Water-soluble Vitamins, RDA, Sources, Deficiency.

Vitamins are a very important part of our diet. These are substances that our body needs in the normal development of our system. Our body cannot synthesize these organic micronutrients and we can only get them from food sources. There are about 15 vitamins essential for humans. They are classified as fat-soluble vitamins and water-soluble vitamins.

Fat-soluble vitamins are A, D, E, and K whereas water-soluble vitamins include the B group and vitamin C.

What are water-soluble vitamins?

As the name suggests, these are a group of vitamins that can easily dissolve in water. They function mainly as enzyme cofactors. Because our body has no storage capacity for water-soluble vitamins, they must be regularly supplied in the diet. If we intake a large amount of these vitamins, they will be excreted out from the body through urine. As a result, we cannot store them in our bodies as we can store fat-soluble vitamins. The body needs water-soluble vitamins in frequent, small doses. Therefore, we should consume them frequently. 

List of water-soluble Vitamins

All B group vitamins and Vitamin C comes under this category. The list of water-soluble vitamins is as follows:

1. Thiamine (Vitamin B1)
2. Riboflavin (Vitamin B2) and FAD
3. Niacin, NAD+ and NADP+
4. Pyridoxine (Vitamin B6)
5. Pantothenic acid and Co-enzyme A
6. Biotin
7. Folic acid
8. Vitamin B12
9. Ascorbic acid (Vitamin C)

Water-soluble vitamins

Water-soluble vitamins include vitamin B-complex and vitamin C and are essential nutrients needed by the body in very small quantities.

B-complex Vitamins

All the vitamins listed above (except 9) are B-complex vitamins. Most of the water-soluble vitamins exert their functions through their respective coenzymes. They are essential for normal metabolism and also serve as the coenzymes in many reactions.

1. Vitamin B1 (thiamin)

Chemical Name: Thiamine

What is thiamin?

It is an important enzyme for carbohydrate metabolism. It plays a role in muscle contraction and conduction of nerve signals. Thiamin also acts as a coenzyme in several carbohydrate metabolic pathways (pentose phosphate pathway, glycolysis, krebs cycle, etc.)

Note: It can be spelt both as thiamin or thiamine.

Structure

It has a substituted pyrimidine ring joined to a substituted thiazole ring by means of a methylene bridge. Thiamine is the only natural compound with a thiazole ring. The vitamin is converted to its active co-enzyme form by the addition of two phosphate groups, with the help of ATP.

Food sources of thiamin:

The aleurone layer of cereals is a rich source of thiamine. Therefore, whole wheat flour and unpolished hand-pound rice have better nutritive value than completely polished refined foods. Yeast is also a very good source. Thiamine is partially destroyed by heat.

Non-vegetarian sources of thiamin are Pork, Fish, and liver.

Vegetarian sources include peas, legumes, nuts, seeds and unpolished rice and food grains.

In addition, whole grains and fortified grain products such as cereal, and enriched products like bread, pasta, rice, and tortillas are sources of thiamin. 

How much thiamine do you need a day?

It depends on calorie intake. Adult females require 1.1 mg/day while adult males require 1.2 mg/day of thiamine as per RDA.

Recommended Intake of vitamin B1 Table

	Age	RDA (mg/day)
INFANTS	0-6 M	0.2
	7-12 M	0.3
CHILDREN	1-3 Yr	0.5
	4-8 Yr	0.6
	9-13 Yr	0.9
FEMALE	14-18 Yr	1.0
	19+ Yr	1.1
MALE	14+ Yr	1.2
LACTATION		1.4
PREGNANCY		1.4

Thiamin deficiency

It is rare in the United States to have a thiamin deficiency. Thiamin deficiency can occur quickly (as less as 14 days). Early symptoms are loss of appetite, constipation and nausea. They may further progress to depression, peripheral neuropathy and unsteadiness.

These are the common thiamin deficiencies:

1. Beriberi: Serious thiamin deficiency may cause this disease. Beriberi means (in singhalese) “weakness”. The early symptoms are anorexia, dyspepsia, heaviness and weakness. The person will also feel weak and become easily tired. Beriberi can be of three types: wet, infantile and dry Beriberi.
   1. Wet Beriberi: the deficiency causes cardiovascular manifestations. Main features of the disease are edema of legs, face, trunk and serous cavities. Palpitation, breathlessness and distended neck veins are also observed.
   2. Dry Beriberi: Unlike wet Beriberi, it affects central nervous system. In this condition, walking becomes a challenge. Peripheral neuritis with sensory disturbance may leads to complete paralysis in the patient.
   3. Infantile Beriberi: As the name suggests, it occurs in infants. Mothers who had thiamin deficiency during their pregnency periods may pass this disease to their newborns. Its symptoms includes sleeplessness and restlessness in newborns
2. Wernicke-Korsakoff syndrome: Another serious thiamin deficiency is Wernicke-Korsakoff syndrome. It is also a type of beriberi but it affects cerbral. Hence, it is called cerebral Beriberi. It develop only in severe thiamin deficiency. Its symptoms are those of encephalopathy (ophthalmoplegia, nystagmus, cerebellar ataxia) plus psychosis.
3. Polyneuritis: It specifically develop in people who consumes alcohol on regular basis. It is because alcohol inhibits intestinal absorbtion of thiamin, resulting in thiamin deficiency.

