Garlic science lacking for cancer health claims: Researchers

By Stephen Daniells

- Last updated on GMT

Related tags Garlic supplements Cancer

No “credible evidence” exists in the literature to support the potential of garlic to reduce the risk of cancer, according to a new review from Korea.

Despite numerous animal and in vitro​ studies reporting a role for garlic in cancer reduction, the human evidence is lacking. Therefore no health claims regarding garlic and cancer can be made, state the Korean researchers.

These conclusions were based on use of the US Food and Drug Administration's system for the scientific evaluation of health claims. Ji Yeon Kim and Oran Kwon from the Korea Food and Drug Administration and Ewha Women's University, respectively, report their findings in the new issue of the American Journal of Clinical Nutrition.

In an accompanying editorial, Richard Rivlin from Weill Cornell Medical College in New York says that the findings should “serve as a stimulus to extend and broaden the interventional approaches to risk reduction by the use of garlic in susceptible populations, and eventually in the general public”​.

Health claims is a massive subject across the world, but particularly in Europe, as the Commission moves to make sure that any claim can be substantiated by scientific studies.

Under the health claims regulation, companies that want to make a claim about what a product can do must have it supported by science. The European Food Safety Authority is evaluating thousands of dossiers before a final decision for an approved list is taken in 2010.

Garlic supplements are worth more than $100m (€79.5m) in the US and are also one of the biggest sellers in the UK market.

Review details

Kim and Kwon searched the literature using Medline and Embase and found 19 human studies that met the inclusion criteria. Studies in both English and Korean were considered.

They concluded that no “credible evidence” exists to support a potential protective role for garlic and various forms of cancer, inclusing breast, gastric, lung, or endometrial cancer.

A small but limited amount of evidence was found to support a relation between garlic and reduced risks of prostate, colon, oral, oesophageal, larynx, kidney, and ovary cancers, they added.

“The number of […] trials that are considered scientifically sound in this analysis is remarkably few, and the number of subjects involved is generally small,”​ said Rivlin. “Thus, the very strict criteria required to make a health claim may not be met by the limited number of studies conducted to date that are currently available.”

Counting chickens before they hatch

Garlic’s role as a potential cancer-preventing agent has already sparked controversy. At the start of 2008, the British Advertising Standards' Agency (ASA) investigated a complaint from the Health Food Manufacturer's Association against Simply Supplements. The company’s adverts reportedly claimed that garlic supplements have a plethora of benefits including inhibiting cancer cell growth.

Following the ASA’s probe, which concluded that the claims had not been substantiated and the advert was therefore misleading, Simply Supplements said it would remove the advert and not use it again.

Source: American Journal of Clinical Nutrition​ January 2009, Volume 89, Number 1, Pages 257-264, doi:10.3945/ajcn.2008.26142"Garlic intake and cancer risk: an analysis using the Food and Drug Administration's evidence-based review system for the scientific evaluation of health claims"​Authors: J.Y. Kim, O. Kwon

Editorial: American Journal of Clinical Nutrition​ January 2009, Volume 89, Number 1, Pages 17-18, doi:10.3945/ajcn.2008.27181"Can garlic reduce risk of cancer?"​Authors: R.S. Rivlin

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