Table of contents
1 Common vitamin deficiency symptoms and their potential cause
2 Vitamin A: for eyes and skin
3 Vitamin B1: essential for carbohydrate metabolism
4 Vitamin B2: for skin, brain, hair, blood and nerves
5 Vitamin B3: for your immune system
6 Vitamin B5: for a stable hormone balance
7 Vitamin B6: for the production of red blood cells
8 Vitamin B9: prevents heart disease
9 Vitamin B12: for DNA synthesis
10 Vitamin C: is needed for the production of collagen
11 Vitamin D: strengthens the bones
12 Vitamin E: neutralizes unstable molecules
13 Vitamin K: essential for blood clotting
14 Frequently asked questions about vitamins

If you're looking for ways to improve your quality of life, you've come to the right place! Vitamins are micronutrients that are essential for your well-being. We explain which vitamins are available and where you can get them reliably.

By definition, vitamins are foods that your body needs to carry out various vital functions. All vitamins are essential for your body and, as the name suggests, essential for your everyday vitality. Only vitamin D and vitamin B3 can be produced by your body. Most vitamins must be taken through your diet. In this article, we explain what role vitamins play in your body, how much you should take and how potential deficiency symptoms can manifest themselves.

Common vitamin deficiency symptoms and their potential cause

Symptom Deficiency of
Lack of concentration Vitamin D
Tiredness Vitamin D, Vitamin B12
Rash on areas that are often exposed to the sun Vitamin B3
Slight bruising/ bruises Vitamin K, Vitamin C
Dementia Vitamin B1, Vitamin B3, Vitamin B12
Sensitive bones Vitamin D
Painful, very red or swollen lips Vitamin B2, Vitamin B3, Vitamin B6
Inflammation of the tongue Vitamin B2, Vitamin C
Abnormal tingling or numbness Vitamin B1
Joint swelling or pain Vitamin C
Cognitive deficits Vitamin B1, Vitamin B3, Vitamin B6, Vitamin B12
Impaired night vision Vitamin A
Clouding of the cornea/blurred vision Vitamin A
Numbness Vitamin B1, Vitamin B12
Frequent bleeding gums or tooth loss Vitamin C

Vitamin A: for eyes and skin

Vitamin A produces the pigments in our eye retina. In addition to the eyes, vitamin A is essential for the health of the skin. The recommended daily intake for adults is approx. 1.0 mg for men and 0.8 mg per day for women.1

What vitamin deficiency symptoms can occur with vitamin A?

Vitamin A deficiency is the main cause of avoidable blindness in children. A lack of vitamin A can cause the following symptoms:

  • Xerophthalmie: dry, thickened conjunctiva and cornea
  • Night -blindness
  • Horny tumors (metaplasia) on the conjunctiva that lead to blurred vision 2

Natural sources of vitamin A

  • Sweet potatoes (961 μg/ 100 g)
  • Carrots (852 μg/ 100 g)
  • Tuna (757 μg/ 100 g)
  • Pumpkin (558 μg/ 100 g)
  • Spinach (524 μg/ 100 g)
  • Honeydew melon (169 μg/ 100 g)

Vitamin B1: Essential for carbohydrate metabolism

Vitamin B1 is particularly important for carbohydrate metabolism.3 It helps to break down and release energy from food. It is therefore indirectly extremely important for the general health of the skin, hair, muscles, brain and nerves.4 The need for vitamin B1 decreases slightly with age. The recommended daily intake of vitamin B1 for adults is between 1.1 and 1.3 mg/day.5

What vitamin B1 deficiency symptoms can occur?

As a result of one Vitamin B1 due to the lack of The Beriberi disease arises where alcoholics suffer particularly often. It leads to peripheral neuropathy. People with this disease have an impairment of sensory, motor and reflex functions. 6

Natural sources of vitamin B1

  • Both fresh and dried fruits
  • Linseed (1.6mg/100g)
  • Salmon (0.3mg/100g)
  • Peas (0.3mg/100g)
  • Tofu (0.2mg/100g)
  • Brown rice (0.2mg/100g)7

Vitamin B2: for skin, brain, hair, blood and nerves

Similar to B1, B2 is extremely important for the health of the skin, brain, hair, blood and nerves, as it also plays an important role in our body's energy metabolism. Men need about 1.3-1.4 mg, women about 1.0-1.1 mg, and pregnant women about 1.3-1.4 mg of vitamin B2 per day.8

What vitamin B2 deficiency symptoms can occur?

