Every entry whose writeup carries a note for under 18. The note is the entry’s own — follow it for the full context. See this in the planner →
Supplements
- ButterburSome rhinitis trials included young people, but the liver-toxicity concern argues for caution and medical guidance.
- CaffeineRecommended limits are lower and scaled to body weight, and a single energy drink routinely exceeds them. Sleep is also more sensitive at this age, and sleep is contributing more to performance than the caffeine is.
- CalciumThe requirement is at its lifetime peak during the growth spurt, around 1,300 mg, higher than at any point in adulthood. Most adult bone mass is laid down by the early twenties, so this is not a deficit you can make up later.
- Creatine MonohydrateThe safety and effect data are overwhelmingly in adults, and sports-medicine position statements generally advise against it under 18 — not because harm has been shown, but because it has not been studied, and because training and food are doing far more at this stage.
- DHEAA hormone precursor sold over the counter, with no place in a body that is still developing its own.
- IronThe requirement rises at puberty for everyone, and again once periods start. Teenage endurance athletes are a recognised risk group — but this is still a case for a ferritin test, not a default supplement.
- TheacrineA stimulant with little safety data in young people — not advised.
- Vitamin D3Bone is being built now, and this is the window that sets peak bone mass. Deficiency is common through winter at higher latitudes, which is why several countries recommend it year-round for this age group.
- Whey ProteinProtein requirements are higher per kilogram while growing, but food almost always meets them. A shake is a convenience here, not a requirement.
- White Willow BarkAvoid in children and teenagers with viral illness, as salicylates carry a theoretical Reye's syndrome risk.
Other situations