In a 13-year-old adolescent with persistent low energy, which vitamin deficiencies should be considered?

Vitamin Deficiencies Causing Low Energy in a 13-Year-Old

The most common vitamin deficiencies causing low energy in adolescents are vitamin D, B vitamins (particularly B12, folate, B6, thiamin, riboflavin, and niacin), and iron deficiency, with vitamin D deficiency being especially prevalent in northern latitudes and among those who train indoors. 1

Primary Vitamin Deficiencies to Consider

Vitamin D Deficiency

• Vitamin D levels should be maintained above 32-50 ng/mL (25(OH)D blood levels) according to Endocrine Society Guidelines. 1
• Vitamin D deficiency is particularly common in northern latitudes during winter months when sunlight hours are reduced, among adolescents who train indoors, those with dark pigmented skin, and those using sunscreen regularly. 1
• Deficiency impairs bone health and metabolic function, contributing to fatigue and reduced energy levels. 1

B Vitamin Complex Deficiencies

• B vitamins (B1/thiamin, B2/riboflavin, B3/niacin, B5/pantothenic acid, B6/pyridoxine, B9/folate, B12/cobalamin) are critical for energy-yielding metabolism, DNA synthesis, and neuronal functions, making them essential for preventing mental and physical fatigue. 2
• Deficiencies manifest in neuromuscular problems and neurological symptoms that can present as low energy and fatigue. 1, 2
• B vitamins play essential roles in basic metabolic pathways supporting fundamental cellular functions, with direct effects on cognitive and psychological processes including fatigue. 2

Iron Deficiency

• Iron requirements are particularly high during adolescent growth, especially in girls following menarche, and iron deficiency impairs high-intensity and endurance performance. 1
• Daily iron recommendations for this age group are 8 mg from ages 9-13 years and 11-15 mg from ages 14-18 years. 1
• Iron deficiency in energy-deficient individuals worsens the hypometabolic state by impairing thyroid hormone synthesis and hepatic conversion of T4 to T3. 3
• Documented effects include decreased motor activity, reduced social interaction, impaired attention to tasks, and cognitive impairment affecting learning and memory. 4

Additional Micronutrient Deficiencies

Vitamin C

• Vitamin C deficiency can contribute to fatigue through its role in energy metabolism and cellular function. 2
• Biochemical indices should be used to assess vitamin C status when evaluating persistent low energy. 2

Magnesium and Zinc

• Both magnesium and zinc play recognized roles in energy-yielding metabolism and can manifest as fatigue when deficient. 2
• These minerals are critical for brain and muscular function, translating into effects on physical and mental fatigue. 2

Diagnostic Approach

Recommended Laboratory Testing

• Serum 25(OH)D levels to assess vitamin D status (target >32 ng/mL). 1
• Complete iron panel: serum iron, ferritin, TIBC, transferrin saturation, and C-reactive protein. 3
• Complete blood count with reticulocyte count and red cell indices to evaluate for anemia. 3
• Thyroid function tests (TSH, free T4, free T3) since low energy states can cause decreased thyroid hormones. 3, 5
• Serum or plasma levels of B vitamins (folate, B12, B6) as nutritional biomarkers. 6

Clinical Assessment Considerations

• Evaluate dietary intake patterns, particularly calcium intake (should be 1500 mg/day through dietary sources with supplementation if required). 1
• Assess for restrictive dietary patterns that may indicate low intake of multiple micronutrients including B vitamins, iron, zinc, magnesium, and vitamins D and E. 5
• Screen for energy availability issues, particularly in physically active adolescents, as low energy availability (<30 kcal/kg fat-free mass per day) causes multiple hormonal and metabolic disruptions. 5

Important Clinical Pitfalls

Energy Deficiency Considerations

• In adolescents with low energy, consider Relative Energy Deficiency (RED-S), which causes vitamin D deficiency, iron deficiency, and multiple hormonal disruptions that compound fatigue. 1, 3
• Weight stability should not be used as an indicator of adequate energy availability, as athletes and active adolescents can be in energy balance while simultaneously in a state of low energy availability. 1
• Low energy availability causes decreased thyroid hormones (T3, T4), which directly contributes to fatigue and must be distinguished from primary vitamin deficiencies. 3, 5

Dietary Assessment Limitations

• Accurate assessment of dietary intake is challenging due to under-reporting, modified intake during reporting periods, and imprecise recording of portion sizes. 1
• Young adults with demanding lifestyles who are physically active and whose dietary behavior is characterized by poor choices and/or regular dieting represent an important at-risk group for inadequate micronutrient intake. 7

Supplementation Considerations

• Iron supplementation should only be provided after confirming iron deficiency through serum ferritin and blood hemoglobin measurements, as supplementation without confirmed deficiency is not beneficial. 1
• Players should consume iron-containing foods with vitamin C and limit intake of absorption inhibitors like tea and coffee. 1
• Micronutrient supplementation must be taken for an adequate period of time to alleviate deficiencies. 7
• Folic acid in doses above 0.1 mg daily may obscure pernicious anemia (vitamin B12 deficiency) by alleviating hematologic manifestations while allowing neurologic complications to progress. 8