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Vitamins

Medical Author: Betty Kovacs, MS, RD
Medical Editor: Melissa Conrad Stöppler, MD

What are vitamins?

Vitamins are an essential part of our diet. Without an adequate amount of vitamins, a deficiency will occur. Vitamins are naturally found in the foods that we consume and are also found in supplements. A well-balanced diet is often enough to meet the vitamin needs of healthy individuals. When a supplementation is needed, it is important to know how much you need to take and the best way to take it.

Vitamin A

Vitamin A has many important functions in your body. It helps regulate your immune system, helps form and maintain healthy teeth, skin, and tissue, it produces the pigments in the retina of the eye, and promotes good vision. A deficiency in this vitamin can lead to problems with any of these. The vitamin A found in plants serves different functions than the vitamin A found in animals. The animal sources of vitamin A are liver, whole milk, and fortified foods, and the plant sources include colorful fruits and vegetables like carrots, spinach, kale, and cantaloupe.

The recommended dietary allowances (RDA) for vitamin A are listed as international units (IU) of retinol activity equivalents (RAE). This is done to account for the different actions of both forms of vitamin A.

The following is the RDA for vitamin A:

Age Males Females Pregnancy Lactation
1-3 years 1,000 IU 1,000 IU N/A N/A
4-8 years 1,320 IU 1,320 IU N/A N/A
9-13 years 2,000 IU 2,000 IU N/A N/A
14-18 years 3,000 IU 2,310 IU 2,500 IU 4,000 IU
19+ years 3,000 IU 2,310 IU 2,565 IU 4,300 IU

Going above the RDA for vitamin A can initially cause nausea, vomiting, irritability, drowsiness, altered mental status, anorexia, abdominal pain, blurred vision, muscle pain with weakness, and/or headache. Over time, this can lead to hypervitaminosis A or vitamin A toxicity. The harmful effects of this are birth defects, reduced bone density that may result in osteoporosis, central nervous system disorders, and liver abnormalities.

Vitamin B1

Vitamin B1 is most commonly known as thiamin. It is involved in numerous body functions, including metabolism of carbohydrates, assisting with muscle functioning, producing hydrochloric acid, and assisting with nervous system functioning. A deficiency can cause weakness, fatigue, nerve damage, and psychosis. When the deficiency becomes severe, it causes a disease known as beriberi. There are many foods that provide thiamin so it's easy to get enough from your diet. Some of these foods are beans, pork, fortified cereal, and enriched rice.

The following is the RDA for thiamin:

Age Males Females Pregnancy Lactation
1-3 years 0.5 mg 0.5 mg
4-8 years 0.6 mg 0.6 mg
9-13 years 0.9 mg 0.9 mg
14-18 years 1.2 mg 1.0 mg
19+ years 1.2 mg 1.1 mg
All ages 1.4 mg 1.4 mg

Vitamin B2

Vitamin B2 is most commonly known as riboflavin. It is needed for converting food to energy, to work as an antioxidant by scavenging damaging free radicals, and to convert vitamin B6 and folate into active forms. Most people meet their needs with a balanced diet. Good sources of riboflavin are milk, spinach, fortified cereal, eggs, and green vegetables. You can be deficient in riboflavin when you don't consume enough riboflavin, but other things that can cause a deficiency are malabsorption syndromes, chronic diarrhea, long-term use of barbiturates, peritoneal dialysis, and alcoholism. The symptoms of a riboflavin deficiency are fatigue, skin irritations, cracks and sores around the corner of the mouth, and sensitivity to light.

The following is the RDA for riboflavin:

Age Males Females Pregnancy Lactation
1-3 years 0.5 mg 0.5 mg N/A N/A
4-8 years 0.6 mg 0.6 mg N/A N/A
9-13 years 0.9 mg 0.9 mg N/A N/A
14-18 years 1.3 mg 1.0 mg 1.4 mg 1.6 mg
19 + years 1.3 mg 1.1 mg 1.4 mg 1.6 mg

Vitamin B3

Vitamin B3 is most commonly known as niacin. It has been shown to help turn carbohydrates into energy, assist with the proper functioning of the nervous and digestive systems, and help maintain healthy skin. There is also evidence that it can help increase HDL or "good" cholesterol levels. Niacin is found in animal products, nuts, green vegetables, legumes, and enriched and fortified cereals

