High Strength Horseradish & Garlic Complex

Garlic is well tolerated and does a few small, useful things. These are the questions our naturopaths ask in store, which are mostly about matching the form to what you want.

A good fit if

• You want winter immune support and you'll take it right through the season
• You're after general heart and cholesterol support and you know the effect is small
• You're happy to take it for months rather than weeks
• You want aged garlic extract specifically, which is the form used in the immune trial

Check with us first if

• You take warfarin or another blood thinner. Garlic may add to the effect, and the evidence is mixed on which way it goes.
• You take antiplatelet medicine or have a bleeding disorder.
• You have surgery coming up. The published advice is to stop high doses 7 to 10 days beforehand.
• You take diabetes medicine, because garlic lowers fasting blood sugar on its own.
• You take HIV medicine. Garlic reduces the effect of saquinavir.
• You're pregnant or breastfeeding. There's no evidence either way for this yet.
• It's for a child. The permitted cold and flu wording comes with its own label statement for adults only or children under 2.

• Fresh clove (item 2307). Best known for: Food-level use, and the reference point for dose. Absorption: Allicin forms on crushing, not in the intact clove. Typical use: About 2.7 g a clove; almost no trials actually used fresh cloves.
• Garlic powder tablets (items 2306, 2308, 2309). Best known for: The most-trialled form for cholesterol and heart support. Absorption: Usually standardised to allicin-yielding potential. Typical use: 900 mg a day is roughly one clove; this is also the form in both clean negative trials.
• Aged garlic extract. Best known for: The immune and cold-severity evidence. Absorption: Ageing converts harsh sulfur compounds to water-soluble S-allyl-cysteine. Typical use: 2.56 g a day in the cold-season trial; not a Schedule 1 name, so it maps to items 459, 2306 or 2307.
• Aged black garlic. Best known for: Milder taste, same S-allyl-cysteine marker. Absorption: Heat-and-humidity ageing. Typical use: One triple-blind trial, small effects, in people already on medication.
• Garlic oil (item 2310). Best known for: A distinct steam-distilled entity. Absorption: Allyl sulfides rather than allicin. Typical use: This is the form with the documented enzyme interaction: it inhibited CYP2E1 by about 22% in older volunteers.
• Odourless or deodorised. Best known for: Sticking with it for months. Absorption: No cached trial compares its allicin release with plain preparations. Typical use: They exist because tolerance for raw garlic is low; we can't tell you they work as well.
• Wild garlic (Allium ursinum, item 461). Best known for: A different species entirely. Absorption: Separately scheduled. Typical use: Garlic evidence doesn't transfer to it.

Reference values. There's no recommended intake for garlic. It's a food and a herb rather than a nutrient, so the NHMRC doesn't set one.

Typical supplemental range. Trials have used anywhere from 80 mg to 4,000 mg a day, for 2 to 24 weeks. The cold-season trial used 2.56 g a day of aged garlic extract for 90 days. Most cholesterol trials used 900 mg a day of garlic powder, which that research put at roughly one fresh clove.

Upper level. Australia's permitted ingredients list (Schedule 1) sets no daily maximum for garlic, and there's no NHMRC upper limit. The highest dose used in the trials we looked at was 4,000 mg a day.

Worth knowing. One review found the cholesterol effects were clearer with lower doses taken for longer, so think months rather than megadoses. We haven't checked every Australian label against the trial doses, so we can't tell you a given product matches them. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Fresh garlic clove: about 2.7 g; 900 mg of garlic powder was described in trial as equivalent to roughly one clove
• Other allium vegetables (onion, leek, chives): separately scheduled ingredients; studied as a dietary category for cancer risk with a null result

This list is the part of the page we will not shorten. If any of it applies to you, talk to one of our naturopaths or your doctor before starting.

• Anticoagulants such as warfarin. Garlic may enhance the effect. One systematic review of trial-level data found no significant change to warfarin's pharmacokinetics, another review of case reports found decreased warfarin concentrations. The evidence conflicts, so this goes to your prescriber.
• Antiplatelet medicines, and anyone with a bleeding disorder. Garlic can alter platelet function and coagulation.
• Before surgery. Published clinical advice is to stop high doses 7 to 10 days beforehand, because garlic can prolong bleeding time.
• Anti-HIV medicines. Garlic reduces the efficacy of saquinavir.
• Glucose-lowering medicines including chlorpropamide. Additive hypoglycaemia has been reported, and garlic lowers fasting glucose and HbA1c on its own.
• Allergy. Allergic contact dermatitis, urticaria, angioedema, pemphigus, anaphylaxis and photoallergy are all recorded, rarely.
• Never put fresh garlic on skin, especially under a dressing. It causes chemical burns.
• Narrow-therapeutic-index medicines generally, including ciclosporin and digoxin. Garlic oil specifically inhibited CYP2E1 by about 22% in older volunteers.
• Breastfeeding. Garlic in a mother's diet changes infant behaviour at the breast. No pregnancy or breastfeeding safety data was located either way.
• Everyone. Breath and body odour are the most consistently documented complaints in trials, along with rash.