Calcium and Vitamin D for Bone Health in Adolescent Girls and Female Athletes: When Is Food Enough and When Are Supplements Indicated? A Narrative Review
Updated: Sep 24
Abstract
Background
Adolescence is a critical period for skeletal growth and mineral acquisition. Adequate calcium and vitamin D intake, sufficient energy and protein availability, normal pubertal development, and appropriate mechanical loading contribute to bone development during this period. Female athletes require particular attention because the potential skeletal benefits of weight-bearing exercise may be attenuated by low energy availability, menstrual dysfunction, and other components of the Female Athlete Triad. In clinical practice, uncertainty remains regarding when food alone is sufficient, when calcium or vitamin D supplementation is appropriate, whether magnesium should routinely accompany calcium, and when laboratory testing or dual-energy X-ray absorptiometry (DXA) should be considered. The contribution of drinking water is also frequently overlooked, particularly with increasing use of reverse-osmosis systems and purified bottled water.
Objective
This narrative review examines current evidence and major professional recommendations concerning calcium, vitamin D, magnesium, diet, drinking-water mineral content, supplementation, menstrual health, laboratory assessment, and DXA in adolescent girls, with specific consideration of female athletes. Its principal aim is to provide a clinically useful distinction between dietary adequacy, supplementation for an identified intake gap, treatment of biochemical deficiency, and investigation of adolescents at increased skeletal risk.
Methods
A targeted narrative review was undertaken using authoritative guidance and peer-reviewed literature relevant to pediatric bone health, nutrient requirements, sports medicine, and pediatric densitometry. Priority was given to recommendations from the National Academies of Sciences, Engineering, and Medicine/Institute of Medicine, National Institutes of Health Office of Dietary Supplements (NIH ODS), American Academy of Pediatrics (AAP), Endocrine Society, International Society for Clinical Densitometry (ISCD), World Health Organization (WHO), and Female Athlete Triad Coalition, together with systematic reviews, randomized controlled trials, and relevant observational or metabolic studies. Searches focused on combinations of adolescent girls, calcium, vitamin D, magnesium, drinking water, reverse osmosis, bone mineral density, peak bone mass, female athlete, menstrual dysfunction, bone stress injury, supplementation, and DXA. Adult data were used for contextual purposes only when pediatric evidence was insufficient. The literature was reviewed through September 2026. Because the objective was narrative synthesis rather than exhaustive systematic evidence retrieval, no meta-analysis or formal study-level risk-of-bias assessment was performed.
Results
For girls aged 9–18 years, the calcium Recommended Dietary Allowance (RDA) is 1,300 mg/day and the vitamin D RDA is 600 IU (15 μg)/day. These values represent total daily intake and should not be interpreted as automatic supplement doses. Food and fortified foods remain the preferred means of meeting calcium requirements. When a persistent dietary shortfall remains after nutrition intervention, supplemental calcium may be used to close the estimated gap. Calcium carbonate and calcium citrate are the most commonly used supplemental forms; carbonate contains a greater proportion of elemental calcium and should generally be taken with food, whereas citrate is less dependent on gastric acidity. Fractional absorption of supplemental calcium is highest at individual doses of approximately 500 mg elemental calcium or less.
Magnesium is relevant to bone and mineral metabolism, but current evidence does not support routine magnesium co-supplementation solely because calcium supplementation is required. Magnesium intake should instead be assessed independently. Drinking water may contribute calcium and magnesium, but concentrations vary considerably. Reverse-osmosis and some purified bottled waters contain little calcium or magnesium, whereas certain mineral waters provide nutritionally meaningful amounts. Low-mineral water should not be described as an independent cause of mineral deficiency; rather, it removes one potential dietary source and may therefore become relevant when total intake is marginal.
In female athletes, calcium and vitamin D adequacy must be considered within a broader assessment of energy status, menstrual function, growth, training, and bone stress injury. Laboratory testing and DXA are best used selectively according to clinical risk rather than as universal screening procedures.
Conclusions
Healthy adolescent girls who achieve adequate calcium and vitamin D intake generally do not require routine calcium supplementation. Persistent intake gaps should first be addressed through food and fortified foods, with supplementation used when necessary to provide the remaining deficit. Magnesium should be included in dietary assessment but should not automatically be paired with calcium. Water source is a potentially relevant component of mineral assessment, particularly when reverse-osmosis or purified water has replaced mineral-containing tap or mineral water. In athletes, adequate energy availability and reproductive health are fundamental to skeletal health and cannot be replaced by mineral supplementation. Treatment doses for diagnosed deficiencies and decisions regarding laboratory testing or DXA require individualized clinical assessment.
