Nutrient requirements change over time as physiology, activity, and lifestyle evolve. Adolescence brings rapid growth and higher micronutrient demands; pregnancy increases needs for specific vitamins and minerals; older adulthood often brings reduced absorption and altered metabolism. Understanding how bioavailability, dietary patterns, and life-stage risks interact helps guide appropriate intake, testing, and safe supplementation.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.

Micronutrients and growth in adolescence

Adolescence is a period of accelerated growth and sexual maturation, which increases requirements for iron, calcium, vitamin D, and B vitamins. Iron supports expanding blood volume and, for menstruating girls, replaces monthly losses; calcium and vitamin D are central to peak bone mass accrual. B vitamins support energy metabolism and neural development. Attention to diet quality—balance of whole grains, dairy or fortified alternatives, lean proteins, fruits, and vegetables—helps meet needs. Plantbased adolescents may require fortified foods or targeted supplementation to ensure adequate iron, B12, and calcium when food sources are limited.

Bioavailability: what affects absorption?

Bioavailability describes how well a nutrient is absorbed and used by the body. Factors include food form (heme vs non-heme iron), nutrient pairings (vitamin C enhances iron absorption), fat content for fat-soluble vitamins, gut health, and medications that alter gastric pH. Seasonality can influence food availability and nutrient intake—fresh produce changes by season, affecting vitamin C and carotenoid intake. Labeling and food preparation methods also matter: cooking can reduce some vitamins while increasing bioavailability of others. Considering these variables helps tailor dietary choices and supplementation strategies across life stages.

Supplementation: when is it appropriate?

Supplementation can fill gaps when dietary intake, increased requirements, or absorption problems lead to deficiency risk. Indications may include pregnancy (folic acid and often iron), confirmed B12 deficiency in long-term plantbased diets, vitamin D in those with low sunlight exposure, and targeted supplements for older adults with documented low levels. Dosage should be guided by testing and clinical context to avoid excess. Testing prior to long-term supplementation is often useful—blood tests for iron status, B12, vitamin D, and others inform appropriate dosing and reduce risk of harmful interactions with medications.

Absorption and metabolism with aging

Aging commonly alters absorption and metabolism: reduced stomach acid can impair B12 and iron absorption, while changes in fat absorption may affect vitamins A, D, E, and K. Kidney function and liver metabolism shifts can alter how the body handles certain vitamins and minerals and their metabolites. Older adults may require different dosage forms (e.g., sublingual B12, methylated B vitamins) or higher intake of certain nutrients. Close attention to interactions—between supplements, prescription drugs, and chronic conditions—is important to prevent adverse effects and optimize nutrient status.

Deficiencies: signs across life stages

Signs of nutrient deficiencies vary by nutrient and age. In teens, iron deficiency may present as fatigue, impaired concentration, or delayed growth; calcium and vitamin D deficits show in bone health over time. During pregnancy, folate deficiency is associated with neural tube defects, and inadequate iron can increase maternal anemia risk. In older adults, B12 deficiency can cause neuropathy and cognitive changes, while vitamin D insufficiency contributes to falls and fractures. Testing is a practical way to confirm suspected deficiencies and inform appropriate supplementation and dosage rather than relying on symptoms alone.

Synergy, interactions, dosage, labeling, and testing

Nutrients often act synergistically: vitamin D supports calcium metabolism, vitamin C enhances iron absorption, and B vitamins work together in energy pathways. Conversely, some nutrients compete—excess zinc can interfere with copper, and high-dose calcium can affect iron absorption. Proper labeling and dosage literacy help consumers choose safe supplements; look for standardized forms and clear dosing on labels and seek products tested by independent labs when possible. Testing before and during supplementation clarifies needs and tracks status. Pregnancy, chronic conditions, and seasonality (less sun exposure in winter) should guide timing and type of testing and any adjustments in dosage.

Conclusion

Adolescence through older adulthood encompasses distinct windows of vulnerability and opportunity for nutrient optimization. Prioritizing diverse whole foods, understanding bioavailability and interactions, using testing to guide targeted supplementation, and adjusting approaches for pregnancy, plantbased diets, and age-related absorption changes can support health across the life course. Individualized assessment with a qualified healthcare professional ensures appropriate dosing and minimizes the risk of deficiencies or harmful interactions.