L-Lysine

What it is

Lysine is one of the protein building blocks that the body cannot make itself. Adults need about 30 mg per kilogram of body weight per day, children 40 mg, infants up to 130 mg. A Western diet usually provides 3 to 7 g per day, that is, considerably more. Rich in lysine are meat, fish, eggs and dairy products, and among plant foods mainly legumes and nuts. Cereals, rice and corn contain little; lysine is even the first limiting amino acid in cereals.

In the body, lysine is more than building material. Carnitine is made from it, which shuttles fatty acids into the mitochondria. In collagen it is converted to hydroxylysine, and in elastin it cross-links the fibers. As a supplement, lysine is usually sold as lysine hydrochloride in tablets or capsules, often also combined with zinc or plant extracts in herpes products.

How it is supposed to work

The herpes thesis goes back to the US physician Griffith and his research group. Herpes simplex viruses need a lot of arginine to replicate. In cell culture, arginine deficiency slowed replication, and lysine, which is chemically similar to arginine, acted as an antagonist. The reasoning: more lysine in the blood displaces arginine from the cells, and the virus has a harder time getting going. This also gave rise to the advice to avoid arginine-rich foods such as nuts, whole grains and legumes and to pay attention to a favorable lysine-arginine ratio.

The second big idea comes from Matthias Rath and Linus Pauling. They regarded lipoprotein(a), a blood lipid that is particularly damaging to blood vessels, as a surrogate for vitamin C in species that cannot make it themselves. In early 1991 came the suggestion that additional lysine could suppress the binding of Lp(a) to the arterial wall. This became the so-called Pauling therapy with vitamin C and lysine against arteriosclerosis.

Smaller ideas concern bone, because lysine increased calcium absorption in one study, and mood, because lysine deficiency intensifies the stress response in animal experiments.

What users report

Among people troubled by herpes, lysine has a good reputation. In an early questionnaire survey of 1,543 respondents, who took an average of 936 mg per day, 84 % said lysine had prevented recurrences or made them less frequent, and 88 % considered it effective. Without a control group, this cannot be separated from chance, expectation and the natural ups and downs of herpes. The reports should still be taken seriously: they show how many people experience a noticeable improvement, and they fit with the positive studies using higher amounts.

What the studies show

Six months of lysine against herpes

Double-blind, placebo-controlled, multicenter: 1,000 mg of L-lysine 3 times daily for 6 months. 27 people on lysine and 25 on placebo completed the study. The lysine group had on average 2.4 fewer herpes episodes, milder symptoms and a shorter healing time, each statistically significant. The study comes from the group that founded the lysine thesis.

Dose comparison in a crossover

41 patients took placebo, 624 mg or 1,248 mg of lysine per day in random order. Only the higher amount reduced the recurrence rate. Neither amount shortened the healing time. This points to dose dependence and explains part of the contradictory results.

Cochrane review 2015

The analysis covered 32 randomized trials with 2,640 participants on 19 preventive measures against cold sores. For lysine, the authors found no evidence of efficacy. Only long-term use of antiviral tablets was clearly preventive, and even their clinical benefit was small.

Where the data stop

For herpes the picture is contradictory. The studies are small, with 21 to 52 evaluable participants, and almost all date from 1978 to 1987. A double-blind study with 21 patients and 400 mg 3 times daily found no benefit, and two further papers already state the failure in their title. The Cochrane review sees no evidence. The mechanism has also not been shown as a chain of action in humans. In cats, where lysine was popular in veterinary practice, it did not lower arginine, did not slow the virus in vitro and did not help clinically. And in a small investigation, herpes patients did not eat differently from healthy people, on average 8.11 g of lysine and 6.32 g of arginine per day.

Rath and Pauling’s heart thesis has never been tested in controlled studies. There is the 1990 hypothesis and 3 case reports that Pauling published in 1993. We have not found a controlled human study testing oral lysine on Lp(a), angina pectoris or heart attacks. For bone, lysine increased calcium absorption in a small short-term study; there are no clinical studies on protection against osteoporosis. Evidence for muscle building is lacking, and anyone who already eats enough lysine does not, by current knowledge, benefit from more.

Status, approval and legal

L-lysine is an essential amino acid and is on the market in Germany as an ingredient of food supplements. In 2013 the BVL (German Federal Office of Consumer Protection and Food Safety) explicitly permitted, by general administrative order, capsules from other EU states with 800 mg of L-lysine per day; there is no statutory maximum amount. In 2011 EFSA assessed applications for health claims on lysine, including immune defense against herpes viruses. Advertising with prevention or treatment of herpes is in any case not permitted for foods, because it concerns a disease.

Safety

Lysine is one of the well-studied amino acids. In 71 studies with amounts up to 17.5 g per day, the most common side effects were nausea, abdominal pain and diarrhea, without increased risk compared with controls. Experts propose 6.0 g per day as the NOAEL for healthy adults. There is, however, a case report of a 44-year-old woman who developed Fanconi syndrome with kidney inflammation under lysine, which progressed to chronic kidney failure, and in animal experiments high intravenous amounts damaged the kidneys. Anyone with kidney disease should therefore take lysine only after consulting a physician. A review also advises pointing out theoretical risks to people with cardiovascular or gallbladder disease. In animal experiments lysine was not harmful to the fetus; systematic data on supplementation during pregnancy and breastfeeding are missing. Because lysine can increase calcium absorption, it makes sense to keep an eye on this with very high calcium intake.

Sources

• Chi et al., Cochrane Database Syst Rev 2015 – prevention of cold sores, 32 RCTs
• Griffith et al., Dermatologica 1987 – L-lysine in frequently recurring herpes, multicenter RCT
• McCune et al., Cutis 1984 – 624 mg and 1,248 mg lysine in a crossover
• DiGiovanna & Blank, Arch Dermatol 1984 – no benefit from 400 mg 3 times daily
• Mailoo & Rampes, Integr Med 2017 – lysine for herpes prevention, review
• Hayamizu et al., Amino Acids 2019 – safety of oral L-lysine intake, systematic review
• Holeček, Int J Mol Sci 2025 – lysine: sources, metabolism, use as a supplement
• Bol & Bunnik, BMC Vet Res 2015 – lysine in feline herpes, systematic review
• Rath & Pauling, Proc Natl Acad Sci USA 1990 – lipoprotein(a) as a surrogate for vitamin C
• BVL general administrative order 13/01/004 – food supplements with L-lysine