Vitamin B2 deficiency It only happens extremely rarely, but the consequences can be varied and serious. In addition to inadequate intake, endocrine anomalies (such as thyroid hormone deficiency) and various diseases of vitamin B2 are caused. 9 The signs and symptoms of a vitamin B2 In the lack of a lack of skin diseases, hyperemia and edema in the mouth and throat, torn corners of mouth, cheilosis (swollen, cracked lips), hair loss, sexual problems, sore throat, itchy and red eyes as well as liver and nerve damage. [ 10.11]

Natural sources of vitamin B2

  • Almonds (1.1mg/100g)
  • Salmon (0.5mg/100g)
  • Mushrooms (0.5mg/100g)
  • Spinach (0.5mg/100g)
  • Eggs (0.5mg/100g)

Vitamin B3: for your immune system

Vitamin B3 is very important for the energy utilization of our food and for the health of our skin, blood cells and brain. It plays a central role in the function of the nerves and liver.12 In adults, the daily requirement of vitamin B3 decreases slightly with age. Men need approx. 14-16 mg per day, women approx. 11-13 mg per day and pregnant/breastfeeding women approx. 14-16 mg per day.13

What vitamin deficiency symptoms can occur?

More difficult Vitamin B3 deficiency leads to a disease called Pellagra. Pellagra causes a rash or a brown discoloration when skin is exposed to sunlight. The skin also develops a rough, sunburn -like appearance. 14 In addition, Pellagra can cause a strikingly red tongue and changes in the digestive tract that lead to vomiting, constipation or diarrhea. Pellagra's neurological complaints include depression, apathy, headache, fatigue, loss of memory, which can lead to aggressive behavior, and visual hallucinations. 15

Natural sources of vitamin B3

  • Tuna (22.1mg/100g)
  • Peanuts (14.4mg/100g)
  • Chicken breast (9.5mg/100g)
  • Portobello mushrooms (6.3mg/100g)
  • Brown rice (2.6mg/100g)

Vitamin B5: for a stable hormone balance

Vitamin B5 is not only important for energy metabolism, like other B vitamins, but also helps in the production of neurotransmitters, steroid hormones, fatty acids and haemoglobin. Adolescents and adult men and women require 6 mg of vitamin B5 per day from the age of 14.16

What vitamin B5 deficiency symptoms can occur?

Since vitamin B5 is contained in almost all foods, a defect rarely occurs, except for people with severe malnutrition. 17 If someone at one Vitamin B5 deficiency suffers, he usually goes hand in hand with a lack of other nutrients, so it is difficult to identify specific effects for a vitamin B5 deficiency. Vitamin B5 deficiency occurs almost exclusively in people who consumed vitamin B5 metabolic antagonists. 18

Natural sources of vitamin B5

  • Sunflower seeds (7 mg/ 100g)
  • Shiitake mushrooms (3.6 mg/ 100g)
  • Salmon (1.9 mg/ 100g)
  • Avocados (1.4 mg/ 100g)
  • Sweet potatoes (0.5 mg/ 100g)

Vitamin B6: for the production of red blood cells

Vitamin B6 helps to regulate homocysteine levels (blood levels of the amino acid homocysteine) and can reduce the risk of heart disease. It supports the conversion of tryptophan into niacin and serotonin, a neurotransmitter that plays a central role in sleep, appetite and mood. Vitamin B6 helps in the formation of red blood cells and influences cognitive abilities and immune function.19 Adult men have a daily requirement of 1.6 mg of vitamin B6 per day. Women 1.4 mg per day or 1.5-1.8 mg per day if pregnant or breastfeeding20

What vitamin B6 deficiency symptoms can occur?

An isolated lack of vitamin B6 is extremely rare and is usually associated with low concentrations of other vitamins of the B complex, such as vitamin B12. A Vitamin B6 deficiency causes biochemical changeswho are becoming more and more obvious with the progressive deficiency.