Keywords: adolescent girls; calcium; vitamin D; magnesium; drinking water; reverse osmosis; female athlete; bone health; peak bone mass; Female Athlete Triad; energy deficiency; bone stress injury; DXA; supplementation.
1. Introduction
Although osteoporosis usually becomes clinically apparent later in life, skeletal health has important developmental origins. Childhood and adolescence are periods of rapid bone growth, modeling, and mineral accumulation, and the amount of bone acquired during growth contributes to the skeletal reserve available in adulthood. This relationship provides a rationale for attention to nutrition and physical activity during adolescence, but it does not establish that supplementation during adolescence independently prevents postmenopausal osteoporosis.
The distinction is important. Peak bone mass is influenced by genetic factors, pubertal development, sex hormones, energy and protein availability, calcium and vitamin D intake, mechanical loading, medical conditions, and medication exposure. No single nutrient can therefore be considered in isolation.
Calcium nevertheless deserves particular attention because requirements rise during periods of rapid skeletal growth. Vitamin D is integral to calcium homeostasis and skeletal mineralization. Magnesium is also physiologically relevant, although its role in routine supplementation is considerably less well established. An additional source of calcium and magnesium—drinking water—is often omitted from dietary assessment. This omission may be increasingly relevant as households replace tap water with reverse-osmosis or commercially purified water.
The issue is particularly complex among female athletes. Weight-bearing and impact exercise can provide an osteogenic stimulus, yet inadequate energy availability and associated reproductive dysfunction may impair bone accrual and increase susceptibility to bone stress injury. Consequently, prescribing calcium without evaluating the broader nutritional and endocrine environment may fail to address the principal determinant of skeletal risk.
This review therefore addresses four practical questions: When is food sufficient? When are calcium or vitamin D supplements appropriate, and in what form? When does magnesium warrant attention? And when should dietary assessment progress to laboratory investigation or DXA?
2. Adolescence and the acquisition of bone mass
Puberty is characterized by rapid changes in skeletal size, geometry, and mineral content. The AAP has emphasized the importance of childhood and adolescence for acquisition of bone mass and the potential implications of inadequate skeletal development for later bone health [3].
Menarche is clinically relevant to skeletal assessment, particularly because menstrual function provides information about reproductive and energy status. It should not, however, be interpreted as the point at which bone-health intervention begins. Considerable skeletal acquisition occurs during pubertal development before menarche.
For practical nutritional purposes, therefore, attention to bone health should extend across late childhood and adolescence rather than begin only after menstrual onset.
This is particularly relevant to athletes. The years during which training volume increases frequently overlap with rapid growth and sexual maturation. Nutritional requirements must therefore support basal physiological function, growth and development, and the additional demands of training and recovery.
3. Calcium requirements during adolescence
The calcium RDA for both girls and boys aged 9–18 years is 1,300 mg/day [1,2].
Age | Calcium RDA |
4–8 years | 1,000 mg/day |
9–13 years | 1,300 mg/day |
14–18 years | 1,300 mg/day |
19–50 years | 1,000 mg/day |
The same 1,300-mg/day RDA applies to pregnant and lactating adolescents aged 14–18 years [1,2].
The RDA refers to total calcium intake. It includes calcium from food, fortified foods and beverages, drinking water, and supplements.
It is therefore incorrect to interpret the recommendation as a prescription for 1,300 mg of supplemental calcium in addition to an adolescent's usual diet.
4. Food as the primary source of calcium
AAP guidance favors dietary calcium and does not recommend routine calcium supplementation for otherwise healthy children and adolescents whose intake is adequate [3].
This position is consistent with a broader nutritional principle: supplementation should address an identifiable need rather than substitute automatically for food.
Useful calcium sources include milk, yogurt, cheese, calcium-fortified plant beverages, calcium-set tofu, fortified foods, and canned fish containing edible bones. The actual calcium content of fortified products varies considerably and should be established from the nutrition label rather than assumed.
A practical nutrition assessment should therefore estimate habitual calcium intake before recommending supplementation.
If an adolescent consumes approximately 900 mg/day against a target of 1,300 mg/day, the estimated deficit is approximately 400 mg/day. The initial intervention is to determine whether this difference can be addressed through ordinary foods or appropriately fortified products.
