Nutrient reference

Energy is the fuel value food provides the body, measured in kilocalories and calculated from a food's protein, fat, and carbohydrate content. Daily needs vary continuously by age, sex, body size, and activity level rather than following one fixed target.

Protein is the macronutrient the body uses to build and repair muscle, bone, skin, and enzymes, supplied by both animal and plant foods. Most healthy adults need a minimum of about 0.8 grams per kilogram of body weight per day, though newer federal guidance suggests higher intakes for optimal health.

Total fat is the macronutrient that supplies the body's most concentrated source of energy and carries fat-soluble vitamins, but its health effects depend heavily on the type of fat consumed rather than the total amount. Unsaturated fats from oils, nuts, and fish are associated with better outcomes than saturated and trans fats from processed and animal-derived sources.

Carbohydrate is the body's primary energy source, made up of sugars, starches, and fiber, and USDA calculates it "by difference" — as the remainder after protein, fat, water, and ash are subtracted from a food's total weight. Carbohydrate quality, not total amount, is what most consistently predicts health outcomes.

Dietary fiber is the part of plant carbohydrate the body cannot digest, and it is one of the most consistently underconsumed nutrients in the American diet. Higher intake is linked to better heart, digestive, and blood-sugar health, with most adults needing 25 to 30 grams a day.

Total sugars covers every mono- and disaccharide in a food, whether naturally occurring — as in fruit or milk — or added during processing. Health guidance on limiting sugar intake targets added sugars specifically, since naturally occurring sugars in whole foods don't carry the same documented risks.

Calcium is the mineral your body uses in the largest amount, building and maintaining bone and tooth structure while also supporting muscle contraction, nerve signaling, and blood clotting. Dairy foods, canned fish with bones, and leafy greens are among its richest dietary sources.

Iron is essential for making hemoglobin, the protein that carries oxygen in red blood cells, and for normal brain development and muscle function. It comes in two dietary forms — heme iron from animal foods and non-heme iron from plants — that the body absorbs at different rates.

Magnesium supports more than 300 enzyme systems in the body, including those involved in energy production, muscle and nerve function, and blood pressure regulation. Nuts, seeds, whole grains, legumes, and leafy greens are its richest everyday dietary sources.

Phosphorus is the second most abundant mineral in the body, forming the structural backbone of bones and teeth and powering cellular energy through ATP. It is so widely present in the food supply — especially dairy, meat, fish, and processed foods — that deficiency is rare.

Potassium is an electrolyte that helps regulate fluid balance, nerve signaling, and muscle contraction, including the heartbeat, and works alongside sodium to help support healthy blood pressure. Fruits, vegetables, legumes, and dairy are among its most reliable dietary sources.

Sodium is an essential electrolyte for fluid balance, nerve function, and muscle contraction, but most people in the United States consume well above the recommended limit. Unlike most Tier-1 minerals, sodium's dietary guidance centers on limiting intake rather than reaching a target.

Zinc is an essential trace mineral needed for immune defense, wound healing, and growth, found richest in oysters, red meat, and legumes.

Copper is an essential trace mineral that supports iron metabolism, connective tissue, and energy production, concentrated in organ meats, shellfish, and cocoa.

Selenium is an essential trace mineral used to build antioxidant and thyroid-regulating proteins, needed in very small amounts and concentrated in Brazil nuts, seafood, and organ meats.

Vitamin C is a water-soluble antioxidant vitamin needed for collagen synthesis, wound healing, and iron absorption, found in the highest amounts in citrus fruit, peppers, and cruciferous vegetables.

Thiamin (vitamin B1) is a water-soluble B vitamin the body needs to convert carbohydrates into energy and to support normal nerve function, found in whole grains, pork, legumes, and seeds.

Riboflavin (vitamin B2) is a water-soluble B vitamin needed for energy metabolism and red blood cell production, found in the highest amounts in organ meats, dairy, eggs, and fortified grains.

Niacin (vitamin B3) is a water-soluble B vitamin used to build energy-metabolism coenzymes, found in the highest amounts in meat, poultry, fish, and fortified grains.

Vitamin B6 (pyridoxine) is a water-soluble B vitamin used in protein metabolism, neurotransmitter and hemoglobin synthesis, and immune function, found in the highest amounts in fish, poultry, organ meats, and legumes.

Folate (vitamin B9) is a water-soluble B vitamin needed for DNA synthesis and red blood cell production, especially important before and during early pregnancy, and found in the highest amounts in leafy greens, legumes, liver, and fortified grains.

Vitamin B12 (cobalamin) is a water-soluble vitamin needed for red blood cell formation and nervous system maintenance, found naturally only in animal foods such as liver, shellfish, meat, and dairy.

Vitamin A, RAE reflects the total vitamin A activity in a food — combining retinol from animal sources with the vitamin-A contribution of plant carotenoids like beta-carotene — and is essential for vision, immune defense, and skin and mucous-membrane health.

Beta-carotene is the orange-yellow plant pigment that gives carrots their color and the most abundant of the roughly 750 known dietary carotenoids.

Vitamin E (alpha-tocopherol) is the only form of vitamin E the body actively maintains in blood — a fat-soluble antioxidant found mainly in plant oils, nuts, and seeds that helps protect cell membranes and support immune function.

Vitamin D (D2 + D3) is the fat-soluble, hormone-like vitamin the body needs to absorb calcium and build bone — found naturally in only a few foods, chiefly fatty fish and egg yolks, and added to many fortified dairy and cereal products.

Vitamin K (phylloquinone) is the plant-derived form of vitamin K, found concentrated in leafy green vegetables and herbs, that the body needs to activate proteins involved in blood clotting and bone building.

Saturated fat is a solid-at-room-temperature dietary fat, found mainly in butter, red meat, and tropical oils, that health authorities recommend limiting because it raises LDL cholesterol and cardiovascular risk.

Trans fat is a dietary fat, mostly created by partially hydrogenating vegetable oils, that raises LDL cholesterol and lowers HDL cholesterol; health authorities recommend eating as little of it as possible.

Cholesterol is a fat-like substance the body both produces and absorbs from animal foods like eggs and organ meats; current guidelines have dropped the old 300 mg/day limit, since saturated and trans fat affect blood cholesterol more than dietary cholesterol does for most people.