Let's look at how people worked out what vitamins are. In 1897 Christiaan Eijkman concluded that a substance in the husk of rice protected against the symptoms he had seen in hens fed milled rice; it was later named vitamin B1. Around 1910 Frederick Hopkins found that young rats fed only pure nutrients stopped growing, but a small amount of milk started their growth again. Hopkins's rat experiments led to the idea that unknown substances, later called vitamins, are needed in small amounts for life processes. Eijkman and Hopkins shared the 1929 Nobel Prize in Physiology or Medicine for discovering vitamins.

In 1912 biochemist Casimir Funk was the first to coin the term vitamin in a research publication accepted by the medical community. The word vitamin comes from vita, meaning life, and amine, a nitrogenous substance essential for life. The discovery of all the vitamins occurred by 1948, and there are 13 vitamins that your body needs.

Chemists worked to identify a vitamin's chemical structure so it could be replicated, and researchers then determined the amounts needed. In 1933 Norman Haworth worked out the molecular structure of vitamin C, which paved the way for making it artificially. Albert Szent-Gyorgyi studied how cells break nutrients down to release energy, and identified vitamin C's role in those processes. Vitamin C helps the body heal wounds, and it is needed to make collagen, a fibrous protein in connective tissue.

In 1934 Henrik Dam showed that hempseed added to chicken feed stopped the slow-to-stop bleeding, and concluded it held a substance, vitamin K, needed for blood to coagulate. Vitamin K helps blood to clot, so cuts and scrapes stop bleeding quickly. Vitamins A, D, E and K are fat-soluble: they dissolve in fat and are stored in the body, and some fat in the diet is needed to absorb them. Vitamin and mineral discovery was the combined work of epidemiologists, physicians, chemists and physiologists.

Vitamin C and the B vitamins dissolve in water and are not stored, so the body needs a fresh supply each day. The body loses unused water-soluble vitamins mostly in urine. Vitamin B12 is not found naturally in fruit, vegetables or grains; it comes from animal foods or fortified foods.

Calcium helps build strong bones and teeth. Vitamin D helps the body absorb calcium, which is needed for normal bone formation. The body makes vitamin D when sunlight shines on the skin, and very few foods naturally contain vitamin D, so many foods are fortified, which means vitamins have been added. As of November 2026, most milk in the United States is fortified with 400 IU of vitamin D per quart.

Minerals are elements from soil and water that plants absorb and animals eat. Iron helps make red blood cells, which carry oxygen around the body, and beans, nuts and dried fruit are plant foods that contain iron. Foods rich in vitamin C, such as citrus, strawberries, tomatoes and potatoes, increase iron absorption, and tea can bind iron so the body cannot use it. Eating some meat, fish or poultry with beans or dark leafy greens can improve absorption of plant iron up to three times.

Sodium is a mineral the body uses to control blood volume and for muscles and nerves to work; table salt is sodium chloride. Iodized salt is table salt with iodine added, and it is the main food source of iodine. Potassium is a mineral found in most foods that helps the heart muscle work and balances fluids in the body. Zinc is needed for the senses of smell and taste.

Your body needs protein to repair cells and make new ones, and protein is found throughout the body, in muscle, bone, skin, hair and almost every other tissue. Beans are a plant food that gives your body protein. Foods from animals such as milk, eggs and fish, and from plants such as soy and beans, both supply the amino acids in protein. Nine amino acids are called essential because they must come from food.

Dietary fibre is found in the cell walls of vegetables, fruits, pulses and cereal grains, and fibre-rich foods include whole grains, beans, vegetables, fruits, nuts and seeds. Fibre is a type of carbohydrate that the body cannot digest. Soluble and insoluble are the two forms of fibre, and most high-fibre foods contain both. Fibre is a part of plant foods that helps other food and waste move through the gut.

Food is broken into tiny pieces so the body can absorb the nutrients it needs. Saliva starts to break down starches in food while the food is still in your mouth. After you swallow, muscles push food down the esophagus into the stomach, and stomach muscles mix food with digestive juices. The small intestine takes digested nutrients into the blood, and the large intestine absorbs water and turns waste into stool.

The first Dietary Guidelines for Americans came out in 1980, and as of November 2026 a new edition has been published every five years since. Different fruits and vegetables contain different mixes of fibre, vitamins and minerals, so a variety gives the body more. Eating a mix of different foods is the best way to get the vitamins and minerals you need.

Words to know

• husk: outer shell
• collagen: tissue protein
• fortified: vitamins added
• fibre: plant food part
• vitamin: needed nutrient