Young athletes on plant-based diets

Adolescent athletes have the highest energy and nutrient requirements of any group relative to body size, because they are growing and training simultaneously.

Combining that with a plant-based diet is entirely possible and warrants professional input rather than being managed from the internet.

Why the requirements are so high

Growth itself requires substantial energy, protein, calcium, iron and zinc.

Training adds to all of them.

Peak bone mass is largely established during adolescence, which makes calcium and vitamin D adequacy during this period consequential for life.

Iron requirements rise sharply, particularly in girls after menarche.

The specific risks

Energy inadequacy, the most common problem.

Plant foods are bulky, adolescent stomachs are not larger than adults', training suppresses appetite, and schedules are chaotic.

The consequences of low energy availability in adolescence are more serious than in adults: impaired growth, delayed or disrupted puberty, and compromised peak bone mass.

Bone consequences during this window are not fully recoverable later.

Iron deficiency, which is common in adolescent athletes generally and more so on plant-based diets.

Calcium and vitamin D inadequacy, during the period when it matters most.

B12, where deficiency in a growing person affects the nervous system.

Disordered eating, where adolescence, sport and dietary restriction is a combination with elevated risk.

The disordered eating question

Worth addressing directly and without alarmism.

Most adolescents adopting plant-based diets do so for ethical or environmental reasons, and it is a normal and reasonable choice.

A minority use it as a socially acceptable route to restriction, and the diet provides cover — refusing food becomes principled rather than conspicuous.

Signs worth taking seriously: dietary restriction extending beyond animal products, weight loss, avoidance of eating with others, excessive exercise, preoccupation with food or body shape, and progressive narrowing of accepted foods.

The presence of these does not mean the plant-based diet is the problem, and it does mean the situation warrants professional assessment.

Sports involving weight categories, aesthetics or endurance carry higher risk generally.

What parents and coaches should do

Get dietetic input. Genuinely. A sports dietitian with paediatric experience, at the outset.

This is not excessive caution — it is the situation where the margin for error is smallest.

Monitor growth. Height and weight, plotted, regularly. Faltering growth is the most sensitive early indicator of inadequate intake.

Monitor menstrual function in girls. Absent or irregular periods in an athlete are never normal and always warrant assessment.

Test iron, at least annually.

Ensure supplementation, particularly B12 and vitamin D.

Make food available constantly. Adolescent athletes need to eat frequently and are frequently not at home when they need to.

Practical measures: food in the bag, food after training, food available on return from school.

Do not restrict fat. Energy density is the constraint.

Do not comment on weight or body shape, which is worth stating explicitly. Adult comments about an adolescent athlete's body are a documented risk factor for disordered eating.

The practical eating pattern

Frequent. Five or six eating occasions rather than three.

Energy dense. Nut butters, oils, dried fruit, smoothies, full-fat plant alternatives.

Protein at every occasion, using soy foods and legumes.

Carbohydrate around training, lower in fibre immediately before.

Fortified foods used deliberately — fortified plant milk and cereals contribute meaningfully.

Familiar and easy. An adolescent will not prepare elaborate food, and a system requiring it will fail.

The supplements

B12, without exception.

Vitamin D, generally.

Iodine, unless intake is reliable.

Algal omega-3, reasonable.

Iron only on the basis of testing.

Creatine in adolescents is a more complicated question with less safety data than in adults, and it should be discussed with a clinician rather than assumed to be equivalent.

Other performance supplements are generally not appropriate for adolescents.

The framing that helps

Adolescents respond badly to being told what to eat and well to understanding why.

The performance framing is generally more effective than the health one: eating enough makes you faster and stronger, under-fuelling makes you slower and gets you injured.

That is also true, which helps.

The reassurance

Adolescents compete successfully at high levels on plant-based diets.

The requirements are demanding and knowable, and the risks come from inadequate planning rather than from the diet.

Get professional input, monitor growth, supplement, and make sure there is always food available.

Anyone supporting an adolescent athlete on a plant-based diet should involve a registered dietitian with relevant experience. Faltering growth, absent menstruation, recurrent injury or signs of disordered eating require prompt medical assessment.