L-Tyrosine

Our naturopaths talk tyrosine through with people every week, and the useful question in store is usually when you'd take it, not whether.

A good fit if

• You have a demanding stretch coming up and want your thinking to hold up through it
• You're choosing between focus or pre-workout products and want the one ingredient with trial doses behind it
• You're happy to take it before the hard days rather than every day

Check with us first if

• You take thyroid medicine, like levothyroxine or liothyronine. Tyrosine is a building block for thyroid hormone and may change how much your body has.
• You have liver problems. This is a group that needs extra care.
• You're pregnant. Its effect in pregnancy isn't known either way.
• You're breastfeeding. Tyrosine passes into breast milk, and there isn't enough research on what that means.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before starting.

• L-tyrosine, free form. Best known for: The form used in the trials, usually as a single 2 g dose. Absorption: Blood levels peak about an hour after a dose, which is when trials tested. Typical use: Taken before a demanding task, or daily through a short, tough stretch.
• N-acetyl-L-tyrosine (NALT). Best known for: A modified, more water-soluble form sold in some sports products. Absorption: We found no human trial comparing it head to head with free tyrosine, so 'better absorbed' is unproven. Typical use: We haven't checked its Australian Schedule 1 status.
• Tyrosine in protein foods. Best known for: Where most people's tyrosine comes from, along with what the body makes from phenylalanine. Absorption: It comes mixed with other amino acids, so it isn't comparable to a single dose. Typical use: Everyday eating. We don't give amounts per serve here.

Reference values. There aren't any. Tyrosine isn't classed as an essential amino acid, so the NHMRC Nutrient Reference Values set no recommended intake for it.

Typical supplemental range. Most trials used a single 2 g dose, taken about an hour before the demanding task. One trial in military cadets gave five daily doses of a drink containing 2 g of tyrosine over a six-day course. Lower doses haven't been tested in the trials we've reviewed, so follow your product's label.

Upper level. None has been set. We found no tolerable upper intake level, and Australia's permitted ingredients list (Schedule 1) has no dose cap for tyrosine. That's a lack of data, not a confirmed safe limit.

Worth knowing. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Cheese and other dairy: tyrosine takes its name from the Greek word for cheese. No verified per-serve figure held
• Meat, poultry and fish: present in all of them. No verified per-serve figure held
• Eggs: present. No verified per-serve figure held
• Soy, legumes, nuts and seeds: the main plant sources. No verified per-serve figure held

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

• MAOI antidepressants, including within about two weeks of stopping one. Don't take it without medical advice.
• Thyroid medicine (levothyroxine, liothyronine). It may change thyroid hormone levels, so talk to your prescriber.
• Pregnancy. Its effect hasn't been established, so take care.
• Breastfeeding. It passes into breast milk, and there isn't enough research.
• Liver problems. Take care.
• Allergy. A rare but serious allergic reaction is possible.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.