What are vitamins?
Vitamins are organic substances that our body needs to function properly, so it is important to ensure a proper vitamins intake in a eating plan that’s part of healthy eating habits. Vitamins are essential micronutrients, which means that the body cannot produce them and therefore they must be obtained from the food that we eat.
Most health organizations identify thirteen vitamins: A, B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), vitamin B9 (folic acid or folate), B12 (cobalamins), C (ascorbic acid), D (calciferols), vitamin E (tocopherols and tocotrienols), and K (phylloquinone and menaquinones).
Vitamins can be classified as either fat soluble or water soluble. Fat-soluble vitamins (A, D, E, K) dissolve in fat and tend to accumulate in the body. Water-soluble vitamins (C and the B-complex vitamins) must dissolve in water before they can be absorbed by the body. Water-soluble vitamins cannot be stored and are excreted through urine when in excess.
Why are vitamins important?
Historically, when intake of vitamins from diet was lacking, the results were vitamin deficiency diseases.
How to ensure an adequate intake of vitamins?
The best way to ensure an adequate intake of all vitamins is to follow a nutrition plan that maximize the variety of healthy foods that you eat. My free weekly meal planner for healthy eating can help you build an healthy eating plan that will avoid any vitamin deficiencies.
If you would like to learn more about the required amounts of the various vitamins, in the website of the Harvard T.H. Chan School of Public Health you can find the Recommended Dietary Allowance (RDA) or Daily Adequate Intake (AI) of all vitamins.
What are the main functions of vitamins?
Learn more about the 13 vitamins:
- Vitamin A
- Vitamin B1 (thiamin)
- Vitamin B2 (riboflavin)
- Vitamin B3 (niacin)
- Vitamin B5 (pantothenic acid)
- Vitamin B6 (pyridoxine)
- Vitamin B7 (biotin)
- Vitamin B9 (folate, folic acid)
- Vitamin B12 (cobalamin)
- Vitamin C
- Choline
- Vitamin D
- Vitamin E
- Vitamin K
Vitamin A
The two main forms of vitamin A in foods are preformed vitamin A (retinoids), and provitamin A (carotenoids such as beta-carotene) that is converted to retinol by our body.
Preformed vitamin A, in the form of retinol, is found only in a limited number of animal foods. However, it is not necessary that vitamin A is introduced in this form: our body is easily able to derive it from carotenoids that are found naturally in plant foods.
| Effect on Health | Presence in food |
|---|---|
| • Is essential for vision, in particular for twilight and night vision • Maintains the health of our skin and mucous membranes • Is needed for bone growth • Plays an important role in the regulation of our immune system and the differentiation of lymphocytes • Foods with carotenoids lutein and zeaxanthin may protect against cataracts • Lycopene, a carotenoid that gives fruits and vegetables a pink or red color, may lower prostate cancer risk • Foods with carotenoids alpha carotene and lycopene may lower lung cancer risk • Carotenoids have antioxidant functions | Retinoids: • Cod liver oil • Liver in general • Eggs • Shrimps • Fish • Butter • Cheese • Milk Beta carotene: • Mauve • Vine leaves • Sweet potatoes • Carrots • Broccoli leaves • Black cabbage • Pumpkins • Melon • Apricots • Spinach • Mangoes • Turnip greens |
Read more about Vitamin A on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamins B
Vitamin B1 (thiamin)
Thiamin plays an important role in the growth and function of various cells, and in the breakdown of nutrients for energy. It must be eaten every day because the liver can only store small amounts of it.
| Effect on Health | Presence in food |
|---|---|
| A deficiency of thiamin can cause congestive heart failure, a condition that prevents the heart from properly pumping blood to the rest of the body. Clinical trials have found that thiamin supplementation can significantly improve heart function in people with heart failure. Thiamin deficiency can lead to neurological problems such as cognitive decline. One form of thiamin deficiency called Wernicke-Korsakoff syndrome cause mental status changes similar to Alzheimer’s disease. | • Yeast • Pork • Fish • Beans, lentils • Green peas • Whole grain cereals (breads, noodles, rice) • Sunflower seeds • Yogurt |
Read more about Vitamin B1 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B2 (riboflavin)
Vitamin B2, or riboflavin, is involved in the growth of cells, energy production, and the breakdown of fats, steroids, and medications. Riboflavin cannot be stored in the body, so any unused riboflavin is excreted in the urine and, when taken in excess, for example from supplements, the urine can take a bright yellow color.
