Vitamins and Minerals: What They Actually Do in the Body

Micronutrients vs. Macronutrients: The Core Distinction

When most people think about nutrition, they think about macronutrients — carbohydrates, proteins, and fats. These are the energy-yielding nutrients your body uses in large amounts. But there's a second category that's just as essential: micronutrients, which include all vitamins and minerals.

The "micro" prefix refers to quantity, not importance. Your body needs these nutrients in milligrams or micrograms rather than grams, but their absence has measurable consequences. To understand how macronutrients fit into the bigger nutrition picture, see our introduction to macronutrients.

The key functional difference: macronutrients provide energy (calories); micronutrients do not. Instead, vitamins and minerals act as cofactors, coenzymes, and structural materials — the tools and building blocks that allow metabolic processes to run correctly.

What Vitamins Actually Do

There are 13 essential vitamins, grouped by how the body handles them:

• Fat-soluble vitamins (A, D, E, K) — These dissolve in fat, are stored in the liver and fatty tissues, and can accumulate over time. Vitamin A supports vision and immune function; vitamin D regulates calcium absorption and bone health; vitamin E acts as an antioxidant; vitamin K is essential for blood clotting and bone metabolism.
• Water-soluble vitamins (C and the eight B vitamins) — These aren't stored in meaningful amounts, so regular dietary intake matters more. The B vitamins collectively support energy metabolism, red blood cell production, and nervous system function. Vitamin C supports collagen synthesis and immune response, and helps the body absorb plant-based iron.

Because fat-soluble vitamins are retained in the body, both deficiency and excess are possible — a reason why high-dose supplementation of these vitamins should only happen under medical supervision.

What Minerals Do — and Why They're Different

Minerals are inorganic elements that your body uses for structural and regulatory purposes. They're divided into two categories based on how much you need:

• Macrominerals (needed in larger amounts): calcium, phosphorus, magnesium, sodium, potassium, chloride, and sulfur. Calcium and phosphorus together form the mineral matrix of bones and teeth. Magnesium participates in hundreds of enzyme reactions. Sodium and potassium regulate fluid balance and nerve signaling.
• Trace minerals (needed in smaller amounts): iron, zinc, selenium, iodine, manganese, copper, and others. Iron is central to oxygen transport via hemoglobin. Iodine is required for thyroid hormone production. For a closer look at three commonly overlooked trace minerals, see our guide to zinc, selenium, and iodine.

Mineral absorption is often influenced by what else is in a meal. For example, vitamin C enhances absorption of non-heme (plant-based) iron, while calcium can compete with iron for absorption when consumed in large amounts at the same time.

What Happens When Intake Falls Short

Micronutrient deficiencies rarely announce themselves immediately. More often, they develop gradually — affecting energy, mood, immunity, and physical health in ways that are easy to attribute to other causes.

Overt deficiency diseases like scurvy (vitamin C) or rickets (vitamin D) are uncommon in the U.S. today, but subclinical insufficiencies — where levels are low enough to impair function without triggering a clinical diagnosis — are more common than most people realize, particularly for vitamin D, iron, calcium, and magnesium.

If you're unsure whether your everyday eating patterns are covering your bases, our micronutrient gap self-assessment offers a practical starting point for reflection.

Getting What You Need Through Food

No single food provides every vitamin and mineral in adequate amounts. The most reliable strategy is dietary variety — eating across different food groups regularly. A genuinely balanced diet isn't about perfection; it's about consistent diversity over time.

Whole foods tend to deliver micronutrients alongside fiber, phytonutrients, and other compounds that support absorption and overall health — advantages that isolated supplements don't replicate. For most adults, the goal should be to build a food pattern that naturally covers micronutrient needs, reserving supplements for specific, identified gaps identified with a healthcare provider's input.

This article is for general informational purposes only and does not constitute medical or dietary advice. Talk to a qualified healthcare professional about your individual nutritional needs, especially if you have a health condition, are pregnant, or are considering supplementation.