Vitamin B6 deficiency is associated with anemia, dermatitis with cheilosis (dandruff on the lips and cracks on the corners of the mouth) and glossitis (swollen tongue), depression and confusion as well as a weakened immune system. People with a slight deficiency cannot have deficiency symptoms or symptoms for months or even years. In infants, a vitamin B6 deficiency leads to irritability, abnormal hearing loss and cramp-like seizures. 21 Kidney diseases in the final stage, chronic renal insufficiency and other kidney diseases can also cause vitamin B6 deficiency. 22

Natural sources of vitamin B6

  • Salmon (0.9 mg/100g)
  • Tofu (0.5 mg/ 100g)
  • Bananas (0.4 mg/ 100g)
  • Potatoes (0.3 mg/ 100g)
  • Sweet potatoes (0.2 mg/ 100g)

Vitamin B9: prevents heart disease

Vitamin B9, also known as folic acid, is essential for the production of red blood cells, can reduce homocysteine ​​levels (blood levels of amino acid homocysteine) and thereby reduce the risk of heart disease. It helps to prevent the brain and spine's birth defects if it is taken early in pregnancy. Adult men and women need approx. 300 µg vitamin B9 per day. Still end approx. 450 µg and pregnant women approx. 550 µg per day. 23

What vitamin B9 deficiency symptoms can occur?

An isolated lack of vitamin B9 is unusual and usually exists in parallel with other nutrient deficits, since it is closely related to poor nutrition, alcoholism and malabsorptive disorders. The megaloblastic anemia, which is characterized by large, abnormal blood cells, is the primary clinical sign of a vitamin B9 deficiency. 25 To the Symptoms of folic acid deficiency count fatigue, feelings of weakness, difficulties of concentration, irritability, headache, palpitations and shortness of breath. 26 A vitamin B9 deficiency can cause pain on the tongue and oral mucosa, changes in skin, hair or fingernail pigmentation, and increased gay stone concentrations in the blood. 27

Natural sources of vitamin B9

  • Soybeans (311 μg/ 100 g)
  • Lentils (181 μg/ 100 g)
  • Asparagus (149 μg/ 100 g)
  • Spinach (146 μg/ 100 g)
  • Broccoli (108 μg/ 100 g)

Vitamin B12: for DNA synthesis

Vitamin B12 supports the lowering of the homocysteine ​​mirror (blood levels of amino acid homocysteine) and can therefore reduce risk of heart disease, as well as vitamin B9. It contributes to the formation of red blood cells and DNA. Vitamin B12 helps with the formation of new cells, with the breakdown of some fatty acids and promotes the growth of the nerve cells. 28 The daily requirement for vitamin B12 for adult men and women is around 4.0 µg per day. Pregnant women need approx. 4.5 µg and breastfeeding women approx. 5.5 µg 29

What happens with vitamin B12 deficiency

Vitamin B12 deficiency Is characterized by fatigue, general weakness, anemia, loss of appetite and weight loss. 30 Neurological problems, such as numbness and tingling in the hands and feet, can occur. 31 Other symptoms of a vitamin B12 deficiency are depression, confusion, equilibrium, dementia, bad memory and pain in the mouth or on the tongue. The neurological symptoms of a vitamin B12 deficiency can also occur without anemia, which is why early diagnosis and intervention is important to avoid incurable damage. 32

Natural sources of vitamin B12

  • Mussels (98.9 μg/ 100 g)
  • Tuna (10.9 μg/ 100 g)
  • Beef (7.5 μg/ 100 g)
  • Eggs (1.1 μg/ 100 g)
  • Milk (0.5 μg/ 100 g)

Vitamin C: is required for the production of collagen

Our body needs vitamin C to form collagen33, a connective tissue that is needed to heal wounds and supports the blood vessel walls. Vitamin C helps in the formation of neurotransmitters (noradrenaline and serotonin). It is also an antioxidant and neutralizes unstable molecules that can damage cells and thus cause cancer34 Adult men need approx. 110 mg, women 95 mg, pregnant women 105 mg and breastfeeding women 125 mg of vitamin C per day.35

What vitamin C deficiency symptoms can occur?

