Work Reviewed: Valenzuela-Gutiérrez, R., Lago-Lestón, A., Vargas-Albores, F., Cicala, F., & Martínez-Porchas, M. (2021). Exploring the garlic (Allium sativum) properties for fish aquaculture. Fish Physiology and Biochemistry, 47(4), 1179–1198. https://doi.org/10.1007/s10695-021-00952-7
Garlic. It’s a polarizing kind of vegetable. Some people can’t get enough, adding the allium to anything from pizza to ice cream and organizing community celebrations centered around it (I’m looking at you, Gilroy Garlic Festival). For others, the pungent veggie just a bit too much, and is best approached for its role in warding off vampires, rather than eating.
Love it or hate it, you may be surprised that garlic is attracting increasing attention in the world of fish aquaculture.
Aquaculture’s high concentrations increases the risk of disease
In industrial fish aquaculture, large numbers of fish are raised in high-density environments. In these conditions, fish are particularly vulnerable to disease transmission: bacterial infections, viruses, fungus, and parasites can spread rapidly when fish are reared at high concentrations. If you’ve heard of some of the disease concerns around terrestrial livestock, this should sound familiar. (And you’ve likely heard of some of these, especially those that go on to threaten human health: swine flu, for example, may have evolved in high-density hog farms before making the leap to human hosts.)
Production on this scale requires careful management of disease risk. Industrial aquaculture relies on antimicrobial pharmaceuticals to fight pathogens and keep fish healthy. However, this tactic is hamstrung by evolution: aquaculture pathogens are beginning to develop resistance to commonly-used antimicrobial drugs. That’s bad news for long-term disease management.
Garlic— a surprisingly powerful ingredient, when it comes to fighting pathogens— may help increase fish health as aquaculture accelerates into the future.
Alliin and Alliinase – a garlicky power couple
Garlic is a complex vegetable, made up of less water and more bioactive chemicals than most vegetables. A pair of compounds found in the garlic clove have a particularly important role to play in garlic’s health benefits.
Garlic cloves contain a compound called alliin, as well as the enzyme, alliinase. In an undisturbed garlic clove, these two compounds casually mind their own business, sequestered in different parts of the plant. But when the clove is cut or crushed, alliin comes into contact with allinase, and the result? Fireworks . Allinase cleaves alliin into pieces, creating allicin— a highly-unstable, highly-volatile firecracker of a compound. Allicin is responsible for the pungent garlic odor that hits you the moment you cut or crush a clove.
It’s also responsible for garlic’s pathogen-fighting punch.
The many virtues of allicin
Ready for a mouthful of beneficial garlic features? Allicin is associated with antibiotic, antiviral, antifungal, antiparasitic, and antioxidant properties.
In other words, allicin— and other garlic compounds derived from allicin— can protect against bacteria (antibiotic), viruses (antiviral), fungus (antifungal), parasites (antiparasitic), and the harmful free radicals that can break down fats, proteins, and DNA (antioxidant).
This makes allicin attractive for aquaculture, which is affected by all these concerns.
Researchers have begun studying the effects of incorporating garlic into aquaculture. While aquaculturists can’t very well offer a fish a plate of garlic bread or an aioli dip, they can add garlic cloves, powder, or oil into industrial fish feeds. They can also bypass getting the fish to eat garlic, and simply infuse it into the water the fish are raised in.
Whether introduced through fish diets or environments, adding garlic has shown a decidedly positive effect on reducing or preventing pathogen infections. In several studies, fish fed garlic have shown higher survival levels than fish not fed garlic; their survival has been attributed to the garlic’s contribution to fighting off pathogen infections. In another study, parasitized fish swam through a garlic bath. After a few minutes in the garlicky water, the external parasites were killed, leaving the fish parasite-free.
Allicin is associated with stimulating the immune system, promoting growth, and supporting healthy gut microbiomes in aquaculture fish, too. Accumulating evidence tends to agree that fish reared with garlic often end up healthier and bigger than fish without— and that is the sort of intervention that means a lot for the aquaculture industry.
Where do we go from here?
Of course, there is no such thing as a cure-all for improved fish health. Indeed, while garlic seems to have positive impacts on pathogen infections and immunity, it has also been associated with decreased reproduction and loss of muscle mass— nothing’s perfect. Besides which, the high concentrations of fish in industrial aquaculture may just present too much of an opportunity for pathogens to spread and evolve drug resistance, no matter how much garlic you add.
Nevertheless, it’s clear that garlic has a lot of benefits for fish raised in aquaculture conditions, and as the industry continues to expand it will doubtless increase research and understanding of the powerful vegetable.
It’s a happy day for garlic lovers. Sorry, vampires.
Hello! I’m a third-year PhD student at University of California, Davis, in the Center for Environmental Policy and Behavior. My research focuses on how coastal communities make decisions around climate change adaptation. I’m lucky to get to explore this question across the West Coast (school!) and the East Coast (home!). When not PhD-ing, I’m happiest when reading, writing, backpacking, or gazing at the sea– whether that’s the Pacific or the Atlantic.