Riboflavin is naturally present in foods. Gut bacteria can produce small amounts of it, but not enough to meet the minimum required daily amount.
| Effect on Health | Presence in food |
|---|---|
In humans, riboflavin has been studied as a prophylactic therapy for preventing migraines. Its activity, in fact, reduces oxidative stress and inflammation of nerves, which are contributors to migraine headaches. It also plays a role in normal mitochondrial activities, and migraines are sometimes caused by mitochondrial abnormalities in the brain. Deficiency of riboflavin can cause health issues. In animal studies, riboflavin deficiency caused brain and heart disorders, and some cancers. Symptoms of riboflavin deficiency are: Cracked lips, sore throat, swelling of the mouth and throat, swollen tongue (glossitis), hair loss, skin rash, anemia, itchy red eyes, cataracts in severe cases. | • Dairy milk • Yogurt • Cheese • Eggs • Lean beef and pork • Organ meats (beef liver) • Chicken breast • Salmon • Almonds • Spinach |
Read more about Vitamin B2 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B3 (niacin)
Niacin can be found in foods as nicotinic acid and nicotinamide. This vitamin can also be created by the body by converting the amino acid tryptophan to nicotinamide. Niacin helps to convert nutrients into energy, create cholesterol and fats, create and repair DNA, and exert antioxidant effects.
| Effect on Health | Presence in food |
|---|---|
| Niacin may have a protective effect for the brain and its deficiency has been linked with cognitive decline such as memory loss, dementia and Alzheimer’s disease. Severe deficiency of niacin causes pellagra, a disease whose symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth. Severe niacin deficiency can also lead to depression, headache, fatigue, memory loss, hallucinations. | • Red meat: beef, beef liver, pork • Poultry • Fish • Brown rice • Nuts, seeds • Legumes • Bananas |
Read more about Vitamin B3 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B5 (pantothenic acid)
Pantothenic acid, also known as vitamin B5, is needed to make coenzyme A (CoA), a substance that supports enzymes in performing metabolic functions, such as breaking down and building fatty acids and fats.
| Effect on Health | Presence in food |
|---|---|
| A deficiency of vitamin B5 is rare, because it is present in a large variety of foods. However, this is possible in people with severe malnutrition or when genetic mutations prevent pantothenic acid to be metabolized. In these cases, the following symptoms can emerge: Headache, fatigue, irritability, restlessness, disturbed sleep, nausea, vomiting, stomach cramps, numbness or burning sensation in hands or feet, muscle cramps. | Given that pantothenic acid is found in all living cells, Vitamin B5 is present in almost all plant and animal foods. The best sources are: • Organ meats (liver, kidney) • Beef • Chicken breast • Mushrooms • Avocado • Nuts, seeds • Dairy milk • Yogurt • Potatoes • Eggs • Brown rice • Oats • Broccoli |
Read more about Vitamin B5 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B6 (pyridoxine)
Vitamin B6, or pyridoxine, in its active form pyridoxal 5’ phosphate (PLP) serves as a coenzyme that supports more than 100 enzymes to perform various functions, such as breaking down macronutrients (proteins, carbohydrates, and fats), maintaining normal levels of homocysteine (whose high levels can cause heart problems); and promoting immune function and brain health.
| Effect on Health | Presence in food |
|---|---|
| Clinical studies provided evidence that high intake of vitamin B6 from foods and higher B6 blood levels were significantly associated with a lower risk of all cancers, in particular gastrointestinal cancers. Solid evidence also confirms that vitamin B6 can treat pregnancy-related nausea, also in its most severe form (hyperemesis gravidarum). A mild deficiency of vitamin B6, which most often is associated with vitamin B12 and folic acid deficiency, may show no symptoms. However, a severe deficiency or prolonged deficiency can give the following symptoms: Microcytic anemia, skin conditions, depression, confusion, and lowered immunity. | • Beef liver • Tuna • Salmon • Chickpeas • Poultry • Some vegetables and fruits, especially dark leafy greens, bananas, papayas, oranges, and cantaloupe |
Read more about Vitamin B6 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B7 (biotin)
Biotin supports enzymes with breaking down fats, carbohydrates, and proteins in food, and it contributes to regulate signals sent by cells and the activity of genes.