An acute Vitamin C deficiency is relatively quick compared to other nutrient deficiencies. Vitamin C deficiency leads to scurvy. 36 The course of the scurvy formation varies greatly, but the first signs can already occur within one month. 37

Initial symptoms can be fatigue, malaise and gingivitis. 38 As the vitamin C deficiency progresses, the collagen synthesis is disrupted and the connective tissue is weakened, which leads to petechia, joint pain, poor wound healing or hyperkeratosis. 39 Other signs of scurvy are depression as well as swollen, bleeding gums and loosening or loss of teeth due to tissue trimmers and capillary weakness (due to the lack of collagen). 40

Natural sources of vitamin C

  • Guava (228 mg/ 100 g)
  • Paprika (128 mg/ 100 g)
  • Kiwi (93 mg/ 100 g)
  • Strawberries (59 mg/ 100 g)
  • Oranges (53 mg/ 100 g)

Vitamin D: strengthens the bones

Vitamin D helps to stabilize normal calcium and phosphorus levels in the blood, which strengthens bones. It also supports the formation of teeth and bones. Vitamin D can be synthesized naturally in the body if you are regularly exposed to the sun. If an adult gets hardly any sunlight in their daily life, they should take about 20 µg per day in the form of a dietary supplement.41

These are the typical vitamin D deficiency symptoms

Rachitis and osteomalacia are classic vitamin D deficiency diseases. In children, vitamin D deficiency causes rachitis, a disease that is characterized by a lack of mineralization of the bone tissue, which leads to soft bones and skeletal deformities. 42

In adults a Vitamin D deficiency lead to osteomalacia, which results in bone weakness. Symptoms of bone pain and muscle weakness can indicate an inadequate vitamin D level, but such symptoms can be subtle and remain undetected in the initial stage. 43

Natural sources of vitamin D

  • Salmon (16.7 μg/ 100 g)
  • Mushrooms (that have been in the sun) (31.9 μg/ 100 g)

Vitamin E: neutralizes unstable molecules

Vitamin E is an antioxidant that neutralizes unstable molecules that can damage cells. It also protects vitamin A and fatty acids from damage. The need for vitamin E decreases with age. Adult men need about 12-15 mg per day and women about 11-12 mg per day.44

What vitamin E deficiency symptoms can occur?

Since the digestive tract requires fat to absorb vitamin E, there is a higher probability of a defect in people with fat absorption disorders than in humans without such disorders. 45 To the Massal symptoms of vitamin E include retinopathy, peripheral neuropathy, skeletal muscle myopathy, ataxia, and an impairment of the immune system. 46

Natural sources of vitamin E

  • Sunflower seeds (26.1 mg/ 100 g)
  • Almonds (25.6 mg/ 100 g)
  • Avocados (2.1 mg/ 100 g)
  • Spinach (2.1 mg/ 100 g)
  • Butternut squash (1.3 mg/ 100 g)

Vitamin K: essential for blood clotting

Vitamin K activates various proteins and calcium and is therefore particularly essential for blood clotting. The recommended daily dose of vitamin K for adult men is approx. 70-80 µg per day. An adult woman needs approx. 60-65 µg per day and approx. 60 µg per day if she is breastfeeding or pregnant.47

What vitamin deficiency symptoms can occur?

Bleeding are the classic signs of one Vitamin K deficiency, although these effects only occur in severe cases. Since vitamin K is required for the carboxylation of osteocalcin in the bone, a vitamin K deficiency can reduce the mineralization of the bones and thus contribute to osteoporosis or a general reduction in bone density. 48

Natural sources of vitamin K

  • Cabbage (419 μg/ 100 g)
  • Broccoli (141 μg/ 100 g)
  • Cabbage sprouts (140 μg/ 100 g)
  • Asparagus (51 μg/ 100 g)
  • Kiwi (40 μg/ 100 g)

Frequently asked questions about vitamins

Which vitamins are lacking in fatigue?

Vitamin B12, C and D deficiencies can cause tiredness. However, as vitamin C deficiency is very rare in developed countries, you should keep an eye on your vitamin B12 and vitamin D levels in particular. Vitamin B12 deficiency inhibits the production of red blood cells, which impair oxygen transport in the body.49 This makes you feel tired or sluggish. Even a small deficiency of vitamin D can lead to fatigue and a general feeling of poor well-being.50

Which vitamins am I missing?

You may find our symptom table may help you to find out which vitamin deficiency you could be suffering from. Nevertheless, you should always discuss any suspicious symptoms or complaints with your doctor. He or she can check for a suspected deficiency by means of a blood test.

Which vitamin deficiency causes dry skin?

