There are 13 essential vitamins your body needs to function properly but cannot produce in sufficient amounts on its own. That’s the defining characteristic of an “essential” nutrient: you have to get it from food or sunlight because your body either can’t make it or can’t make enough. These 13 vitamins are A, C, D, E, K, and the eight B vitamins (B1, B2, B3, B5, B6, B7, B9, and B12).
Fat-Soluble vs. Water-Soluble Vitamins
The 13 essential vitamins split into two groups based on how your body absorbs and stores them, and this distinction matters more than you might think.
Fat-soluble vitamins (A, D, E, K) dissolve in fat and get stored in your body’s tissues and liver. Because they accumulate over time rather than being flushed out, you don’t need to consume them every single day. The flip side is that taking too much can lead to toxic buildup. These vitamins absorb best when you eat them alongside some dietary fat, which is why drizzling olive oil on a salad or eating salmon with leafy greens is more than just tasty.
Water-soluble vitamins (C and all eight B vitamins) dissolve in water and are absorbed easily by the body. Your kidneys filter out whatever you don’t need, so excess amounts generally leave through urine rather than accumulating. This also means your body doesn’t maintain large reserves, so you need a steady, regular intake from your diet.
What Each Vitamin Does
Vitamin A
Vitamin A helps form and maintain healthy skin, teeth, bones, and the tissue in the back of your eye that creates vision. It also supports your immune system and mucous membranes. Adults need about 900 micrograms per day for men and 700 for women. Good sources include sweet potatoes, carrots, spinach, and liver. Your body can convert beta-carotene from orange and dark green vegetables into vitamin A as needed.
Vitamin C
Vitamin C is an antioxidant that promotes healthy gums, helps your body absorb iron, maintains healthy tissue, and is essential for wound healing. Men need about 90 mg per day, women about 75 mg. Citrus fruits, bell peppers, strawberries, and broccoli are all rich sources. Because it’s water-soluble, your body doesn’t store it long, so daily intake matters.
Vitamin D
Vitamin D helps your intestines absorb calcium, making it critical for bone and tooth health. It also helps maintain proper blood levels of calcium and phosphorus. Adults need 600 IU per day, rising to 800 IU after age 70. Your skin produces vitamin D when exposed to sunlight. Exposing bare arms and legs to midday sun for 5 to 30 minutes twice a week may be enough, but this varies enormously. People with darker skin may need up to ten times longer to synthesize the same amount. If you live above about 40 degrees latitude (think Boston or further north), there isn’t enough UVB radiation for your skin to make vitamin D from roughly November through early March.
Vitamin E
Vitamin E is an antioxidant that helps your body form red blood cells and use vitamin K. Adults need about 15 mg per day. Nuts, seeds, sunflower oil, and spinach are reliable sources. Globally, an estimated 67% of the population doesn’t get enough vitamin E from food alone.
Vitamin K
Without vitamin K, your blood would not clot normally. There’s also evidence it plays a role in bone health. Men need about 120 micrograms per day, women about 90. Leafy greens like kale, spinach, and broccoli are the best dietary sources.
The Eight B Vitamins
The B vitamins work together to convert food into energy, but each has distinct roles:
- B1 (thiamin): Converts glucose into energy and supports nerve function. Severe deficiency causes beriberi, which affects the heart, muscles, and nervous system. Adults need about 1.1 to 1.2 mg per day.
- B2 (riboflavin): Involved in energy production and helps maintain skin and vision health. Deficiency is rare on its own but tends to show up alongside other B vitamin shortfalls. A 2024 global analysis estimated that 55% of the world’s population has inadequate riboflavin intake.
- B3 (niacin): Helps convert carbohydrates, fat, and alcohol into energy while supporting skin, digestive, and nervous system health. Severe deficiency causes pellagra, characterized by dementia, diarrhea, and dermatitis.
- B5 (pantothenic acid): Needed to metabolize carbohydrates, proteins, and fats, and to produce red blood cells. Deficiency is extremely rare because B5 is found in such a wide range of foods.
- B6: Supports protein metabolism, red blood cell formation, immune function, and certain brain chemicals. Adults need 1.3 mg per day, increasing slightly after age 50.
- B7 (biotin): Needed for energy metabolism, fat synthesis, and processing amino acids. Deficiency is very rare because the body requires only small amounts.