| Effect on Health | Presence in food |
|---|---|
| In case of biotin deficiency, the following symptoms can occur: Thinning hair; scaly skin rashes around eyes, nose, mouth; brittle nails. | • Beef liver • Eggs (cooked) • Salmon • Avocados • Pork • Sweet potato • Nuts, seeds |
Read more about Vitamin B7 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B9 (folate, folic acid)
Vitamin B9 can be found in foods in the form of folate, and in supplements as folic acid, which is better absorbed than folate. The body normally absorbs 50% of folate and 85% of folic acid.
Vitamin B9 contributes to forming DNA and RNA, is involved in protein metabolism, is needed to produce healthy blood cells, and it helps to break down homocysteine, which is an amino acid that can have a harmful effect in the body when present in excess. Vitamin B9 is also very important to sustain rapid growth like during pregnancy for the development of the fetus.
| Effect on Health | Presence in food |
|---|---|
| A low intake of folate is linked to birth defects of the spine (spina bifida) and brain (anencephaly); getting enough folate can greatly reduce the incidence of these conditions. A number of studies and reviews show that folic acid supplementation may be associated with a reduction in the risk of stroke and in stroke death rates. A deficiency of vitamin B9 can cause, weakness, fatigue, irregular heartbeat, shortness of breath, difficulty concentrating, hair loss, pale skin, mouth sores. | Folic acid, which is the vitamin B9 form that can be found in supplements, is better absorbed than folate. Folate can be commonly found in a large variety of foods, such as: • Dark green leafy vegetables (turnip greens, spinach, romaine lettuce, asparagus, Brussels sprouts, broccoli) • Beans • Peanuts • Sunflower seeds • Fresh fruits, fruit juices • Whole grains • Liver • Seafood • Eggs |
Read more about Vitamin B9 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin B12 (cobalamin)
Vitamin B12 is used in our body to form red blood cells and DNA, and it’s needed for the development of the brain and of nerve cells.
| Effect on Health | Presence in food |
|---|---|
| Up to 15% of the general population has a vitamin B12 deficiency. Not eating animal products, such as meat, fish, poultry, or dairy can cause a vitamin B12 deficiency. The simple reason is that vitamin B12 is naturally only found in animal products. People following a vegetarian or vegan diet are recommended to take vitamin B12 to avoid such deficiency. During pregnancy, vitamin B12 is needed for adequate neurologic development of the fetus so supplementation is particularly important in vegetarian and vegan pregnant women. A deficiency can happen more in general in case of intestinal or digestive disorders that can cause malabsorption. A vitamin B12 deficiency can cause megaloblastic anemia, pernicious anemia, fatigue and weakness, nerve damage with numbness, tingling in the hands and legs. Memory loss, confusion. Dementia, depression, seizures. | • Fish, shellfish • Liver • Red meat • Eggs • Poultry • Dairy products such as milk, cheese, and yogurt |
Read more about Vitamin B12 on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin C
Vitamin C has a fascinating history that started with the discovery that eating citrus fruits prevented sailors from dying from scurvy during their long journeys over the sea. It was later discovered that the prevention of scurvy is actually due to the vitamin C that can be found in these fruits.
| Effect on Health | Presence in food |
|---|---|
| Vitamin C is a powerful antioxidant that can neutralize harmful free radicals. It helps controlling infections and healing wounds, and it’s needed to make collagen that’s important for our nervous and immune systems, and for our bones, cartilage, and blood. It’s also involved in producing hormones and chemical messengers needed in the brain and nerves. Vitamin C is also involved in the body’s immune system by stimulating the activity of white blood cells. Eating foods rich in vitamin C may also lower the risk for some cancers, including those of the mouth, esophagus, stomach, and breast. Vitamin C may also protect against cataracts. | Vitamin C can be found primarily in fruits and vegetables, in particular: • Citrus (oranges, kiwi, lemon, grapefruit) • Bell peppers • Strawberries • Tomatoes • Cruciferous vegetables (broccoli, Brussels sprouts, cabbage, cauliflower) • White potatoes |
Read more about Vitamin C on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Choline
The body can also produce small amounts of choline on its own in the liver, but not enough to meet daily needs. So, it’s important to regularly eat foods that contain choline.
