Ever wonder why your grandmother tossed a few extra cloves of garlic into the soup pot whenever someone caught a cold? Turns out she wasn't just chasing flavour — garlic has been studied for decades for its effects on cholesterol, blood pressure, and more. Let's separate the folk wisdom from what the research actually shows.
Garlic (Allium sativum) is a bulb vegetable in the same plant family as onion, leek, and shallot — the aromatics that form the base of so much Southeast Asian cooking, from a simple sambal to the fragrant oil poured over char kway teow. When you crush or chop a clove, an enzyme reaction produces a compound called allicin, which is responsible for garlic's sharp smell and much of its studied activity.
People have used garlic for both cooking and health purposes for thousands of years, with ancient writings from Egypt, Greece, and India describing its use for a variety of health problems, such as headache, pneumonia, throat conditions, and gastrointestinal disorders. Today it's sold as raw cloves, garlic powder, aged garlic extract, and standardised supplement tablets, and it's currently promoted as a dietary supplement for helping manage high blood cholesterol, high blood pressure, and diabetes, along with claims around cancer prevention and immune support.
This is where garlic has the strongest track record. Research consistently shows garlic supplements may reduce levels of total cholesterol and low-density lipoprotein (LDL) cholesterol to a small extent in people who have high blood cholesterol levels. A closer look at the evidence found that a 2016 meta-analysis of 39 randomized controlled trials involving 2,300 participants found garlic effective in reducing total cholesterol and LDL-C by around 10 percent if taken for more than 2 months by people with mildly elevated levels. It's worth being realistic, though — a review concluded that garlic supplements can lower cholesterol if taken for more than 2 months, but their effect is modest compared with cholesterol-lowering medication. For someone juggling chicken rice, char kway teow, and the occasional laksa, garlic isn't a fix for a high-fat diet, but it may offer a small supporting nudge alongside proper meals and movement.
Limited evidence suggests that garlic supplements may reduce blood pressure to a small extent in people who have high blood pressure. A dedicated review of the data found that a 2015 systematic review and meta-analysis of nine double-blind trials involving 482 participants found some evidence suggesting that garlic preparations may lower blood pressure in hypertensive individuals, though the evidence is not strong. This matters in a region where hawker fare like char kway teow and laksa often runs high in sodium — garlic won't cancel that out, but it's a reasonable everyday addition rather than a reason to avoid seasoning altogether.
Garlic has also been studied for its effect on blood glucose. Findings suggest taking garlic powder by mouth seems to reduce pre-meal blood sugar levels by a small amount in people with or without diabetes, working best when taken for at least three months. It's a modest effect rather than a substitute for medical management, but it adds to garlic's overall profile as a food with mild metabolic benefits — relevant given how common Type 2 diabetes is across Singapore and Malaysia.
Garlic's reputation as a cold-fighter is popular, but the science is more cautious here. A Cochrane review concluded there is insufficient clinical trial evidence regarding the effects of garlic in preventing or treating the common cold, though garlic is probably safe for most people in the amounts usually eaten in foods, while supplements may increase bleeding risk, so people on blood thinners should use caution. Garlic does contain allicin, a compound with recognised antibacterial properties, which is part of why it's been used traditionally against infections for centuries — but that's different from proven cold prevention in a bottle of capsules.
How you prepare garlic changes what your body actually gets from it. Allicin doesn't exist in a whole clove — it only forms once you crush, chop, or chew garlic, triggering an enzyme reaction. Cooking garlic quickly destroys the allicin that does form, since heat causes it to break down into other sulphur compounds, many of which remain physiologically active in their own right. This means a fresh, raw, crushed clove stirred into a dip delivers a different mix of compounds than the fragrant, oil-fried garlic bits scattered over a bowl of ban mian.
Supplement forms vary too. Standardised garlic powder tablets are formulated to release their active compounds in the gut, and research comparing different preparations found that cooked or acidified garlic foods actually gave higher allicin bioavailability than expected — boiled, roasted, and pickled forms all showed measurable absorption, while black garlic showed very little. In practice, this means there's no single "best" way to eat garlic for benefits — raw, cooked, and aged forms each bring a slightly different chemical profile to the table.
For most people, garlic eaten as food is considered safe — after all, it's been part of daily cooking across cultures for millennia. The main day-to-day downsides are cosmetic and digestive: breath and body odor, heartburn, and upset stomach, which tend to be more noticeable with raw garlic.
Concentrated garlic supplements are a different story and deserve more caution. Some people have allergic reactions to garlic, and taking garlic may increase the risk of bleeding — this matters especially for anyone on blood-thinning medication, as garlic is among the nonprescription or herbal products that may interact with warfarin. Garlic supplements have also been shown to interfere with certain prescription drugs, since garlic has been found to interfere with the effectiveness of some drugs, including saquinavir, a medication used to treat HIV infection. Because of the bleeding risk, it's sensible to stop garlic supplements before any planned surgery or dental procedure and to flag garlic use to your doctor beforehand — the same caution NCCIH gives around anticoagulants and aspirin applies here.
One safety note that surprises many people: raw garlic should never be applied directly to skin as a home remedy. Fresh, raw garlic contains chemicals that can burn the skin, and pure garlic essential oil shouldn't be applied undiluted either. Cases of genuine chemical burns from garlic poultices — a folk remedy still used in some households — have been documented in medical literature, so if you're tempted to try this for a sore throat or muscle ache, it's worth skipping.
People with allergies to onion, leek, or chives should also be cautious, since garlic is closely related to these plants, and people allergic to them may be more likely to react to garlic too. Pregnant or breastfeeding women should stick to food-level amounts rather than concentrated supplements, and anyone with an upcoming health screening — increasingly common thanks to HPB's push for regular checks — should mention any supplement use to their doctor.
Garlic earns its place as one of the more evidence-backed kitchen ingredients — not as a miracle cure, but as a small, consistent supporting player for heart health, blood sugar, and everyday cooking flavour. Whether it's minced fresh into a sambal, fried until golden for a bowl of noodles, or taken as a standardised supplement, the effects tend to be modest and cumulative rather than dramatic. For most people in Singapore, Malaysia, and beyond, the simplest approach is also the most sensible one: keep using garlic generously in your everyday cooking, and if you're considering a concentrated supplement on top of that, have a quick chat with your doctor first — especially if you're on blood thinners or have surgery coming up.
This article is for general informational purposes and is not a substitute for professional medical advice. Please consult a qualified healthcare professional before making any changes to your diet or supplement routine.
Ask Elaine how this applies to your goals and routine — free, no pressure.