One of the best-known symptoms of a vitamin D deficiency is dry skin. Vitamin D is particularly important for the health of your skin as it stimulates receptors that are responsible for the formation of the skin barrier, which is essential for protecting the skin.51

What are the symptoms of vitamin B deficiency?

There are many different B vitamins that fulfill different functions in the body. It is important not to pigeonhole them all, as deficiencies of these different vitamin B variations can lead to different symptoms. Our symptom table should give you a good overview.

What do vitamins do in the body?

Vitamins enable a wide variety of functions in our body. Without vitamins, our body would not be able to perform vital tasks such as converting food into energy, building and maintaining bones, teeth, muscles, skin, blood and hair, as well as maintaining the functionality of our brain, eyes, nervous and immune systems.

Which vitamins for listlessness?

A deficiency of many different vitamins and minerals can lead both directly and indirectly to listlessness. The lack of motivation is often accompanied by tiredness and concentration problems. A lack of B vitamins, vitamin D or the minerals iron and magnesium can cause listlessness particularly quickly.52

Which vitamins to take together Table?

To provide your body with the best conditions for efficient absorption of nutrients into the blood, you should consider taking the following nutrients in combination. Some nutrients complement or interfere with each other's function in your body - so depending on what and when you eat, you may gain or miss out on the benefits of these healthy foods (and supplements).

Calcium and vitamin D
Most of the ingested calcium in our bodies is stored in our bones and vitamin D helps with the absorption, transportation and deposition of this calcium in our bones.53

Vitamin D and healthy fatty acids
Vitamin D is one of the fat-soluble vitamins. This means that it must be mixed with fat in order to be absorbed by the body. It is therefore advisable to combine vitamin D-rich foods with a high-quality fat such as olive oil, linseed, avocado, fish, chia seeds or nuts.54

Iron and vitamin C (especially for vegetarians)
Iron can be obtained from plant and animal foods. Although plant foods contain a lot of iron, it can often only be absorbed to a limited extent due to other substances - such as oxalic acid in spinach. Vitamin C compensates for this absorption-inhibiting effect as it promotes iron absorption.55

How do you notice that you have a lack of vitamins?

Symptoms of a vitamin lack can be very diverse and depend on the respective vitamin. Frequent signs are fatigue, weakness in concentration, susceptibility to infect, dry skin, brittle nails and hair, muscle weakness or mood swings. Since these symptoms can also occur in other diseases, a medical clarification with a blood test is advisable if a vitamin deficiency is suspected.

What is the most common vitamin deficiency?

According to the national consumption study, an inadequate supply of vitamin D is widespread in Germany, especially in the winter months. Since vitamin D is mainly formed by the skin of the skin, many people have a deficiency if they are too little outdoors. Folic acid, iodine and iron are also among the critical nutrients in which there is often an undersupply.