Thiamine Toxicity

Thiamine is regarded safe. It does not have any adverse effects after taking high amounts of thiamine from food or supplements. This is because excess thiamine will quickly pass from the body through urine.

2. Vitamin B2

Chemical name: Riboflavin

Chemically identical compounds: Lactoflavin (milk), hepatoflavin (liver) and ovoflavin (eggs)

Vitamin B2 is a heat-stable compound and produced by green plants and micro-organisms. It is important for the growth, development and function of the cells in the body. Riboflavin is also used as a food colouring substance.

Structure

Riboflavin has a dimethyl isoalloxazine ring to which a ribitol is attached. Ribitol is the alcohol of ribose sugar.
Riboflavin (heat-stable) will convert to its active coenzyme forms (FMN and FAD) with the help of ATP.

Food sources for riboflavin

Non-vegetarian sources: eggs, organ meats (liver and kidney), and fish.

Vegetarian sources: dark green leafy vegetables, broccoli, legumes, mushrooms, milk, persimmons, and whole and enriched grain products.

Among vegetarian and non-vegetarian sources, good sources are fish, whole cereals, legumes and green leafy vegetables.

In addition, Yeast extract spread is also exceptionally rich in riboflavin.

How much B2 vitamin should I take?

The Recommended Dietary Allowance (RDA) for riboflavin is 1.3 mg/day for adult males and 1.1 mg/day for adult females. During pregnancy, lactation and old age, One should take an additional 0.2 to 0.4 mg /day of riboflavin.

Recommended Intake of Vitamin B2 Table

	Age	Recommended Intake (mg/day)
INFANTS	0-6 M	0.3
	7-12 M	0.4
CHILDREN	1-3 Yr	0.5
	4-8 Yr	0.6
	9-13 Yr	0.9
FEMALE	14-18 Yr	1.0
MALE	18 + Yr	1.3
PREGNANCY		1.4
LACTATION		1.6

Riboflavin deficiency

Natural deficiency of riboflavin in humans is not common because riboflavin is produced by intestinal flora. Riboflavin deficiency usually accompanies other deficiency diseases such as beriberi, pellagra and kwashiorkor.

Most of the symptoms of riboflavin deficiency are visible on the skin and mucous membrane.

Some of the riboflavin deficiencies are:

1. Glossitis: Inflammation of the tongue.
2. Magenta coloured tongue
3. Cheilosis: corners of the mouth become inflamed. Also, cracking and pain at the corners of the mouth.
4. Angular stomatitis: An inflammatory condition which causes swollen red patches at corners of the mouth.
5. Circumcorneal vascularization (sight-threatening condition): It is the in-growth of new blood vessels from the pericorneal plexus into avascular corneal tissue as a result of oxygen deprivation.
6. Proliferation of the bulbar conjunctival capillaries is the earliest sign of riboflavin deficiency.

Riboflavin Toxicity

No problems with the overconsumption of riboflavin.

3. Vitamin B3

Chemical Name: Niacinamide, Nicotinic Acid, Niacin.

Other Name: Niacin is also called as Pellagra preventing factor of Goldberger.

Coenzyme forms: NAD⁺(Nicotinamide adenine dinucleotide) and NADP⁺(Nicotinamide adenine dinucleotide phosphate)

Niacin involves in energy production and critical cellular functions. An interesting point about niacin is that it is the only B vitamin our body can produce from another nutrient (amino acid tryptophan).

Structure

Niacin is a pyridine derivative. Structurally, it is pyridine 3-carboxylic acid. Niacinamide is the acid amide. In NAD+ or NADP+, the reactive site is the carbon atom 4 and the nitrogen atom of the nicotinamide ring.

Food sources of Niacin

Vegetarian sources: whole cereals, legumes, peanut, broccoli, carrots, nuts, seed, sand rice polishing.

Non-vegetarian sources: liver, fish, chicken, beef, tuna, salmon, and eggs.

In addition, dried yeast, rice polishing and fishes are among some of the richest food sources of niacin.

