vitamin B17, a compound found in some plant foods, isn't actually a vitamin, and it's not an essential nutrient. It's also not a cure for cancer.
What Is B17?
B17 is another name for a compound called laetrile, which is made from the plant chemical amygdalin, a natural substance found in B17 sources including the pits of fruits, raw nuts, sorghum and lima beans. Amygdalin produces hydrogen cyanide, which is converted to cyanide in the body. Although it is called vitamin B17, the American Institute of Nutrition Vitamins has not approved it as a vitamin.
Amygdalin from bitter almonds has been used in traditional Chinese medicine to treat abscesses and remove blood stasis, the slowing or pooling of blood that may cause pain and other symptoms. It was first used as an anticancer agent in Russia, with reportedly positive results, as early as 1845, according to an article published in PDQ Cancer Information Summaries in March 2017.
Amygdalin was administered to cancer patients in the U.S. for the first time in the 1920s in pill form, but it was found to be too toxic and was discontinued. However, years later, in the 1950s, an allegedly non-toxic intravenous version was patented as Laetrile.
Is It Effective?
Laetrile gained popularity in the 1970s, at a time when there were few effective cancer treatments, and chemotherapy side effects were hard to control. By 1978, around 75,000 Americans had tried laetrile, according to Beth Israel Lahey Health Winchester Hospital.
When the National Cancer Institute reviewed selected cases submitted by doctors lauding the effectiveness of the drug, six out of 67 cases showed tumor shrinkage benefits, reports the National Institutes of Health. Two of those cases had complete response, and the other four showed a reduction in tumor size.
But follow-up studies sponsored by the National Cancer Institute did not show that laetrile had any effect on cancer. A Phase II trial involved 175 patients, most of whom had breast, colon or lung cancer. By the end of the study, cancer had grown in half of the patients, and it had grown in all the patients by seven months post-treatment.
Although patients reported an improvement in their symptoms, including the ability to work and take part in other activities, those benefits did not continue after the treatment had ended.
According to the NIH, no controlled trials have been conducted that compare the results of the treatment in one group against a group not receiving the treatment. A review of research published in the Cochrane Database of Systematic Reviews in April 2015 and updated in 2018 searched eight databases and two registers for studies demonstrating the effectiveness of laetrile or amygdalin in the treatment of cancer.
The review authors reported that they found no studies that matched their criteria, and thus concluded that any reported beneficial effects against cancer are not supported by sound clinical data.
Side Effects and Dangers
In addition to not being effective, the review authors also concluded that laetrile and amygdalin have serious risks of adverse effects from cyanide poisoning. According to NIH, some potential side effects of treatment with laetrile include:
- Nausea and vomiting
- Blue skin caused by decreased blood oxygen
- Liver damage
- Very low blood pressure
- Droopy eyelids
- Nerve damage leading to trouble walking
Side effects increase when the treatment is taken orally. In addition, side effects can be made worse in combination with any of the following during treatment:
- Consuming raw almonds or crushed fruit pits
- Eating certain fruits and vegetables, including celery, peaches, bean sprouts and carrots
- Taking high-dose vitamin C supplements
Cancer Research UK reports that people taking laetrile should also avoid these B17 foods:
- Mung, lima butter and other beans
- All nuts
- Flax seeds
Avoid Taking Vitamin B17
Due to a lack of evidence of its benefits for cancer treatment, as well as a long list of potential adverse side effects, including death, laetrile has been banned in the U.S. by the Food and Drug Administration. According to the researchers of the Cochrane Database of Systematic Reviews, the risk-balance of either amygdalin or laetrile as a cancer treatment is "unambiguously negative."
Laetrile is still available outside of the United States, and some people may seek treatment with formulations produced in Mexico. NIH warns that the manufacture of laetrile isn't regulated, and that different batches can vary both in contents and purity. According to the Memorial Sloan Kettering Cancer Center, there have been reports of contamination and adulteration in both oral and injectable products.
Warnings From the FDA
When you have cancer, you may be tempted to try any treatment — mainstream or alternative — if there's a glimmer of a hope it can help. Websites that promote laetrile as a cure for cancer can be convincing and give false hope to people in vulnerable situations. However, Cancer Research UK urges people not to give up traditional cancer treatments for unproven alternatives that are not supported by any reputable cancer treatment organizations.
The FDA warns of other scams aimed at cancer patients and their families that promise "cures" in what are often bogus treatments falsely labeled as dietary supplements. These scams may come in the form of powders, pills, creams, kits, teas and oils, and they may promise to be "all-natural."However, these unregulated products are at best completely ineffective and a waste of money, and at worst, dangerous. They are especially harmful if they interfere with proven, effective cancer treatments.
When confronted with these fraudulent products, the FDA says consumers can spot red flags by recognizing certain phrases in the literature or on labeling. These include:
- "Treats all forms of cancer"
- "Miraculously kills cancer cells and tumors"
- "Shrinks malignant tumors"
- "Selectively kills cancer cells"
- "More effective than chemotherapy"
- "Attacks cancer cells, leaving healthy cells intact"
- "Cures cancer"
If you're interested in trying an experimental treatment for cancer, there are always clinical trials accepting participants. Your doctor can help you identify a trial for which you might qualify and help you decide whether it's the right course of treatment for you.
- NIH: "NCI Dictionary of Cancer Terms"
- PDQ Cancer Summaries: "Laetrile/Amygdalin (PDQ®)"
- Beth Israel Lahey Health Winchester Hospital: "Laetrile: An Unproven Cancer Treatment"
- NIH: "Laetrile/Amygdalin (PDQ®)–Patient Version"
- Cochrane Database of Systematic Reviews: "Laetrile Treatment for Cancer"
- Cancer Research UK: "Laetrile (Amygdalin or Vitamin B17)"
- Memorial Sloan Kettering Cancer Center: "Amygdalin"
- FDA: "Products Claiming to 'Cure' Cancer Are a Cruel Deception"