| Effect on Health | Presence in food |
|---|---|
| Choline is converted into a neurotransmitter called acetylcholine, which is important for muscle contraction, for pain responses, and and for brain functions of memory and thinking. Most choline is converted into phosphatidylcholine by the liver, which is needed to build fat-carrying proteins and to break down cholesterol. Choline is also a nutrient for the gut bacteria that populate our gut. | • Beef, beef liver • Egg yolks • Chicken breast • Fish • Shiitake mushrooms • Potatoes • Legumes (beans, peanuts) • Milk • Yogurt • Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, cabbage) • Sunflower seeds |
Read more about Choline on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin D
Vitamin D is called the “sunshine vitamin” because our skin can produce vitamin D when exposed to the natural ultraviolet-B (UVB) rays. 10 / 15 minutes of exposure of a sufficient area of the skin (at least face, neck, harms and legs) to direct sunlight midday without sunscreen protection are normally sufficient to ensure the daily required intake of vitamin D. However, unfortunately most people do not have sufficient levels of vitamin D due to lack of sufficient exposure to sunlight. Few foods contain vitamin D, so for most people it’s normally difficult to have a sufficient intake of vitamin D only from food. In these cases, the best way to ensure an adequate intake of this important vitamin is through supplementation.
| Effect on Health | Presence in food |
|---|---|
| Vitamin D is not only a nutrient we eat but also a hormone produced by our body. Vitamin D is fat-soluble vitamin that helps absorb and retain calcium and phosphorus, which critical for building bone. Vitamin D can reduce cancer cell growth, help control infections and reduce inflammation. Many of the organs and tissues in our body have receptors for vitamin D, which suggest important roles beyond bone health. | • Cod liver oil • Salmon • Swordfish • Tuna fish • Sardines • Beef liver • Egg yolk |
Read more about Vitamin D on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin E
Vitamin E is a fat-soluble vitamin that acts as an antioxidant that help fighting free radicals that can damage cells. It enhances immune function and prevents clots from forming in heart arteries.
| Effect on Health | Presence in food |
|---|---|
| Vitamin E is an antioxidant that neutralizes unstable molecules that can damage cells. It protects vitamin A and certain lipids from damage. Vitamin E may help prevent Alzheimer’s disease. | Vitamin E is found in plant-based oils, nuts, seeds, fruits, and vegetables. • Wheat germ oil • Sunflower, safflower, and soybean oil • Sunflower seeds • Almonds • Peanuts, peanut butter • Beet greens, collard greens, spinach • Pumpkin • Red bell pepper • Asparagus • Mango • Avocado |
Read more about Vitamin E on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
Vitamin K
Vitamin K is a fat-soluble vitamin that comes in two forms:
Phylloquinone, found in green leafy vegetables like collard greens, kale, and spinach.
Menaquinones, found in some animal foods and fermented foods. Menaquinones can also be produced by bacteria in the human body.
Vitamin K plays a role in blood clotting and in the building of bones.
| Effect on Health | Presence in food |
|---|---|
| Activates proteins and calcium, which are essential to blood clotting. May help prevent hip fractures. | Intestinal bacteria make a form of vitamin K that accounts for half your requirements. If you take an anticoagulant, keep your vitamin K intake consistent. Phylloquinone • Green leafy vegetables including collard and turnip greens, kale, spinach, broccoli, Brussels sprouts, cabbage, lettuces • Soybean and canola oil Menaquinones • Natto (fermented soybeans) • Smaller amounts in meat, cheese, eggs |
Read more about Vitamin K on The Nutrition Source of the Harvard T.H. Chan School of Public Health.