The following is the RDA for niacin:

Age Males Females Pregnancy Lactation
1-3 years 6 mg 6 mg N/A N/A
4-8 years 8 mg 8 mg N/A N/A
9-13 years 12 mg 12 mg N/A N/A
14-18 years 16 mg 14 mg 18 mg 17 mg
19+ years 16 mg 14 mg 18 mg 17 mg

Pellagra is the disease that occurs due to a severe niacin deficiency. The symptoms of pellagra are known as the four Ds: dermatitis, diarrhea, dementia, and death. Prior to this, the symptoms of a niacin deficiency will involve the digestive system (diarrhea, vomiting, bright red tongue), the skin (dark pigmented rash that develops symmetrically in areas exposed to sunlight, thick and scaly skin), and the nervous system (fatigue, depression, headache, apathy, disorientation, and memory loss).

Vitamin B6

Vitamin B6 comes in three forms and plays a role in red blood cell metabolism, making hemoglobin, assisting in the proper functioning of the nervous and immune systems, taking part in protein metabolism, and making the neurotransmitters serotonin and norepinephrine. It is found in many foods so it's easy to consume enough through your diet. Some foods that contain vitamin B6 are bananas, potatoes, chicken breast, garbanzo beans, seeds, and roast beef.

The following is the RDA for vitamin B6:

Age Males Females Pregnancy Lactation
1-3 years 0.5 mg 0.5 mg N/A N/A
4-8 years 0.6 mg 0.6 mg N/A N/A
9-13 years 1.0 mg 1.0 mg N/A N/A
14-18 years 1.3 mg 1.2 mg 1.9 mg 2.0 mg
19-50 years 1.3 mg 1.3 mg 1.9 mg 2.0 mg
51+ years 1.7 mg 1.5 mg

Symptoms of a B6 deficiency are depression, confusion, sores or ulcers on the mouth, ulcers at the corners of the mouth, confusion, and irritability. Excess amounts can cause problems as well. Taking a supplement with over 1,000 mg/day has been shown to cause sensory neuropathy. Symptoms of this include difficulty walking and pain and numbness of the extremities.

Vitamin B12

Vitamin B12 is a very important water-soluble vitamin. It is needed for producing and maintaining new cells (nerve and red blood cells) and for making DNA. Without enough vitamin B12, you are at risk for pernicious anemia. The symptoms of B12 deficiency are fatigue, constipation, weakness, loss of appetite, weight loss, and numbness and tingling in the hands and feet. You may also experience a difficulty in maintaining balance, confusion, dementia, depression, and poor memory. Fortunately, you can get enough in your diet by consuming animal foods like beef, salmon, trout, tuna, chicken, eggs, and yogurt. You can also get it from fortified cereals.

The following is the RDA for vitamin B12:

Age Males and Females Pregnancy Lactation
1-3 years 0.9 mcg N/A N/A
4-8 years 1.2 mcg N/A N/A
9-13 years 1.8 mcg N/A N/A
14-19 years 2.4 mcg 2.6 mcg 2.8 mcg
19+ years 2.4 mcg 2.6 mcg 2.8 mcg

Some medications, stomach or intestinal disorders, old age, and a diet free of meat and meat products can increase the risk of vitamin B12 deficiency. Your doctor can perform a blood test to determine if you need to take a supplement.

Vitamin C

Vitamin C is mostly known for its ability to help with colds, but it has many more important functions in your body. Vitamin C is needed for the growth and repair of tissues in all parts of your body. It helps with the structural part of blood vessels, ligaments, and tendons. It also is an antioxidant, meaning that it protects your body from dangerous products of metabolism called free radicals, which are linked to cancer and other diseases. There are plenty of rich sources of vitamin C so you can reach your needs without a supplement by balancing your diet. Foods that are high in vitamin C are red peppers (higher than oranges), guava, oranges, kiwi, brussels sprouts, and broccoli.