About half of the requirement of niacin is met by the conversion of tryptophan to niacin. About 60 mg of tryptophan will yield 1 mg of niacin.

Daily recommended dose of Niacin

The normal requirement of niacin is 16 mg/day for adult males and 14 mg/day for adult females. For pregnant women, it is 18 mg/day while for breastfeeding women, it is 17 mg/day.

The maximum daily intake for adults of all ages is 35 mg/day.

Recommended Intake of Niacin Table

	Age	Recommended Intake (mg/day)
INFANTS	0-6 M	2
	7-12 M	4
CHILDREN	1-3 Yr	6
	4-8 Yr	8
	9-13 Yr	12
FEMALE	14-18 Yr	14
MALE	18+ Yr	16
PREGNENCY		18
LACTATION		17

Niacin Deficiency

The niacin deficiency is as follows:

1. Pellagra: In italian, it means “rough skin”. Most commonly, it occurs in women rather than men. The disease involves skin, gastrointestinal tract and CNS. The symptoms of pellagra are dermatitis, diarrhrea and dementia. In early stages, bright red erythema occurs, especially in the feet, ankles and face (dermatitis). The diarrhea may be in the form of loos stool, often with blood and mucus. This may lead to weight loss. Dementia occurs in chronic niacin deficiency. In mild cases, irritability, poor memory and inability to concentrate are some of the early symptoms.

Most commonly, pellagra is seen among people whose staple diet is corn and maize. This is because niacin is present in its bound form in maize. Therefore, it is unavailable to our body as it cannot utilize it. Further, tryptophan content is low in maize (Tryptophan can be replaced with niacin). About 60 mg of tryptophan will yield 1 mg of niacin.

Niacin Toxicity

Although it is a water-soluble vitamin, overconsumption of niacin through supplements may cause certain problems. Consuming a higher amount of supplements beyond 35mg/day may result in flushed skin, rashes, hypotension symptoms, or liver damage. However, it does not cause any problems if obtained from food sources.

4. Vitamin B6

Chemical name: Pyridoxine, pyridoxal, and pyridoxamine.

It is important for amino acid metabolism and its requirement usually increases with high protein intake.

Structure

Collectively, vitamin B6 represents the above three compounds. Vitamin B6 compounds differ from each other in the structure of a functional group attached to the 4th carbon in the pyridine ring.

Pyridoxine is the primary alcohol while pyridoxal is an aldehyde. On the other hand, pyridoxamine is an amine. Pyridoxal and pyridoxamines are present in animal foods whereas pyridoxine is present in plants. An interesting point about pyridoxine is that we can convert it to pyridoxal and pyridoxamine but the latter two cannot form pyridoxine.

Food Sources for Vitamin B6

Non-vegetarian sources: egg yolk, fish, and organ meats

Vegetarian sources: Pistachio nuts, sunflower seeds, starchy vegetables, legumes, wheat, corn, cabbage and fortified cereals.

Daily recommended dose of Vitamin B6

Vitamin B6 requirements are related to protein intake and not to calorie intake. The RDA for vitamin B6 is 1.3 mg/day for adult males and females through age fifty. An intake of 2.5mg/day is recommended during pregnancy, lactation and old age.

Recommended Intake of vitamin B6 Table

	Age	Recommended Intake (mg/day)
INFANTS	0-6 M	0.1
	7-12 M	0.3
CHILDREN	1-3 Yr	0.5
	4-8 Yr	0.6
	9-13 Yr	1.0
FEMALE	14-18 Yr	1.2
	19-50 Yr	1.3
	51+ Yr	1.5
MALE	14-18 Yr	1.3
	19-50 Yr	1.3
	51+ Yr	1.7
PREGNENCY		1.9
LACTATION		2.0

Vitamin B6 Deficiency

The deficiency of vitamin B6 is rare. It may occur in women taking oral contraceptives and also be observed in alcoholics and infants. Some of the vitamin B6 deficiencies are:

1. Neurological Manifestations: Vitamin B6 deficiency is usually associated with neurological symptoms such as depression, irritability, nervousness and mental confusion. Convulsion and peripheral neuropathy are also visible in severe vitamin B6 deficiency.
2. Hematological Manifestations: Hypochromic microcytic anemia may occur due to the reduction in heme production.
3. Dermatological Manifestations: Deficiency of B6 will also affect tryptophan metabolism. Since niacin is produced from tryptophan, B6 deficiency in turn leads to niacin deficiency which is manifested as pellagra.

Toxicity of Vitamin B6

Overconsumption of naturally occurring vitamin B6 from food sources does not have adverse health effects, but chronic excess doses of vitamin B6 from supplements have been known to result in nerve damage. More than 100mg/day of vitamin B6 may cause neurological damage.

