Do I need supplements?
Usually, no. Supplements can help with specific gaps, convenience needs, or performance goals, but they do not replace calorie balance, adequate protein, enough fruits and vegetables, sleep, training consistency, and medical care when needed.
The top contenders are usually simple. Creatine monohydrate has strong evidence for strength, power, and lean-mass support, with emerging evidence of possible cognitive benefits, too, and a good safety profile in healthy adults. Omega-3 supplementation, usually from fish oil or algae oil, can be useful when fatty-fish intake is low, which is common even in otherwise healthy diets. Vitamin D is also worth considering because many people get little sunlight, and dietary intake alone may not support levels that are adequate for their health context; it is especially relevant for bone health, immune function, mood, and general health. A basic multivitamin can function as a modest "insurance policy" against gaps in a repetitive or low-variety diet, though it should not be treated as a substitute for nutrient-dense food.
Whey protein can also be useful if you count it as a supplement, but its main value is convenience: it helps you hit protein targets when whole-food protein is impractical. Caffeine can support alertness and performance in some contexts, but many people already get enough from coffee, tea, or other caffeinated beverages, so it does not necessarily require a pill or pre-workout product.
More refined supplementation should be more specific. The best reason to add a supplement is a known deficiency, a likely dietary gap, a well-defined performance goal, or a specific symptom pattern that you are investigating carefully. Examples might include iron, B12, magnesium, electrolytes, targeted gut-health products, or other nutrients depending on diet, bloodwork, sweat loss, medications, training demands, and medical context.
Many supplements have not been robustly tested in the way their marketing implies. Some are probably benign at reasonable doses, aside from cost, but "probably harmless" is not the same as effective. A reasonable approach is expected value: What is the plausible benefit, what is the evidence, what is the cost, what are the risks, and how will you know whether it is helping?
If you are pregnant, have kidney disease, take medications, have a medical condition, have a known deficiency, or are considering high-dose or multi-ingredient supplements, ask a physician, pharmacist, or registered dietitian first. The boring hierarchy still wins: food quality, calories, protein, training, sleep, and consistency first; supplements second.
For athletes subject to drug testing, supplement risk is not just physiology; it is contamination, labeling accuracy, and sport-specific rules, so use third-party-tested products and check the relevant rules before assuming a supplement is allowed.