Garlic has quite the reputation. For many cooks, it’s the go-to addition that transforms bland and flavourless dishes into delicious feasts.
But it’s not just its tasty properties that garlic is renowned for. For thousands of years, people have turned to this humble bulb for its supposed health benefits, using it to treat everything from infections to digestive issues.
Today, this tiny but mighty ingredient is lauded for anti-cancer properties, anti-inflammatory effects and – perhaps most prominently – improving cardiovascular health by reducing cholesterol in the blood.
It’s not just a staple of the home cook’s larder – it’s a functional health booster, sold to wellness enthusiasts in powdered, concentrated supplements.
But does it actually lower cholesterol?
While there has been a lot of research suggesting that this ingredient is beneficial to our bodies, the science of garlic’s cholesterol-busting abilities is far from clear-cut.
Almighty allicin
Cholesterol – particularly LDL or ‘bad’ cholesterol – causes the build-up of fatty plaque deposits in our arteries, which can then lead to heart disease. The World Heart Federation estimates that high cholesterol is responsible for 3–4 million deaths every year.
Lowering cholesterol is one of the easiest routes to dramatically reducing a person’s risk of heart disease.
One of the ways that garlic could help to lower cholesterol is through its sulphur-containing compounds, specifically one named allicin.
Garlic doesn’t actually contain allicin in its raw, unprocessed form. It needs to be crushed or cut first to break down its cell walls, which releases various other compounds and enzymes.
“When crushed, it reacts with the air to make allicin, which gives garlic its pungent smell, taste and potential health benefits,” says Dell Stanford, senior dietitian at the British Heart Foundation.
Once crushed, it takes about 10 to 15 minutes for the allicin to form.
“Garlic contains an impressive array of bioactive compounds, like allicin,” Stanford says.
According to Stanford, lab studies have found these compounds, “appear to have antioxidant and anti-inflammatory effects, plus they may modestly influence cholesterol metabolism and reduce blood pressure – hence the long association with heart health.”
Most cholesterol in our bloodstream isn’t from what we eat. It’s actually created by our livers. Allicin can hold back the liver from forming cholesterol by affecting the enzyme HMG-CoA reductase (HMGCR). This is the same enzyme targeted by cholesterol-lowering statin medicines.
Allicin and other compounds in garlic may also lessen the absorption of cholesterol in the intestines and increase cholesterol breakdown and excretion from the body.
A complicated compound
Working out how to best take advantage of garlic’s potential cholesterol-busting power is where the science gets tricky.
As with anything in nutrition research, it can be difficult to zero in on the effects of a single foodstuff and be confident that it’s having a potent effect.
The research on garlic and cholesterol offers a mixed picture on the relationship between the two. Some papers have shown a measurable reduction in overall cholesterol and LDL after taking some form of garlic. Others have concluded there is little to no effect.
The mixed results are partly due to the various forms of garlic that are out there – and the different ways scientists have tested them, says Stanford.
“It’s a big leap from being able to demonstrate mechanisms in cells in laboratory studies to demonstrating meaningful benefits in humans,” she says.
“Although garlic has been heavily researched, human studies use different forms of garlic – fresh garlic, garlic powder, extract, oil and supplements, as well as aged and black garlic – in different doses, for different lengths of time in different numbers and types of people. This makes it very difficult to compare and interpret studies.
“What’s more, garlic seems to have a slightly larger effect on people with existing raised cholesterol and a lesser effect on healthy people.”
Allicin is also unstable. Once it has formed, it degrades rapidly – you need to consume it quickly for it to have a chance to work in the body.
In short, it’s no good just eating a whole clove of garlic every day. It has to be prepared in the right way.
How to garlic
Let’s start with the stuff that most commonly goes into our recipes: fresh white garlic.
When cooked, research shows that garlic is significantly less powerful in the body. So to enjoy the cholesterol-lowering benefits, you’re better off crushing fresh garlic into a salad than throwing a few cloves into a bolognese.
There are other types of garlic, of course. Aged black garlic is attracting the interest of researchers and gourmands alike.
“It’s biochemically quite different to fresh garlic,” Stanford says. “Following the fermentation process, aged and black garlic contains much less allicin, but more polysulfides such as S-allycysteine (SAC).
“This compound is more stable and less volatile than allicin and it’s being used to make standardised garlic preparations for use in studies.”
Some of those studies have shown early promise for black garlic in improving the blood fat management of people who take it. It’s also been shown to be effective at reducing blood pressure.
A third possibility is garlic-based supplements. Garlic’s reputation as a superfood has inevitably led to companies creating and selling capsules, powders and oils that contain concentrated levels of allicin, SAC and other compounds.
Of these, ‘kyolic’ garlic is the most powerful, says Prof Karin Ried, director of research at the National Institute of Integrative Medicine in Australia.
“Kyolic aged garlic extract is the most potent and delivers a stable dosage for cardiovascular benefits,” she says. “Dietary intake is good for the immune system but doesn’t contain the dosage required for vascular benefits.”
Ried’s research on kyolic aged garlic found that it could also reduce blood pressure in patients with hypertension, as well as having the potential to improve arterial stiffness, inflammation and gut microbial profile.
One note on the supplements lining shelves in health food stores: you might notice that the packaging and marketing rarely claims these products lower cholesterol. Instead, it’ll say something like it “supports normal heart function”.
That’s because, again, the research is early, scrappy and mixed, Stanford says.
“Although some studies suggest that garlic supplements have the potential to lower cholesterol levels, the evidence is too limited and inconsistent to recommend taking them for any health benefits.
“Current UK dietary guidelines do not recommend taking garlic supplements; it’s much better to include fresh garlic as part of a healthy diet.”
The (flavourful) verdict
Remember that lowering cholesterol is only important for people whose levels are already high, and for some who have specific cardiometabolic conditions.
“Cholesterol is needed in the body as a building block for vitamin D and steroid hormone production,” Ried says.
“Also, the brain consists of 60 per cent fat, mainly cholesterol. Therefore, you don’t want to reduce your cholesterol levels too much, but rather balance [HDL and LDL] cholesterol.”
Garlic is an undeniably healthy ingredient to have in your cupboard and your diet, but the research on its ability to lower cholesterol is mixed – particularly in the forms that most of us consume.
Researchers stress that more long-term research is needed with standardised ways of ingesting it.
With the possible exception of pungent breath, there’s no real downside to increasing the amount of garlic in your diet. Just don’t think of it as medicine.
“Enjoy fresh white or aged black garlic to flavour your food; they contain bioactive compounds that may help keep you healthy,” Stanford says.
“Following a balanced, healthy diet is a much more evidence-based way to lower your cholesterol. Be sure to include porridge oats, beans, wholegrains, fruit and vegetables and unsaturated fats from olive or vegetable oil, nuts and seeds and oily fish.”
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