Only when the gap persists should supplementation become necessary.
This can be summarized as:
Assess intake → optimize food → reassess intake → identify the residual gap → supplement the residual gap when necessary.
5. What does supplementation add?
Randomized trials have reported improvements in selected measures of bone mineral acquisition when additional calcium was provided to adolescent girls, particularly when baseline calcium intake was relatively low [4,5].
These findings should be interpreted in the context of the broader evidence.
A meta-analysis of 19 randomized trials involving 2,859 children found no significant effect of calcium supplementation on femoral-neck or lumbar-spine BMD. Small effects were identified for total-body bone mineral content and upper-limb BMD, but the investigators considered them unlikely to translate into a clinically important reduction in fracture risk [6].
The evidence therefore supports achieving adequate calcium intake but does not support routine supplementation of calcium-replete healthy children in an attempt to produce bone density above that achievable through adequate nutrition.
Similarly, evidence that calcium supplementation during adolescence directly prevents postmenopausal osteoporosis decades later is lacking. The appropriate inference is more conservative: adequate calcium intake forms one component of the nutritional and physiological environment necessary for normal bone acquisition.
6. Prescribing calcium: elemental calcium matters
When supplementation is required, the clinically relevant quantity is elemental calcium, not the total mass of the calcium compound [7].
Calcium carbonate and calcium citrate are the most commonly used preparations.
6.1 Calcium carbonate
Calcium carbonate contains approximately 40% elemental calcium by weight. Because dissolution depends to a greater extent on gastric acidity, it should generally be taken with food [7].
Its relatively high elemental calcium content allows the required calcium dose to be delivered using a smaller quantity of compound.
6.2 Calcium citrate
Calcium citrate contains approximately 21% elemental calcium by weight. It is less dependent on gastric acidity and may be taken with or without food. It may be preferable when calcium carbonate is poorly tolerated or when reduced gastric acidity is clinically relevant [7].
6.3 Dose size
Fractional absorption decreases as the amount of supplemental calcium consumed at one time increases. NIH ODS identifies approximately 500 mg elemental calcium or less per administration as the range in which fractional absorption is highest [7].
Thus, if supplementation is required:
the daily supplemental dose should reflect the dietary shortfall, and larger supplemental requirements should generally be divided into individual doses of approximately ≤500 mg elemental calcium when practical.
This is an administration principle, not a recommendation that every adolescent receive 500 mg/day.
7. Vitamin D
The vitamin D RDA for adolescents is 600 IU (15 μg)/day [1,8].
As with calcium, the RDA represents a nutritional intake target rather than an automatic additional supplement prescription.
Vitamin D is available principally as vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). Both can increase serum 25-hydroxyvitamin D concentrations.
The 2024 Endocrine Society clinical practice guideline distinguishes empiric nutritional/preventive vitamin D use from indiscriminate biochemical screening and treatment of established disease [9].
This distinction is essential to clinical interpretation:
nutritional intake and treatment of vitamin D deficiency are not the same intervention.
A healthy adolescent should meet recommended intake. An adolescent with clinically identified vitamin D deficiency requires an individualized treatment plan based on diagnosis, severity, underlying risk factors, and follow-up assessment.
For this reason, therapeutic high-dose vitamin D regimens should not be converted into general population recommendations.
8. Serum calcium and vitamin D assessment
Serum calcium is tightly homeostatically regulated and is not an appropriate measure of habitual calcium intake [7].
An adolescent may therefore have normal circulating calcium despite consuming inadequate dietary calcium.
Nutritional calcium adequacy should primarily be assessed from dietary intake, whereas serum calcium should be measured when the clinical question concerns calcium homeostasis or an underlying medical disorder.
When vitamin D status requires biochemical evaluation, serum 25-hydroxyvitamin D [25(OH)D] is the appropriate marker.
Routine 25(OH)D testing of every healthy adolescent is not supported. AAP guidance favors targeted evaluation in children and adolescents with clinical conditions associated with skeletal fragility [3]. Contemporary Endocrine Society guidance similarly discourages unnecessary routine testing in otherwise healthy populations [9].
9. Magnesium and adolescent bone health
Magnesium should not be omitted from a discussion of mineral nutrition and skeletal physiology.
The RDA is 240 mg/day for ages 9–13 years. For girls aged 14–18 years, it increases to 360 mg/day [10].
