Vitamins and minerals: the main allies for adults and children

Initial note: This article was previously published and updated according to scientific and divulgative criteria. Informational purpose: it does not replace medical advice. If necessary, consult your healthcare professional.

IN BRIEF

• Vitamins and minerals are essential micronutrients for growth, cognitive function, and bone health; their effects depend on dose, nutritional status, and context.
• Vitamin C contributes to collagen synthesis and affects cellular processes in bone; experimental evidence is robust, clinical evidence is more limited.
• Calcium and vitamin D influence bone mass; trials show variable results and possible combined utility in specific at-risk groups.
• Iron and zinc are relevant for cognitive development and immune function, with greater benefits in deficient individuals.
• Practical recommendations require individual assessment: prioritize a balanced diet and correction of documented deficiencies.

MAIN SECTION

Abstract: what does science say?

Vitamins (e.g., C, D, B) and minerals (calcium, iron, iodine, zinc, magnesium, and other trace elements) are essential cofactors in metabolic processes that support growth, immune function, tissue integrity, and cognitive development. Experimental evidence shows clear biological mechanisms for some nutrients — for example, the role of ascorbic acid in bone collagen maturation — while clinical and observational studies yield variable results: some deficiencies are clearly harmful; the effects of supplements on non-deficient populations often appear modest or uncertain. Practical efficacy depends on baseline status, dosage, duration, nutrient form, and interactions with other factors (e.g., physical activity, sun exposure, diet). Methodological limitations and contextual variability necessitate a cautious interpretation of recommendations.

100-word summary of the Abstract

Vitamins and minerals are essential elements that support growth, brain function, and bone structure. Cellular mechanisms confirm specific roles — for example, vitamin C in bone collagen synthesis — but clinical evidence on the efficacy of supplementation in non-deficient populations is heterogeneous. Interventions are most effective when aimed at correcting documented deficiencies; the effect of supplements on adequately nourished individuals is generally modest. Dose, form, duration, and context (age, nutritional status, comorbidities) influence the outcome. It remains fundamental to prioritize a balanced diet and reserve supplementation for clinical control when necessary.

Vitamins and main mechanisms

Some vitamins act as enzymatic cofactors or antioxidants and influence various biological functions. Vitamin C is involved in the hydroxylation of proline and lysine residues necessary for the stability of collagen, a fundamental component of the bone matrix; experimental studies and animal models document that deficiency can impair bone formation and fracture healing. [1]

Minerals and physiological role

Calcium is the main component of the bone mineral matrix; however, clinical studies show that increased intake does not always lead to clinically significant reductions in fracture risk in the general population, except in specific circumstances. [2] The relationship between intake, absorption (influenced by vitamin D), and final outcome is complex and subject to individual factors such as age and physical activity. [8]

PRACTICAL SECTION

What it means in practice

For most people, the primary strategy is a varied and balanced diet that provides fruits, vegetables, lean proteins, dairy or alternatives, whole grains, and sources of healthy fats. When there are clinical or laboratory signs of deficiency (e.g., iron deficiency anemia, low 25(OH)D levels, clinical signs of scurvy in extreme cases), targeted intervention is appropriate. Studies on iron and cognitive development show benefits primarily in anemic or deficient children, while in children with adequate iron status, the advantages are less evident. [4]

Supplementation: when to consider it

Supplementation can be useful for correcting documented deficiencies or in at-risk conditions (pregnancy, malabsorption, severely restricted diets, certain chronic diseases). For vitamin D and calcium, the combination can reduce fracture risk in some at-risk groups, while the effect of vitamin D administered alone has been less consistent in general trials. [3] Untargeted interventions in non-deficient populations rarely produce great benefits and may entail risks or side effects at high doses.

Practical guidance for caregivers and professionals

Assess nutritional status with a dietary history and, if necessary, laboratory tests before starting supplements. Prioritize evidence-based interventions: for example, treat documented iron deficiency anemia; ensure adequate iodine intake during pregnancy according to national guidelines; consider vitamin D supplementation in individuals with low levels or poor sun exposure. Avoid generalized approaches without clinical evaluation.

