3 Micronutrients and Water
Learn how vitamins, minerals, water, and electrolytes support body functions, where they come from, and how to interpret nutrient reference values and risks.
What do
Vitamins and minerals are : they are needed in small amounts and do not provide energy, but enable normal growth, maintenance, and metabolism. Vitamins are organic compounds, whereas minerals are elements. Neither group can replace the other, and taking more than needed does not necessarily improve health.
The functions, food sources, requirements, and risks of individual nutrients differ. Needs also vary across life stages, and risk depends on dose, duration, whether a nutrient comes from food or supplements, health conditions, and life stage.
Vitamin groups and food sources
Vitamins are commonly grouped by how they dissolve. A, D, E, and K are absorbed along with dietary fat and can be stored in the body. Vitamin A supports vision and immune function; vitamin D helps regulate calcium and bone health; vitamin E acts in antioxidant systems; and vitamin K is needed for blood clotting and bone proteins.
, including vitamin C and the B vitamins, generally circulate in watery body fluids. B vitamins help enzymes release or use energy from food and support processes such as red blood cell formation and nerve function. Vitamin C contributes to collagen formation, antioxidant defense, and iron absorption.
Food sources vary. Leafy greens and orange vegetables provide carotenoids, which the body can convert to vitamin A. Fortified foods and fatty fish can provide vitamin D; nuts, seeds, and oils provide vitamin E; and leafy greens provide vitamin K. Whole grains, legumes, meat, eggs, and fortified grains provide different B vitamins. Fruits and vegetables are important sources of vitamin C.
Minerals and their roles
Major minerals are needed in relatively larger amounts. They include calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Trace minerals are needed in smaller amounts and include iron, zinc, iodine, selenium, copper, manganese, fluoride, chromium, and molybdenum.
Calcium and phosphorus help build bone. Iron carries oxygen in hemoglobin, zinc supports many enzymes and immune functions, and iodine is needed to make thyroid hormones. Food sources include dairy or fortified alternatives for calcium; meat, beans, and fortified grains for iron; seafood and iodized salt for iodine; and nuts, seeds, legumes, and whole grains for magnesium and zinc.
Inadequacy, excess, and supplement safety
Nutrient inadequacy and excess can have different effects. The following are examples, not an exhaustive list; each vitamin and mineral has distinct deficiency and toxicity patterns.
Vitamin A: Supports vision, cell growth, and immune function. Deficiency can impair vision; excessive preformed vitamin A can damage the liver and harm fetal development.
Vitamin C: Supports collagen formation and helps absorb nonheme iron. Severe deficiency causes scurvy; very high supplemental intakes can cause gastrointestinal effects.
Vitamin D: Helps regulate calcium and bone health. Deficiency can impair bone mineralization; excessive supplements can cause dangerously high blood calcium.
Calcium: Supports bone structure, muscle contraction, and signaling. Long-term inadequacy can compromise bone health; excess, especially from supplements, can cause harm.
Iron: Supports oxygen transport and energy-related enzymes. Deficiency can lead to iron-deficiency anemia; excess can be toxic, especially to children or people with iron-overload disorders.
Iodine: Is needed for thyroid-hormone production. Too little or too much can disrupt thyroid function.
Supplements can contribute to excess, and some nutrients can interact with medicines. A varied diet is a sound foundation; supplements are most appropriate when a need or clinical reason has been identified.
Nutrient reference values
In the United States, provide reference values for healthy people. The is intended to meet the needs of nearly all healthy people in a particular age and sex group. An is used when evidence is insufficient to set an RDA.
The is the highest usual daily intake unlikely to pose a risk for most people; it is not a target. Requirements vary with age, sex, pregnancy, and lactation. For instance, iron needs differ substantially by life stage, so one number cannot serve everyone. Food-label Daily Values (%DV) help compare products but are not individualized prescriptions. These reference values are planning and assessment benchmarks, not individual diagnoses.
Water and hydration
Water is the body’s main solvent and transport medium. It supports chemical reactions, helps regulate temperature, maintains blood volume, and enables waste removal. Total water intake comes from drinking water, other beverages, and moisture in foods.
Needs vary with activity, heat, illness, diet, and other individual factors. Thirst and regular access to fluids help most healthy people maintain hydration in ordinary conditions. For adults ages , the Adequate Intake for total water is for men and for women. These amounts include water from food and all beverages, not just plain water, and are population reference values rather than fixed fluid prescriptions. Greater losses, such as during prolonged exercise or heat exposure, may increase needs. Excessive water intake over a short time can overwhelm the body’s ability to maintain fluid balance.
and fluid balance
are charged minerals dissolved in body fluids. Sodium and chloride are abundant outside cells, while potassium is the main positively charged ion inside cells. Together with other , they help regulate fluid distribution, nerve signaling, muscle contraction, and acid–base balance.
Sodium and chloride are found largely in salt and many processed foods. Potassium is common in vegetables, fruits, beans, and dairy foods. Electrolyte balance depends on intake as well as fluid losses and regulation by the kidneys and hormones.
Too little or too much water or an electrolyte can disturb normal function. Abnormal blood sodium may occur with changes in water balance, while low potassium can impair muscle and heart function. Both deficiency and excess may be serious. Risk can be affected by illness, medicines, kidney function, heavy sweating, vomiting, or diarrhea. An electrolyte imbalance is not always corrected simply by drinking water or taking a supplement; the cause matters.