Magnesium participates in numerous enzymatic reactions and contributes to mineral metabolism and bone structure. Severe magnesium deficiency also has important clinical implications for calcium homeostasis.
Nevertheless, physiological importance does not establish an indication for routine supplementation.
A randomized, double-blind, placebo-controlled study by Carpenter and colleagues investigated magnesium supplementation in healthy girls aged 8–14 years whose magnesium intake was below 220 mg/day. Participants received 300 mg/day elemental magnesium as magnesium oxide for one year. Greater integrated hip bone mineral content accrual was observed in the magnesium group, although effects at individual skeletal sites were not uniformly significant [11].
The study provides evidence that magnesium deserves consideration when intake is low. It does not establish that all adolescent girls should receive magnesium or that magnesium must accompany calcium supplementation.
A separate metabolic study in adolescent girls found that increasing calcium intake did not adversely affect magnesium absorption or balance [12].
Current evidence therefore supports the following interpretation:
Magnesium adequacy matters, but calcium supplementation does not itself create an indication for magnesium supplementation.
Dietary magnesium should be evaluated independently. Food sources—including legumes, nuts, seeds, whole grains and green leafy vegetables—remain preferable when adequate intake can be achieved.
The tolerable upper intake level for magnesium from supplements and medications is 350 mg/day for adolescents aged 9–18 years [10]. This limit does not include naturally occurring magnesium in food.
10. Drinking water: an overlooked source of calcium and magnesium
Drinking water is not nutritionally inert.
The WHO has recognized that drinking water may contribute to calcium and magnesium intake and that treatment processes can alter mineral composition [13]. The magnitude of this contribution depends on the original water source and the treatment applied.
This distinction has become relevant with increased use of household filtration, reverse-osmosis systems, and commercially purified bottled water.
10.1 Reverse-osmosis water
Reverse osmosis is designed to remove dissolved substances and consequently removes substantial amounts of calcium and magnesium.
A recent community-based analysis comparing household filtration methods found markedly lower calcium and magnesium concentrations in reverse-osmosis-treated water than in unfiltered tap water, whereas ordinary pitcher filtration had a much smaller effect on mineral content [14].
This finding should not be interpreted to mean that reverse-osmosis water independently causes magnesium or calcium deficiency.
Rather:
when mineral-containing drinking water is replaced with demineralized water, a potential source of dietary calcium and magnesium is removed.
Whether this has nutritional significance depends on the remainder of the diet.
For a person obtaining abundant calcium and magnesium from food, the difference may be negligible. For an adolescent whose intake is already marginal, removal of a previously meaningful water contribution could increase the nutritional shortfall.
10.2 Bottled water
Bottled water should not be treated as a single nutritional category.
Published analyses demonstrate large differences among products. In one investigation of 92 bottled waters, calcium concentrations ranged from less than 0.1 mg/L to approximately 360 mg/L, while magnesium ranged from less than 0.01 mg/L to approximately 106 mg/L [15].
Consequently, some mineral waters can contribute meaningfully to calcium and magnesium intake, whereas purified bottled waters may provide almost none.
The term bottled water therefore provides insufficient information for nutritional assessment.
10.3 Implications for dietary assessment
A more complete mineral history should include the patient's principal source of drinking water:
tap water; conventionally filtered water; reverse-osmosis water; purified bottled water; spring water; or mineral water.
Where mineral content is known, calcium and magnesium supplied by water can reasonably be included in the assessment of total intake.
Where reverse-osmosis or purified water is consumed, meaningful calcium or magnesium content should not be assumed unless the system remineralizes the water or the manufacturer's analysis confirms mineral concentrations.
Thus, total mineral exposure can be conceptualized as:
foods + fortified foods/beverages + mineral contribution from water + supplements.
This approach is preferable to considering supplements in isolation.
11. The female athlete: exercise does not guarantee skeletal protection
Physical activity can provide an important osteogenic stimulus. Weight-bearing, impact, and multidirectional loading are particularly relevant to skeletal adaptation.
The benefits of exercise, however, depend partly on the physiological environment in which training occurs.
The 2025 Female Athlete Triad Coalition consensus update describes three interacting domains: energy status, reproductive function, and bone health [16,17].
This model is especially important during adolescence.
An adequately nourished, eumenorrheic athlete exposed to appropriate mechanical loading may develop favorable skeletal characteristics. Conversely, high training expenditure combined with inadequate energy intake may disrupt reproductive function and compromise bone acquisition.
