A young athlete's body is trying to do two demanding things at once — grow, and recover from training — and both draw on the same pool of energy and nutrients. Get the balance wrong and one gets short-changed, usually growth, because a training body will always prioritise immediate recovery over long-term development. This guide covers what growing kids in sport specifically need more of, sourced from UK government dietary reference values rather than general "eat healthy" advice, and why the single biggest risk in this area isn't a missing vitamin — it's simply not eating enough.
The real risk: under-fuelling, not a missing nutrient
Parents searching this topic often expect the answer to be about a specific supplement or superfood. It's rarely that. The far more common and more serious issue in young athletes is chronic under-fuelling — not eating enough overall to cover both training demands and normal growth. When this happens consistently, it can affect growth, bone development, immune function, mood and injury risk, and it's frequently invisible day-to-day because a child can look and perform fine for a while before the effects show up. The fix is almost always more consistent food across the day, not a targeted fix for one nutrient — which is why this page leads with that, before the specific figures below.
Calcium: building bone density while it still counts
Childhood and the teenage years are when the skeleton builds the vast majority of the bone density it will ever have — bone mass built now is largely locked in for life, which makes this the single most important window for calcium intake a person will ever have. Combined with the loading effect of sport (see our Safe Strength guide), this is a genuine opportunity, not just a maintenance requirement.
UK Reference Nutrient Intakes for calcium, by age band:
- Ages 6-9: 550mg/day
- Ages 10-16, boys: 1,000mg/day
- Ages 10-16, girls: 800mg/day
Good everyday sources: milk, yoghurt, cheese, fortified plant milks, tinned fish with bones (like sardines), and green leafy vegetables. Three portions of dairy or a fortified alternative across the day covers most of this range for most kids without needing to count milligrams.
Vitamin D: the one nutrient UK kids are routinely short on
Vitamin D helps the body absorb calcium and is essential for bone health, but the UK's latitude means sunlight alone isn't a reliable source for most of the year — this is one of the few nutrients where official guidance recommends a supplement as standard, not just as a fallback. The UK government recommends all children from age 1 take a daily vitamin D supplement of 10 micrograms, year-round, regardless of diet or how much time they spend outdoors. This applies to every child, not just those in intensive training, but it's worth flagging here because vitamin D deficiency can affect bone health and recovery in ways that could be mistaken for overtraining or growing pains.
Iron: a bigger gap for girls from puberty
Iron supports oxygen transport to muscles — genuinely relevant to sports performance, not just general health — and requirements shift noticeably at puberty, particularly for girls, once menstruation begins.
UK Reference Nutrient Intakes for iron, by age band:
- Ages 6-9: 8.7mg/day
- Ages 10-16, boys: 11.3mg/day
- Ages 10-16, girls: 14.8mg/day
Good sources: red meat, chicken, fish, beans and lentils, fortified breakfast cereals, and dark green vegetables — paired with a source of vitamin C (citrus fruit, peppers, tomatoes) at the same meal, which meaningfully improves how much iron the body absorbs from plant sources in particular. A young athlete who seems unusually tired, is struggling to recover between sessions, or has noticeably reduced performance is worth a GP conversation about iron levels, especially for a teenage girl in a high training load.
What a growth-supporting day of eating actually looks like
Rather than tracking individual nutrients meal by meal, the practical approach that reliably covers all of the above is building meals around the NHS Eatwell Guide pattern — plenty of fruit and vegetables, wholegrain carbohydrates, a protein source at each meal, dairy or fortified alternatives, and small amounts of unsaturated fats — with the daily vitamin D supplement added on top regardless of how well the rest of the diet is going. This whole-pattern approach naturally covers calcium and iron for most kids without needing to calculate milligrams at every meal, and it's a far more sustainable habit than nutrient-by-nutrient tracking.
Common mistakes
Assuming a good-looking diet is automatically enough during a growth spurt. Needs can jump noticeably during a growth spurt — see our Build Strength guide for more on adjusting portions as training and growth demands rise together.
Skipping the vitamin D supplement because a child "eats healthily." Diet alone rarely provides enough vitamin D in the UK, regardless of how good the rest of the diet is — this is genuinely a supplement-the-default nutrient, not a food-first one.
Missing iron changes at puberty, especially for girls. The jump in iron needs at this stage is substantial and easy to miss if you're still planning meals around a younger child's requirements.
Treating fussy eating and growth nutrition as separate problems. If a child's diet is genuinely restricted, that's the priority to work on — see our Fussy Eaters guide for practical, no-pressure strategies that don't turn mealtimes into a fight.
Frequently asked questions
How much calcium does my child need for healthy bone growth? UK guidance sets this at 550mg/day for ages 6-9, 1,000mg/day for boys aged 10-16, and 800mg/day for girls aged 10-16. Three portions of dairy or a fortified alternative across the day typically covers this for most children.
Does my child need a vitamin D supplement? Yes — UK government guidance recommends all children from age 1 take a daily 10 microgram vitamin D supplement year-round, regardless of diet, because the UK's climate makes sunlight an unreliable source for most of the year.
How much iron does a young athlete need? 8.7mg/day for ages 6-9, rising to 11.3mg/day for boys aged 10-16 and 14.8mg/day for girls aged 10-16 — the increase for girls reflects the onset of menstruation and is a meaningfully bigger jump than for boys the same age.
What's the biggest nutrition risk for a growing young athlete? Not eating enough overall, consistently, rather than any single missing nutrient. Chronic under-fuelling can affect growth, bone development, immunity and injury risk, often without obvious day-to-day symptoms.
How do I know if my child isn't eating enough for their training load? Watch for persistent tiredness, slower recovery between sessions, dips in performance, or growth that seems to be plateauing. Any of these are worth raising with a GP rather than guessing.
This page provides general educational guidance and is not a substitute for advice from a GP, health visitor, or registered dietitian — particularly if you're concerned about your child's growth, energy levels, or nutrient intake.