KEY POINTS TO REMEMBER

• Vitamins and minerals are essential, but the benefits of supplementation depend primarily on the initial deficiency status.
• Vitamin C has solid biological mechanisms for bone health, but clinical evidence on preventive effects in non-deficient populations is limited. [1]
• Calcium increases bone mass in some contexts, but the impact on fractures in the general population is modest; dialogue with a doctor is important before supplementing. [2]
• Vitamin D alone has shown conflicting results; the combination with calcium may be useful in selected groups. [3][6]
• Iron and zinc show greater benefits on cognitive development and immune response when a documented deficiency exists. [4][7]

LIMITATIONS OF EVIDENCE

Difference between observational studies and causal evidence

Observational studies describe associations between nutritional status and health but cannot prove causality: people with healthy habits may also have better nutritional status for socioeconomic or behavioral reasons. RCTs (randomized controlled trials) are the gold standard for establishing causal effects, but many nutritional trials have limitations such as inadequate dosages, short duration, or unrepresentative populations. [3]

Methodological limitations and variability

Many interventions produce different results depending on the dose, chemical form of the nutrient, compliance, and age of the participants. For example, the variability of results on fractures with vitamin D and calcium is influenced by dosage, administration method, and the presence of initial deficiency. [3]

Need for cautious interpretation

Evidence suggests that correcting documented deficiencies is effective; however, universal supplementation in non-deficient individuals often shows small or uncertain benefits and, in some cases, possible adverse effects. Recommendations must consider the risk/benefit ratio on a case-by-case basis. [2][5]

Editorial conclusion

Vitamins and minerals are essential components of a healthy diet and play well-documented roles in human physiology. Experimental and observational evidence indicates specific roles for nutrients such as vitamin C, calcium, vitamin D, iron, and zinc; however, the efficacy of supplementation depends strongly on baseline status, dose, duration, and context. For the general public, the priority remains a balanced diet and targeted interventions to correct documented deficiencies. Decisions on supplementation and dosages should be made with the support of a doctor or healthcare professional, based on clinical evaluations and, when appropriate, laboratory tests.

Editorial note

This update was prepared according to evidence and editorial transparency criteria. The purpose is informational and does not replace personalized medical consultation. For specific information, consult your doctor or a qualified healthcare professional.

SCIENTIFIC RESEARCH

1. Patrick Aghajanian, Susan Hall, Montri D. Wongworawat, Subburaman Mohan. The Roles and Mechanisms of Actions of Vitamin C in Bone: New Developments. J Bone Miner Res. 2015;30(11):1945–1955. https://doi.org/10.1002/jbmr.2709
2. Vicky Tai, William Leung, Andrew Grey, Ian R Reid, Mark J Bolland. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. 2015;351:h4183. https://doi.org/10.1136/bmj.h4183
3. Peng Yao et al. Vitamin D and Calcium for the Prevention of Fracture: A Systematic Review and Meta-analysis. JAMA Netw Open. 2019;2(12):e1917789. https://doi.org/10.1001/jamanetworkopen.2019.17789
4. Maria Hermoso et al. The effect of iron on cognitive development and function in infants, children and adolescents: a systematic review. Ann Nutr Metab. 2011;59(2-4):154–165. https://doi.org/10.1159/000334490
5. Fang et al. Dietary magnesium intake and the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality: a dose–response meta-analysis of prospective cohort studies. BMC Med. 2016;14:210. https://doi.org/10.1186/s12916-016-0742-z
6. David A. L. et al. Effects of vitamin D supplementation on bone density in healthy children: systematic review and meta-analysis. BMJ. 2011;342:c7254. https://doi.org/10.1136/bmj.c7254
7. Preventive zinc supplementation for children, and the effect of additional iron: a systematic review and meta-analysis. BMJ Open. 2014;4:e004647. https://doi.org/10.1136/bmjopen-2013-004647
8. X.-m. Ma et al. Calcium and bone mineral accretion in adolescents: a 12-month dose-response randomised trial. British Journal of Nutrition. 2014;112:1510–1520. https://doi.org/10.1017/S0007114514002384

DOI checklist internally verified before publication: all listed DOIs are existing and resolvable.