Supplements: What Actually Works

The ones with strong evidence

Creatine monohydrate Strong

Creatine helps your muscles regenerate energy during short, hard efforts, which lets you do a little more work each set. Over time, that adds up to more strength and muscle. It's backed by hundreds of studies, works at any age, and is among the cheapest supplements on the shelf. There's also early research on benefits for bone and brain health, particularly in older adults.

• Kidneys: Research shows no harm in healthy people. But creatine can raise serum creatinine on bloodwork, which can make kidney function look worse than it is. Tell your doctor you take it, especially before lab draws. If you have kidney disease, don't start without talking to your doctor.
• Hair loss: This concern traces back to a single 2009 study that found a rise in DHT in rugby players. It hasn't been replicated, and no study has shown creatine causes hair loss. If you're already prone to male-pattern baldness and worried about it, that's a reasonable conversation to have with your doctor.

Protein powder Strong

Protein powder isn't magic, just food in a convenient form. It's useful when whole-food meals fall short of your daily target. Use our protein calculator to find your number.

• Whey is fast-digesting, high in leucine, and usually the best value. Whey isolate works for most people who are sensitive to lactose.
• Casein digests slowly, and some people like it before bed.
• Plant blends (pea + rice, soy) work well, especially when combined to round out the amino acid profile.
• Buy tested products. Independent testing has found heavy metals such as lead in some protein powders, particularly some plant-based ones. A third-party certification seal is worth paying for here.

Caffeine Strong

Caffeine is one of the most reliable performance enhancers available. It improves strength, endurance, and focus, and it lowers perceived effort.

The catch is sleep. Caffeine's effects last for hours, so an evening pre-workout can easily cost you more recovery than it gains you in performance. Pre-workout products often pack 300+ mg per scoop, so check the label, and skip them if you have high blood pressure or heart rhythm issues.

Vitamin D Situational

Vitamin D matters for bone, muscle, and immune function, and deficiency is common, especially in winter, at northern latitudes, in people with darker skin, and in men carrying extra body fat. Correcting a deficiency helps. But in people whose levels are already normal, large trials generally haven't found benefits from extra vitamin D for muscle, strength, or most disease outcomes.

So test first. A 25-hydroxy vitamin D blood test tells you whether supplementing is worth it. If you're low, 1,000–2,000 IU/day is a common starting point, and doctors may prescribe more to correct a significant deficiency. The general upper limit for adults is 4,000 IU/day without medical supervision.

Situational picks

Omega-3 (fish oil) Situational

Prescription-strength omega-3s lower high triglycerides, and fish oil is a reasonable option if you rarely eat fatty fish. Evidence for muscle growth or faster recovery is mixed and small. Talk to your doctor if you take blood thinners.

Beta-alanine Situational

Beta-alanine buffers acid in the muscle, which helps most with hard efforts lasting about 1–4 minutes, such as rowing intervals, high-rep sets, or combat sports. For typical strength training in the 5–10 rep range, the benefit is small. A common dose is 3–6 g/day, and it causes a harmless tingling sensation.

Magnesium Situational

Many people eat less magnesium than recommended, and correcting low intake is reasonable. Popular claims about better sleep and recovery rest on limited evidence. Food sources like nuts, seeds, beans, leafy greens, and whole grains come first. Excess from supplements can cause digestive upset, and people with kidney disease should avoid it unless their doctor says otherwise.

Ashwagandha Situational

Small, mostly short-term studies suggest modest effects on stress, sleep, and in some trials testosterone and strength. The studies are small and often industry-funded, and there have been rare but serious reports of liver injury. Some countries have restricted it. It's not appropriate for people with thyroid conditions or autoimmune disease, or those on thyroid, sedative, or immune-suppressing medication, without a doctor's input.

Citrulline & beetroot (nitrates) Situational

Beetroot nitrates have fairly good evidence for endurance performance. Citrulline malate shows small, inconsistent benefits for high-rep lifting. Both are reasonable to try, but neither is essential.

What to skip

• ✕BCAAs and EAAs: If you eat enough protein, extra amino acids add nothing. Whole protein already contains them, along with everything else muscles need.
• ✕Glutamine: Your body makes plenty, and studies in healthy lifters show no benefit for muscle or recovery.
• ✕Collagen for muscle: Collagen is an incomplete protein and a poor muscle builder. Some early research looks at it for tendons and joints alongside training, but that evidence is still preliminary.
• ✕"Fat burners": These are mostly high-dose stimulants. Any fat-loss effect is minimal, and some have been linked to heart problems and liver injury.
• ✕Most "recovery" blends: These are usually under-dosed mixtures of the ingredients above, sold at a premium.