Food is made up of six major components: carbohydrates, proteins, fats, vitamins, minerals, and water. These nutrients work together to fuel your body, build and repair tissues, regulate chemical processes, and keep everything running. Beyond these core six, food also contains plant compounds called phytonutrients and, in the case of processed foods, various additives. Here’s what each component actually does.
Carbohydrates: Your Body’s Preferred Fuel
Carbohydrates are your body’s primary energy source, providing 4 calories per gram. They break down into glucose, which powers everything from brain function to muscle movement. Not all carbohydrates behave the same way, though, and the differences matter.
Simple carbohydrates are made of one or two sugar molecules linked in a basic chemical structure. Table sugar, honey, and the natural sugars in fruit fall into this category. Your body absorbs them quickly, which is why a piece of candy gives you a fast energy spike.
Complex carbohydrates contain three or more sugar molecules bonded in longer chains. Starchy foods like potatoes, rice, and whole grains are packed with these longer glucose chains, so they take more time to digest and deliver energy more steadily. Fiber is a special type of complex carbohydrate your body can’t actually digest. Its main components, cellulose, hemicellulose, and pectin, pass through your digestive tract mostly intact. Along the way, fiber feeds beneficial gut bacteria, adds bulk to stool, and helps keep digestion regular.
Proteins: Building Blocks for Growth and Repair
Proteins are assembled from smaller units called amino acids, which your body uses to build muscle, repair damaged tissue, produce hormones, and create chemical messengers in the brain. Protein also provides 4 calories per gram, though your body prefers to use it for structural and chemical jobs rather than burning it for energy.
Of the twenty amino acids your body needs, nine are considered essential because your cells cannot manufacture them. These nine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine, must come from the food you eat. Animal sources like meat, eggs, and dairy typically supply all nine in a single serving. Plant sources like beans, lentils, and nuts can cover them too, but you generally need to eat a variety throughout the day.
The updated 2025 Dietary Guidelines for Americans suggest adults consume 1.2 to 1.6 grams of protein per kilogram of body weight per day. That’s 50 to 100 percent more than previous minimum recommendations, reflecting growing evidence that higher protein intake supports muscle maintenance, especially as people age.
Fats: Energy Storage and Cell Structure
Fat is the most calorie-dense component of food at 9 calories per gram. It cushions organs, insulates your body, helps you absorb certain vitamins, and forms the structural backbone of every cell membrane. Fats are divided into four main types based on their chemical structure.
Saturated fats have the maximum number of hydrogen atoms attached to their carbon chain, making them solid at room temperature (think butter or coconut oil). Monounsaturated fats have a single gap in that hydrogen chain, while polyunsaturated fats have multiple gaps. Both unsaturated types tend to be liquid at room temperature, like olive oil or sunflower oil. Your body cannot make certain polyunsaturated fats, particularly omega-3 and omega-6 fatty acids, so these are considered essential and must come from food.
Trans fats occur when hydrogen atoms sit on opposite sides of a gap in the carbon chain instead of the same side. Small amounts exist naturally in some animal products, but most trans fats in the food supply were artificially created through industrial processing. Current guidelines recommend keeping saturated fat below 10 percent of your total daily calories.
Vitamins: Chemical Regulators
Vitamins are organic compounds your body needs in small amounts to run hundreds of chemical reactions. They split into two categories based on how your body handles them.
Fat-soluble vitamins (A, D, E, and K) dissolve in fat and get stored in your tissues, particularly the liver. Because your body holds onto them, they don’t need to be replenished every single day, but that storage capacity also means they can build up to harmful levels if you take excessive supplements. Water-soluble vitamins (the B vitamins and vitamin C) dissolve in water and pass through your system much faster. Your body doesn’t store them in significant amounts, so you need a regular supply from food.
Minerals: Structural and Functional Support
Minerals are inorganic elements that your body uses for everything from building bones to conducting nerve signals. They’re grouped by how much you need each day.
Major minerals are those required in amounts greater than 100 milligrams per day. Calcium, potassium, sodium, magnesium, phosphorus, and chloride all fall into this group. Calcium and phosphorus give bones and teeth their rigidity. Sodium and potassium manage fluid balance and allow nerves to fire properly.
Trace minerals are needed in amounts of 100 milligrams or less per day. Iron, zinc, copper, selenium, iodine, and fluoride are common examples. Iron carries oxygen in your blood, zinc supports immune function, and iodine is essential for thyroid hormones. The small quantities required don’t make them optional. Deficiencies in trace minerals can cause serious problems, from anemia (iron) to impaired immune response (zinc).
Water: The Overlooked Essential
Water makes up roughly 60 percent of your body weight and participates in nearly every biological process. It forms the base of blood plasma, which transports nutrients, oxygen, and chemical messengers to cells throughout your body. The fluid surrounding your cells carries nutrients in and waste products out. Water also regulates body temperature through sweating and evaporation, cushions joints, and serves as the medium in which most chemical reactions take place. Many whole foods, especially fruits and vegetables, are mostly water by weight.
Phytonutrients: Plant-Based Compounds
Beyond the classic six nutrients, plant foods contain thousands of biologically active compounds called phytonutrients (or phytochemicals). These aren’t essential for survival the way vitamins and minerals are, but they have measurable effects on health. The major classes include polyphenols, flavonoids, carotenoids, alkaloids, and glucosinolates.
Flavonoids, found in berries, tea, and dark chocolate, act as antioxidants and influence cell signaling pathways involved in inflammation. Carotenoids, the pigments that make carrots orange and tomatoes red, support eye health and immune function. Glucosinolates, concentrated in cruciferous vegetables like broccoli and Brussels sprouts, activate detoxification enzymes in your cells that help neutralize potentially cancer-causing compounds. Alkaloids include familiar stimulants like caffeine. Some polyphenols, particularly those in soy, interact with hormone receptors and may influence bone health and hormone regulation.
Food Additives in Processed Foods
Processed and packaged foods often contain non-nutritive components added for specific purposes. Preservatives slow spoilage from mold, bacteria, fungi, and yeast, and help prevent dangerous contamination like botulism. A subgroup of preservatives, antioxidants, keeps fats and oils from going rancid and stops cut fruit from browning.
Emulsifiers, stabilizers, and thickeners give processed foods the texture and consistency you expect, keeping ingredients from separating or becoming grainy. Leavening agents make baked goods rise. Natural and artificial flavors, sweeteners, and spices enhance taste. Other additives control acidity or help maintain flavor in reduced-fat products. The U.S. Food and Drug Administration requires that all additives in the food supply are reviewed for safety, though the conversation about long-term effects of some newer additives continues to evolve.