Thus:
high exercise exposure + adequate energy availability is fundamentally different from high exercise exposure + chronic energy deficiency.
The latter may be associated with menstrual dysfunction, impaired bone accrual, and bone stress injury [16,17].
12. Calcium and vitamin D cannot compensate for low energy availability
A female athlete can meet calcium and vitamin D recommendations and still experience impaired skeletal health if energy availability is chronically inadequate.
This has direct implications for nutritional practice.
When an athlete presents with menstrual dysfunction, recurrent bone stress injuries, restrictive eating, abnormal growth, or other features suggestive of inadequate energy availability, treatment should not begin and end with calcium tablets.
Assessment should address total energy intake, carbohydrate and protein availability, meal timing, training expenditure, growth, menstrual function, psychological and behavioral factors, and overall micronutrient adequacy.
The 2025 Female Athlete Triad consensus places restoration of adequate energy status at the center of treatment and supports multidisciplinary management involving medical and nutrition professionals [17].
Calcium and vitamin D remain necessary components of care, but they cannot substitute for adequate energy availability.
13. Menstrual function as a clinical marker
Menstrual history is an important component of the skeletal assessment of adolescent girls, particularly athletes.
Relevant information includes age at menarche, time since menarche, cycle frequency, prolonged intervals without menstruation, changes in menstruation following increased training or dietary restriction, and other symptoms suggesting endocrine or gynecological disease.
Menstrual irregularity during early postmenarchal development requires age-appropriate interpretation. Nevertheless, prolonged or recurrent menstrual dysfunction should not automatically be considered a normal consequence of athletic training.
The Triad consensus emphasizes evaluation of menstrual abnormalities within the broader context of energy status and bone health [16,17].
14. When laboratory evaluation is warranted
Routine extensive laboratory testing is unnecessary in healthy adolescents with normal growth, adequate nutrition, normal menstrual development, and no evidence of skeletal fragility.
Testing becomes appropriate when the clinical history or examination raises concern for metabolic, endocrine, nutritional, renal, gastrointestinal, hematologic, or other disease.
Depending on the differential diagnosis, clinician-directed investigation may include 25(OH)D, serum calcium with albumin or ionized calcium when appropriate, phosphorus, magnesium, alkaline phosphatase, parathyroid hormone, renal and hepatic chemistry, complete blood count, iron indices, thyroid testing, and targeted reproductive or gastrointestinal investigations.
This is not a universal screening panel.
The choice of tests should be driven by the clinical presentation.
15. DXA in children and adolescents
DXA is the preferred clinical method for assessing bone mineral content and areal bone mineral density in children and adolescents, but it is not a population screening test.
The ISCD recommends DXA as part of comprehensive skeletal assessment in patients with increased fracture risk when the result is expected to influence clinical management [18].
Preferred pediatric sites include the posterior-anterior lumbar spine and total body less head.
Pediatric interpretation differs substantially from adult interpretation.
Z-scores—not T-scores—should be used.
A pediatric diagnosis of osteoporosis should not be made on densitometric criteria alone.
In the absence of vertebral compression fractures, ISCD criteria require both a clinically significant fracture history and a BMD Z-score ≤−2.0. A clinically significant fracture history is defined as at least two long-bone fractures by age 10 years or at least three long-bone fractures at any age through 19 years [18].
One or more vertebral compression fractures occurring without high-energy trauma or local disease indicate osteoporosis irrespective of BMD.
The term osteopenia should not be used in pediatric DXA reports [18].
16. DXA and the adolescent female athlete
Athletic participation alone is not an indication for DXA.
The decision should instead reflect cumulative skeletal risk.
Relevant considerations include prolonged menstrual dysfunction, substantial or persistent energy deficiency, clinically important weight loss or low weight, eating disorders, recurrent bone stress injuries, low-trauma fractures, chronic diseases or medications affecting bone, and other evidence of impaired skeletal health [17].
This risk-based approach is more clinically meaningful than routine age-based screening.