The following is the RDA for vitamin C:

Age Males Females Pregnancy Lactation
1-3 years 15 mg 15 mg N/A N/A
4-8 years 25 mg 25 mg N/A N/A
9-13 years 45 mg 45 mg N/A N/A
14-18 years 75 mg 65 mg 80 mg 115 mg
19 + years 90 mg 75 mg 85 mg 120 mg

Scurvy is a disease caused by a severe vitamin C deficiency. It's not common any longer, but it can still occur. You can experience a deficiency without getting scurvy. The symptoms are feeling weak, tired, and irritable, dry and splitting hair, bleeding gums, rough, dry, scaly skin, gingivitis, easy bruising, anemia, and a decreased ability to fight infection. Excess intakes can cause stomach upset, diarrhea, and possibly kidney stones.

Vitamin D

Vitamin D is known by most as the sunshine vitamin. The ultraviolet rays from the sunlight help your body produce vitamin D when they hit your skin for at least 10 minutes. The sunlight is not the only way to get vitamin D. Foods like seafood, mushrooms, and egg yolks naturally contain this vitamin, and other foods have it added so you can reach your needs with your diet.

Vitamin D is needed to maintain blood levels of calcium and phosphorus. A deficiency in children can cause rickets, a disease that causes soft, weak bones; this results in skeletal deformities (bowed legs), impaired growth, bone pain, and dental problems. In adults, a deficiency can cause osteomalacia and osteoporosis.

The recommendations for vitamin D are listed as an adequate intake in micrograms (mcg) and international units (IU):

Age Vitamin D
Birth to 13 years 5 mcg (200 IU)
14-18 years 5 mcg (200 IU)
19-50 years 5 mcg (200 IU)
51-70 years 10 mcg (400 IU)
71+ years 15 mcg (600 IU)

Vitamin E

Vitamin E naturally occurs in eight different chemical forms, but the only one that meets human requirements is alpha-tocopherol. It's needed to maintain cell integrity and act as a powerful antioxidant. Vitamin E is a fat-soluble vitamin, so foods like nuts, seeds, and vegetable have a high content. While deficiency is rare, it can happen. Symptoms of vitamin E deficiency are peripheral neuropathy, impaired immune system, retinopathy, and skeletal myopathy.

The following is the RDA for vitamin E:

Age Males and Females Pregnancy Lactation
1-3 years 6 mg (9 IU) N/A N/A
4-8 years 7 mg (10.5 IU) N/A N/A
9-13 years 11 mg (16.5 IU) 15 mg (22.5 IU) 19 mg (28.5 IU)
14 + years 15 mg (22.5 IU) 15 mg (22.5 IU) 19 mg (28.5 IU)

Vitamin K

Vitamin K is known by many people taking blood-thinner medications. It is limited by them because of its role in blood clotting. The goal when taking blood thinners is to consume a consistent amount of vitamin K, not to eliminate it from your diet. A deficiency in vitamin K can lead to defective blood clotting and increased bleeding. The foods with the highest amount of vitamin K are kale, spinach, turnips, collards, mustard greens, and brussels sprouts.

There is no data to establish an RDA for vitamin K. Therefore, adequate intakes (AI) have been established:

Age Males Females Pregnancy Lactation
0-6 months 2.0 mcg 2.0 mcg N/A N/A
7-12 months 2.5 mcg 2.5 mcg N/A N/A
1-3 years 30 mcg 30 mcg N/A N/A
4-8 years 55 mcg 55 mcg N/A N/A
9-13 years 60 mcg 60 mcg N/A N/A
14-18 years 75 mcg 75 mcg 75 mcg 75 mcg
19+ years 120 mcg 90 mcg 90 mcg 90 mcg

A well-balanced diet is often enough to reach all of your recommended vitamins. Certain medical conditions, dietary restrictions, and medications can require that you take a vitamin K supplement in order to reach your goals. It's best to work with a health-care professional to determine how much you should take. Excess quantities can be as dangerous as not consuming enough. The key is always to give your body the optimal levels for optimal health.

REFERENCE:

Kovacs, Betty. "Vitamins and Calcium Supplements." MedicineNet.com. Mar. 26, 2009. <https://www.rxlist.com/vitamins_and_calcium_supplements/article.htm>.

Reviewed by:
Tova Alladice, M.D.
American Board of Physical Medicine & Rehabilitation

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