You might be interested in that too

1 3

Sources

  1. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  2. Alfred Sommer, Vitamin A Deficiency and Clinical Disease: An Historical Overview, The Journal of Nutrition, Volume 138, Issue 10, October 2008, Pages 1835-1839, 
  3. Manzetti S, et al. Thiamine function, metabolism, uptake, and transport. Biochemistry. 2014; 53(5):821-35.
  4. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  5. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  6. Bettendorff L. Thiamine. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:261-79.
  7. Bemeur C, Butterworth RF. Thiamine. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:317-24.
  8. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  9. Rivlin RS. Riboflavin. In: Coates PM, Betz JM, Blackman MR, et al, eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:691-9.
  10. Said HM, Ross AC. Riboflavin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:325-30.
  11. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  12. Kirkland JB. Niacin. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease, 11th ed. Baltimore, MD: Williams & Wilkins; 2014:331-40.
  13. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  14. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press, 1998.
  15. Penberthy WT, Kirkland JB. Niacin. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition, 10th ed. Washington, DC: Wiley-Blackwell; 2012:293-306.
  16. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  17. Miller JW, Rucker RB. Pantothenic acid. In: Erdman JW, Macdonald IA, Zeisel SH, eds. Present Knowledge in Nutrition. 10th ed. Washington, DC: Wiley-Blackwell; 2012:375-90.
  18. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  19. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  20. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  21. McCormick D. Vitamin B6. In: Bowman B, Russell R, eds. Present Knowledge in Nutrition. 9th ed. Washington, DC: International Life Sciences Institute; 2006.
  22. Mackey A, Davis S, Gregory J. Vitamin B6. In: Shils M, Shike M, Ross A, Caballero B, Cousins R, eds. Modern Nutrition in Health and Disease. 10th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005.
  23. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  24. Carmel R. Folic acid. In: Shils M, Shike M, Ross A, Caballero B, Cousins RJ, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2005:470-81.
  25. Stover PJ. Folic acid. In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2012:358-68.
  26. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Thiamine, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academy Press; 1998.
  27. Ho RC, Cheung MW, Fu E, et al. Is high homocysteine level a risk factor for cognitive decline in elderly? A systematic review, meta-analysis, and meta-regression. Am J Geriatr Psychiatry 2011;19:607-17. 
  28. Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, DC: International Life Sciences Institute Press, 1996.
  29. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  30. Bernard MA, Nakonezny PA, Kashner TM. The effect of vitamin B12 deficiency on older veterans and its relationship to health. J Am Geriatr Soc 1998;46:1199-206.
  31. Healton EB, Savage DG, Brust JC, Garrett TF, Lindenbaum J. Neurological aspects of cobalamin deficiency. Medicine 1991;70:229-44.
  32. Bottiglieri T. Folate, vitamin B12, and neuropsychiatric disorders. Nutr Rev 1996;54:382-90.
  33. Cook GC. Scurvy in the British Mercantile Marine in the 19th century, and the contribution of the Seamen's Hospital Society. Postgraduate Medical Journal. 2004; 80(942):224-9.
  34. Jacob RA, Sotoudeh G. Vitamin C function and status in chronic disease. Nutr Clin Care 2002;5:66-74.
  35. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  36. Wang AH, Still C. Old world meets modern: a case report of scurvy. Nutr Clin Pract 2007;22:445-8.
  37. Levine M, Conry-Cantilena C, Wang Y, Welch RW, Washko PW, Dhariwal KR, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci U S A 1996;93:3704-
  38. Francescone MA, Levitt J. Scurvy masquerading as leukocytoclastic vasculitis: a case report and review of the literature. Cutis 2005;76:261-6.
  39. Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr 1999;69:1086-107.
  40. Stephen R, Utecht T. Scurvy identified in the emergency department: a case report. J Emerg Med 2001;21:235-7.
  41. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  42. Wharton B, Bishop N. Rickets. Lancet 2003;362:1389-400.
  43. Cranney C, Horsely T, O'Donnell S, Weiler H, Ooi D, Atkinson S, et al. Effectiveness and safety of vitamin D. Evidence Report/Technology Assessment No. 158 prepared by the University of Ottawa Evidence-based Practice Center under Contract No. 290-02.0021. AHRQ Publication No. 07-E013. Rockville, MD: Agency for Healthcare Research and Quality, 2007. 
  44. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  45. Kowdley KV, Mason JB, Meydani SN, Cornwall S, Grand RJ. Vitamin E deficiency and impaired cellular immunity related to intestinal fat malabsorption. Gastroenterology 1992;102:2139-42
  46. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids external link disclaimer. Washington, DC: National Academy Press, 2000.
  47. D. (2020). Reference values for nutrient intake. Retrieved August 02, 2020,
  48. Jagannath VA, Fedorowicz Z, Thaker V, Chang AB. Vitamin K supplementation for cystic fibrosis. The Cochrane database of systematic reviews 2013;4:CD008482. 
  49. Tardy, A. L., Pouteau, E., Marquez, D., Yilmaz, C., & Scholey, A. (2020). Vitamins and Minerals for Energy, Fatigue and Cognition: A Narrative Review of the Biochemical and Clinical Evidence. Nutrients, 12(1), 228. https://doi.org/10.3390/nu12010228
  50. Ecemis, G. C., & Atmaca, A. (2013). Quality of life is impaired not only in vitamin D deficient but also in vitamin D-insufficient pre-menopausal women. Journal of endocrinological investigation, 36(8), 622-627.
  51. Gani, L. U., & How, C. H. (2015). PILL Series. Vitamin D deficiency. Singapore medical journal, 56(8), 433-437.
  52. Black M. M. (2003). Micronutrient deficiencies and cognitive functioning. The Journal of nutrition, 133(11 Suppl 2), 3927S-3931S.