The Ingredient Files

Collagen (hydrolyzed collagen, collagen peptides) is sold for skin beauty and joints.

Creatine is one of the rare supplements that genuinely works.

Lutein (and its partner zeaxanthin) are carotenoids that make up the macular pigment accumulating in the central retina, and are widely sold as 'eye supplements.' The evidence splits by use.

For easing constipation and preventing migraine, the evidence is moderate (grade B).

Melatonin is a hormone secreted at night by the brain's pineal gland to regulate the body's 24-hour (circadian) rhythm, and it is also widely sold as a supplement.

Milk thistle (silymarin, extracted from the seeds of the Silybum marianum plant) is the classic 'liver supplement,' widely sold to take around drinking or when liver numbers are a worry.

The most solid effect of omega-3 is lowering triglycerides (greater at higher doses).

Probiotics are not a one-size-fits-all fix for gut health; the evidence splits by use.

Red ginseng is steamed, dried Panax ginseng, and is the best-selling health functional food in Korea.

Vitamin C is an essential nutrient you cannot do without - a prolonged lack causes scurvy (bleeding gums, bruising, slow wound healing), and there is no dispute that filling that deficiency works.

For people with low blood levels, vitamin D has solid evidence for correcting the shortfall, but the broad disease-prevention benefits many people hope for rest mostly on weak evidence.

Ashwagandha (Withania somnifera) is a herb from Indian Ayurveda, now a flagship 'adaptogen' supplement sold for stress, sleep, and testosterone.

Berberine is a yellow alkaloid found in the roots of plants like Coptis and barberry, recently popular on social media as a 'natural Ozempic' supplement for blood sugar and weight.

Biotin (vitamin B7) is widely sold as a hair, skin, and nail supplement, but the evidence that it improves appearance in healthy people is weak.

The common wisdom that 'calcium is good for bones' is only half right.

Chondroitin really is a component of cartilage, and supplement raw material is mostly extracted from animal cartilage such as cow or shark.

Curcumin is the yellow active compound of turmeric, sold as a natural anti-inflammatory and catch-all.

Garcinia cambogia is derived from the rind of a tropical fruit, and its active compound - hydroxycitric acid (HCA) - is widely sold as a weight-management supplement.

Green tea extract concentrates the catechins (chiefly EGCG) from green tea (Camellia sinensis) leaves, and it is sold most widely as a 'natural diet' aid.

Iodine is a mineral the body must have to make thyroid hormone, so severe deficiency impairs children's cognitive development.

Iron is a mineral where the whole question is who is actually deficient.

L-theanine is an amino acid in green tea, known for giving a sense of relaxation without caffeine.

Potassium is one of the better-evidenced entries here.

Propolis is a resinous material honeybees make by mixing plant exudates with their own secretions, and in Korea it is sold mainly on an 'immunity, throat, and cold' image.

Red yeast rice is sold as a natural way to manage cholesterol, but more precisely it is a statin that happens to grow in a natural product.

Selenium is widely marketed for antioxidant, immune, and cancer-prevention benefits, but well-designed large trials have shown little of this in people who already have enough selenium.

Vitamin A is most clearly valuable when it corrects a shortfall in people who are deficient.

Vitamin B12 (cobalamin) is an essential nutrient required for making red blood cells and for nerve function, and it is also widely sold as an 'energy and fatigue' supplement.

Vitamin B6 (pyridoxine) has evidence for easing nausea and vomiting in pregnancy (morning sickness) and is used as a first-line option in several guidelines, though the quality of that evidence is mostly low and the effect is modest.

Vitamin K2 (menaquinone) is heavily marketed as 'good for bones and arteries,' but it is an ingredient where surrogate markers and hard outcomes diverge sharply.

The evidence for zinc splits by purpose.

Beta-alanine is an amino acid that raises muscle carnosine, which helps buffer the acid (hydrogen ions) that builds up during high-intensity exercise.

Coenzyme Q10 (ubiquinone) helps produce energy in mitochondria and acts as an antioxidant, and is sold for 'vitality, heart, and anti-aging.' The evidence splits sharply by use.

Folate's most solid effect is preventing fetal neural tube defects (spina bifida, anencephaly) when taken around the time of conception - the evidence is very strong (grade A).

Glucosamine is sold widely as a joint supplement, but its report card from large independent trials is thin.

NMN is the immediate precursor the body uses to make NAD+ (a coenzyme central to energy metabolism and DNA repair), and it is marketed with anti-aging claims that it 'slows aging and extends lifespan.' Pulling together the human trials, the one thing NMN clearly does is raise blood NAD+ concentrations (consistent across several randomized trials).

Resveratrol is a polyphenol in grape skins, red wine, peanuts, and berries, sold on the back of the 'red wine health secret' (the French paradox) and sirtuin (SIRT1) / anti-aging / longevity marketing.

Taurine is an amino sulfonic acid abundant in the body, best known as an energy-drink ingredient.

Vitamin E (tocopherol) is a fat-soluble antioxidant nutrient that protects cell membranes, long sold as high-dose supplements under an 'antioxidant equals heart, anti-aging, immunity' image.