A–Z index
Browse everything on the site in alphabetical order. Jump to Symptoms A–Z
Herbs & supplements A–Z
A
- Ashwagandha (Withania somnifera)Ashwagandha is a shrub long used in India's Ayurvedic medicine; most supplements use extracts of its root. In a 2026 analysis of 10 trials, it reduced anxiety compared with placebo, but results varied widely between trials and certainty was rated low to moderate. It may also lower cortisol, a stress hormone.
- Asian GinsengAsian ginseng is an herb used in traditional Chinese medicine. It is native to the Far East, including Korea, northeastern China and far-eastern Siberia. Most of the clinical trials have been small and shorter than 3 months.
C
- ChamomileThere are two types of chamomile: German chamomile and Roman chamomile. Some preliminary studies suggest that a chamomile supplement might be helpful for generalized anxiety disorder. There's very little information on its effect on insomnia, and the one study a 2019 review found showed no benefit.
- Collagen (Hydrolyzed Peptides)Collagen is a protein your body makes to support your skin and bones, and it makes less as you age. Studies of collagen supplements for skin show benefits, but the research is disputed: one analysis found the benefit only in industry-funded studies, and a published rebuttal disputes how those studies were classified.
- Creatine (Monohydrate)Creatine helps your muscles make quick energy for short bursts of effort. With resistance training, it increases strength, power and lean muscle mass. Its effect on thinking and memory is less clear.
I
- Iron (Bisglycinate)Iron helps your blood carry oxygen. People who are pregnant or have heavy periods are more likely to get too little, and vegetarians need more iron than people who eat meat. Too much iron can cause problems, so check with your doctor before taking it.
L
- L-TheanineL-theanine is an amino acid found in green and black tea. Small studies suggest it may support a relaxed but alert state, but the evidence is limited. It's often paired with caffeine, but one study found it didn't reduce caffeine jitters.
- LavenderLavender is an aromatic, evergreen plant native to the Mediterranean region. Small studies suggest oral lavender might help with anxiety and possibly depression, but more high-quality research is needed.
- Lion's Mane Mushroom (Hericium erinaceus)Lion's mane is an edible mushroom promoted for memory and mood. In lab studies it boosts nerve growth factor, but human evidence is limited to a few small trials.
M
- Magnesium (Glycinate & Citrate)Magnesium is a mineral your body uses for hundreds of jobs, including muscle and nerve function and blood sugar and blood pressure control. In a small review of older adults, it helped people fall asleep a little faster, but the evidence was rated low quality. It may also help prevent migraines.
- Magnesium L-ThreonateThis is a form of magnesium studied for brain effects. The rat study it's based on didn't compare it with other magnesium forms, human research is still early, and all three human trials so far have company ties (see the research section).
- MelatoninMelatonin is a hormone your body makes to help control sleep. A Cochrane review found it prevents or reduces jet lag on long flights, and it modestly shortens the time it takes to fall asleep. In a 2024 analysis, the effect grew with dose up to about 4 mg.
O
- Omega-3 Fish Oil (EPA/DHA)Fish oil supplies EPA and DHA, omega-3 fats found in fish. It lowers triglycerides. For heart attacks and strokes, results are mixed: one major trial of high-dose prescription EPA found a benefit, two others didn't, and the American Heart Association doesn't recommend omega-3 supplements for people without high heart-disease risk. It may slightly help joint pain in rheumatoid arthritis. A Cochrane review found a small effect on depressive symptoms but rated the evidence very low certainty.
P
- PassionflowerPassionflower is a climbing vine native to the southeastern United States and Central and South America. It has traditionally been used as a sedative. NCCIH says it might help to reduce symptoms of anxiety and might improve total sleep time in adults with insomnia, but its effects on falling asleep and staying asleep are mixed.
- ProbioticsProbiotics are live bacteria and yeasts taken for a health benefit. The best evidence is for specific strains: some lower the risk of diarrhea from antibiotics, and some ease IBS symptoms such as stomach pain. Results depend on the strain, so one product isn't interchangeable with another.
R
- RhodiolaRhodiola grows in cold regions and at high altitudes in Europe, Asia and North America. Today it is promoted for improving mood and cognition, increasing energy and reducing stress. NCCIH says we haven't learned enough to say whether it is useful for any health-related purpose.
S
- St. John's WortSt. John's wort is a plant with yellow flowers that has been widely used in traditional medicine. It may be helpful for mild or moderate depression, but it's uncertain whether this holds for severe depression or for longer than 12 weeks. For other conditions, the evidence is insufficient to allow definite conclusions.
V
- ValerianValerian is a plant native to Europe and Asia; it also grows in North America. The evidence on whether it helps with sleep problems is inconsistent, and the American Academy of Sleep Medicine recommends against it for chronic insomnia. There is not enough evidence to say whether it is useful for any health condition.
- Vitamin B12
- Vitamin C (Ascorbic Acid)Vitamin C is a vitamin your body can't make, so it has to come from food or supplements. Your body needs it to make collagen and to absorb iron from plant foods. Taking it regularly doesn't prevent colds for most people, but it may make them slightly shorter.
- Vitamin D3 with K2Vitamin D helps your body absorb calcium, and your skin makes it from sunlight. K2 is often paired with it on the theory that it steers calcium into bones rather than arteries. One trial found no effect on heart-valve calcium; a newer one found slower calcium buildup in the heart's arteries on scans, but it's not known whether that prevents heart attacks.
Z
- ZincZinc is a mineral your body needs for immune function, wound healing and hundreds of enzymes. Zinc lozenges started early in a cold may shorten it by about 2 days, but the evidence is low certainty, and zinc doesn't seem to prevent colds.
Symptoms A–Z
Each one opens a search for that symptom.