Understanding the Different Types of Vitamins

Vitamins are substances the body needs in small amounts to grow, develop and function normally. There are 13 of them, and with few exceptions they have to come from food. They are usually divided into two groups according to how the body absorbs and stores them, a distinction that explains why some can build up to harmful levels and others cannot.

The two groups

Fat-soluble vitamins

Vitamins A, D, E and K dissolve in fat. They are absorbed along with fats in the diet and stored in the liver and fatty tissue. Because the body holds on to them, you do not need them every single day, but taking large amounts over time can cause them to accumulate.

Water-soluble vitamins

Vitamin C and the B vitamins dissolve in water. The body uses what it needs and removes most of the excess in urine, so a regular intake matters. Vitamin B12 is an exception: the liver can store it for years.

The fat-soluble vitamins at a glance

• Vitamin A: needed for normal vision, the immune system and healthy skin. Found in liver, dairy, eggs and, as beta-carotene, in orange and dark green vegetables.
• Vitamin D: helps the body absorb calcium for bones and teeth, and supports muscles and the immune system. Made in the skin in sunlight and found in oily fish and fortified foods.
• Vitamin E: an antioxidant that helps protect cells. Found in vegetable oils, nuts and seeds.
• Vitamin K: needed for blood clotting and healthy bones. Found in green leafy vegetables.

The water-soluble vitamins at a glance

• Vitamin C: needed to make collagen, helps wounds heal and improves the absorption of iron from plant foods. Found in citrus fruit, peppers, berries and broccoli.
• Thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5) and biotin (B7): help the body release energy from food.
• Vitamin B6: involved in protein metabolism and making red blood cells.
• Folate (B9): needed to make DNA and for cell division. Especially important before and during early pregnancy.
• Vitamin B12: keeps nerve and blood cells healthy. Found naturally only in animal foods.

How much is enough?

Recommended amounts differ by age, sex and life stage. On U.S. labels, the percent Daily Value shows how much one serving contributes to a typical day’s needs.

Can you have too much?

Yes. Tolerable upper intake levels exist for several vitamins. Fat-soluble vitamins are the main concern because they are stored. For example, too much preformed vitamin A can cause liver damage and, in pregnancy, birth defects. Very high doses of some water-soluble vitamins also cause problems: large amounts of vitamin B6 over a long period can damage nerves.

Who may need more

• People who are pregnant or planning a pregnancy (folic acid)
• Older adults (vitamins B12 and D)
• People who follow a vegan diet (vitamin B12)
• People who get little sun exposure (vitamin D)
• People with conditions that affect absorption

A doctor or dietitian can assess whether a supplement is appropriate.

Food first

Health authorities agree that most people can get the vitamins they need from a balanced diet of vegetables, fruit, whole grains, protein foods and dairy or fortified alternatives. A supplement such as our Daily Multivitamin can complement the diet but does not replace it.

The bottom line

Thirteen vitamins, two groups: fat-soluble vitamins are stored, most water-soluble ones need regular topping up. A varied diet covers most needs. Browse single vitamins and combinations in our vitamins and nutrition department.

Sources

1. MedlinePlus. Vitamins.
2. NHS. Vitamins and minerals.
3. NIH Office of Dietary Supplements. Dietary Supplement Fact Sheets.