L-Lysine

People buy lysine for three different reasons, and the evidence really only speaks to one of them. These are the questions our naturopaths ask in store.

A good fit if

• Cold sores are why you're looking, and you're willing to take the dose used in the trials rather than one tablet
• You eat little meat, fish, dairy or legumes, which is where a real shortfall can happen
• You know the evidence is mixed and want the detail rather than a slogan
• You'd rather use the powder to reach several grams a day than swallow three tablets

Check with us first if

• You're pregnant, breastfeeding or planning a pregnancy. We found no supplement trials in these groups, and that's a gap, not a reassurance.
• It's for a child or teenager. Two products in our range are marketed to young people, and there's no trial in children behind them.
• You have kidney problems. There's a case report we couldn't get hold of and check, so we won't describe it or guess.
• You already take prescribed calcium. Lysine raised calcium absorption from the gut in the one study that measured it.
• You take a pre-workout or nitric oxide formula, which usually contains arginine.
• You're thinking about more than 6 g a day, which is above the point the safety reviews cover.
• You're buying it for anxiety or muscle. Neither result comes from lysine on its own.

• Lysine (Schedule 1 item 3111). Best known for: The plain amino acid, and the usual form in most Australian products. Absorption: We found no trial comparing it directly with the hydrochloride. Typical use: Allowed in listed medicines with no specific requirements, no warning statement, no dose limit and no restriction on how it's taken.
• Lysine hydrochloride (Schedule 1 item 3112). Best known for: Cold sores. Both of the trials that matter used L-lysine monohydrochloride. Absorption: The same gap; we found no comparison trial. Typical use: It's a salt, so part of the weight on the label is chloride, and the lysine per tablet is lower than the number on the front unless the label says otherwise.
• "L-lysine" (the name on most labels). Best known for: All uses; the L- describes the molecule's shape, and it isn't a separate ingredient in law. Absorption: Not applicable. All the lysine your body uses from food is the L-form. Typical use: Schedule 1 lists LYSINE and LYSINE HYDROCHLORIDE; there's no L-LYSINE entry, and products labelled that way are legal.
• Powder. Best known for: Getting to grams a day without swallowing three tablets. Absorption: No trial has compared powder with tablets. Typical use: This is practical reasoning rather than clinical: the trial dose is easier to reach with a scoop.
• Zinc, magnesium, calcium and copper lysinate. Best known for: Delivering the mineral; the lysine is the carrier and the mineral is the active. Absorption: The finding on lysine and calcium absorption used free lysine plus a dose of calcium, not calcium lysinate, so it doesn't carry over. Typical use: Calcium and magnesium lysinate are for medicines taken by mouth only; zinc lysinate is capped at 50 mg of zinc a day and copper (II) lysinate at 5 mg of copper.
• Hydroxylysine (Schedule 1 item 2654) and lauroyl lysine (item 2953). Best known for: Neither is a lysine supplement you swallow. Hydroxylysine is a modified lysine found in collagen, and lauroyl lysine is an ingredient used in skin products. Absorption: None found for either. Typical use: We found no human supplement trial of hydroxylysine; lauroyl lysine is for the skin only, not for the eye or damaged skin, at 5.0% or less.

Reference values. There isn't one. The NHMRC sets requirements for protein, not for individual amino acids, and has no figure for lysine. The international figure used in research is the FAO/WHO/UNU requirement of 30 mg per kilogram a day. That's about 2.1 g for a 70 kg adult, which an ordinary mixed diet covers easily.

Typical supplemental range. Australian products are commonly 1,000 to 1,200 mg a tablet. That figure comes from the product names in our range rather than label data, so read the pack. The trial doses are more useful. For cold sores, the trial that worked used 1,000 mg three times a day (3 g) for six months. The same research found 1,000 mg a day made no difference to how often cold sores came back, and a 2017 review put the useful dose above 3 g a day. A study on muscle protein used about 80 mg per kilogram a day, roughly 5.6 g for a 70 kg adult.

Upper level. Australia's permitted ingredients list (Schedule 1) sets no maximum daily dose for lysine. Two systematic reviews covering 71 studies set a provisional safe level of 6 g a day for healthy adults, based on gut symptoms rather than anything serious. That's guidance, not a legal limit, and the authors of the 6 g trial note that safety above that amount, or beyond eight weeks, isn't known.

Worth knowing. With lysine, the dose is everything. One tablet a day is the dose that failed in trials, so any mention of the cold sore evidence needs to include the dose that produced it. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Beef, skirt steak: 5,619 mg per 170 g: about five 1,000 mg tablets
• Chicken breast, lean: 5,241 mg per 170 g
• Tuna: 4,670 mg per 170 g fillet
• Tofu, firm: 2,225 mg per cup
• Milk: 1,382 mg per 475 mL
• Navy beans, canned: 1,381 mg per cup

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Pregnancy, breastfeeding or planning a pregnancy. We found no trial of lysine supplements in any of these groups.
• Children and teenagers, including products sold as growth or step-up formulas. We found no trial in children.
• Kidney problems. There's a case report about the kidneys that we couldn't check, so talk to your doctor.
• If you already take prescribed calcium, because lysine increased how much calcium was absorbed in the one study that looked.
• If you take pre-workouts containing arginine, because the two amino acids share the same transport route.
• Doses above 6 g a day, where there's no published safety data at all.
• Expecting it to work at one tablet a day, which is the dose that failed.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.