17. Comparison of principal recommendations
Clinical question | Evidence-based interpretation |
Calcium requirement, age 9–18 | 1,300 mg/day total intake |
Vitamin D requirement | 600 IU (15 μg)/day total intake |
Healthy adolescent meeting calcium needs through diet | No routine calcium supplement |
Dietary calcium below target | Optimize food/fortified foods first |
Persistent calcium gap | Consider supplemental elemental calcium sufficient to close gap |
Calcium carbonate | ~40% elemental calcium; preferably with food |
Calcium citrate | ~21% elemental calcium; less dependent on gastric acidity |
Large supplemental calcium requirement | Prefer divided administration; fractional absorption highest at approximately ≤500 mg elemental calcium per dose |
Vitamin D deficiency | Separate from maintenance nutrition; clinician-directed treatment |
Magnesium adequate | No evidence-based requirement to add magnesium to calcium |
Magnesium intake low | Improve food intake; supplement selectively if clinically appropriate |
RO/purified water | May contain very little Ca/Mg; assess total diet |
Mineral water | May contribute meaningful Ca/Mg; check label/composition |
Healthy asymptomatic adolescent | No routine DXA or broad laboratory screening |
Menstrual dysfunction/bone stress injury/other skeletal risk | Broader medical and nutrition evaluation; consider targeted labs and DXA |
18. A practical clinical nutrition pathway
The evidence supports a sequential rather than supplement-centered approach.
Step 1: Establish developmental and clinical context
Assess age, growth trajectory, pubertal development, menstrual history, medical conditions, medications, fracture history, and athletic participation.
Step 2: Assess the complete diet
Estimate calcium, vitamin D, magnesium, energy, protein, and overall dietary adequacy.
Step 3: Ask about water
Determine whether habitual drinking water is tap, conventionally filtered, reverse osmosis, purified bottled, spring, or mineral water.
Where calcium and magnesium concentrations are known and nutritionally meaningful, include them in estimated intake.
Step 4: Correct food-level inadequacy
Use calcium- and magnesium-containing foods and appropriately fortified foods to address dietary gaps whenever practical.
Step 5: Calculate the remaining calcium gap
For adolescents aged 9–18:
1,300 mg/day target − estimated intake = approximate residual calcium gap.
Step 6: Supplement only when necessary
If the gap cannot reasonably be closed through food, consider supplemental elemental calcium sufficient to address the residual shortfall.
Step 7: Distinguish nutritional supplementation from treatment
Vitamin D deficiency, hypocalcemia, significant hypomagnesemia, metabolic bone disease, and other biochemical abnormalities require medical diagnosis and individualized treatment rather than routine nutrition supplementation.
Step 8: Escalate assessment when skeletal risk is present
Menstrual dysfunction, recurrent bone stress injury, low-trauma fractures, significant dietary restriction, abnormal growth, or suspected underlying disease should prompt targeted clinical investigation and consideration of DXA where appropriate.
19. Implications for long-term osteoporosis prevention
The objective of adolescent bone-health nutrition should be stated accurately.
Current evidence does not demonstrate that routine calcium, vitamin D, or magnesium supplementation of adequately nourished adolescent girls prevents postmenopausal osteoporosis decades later.
The more defensible objective is to avoid preventable constraints on normal skeletal acquisition.
Adequate calcium and vitamin D intake, sufficient energy and protein, adequate magnesium and other micronutrients, normal pubertal and reproductive development, and appropriate mechanical loading collectively create an environment favorable to bone acquisition.
For athletes, this means preserving the skeletal benefits of physical activity while avoiding chronic energy deficiency and reproductive dysfunction.
Long-term skeletal prevention should therefore not be conceptualized as giving adolescents supplements against future osteoporosis. It should be understood as protecting normal bone development during a period when substantial skeletal acquisition is physiologically expected.
20. Conclusions and Clinical Reference
The available evidence supports a food-first, risk-stratified approach to bone-health nutrition in adolescent girls.
For girls aged 9–18 years, the calcium RDA is 1,300 mg/day total intake, and the vitamin D RDA is 600 IU (15 μg)/day total intake. These values are nutritional targets and should not be interpreted as routine supplemental doses.
When food is enough
A healthy adolescent whose habitual diet provides approximately 1,300 mg/day of calcium and adequate vitamin D does not require routine calcium supplementation.
Food and appropriately fortified foods should remain the primary intervention when intake is below target.
When food plus calcium supplementation is appropriate
If dietary intervention does not consistently close the calcium deficit, supplementation may be used to provide the remaining gap rather than automatically supplying 1,300 mg/day as a supplement.
The prescription should specify elemental calcium.
Calcium carbonate contains approximately 40% elemental calcium and should generally be taken with food.
Calcium citrate contains approximately 21% elemental calcium, is less dependent on gastric acidity, and may be taken with or without food.
