The Statement
A social media meme extolling the health benefits of black garlic claims that it helps to prevent 14 types of cancer.
The Facebook post features a picture of a dissected head of black garlic and text that reads: “Black garlic has 2X the antioxidant level of white garlic. It helps prevent 14 types of Cancer and has powerful healing benefits.
At the time of publication, the December 16 post from a user in Australia had gathered more than 200 shares, 530 reactions and 18,000 views. The Instagram account credited in the meme had been liked more than 28,400 times.
The Analysis
Black garlic is garlic that has been fermented with heat – and while it may not give you bad breath like the raw product, the post’s claim that it can prevent cancer carries only a faint whiff of truth.
Black garlic has been consumed for centuries in countries such as South Korea, Japan and Thailand. It is produced when a raw garlic bulb is heated at a moderate temperature (60-90C) in a high-humidity environment for an extended period, fermenting the product and turning its cloves black.
According to a WebMD article, the “garlic’s texture and flavour change as well. It’s softer, chewier, and sweeter than regular raw garlic”.
Regarding health benefits, a South Korean laboratory study in 2016 noted that aged black garlic had been shown to have “strong anti-oxidant activity” in numerous pieces of research.
It found that a black garlic extract cut “reactive oxygen species“, or so-called free radicals that can cause cellular damage, to less than half the levels found when a raw garlic extract was used (figure 1). However, the study identified that raw garlic demonstrated higher anti-inflammatory properties (figure 2).
Studies in mice and rats also demonstrated black garlic’s potential anti-allergic and anti-cholesterol effects.
A 2014 laboratory study found aged black garlic extract (ABGE) may reduce colon cancer cell growth, while an earlier study using mice showed black garlic helped prevent the growth of gastric cancer cells. However, both concluded that further assessment in clinical trials was needed.
Another 2014 laboratory study using cell samples reported that black garlic had potential therapeutic value in the treatment of leukemia.
On the benefits of garlic more broadly, the American Institute for Cancer Research said that while laboratory research showed allium compounds in garlic offer anti-cancer activity, “support for garlic lowering cancer risk is lacking in human studies”.
“Questions remain on how well humans absorb the allium compounds formed from garlic, and the amount people need to experience the benefits that lab studies suggest may occur,” it noted.
Experts contacted by AAP FactCheck said there is no robust evidence to support the claim that black garlic helps prevent 14 cancers.
Tom Gonda, adjunct research professor at UniSA Cancer Research Institute, said he was sceptical of such claims as those contained in the meme.
“I’m generally sceptical about claims around one ‘super’ or ‘miracle’ food or another preventing or curing cancer,” Prof Gonda told AAP FactCheck in an email.
“Usually they’re based on limited or unreliable data, and rarely have any plausible mechanism of action behind them. The best evidence for reducing cancer risk – not eliminating it – is around the things most people already know: healthy and balanced diet, exercise, avoiding obesity, and so on.”
Kathryn Bradbury, a senior research fellow at the University of Auckland and expert in nutritional epidemiology, said evidence about garlic’s influence on tumour development was lacking in human studies.
“There is some evidence from laboratory-based studies that garlic may influence tumour development, and studies in rodents have shown that some garlic extracts may inhibit cancer,” Dr Bradbury said via email.
“However, the evidence from human studies is not convincing. Several studies have followed thousands of people over time to see if those who eat more garlic are less likely to develop cancer.
“The results are mixed: there is no consistent evidence from these long-term studies that people who eat more garlic are less likely to get cancer.”
A 2015 article by US academics published in Cancer Prevention Research noted that epidemiological studies showed “some protective associations” associated with alliums – which include onions and garlic – however problems in assessing people’s consumption made research difficult.
“If garlic consumption does reduce the risk of cancer, the amount needed to lower risk remains unknown,” the article said.
Dr Bradbury agreed that black garlic has a different composition to white garlic, however “most human studies have not examined them separately”.
“The World Cancer Research Fund systematically reviews all the evidence on food and cancer and concludes that non-starchy vegetables (which include garlic but also green, leafy vegetables and cruciferous vegetables like broccoli) probably decrease the risk of aerodigestive cancers and some other cancers.
“The specific claim that black garlic can reduce 14 types of cancer is not currently backed up by robust evidence.”
Memes containing similar claims to those in the post have been addressed here and here.
The Verdict
There is no conclusive medical evidence that black garlic can prevent 14 different types of cancer as claimed in the Facebook post, although there are studies that suggest it has stronger antioxidant properties than raw or white garlic.
Experts told AAP FactCheck there is a lack of robust proof of garlic’s anti-cancer properties based on human studies.
Partly False – Content that has some factual inaccuracies.
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