- B9 (folate): Essential for red blood cell formation, DNA synthesis, and cell growth. It’s especially critical during pregnancy because it helps develop the fetal nervous system and reduces the risk of neural tube defects like spina bifida. Adults need 400 micrograms per day. An estimated 54% of the global population has inadequate folate intake.
- B12: Helps produce and maintain the protective coating around nerve cells, supports mental function, and aids red blood cell formation. Adults need 2.4 micrograms per day. Because B12 is found almost exclusively in animal products, people following plant-based diets are at higher risk of deficiency.
Common Deficiencies Worldwide
Vitamin deficiencies are far more widespread than most people realize. A 2024 modeling analysis published in The Lancet Global Health estimated that over 5 billion people globally don’t consume enough vitamin E, while more than 4 billion fall short on iron, riboflavin, folate, and vitamin C. Among children under 5, more than one in two are deficient in iron, zinc, or vitamin A. Among women aged 15 to 49, two in three are deficient in iron, zinc, or folate.
These gaps aren’t limited to developing countries. Vitamin D deficiency is common in northern latitudes where winter sunlight is too weak for skin synthesis. B12 deficiency affects older adults whose bodies become less efficient at absorbing it from food, as well as vegans and vegetarians who don’t supplement. Folate inadequacy remains a concern for women of childbearing age because the need spikes early in pregnancy, often before someone even knows they’re pregnant.
Food Sources vs. Supplements
Your body absorbs and uses vitamins from whole foods more effectively than from most supplements. Food delivers vitamins alongside fiber, minerals, and other compounds that can enhance absorption. Natural vitamin E, for example, is absorbed twice as efficiently as its synthetic form.
The evidence on supplement benefits is mixed at best. Several large reviews have found no clear evidence that single vitamin supplements or antioxidant combinations (including beta-carotene, vitamins A, C, and E) reduce the risk of death or cancer. One major study tracking high-dose multivitamin use over nearly five years found no beneficial effect on heart health. More concerning, beta-carotene supplements have been shown to increase cancer risk in smokers, and high-dose synthetic vitamin A and E may raise the risk of premature death. There’s also evidence that synthetic folic acid can build up in the body in ways that natural folate from food does not, potentially raising cancer risk.
This doesn’t mean supplements are never useful. They fill a genuine gap for people who can’t get enough from food alone, such as B12 for vegans, vitamin D for people in northern climates, or folate for women planning a pregnancy. The key distinction is between targeted supplementation for a specific shortfall and blanket megadosing “just in case.”
How to Absorb More From Food
Certain food pairings significantly boost how much of a vitamin your body actually takes in. Pairing vitamin C-rich foods with iron-rich plant foods (think spinach salad with citrus dressing, or hummus with bell peppers) helps your body absorb the iron that would otherwise pass through. Eating fat-soluble vitamins with a source of healthy fat makes a real difference: tomatoes with olive oil, for instance, improves your body’s uptake of lycopene, a powerful antioxidant. Combining calcium-rich foods with vitamin D sources (like milk with fortified cereal, or salmon with broccoli) helps your intestines pull in more calcium.
Cooking method matters too. Water-soluble vitamins like C and the B vitamins can leach into cooking water, so steaming or roasting vegetables preserves more of their vitamin content than boiling. Fat-soluble vitamins are more heat-stable, but prolonged high-temperature cooking still degrades them over time.
Upper Limits and Toxicity
More is not always better. Several vitamins have established upper intake limits beyond which you risk real harm. Preformed vitamin A (from animal sources and supplements, not beta-carotene from vegetables) tops out at 3,000 micrograms per day for adults. Exceeding this over time can cause liver damage, headaches, and bone thinning. Vitamin D’s upper limit is 4,000 IU per day; too much causes calcium to build up in your blood, leading to nausea, kidney problems, and weakness. Vitamin B6 has an upper limit of 25 to 100 mg per day (depending on the guideline), and chronic excess can cause nerve damage in the hands and feet. Folic acid from supplements is capped at 1,000 micrograms per day.
For most water-soluble vitamins, including B1, B2, B5, B7, and B12, no upper limit has been established because excess amounts are readily excreted. That said, “no established limit” doesn’t mean unlimited amounts are safe. It simply means the evidence hasn’t identified a clear toxicity threshold. Getting your vitamins primarily from a varied diet of whole foods is the most reliable way to stay within safe ranges while covering your needs.