When larger supplemental quantities are required, administration should generally be divided so that individual doses are approximately 500 mg elemental calcium or less, because fractional absorption is greatest at lower individual doses.
Vitamin D
The nutritional target for healthy adolescents is 600 IU/day total vitamin D intake.
Nutritional supplementation used to meet this requirement must be distinguished from treatment of vitamin D deficiency. Therapeutic doses for diagnosed deficiency require clinician-directed selection, duration, and follow-up and should not be inferred from the population RDA.
Magnesium
Magnesium is relevant to bone and mineral physiology and should be included in nutritional assessment.
The RDA is 240 mg/day at ages 9–13 and 360 mg/day for girls aged 14–18.
Current evidence does not support routinely adding magnesium simply because calcium supplementation is required.
When magnesium intake is inadequate, food sources should be improved first where practical. Supplementation may be considered when dietary inadequacy persists or deficiency is clinically suspected or established.
The 350-mg/day upper limit for adolescents applies to supplemental/medication-derived magnesium, not magnesium naturally present in food.
Drinking water
Water source should be included in mineral assessment.
Reverse-osmosis and many purified waters contribute little calcium or magnesium unless they are subsequently remineralized. Their use should not be described as an independent cause of mineral deficiency, but replacing mineral-containing water with demineralized water can remove a meaningful source of calcium or magnesium from the diet.
Bottled water cannot be classified uniformly. Purified bottled water may contain negligible minerals, whereas certain mineral waters contain substantial calcium and magnesium.
Accordingly, calcium and magnesium assessment should consider:
food + fortified foods and beverages + documented mineral contribution from drinking water + supplements.
For adolescents consuming substantial quantities of water, including athletes, this distinction may be particularly relevant when overall mineral intake is marginal.
Female athletes
Athletes should not automatically receive higher calcium or vitamin D doses solely because they exercise.
Adequate energy availability, normal growth, menstrual/reproductive function, and appropriate recovery are fundamental to skeletal health. Calcium and vitamin D supplementation cannot correct the skeletal consequences of persistent energy deficiency.
Menstrual dysfunction, restrictive eating, recurrent bone stress injuries, significant changes in growth or weight trajectory, and low-trauma fractures should prompt broader clinical and nutrition assessment.
Laboratory testing
Normal serum calcium does not establish adequate dietary calcium intake.
Dietary calcium adequacy should primarily be assessed from intake.
When vitamin D testing is clinically indicated, serum 25(OH)D is the relevant biochemical marker.
Broad laboratory testing should remain targeted to clinical indications rather than routinely performed in every healthy adolescent.
DXA
DXA should not be used as universal screening in healthy adolescent girls or athletes.
It should be considered when skeletal risk is sufficiently elevated and the result is expected to influence management.
Pediatric DXA interpretation requires Z-scores rather than T-scores, and osteoporosis should not be diagnosed from bone density alone.
Final clinical principle
The evidence supports the following hierarchy:
adequate energy intake and normal growth/pubertal development → food-based calcium, vitamin D, and magnesium adequacy → consideration of drinking-water mineral contribution → targeted supplementation for persistent nutritional gaps → medical investigation of suspected deficiency or disease → risk-directed DXA and specialist management when skeletal fragility is suspected.
The aim is not maximal mineral supplementation. It is adequate mineral availability within an overall nutritional, hormonal, and mechanical environment that supports normal skeletal development.
Educational and Clinical Disclaimer
This narrative review is intended for educational, academic, and professional-reference purposes only. It does not constitute individualized medical advice, diagnosis, or a prescription.
Recommended Dietary Allowances are population-level nutrient intake targets and should not be interpreted as treatment doses for an individual child or adolescent. Supplement requirements, formulation, dose, duration, timing, drug–nutrient interactions, laboratory monitoring, and decisions regarding DXA or specialist referral should be determined by an appropriately qualified healthcare professional after consideration of age, growth and pubertal development, habitual dietary and water intake, medical history, medications, kidney and gastrointestinal function, menstrual status, athletic participation, fracture history, laboratory findings, and other individual risk factors.
Treatment of vitamin D deficiency, hypocalcemia, clinically significant magnesium deficiency, metabolic bone disease, malabsorption, kidney disease, eating disorders, or Female Athlete Triad-related abnormalities requires individualized clinical assessment. High-dose calcium, vitamin D, or magnesium therapy should not be initiated in a child or adolescent solely on the basis of information contained in this review.
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