Happy #FactFriday everyone!
I'm coming at you with some more myth-busting, today it's about garlic!
Garlic is an allium vegetable. Alliums contain a range of nutrients that many claim have health benefits. There is some research that indicates garlic consumption may decrease risk of certain cancers.
However there are some concerns with the research.
Firstly, the strongest evidence in support of garlic’s health benefits is research carried out in animals or in vitro* (see below) rather than in humans. This makes it difficult to assess its true impact in our populations.
Another problem is that different forms of garlic are used in most studies- from raw garlic, to garlic capsules (containing powder) to garlic oil. The use of different processing methods means that studies are difficult to compare.
Additionally, these processes change nutrient content and affect the bioavailability of the active ingredient allicin.
The research often fails to account for many potential confounding factors, such as physical activity, socioeconomic status, other foods consumed, education level and many more factors we know affect health and disease risk.
The EPIC-EURGAST study (Gonzalez et al. 2006) assessed consumption of a range of foods and cancer incidence in a large population. They note that a reduction in risk of intestinal cancers was associated with increases in vegetable, garlic and onion consumption. However, self-administered questionnaires were used to assess dietary intakes at the point of enrollment to the study. Self-administered questionnaires are associated with many issues, including higher estimations of “healthy” food consumption. Additionally, this methodology did not account for dietary or lifestyle changes throughout the follow-up period (6.5 years), which may have affected the results.
Kim & Kwon (2009) concluded that they “found no credible evidence to support garlic”, with regards to reduction in risk of gastric, breast, lung or endometrial cancer.
Another review by Silagy & Neil (1994) assessed only randomised controlled trials using garlic powder and found insufficient evidence for its effectiveness.
Fleischauer & Arab (2001) noted several problems with the literature in their review, including low study power, poor adjustment for confounders, publication bias and a high proportion of animal and in vitro studies.
I could find no literature to convince me of any benefit to regular allicin or garlic supplementation. These supplements can be expensive and there is some concern regarding the safety of these products for long-term use. Aside from the burping, flatulence, reflux and bad breath that many people experience, some studies indicate potential drug interactions, which can be dangerous. Please do not opt for supplements if you are on any medication without the supervision of a healthcare professional.
As mentioned above, different processing affects the content- so we know very little about many of the supplements available on the high street. We don't know how or where the original garlic was grown, when and how it was harvested, how it was stored before use, the specifics of the processing etc. But all things all affect the product.
(Note: this is the case with many food supplements available on the high street- we aren't and can't be 100% sure what's in them).
We are not yet sure of any true benefits from allicin or garlic, more research is needed. In nutritional science, it takes years to gather enough good quality data and for consensus to be achieved among researchers, academics and professionals.
The best thing we can all do for health is aim for a varied diet that contains a range of vegetables, fruit, wholegrains, dairy, protein, fat and a bit of the foods that you love.
Take home message:
It is important to remember that studies such as those mentioned here show us associations, but do not prove causation.
Include garlic in your diet if you enjoy it, but don't expect major health benefits from garlic alone. Single foods do not change our health (watch my video on that here).
Remember that most of the time supplements are unnecessary, but expensive. The main result is generally expensive urine!
*in vitro means "in glass" in Latin. The term is used to describe experiments and studies done on cells outside an organism. E.G. in vitro fertilisation.
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