5. Vitamin B5

Chemical Name: Pantothenic acid

Other Name: Formerly known as chick anti-dermatitis factor or filtrate factor. It also has a metabolic role as ‘coenzyme A‘.

Vitamin B5 involves energy production, the formation of hormones, and the metabolism of fats, proteins, and carbohydrates from food.

Structure

Pantothenic acid consists of two components: Pantoic acid and beta-alanine in the amide linkage. Pantothenic acid and beta-mercaptoethanol amine are parts of coenzyme A.

Food Sources of Vitamin B5

It is widely present in plants and animals.

Non-vegetarian sources: eggs, fish, liver, kidney and yeast.

Vegetarian sources: broccoli, whole grains, seeds and avocados.

Vitamin B5 is also present in yoghurt and milk. Moreover, the normal bacterial flora in the intestines can synthesize vitamin B5.

Daily recommended dose of Vitamin B5

The exact requirement for vitamin B5 for us is not clearly known. However, a daily intake of 5mg/day for both adult males and females is suggested.

Recommended Intake of vitamin B5 Table

	Age	Recommended Intake (mg/day)
INFANTS	0-6 M	1.7
	7-12 M	1.8
CHILDREN	1-3 Yr	0.5
	4-8 Yr	2
	9-13 Yr	3
FEMALE	14-18 Yr	4
MALE	18 + Yr	5
PREGNANCY		6
LACTATION		7

Pantothenic Acid Deficiency

The deficiency of vitamin B5 is very rare due to its wide availability in both plant and animal food sources. However, there are certain cases in which vitamin B5 deficiency may occur.

1. Gopalan’s Burning Foot Syndrome: Dr. Gopalan, a world renowed nutritionist (from India), linked the burning feet sundrome with vitamin B5 deficiency. The symptoms of the deficiency includes munbness in the toes, sleep disturbances, and fatigue.
2. Vitamin B5 deficiency in experimental animals results in anemia, fatty liver, decreased steroid synthesis, etc.

Toxicity of Vitamin B5

Overconsumption of vitamin B5 does not cause any problem. Rarely, diarrhoea and gastrointestinal distress will occur in larger amounts.

6. Vitamin B7: Biotin

Chemical Name: Biotin

Other Name: Vitamin H, anti-egg white injury factor.

It directly participates as a coenzyme in the carboxylation reactions. As a coenzyme, it is important in lipogenesis, gluconeogenesis, Krebs cycle, and the catabolism of the branched-chain amino acids.

Structure

Biotin is a sulphur-containing B-complex vitamin. Its structures result from the fusion of imidazole and thiophene ring with a valeric acid side chain. The carboxyl group forms an amide linkage with the epsilon amino group of a lysine residue in the apo-enzyme.

Food Sources of Biotin

Like vitamin B5, it is also widely present in plant and animal food sources.

Non-vegetarian sources: Liver, kidney, egg yolk, and fish.

Vegetarian sources: Broccoli, spinach, tomatoes, mushrooms, cheese, nuts, legumes and grains.

Dairy products also provide biotin. Moreover, the normal bacterial flora in the intestines can synthesize biotin.

Daily recommended dose of Biotin

The daily requirement for Biotin is 30 mcg/day for adult males and females.

Daily recommended dose of Biotin Table

	Age	Recommended Intake (mcg/day)
INFANTS	0-6 M	5
	7-12 M	6
CHILDREN	1-3 Yr	8
	4-8 Yr	12
	9-13 Yr	20
FEMALE	14-18 Yr	25
	19-50 Yr	30
	51+ Yr	30
MALE	14-18 Yr	25
	18+ Yr	30
PREGNANCY		30
LACTATION		35

Biotin Deficiency

Biotin deficiency is uncommon since it is widely present in food sources. The symptoms of biotin deficiency include anaemia, loss of appetite, nausea, dermatitis, glossitis, etc. Biotin deficiency may also result in hallucinations, muscle pain, hair loss, skin rashes, and brittle nails. The deficiency may be associated with the following two causes:

1. Prolonged use of antibacterial drug that may result in the destruction of intestinal flora.
2. High consumption of raw eggs. The raw egg white contain avidin, that tightly binds to biotin and block its absorption. However, consumption of an occasional raw egg will not cause its deficiency.

Toxicity of Biotin

A high dose of biotin related toxicity is not observed.

7. Vitamin B9

Chemical Name: Folic acid, folinic acid.

Other names: Folacin or folate

Folic acid promotes red blood cell formation and lowers the risk for neural tube birth defects. Folate may also play a role in reducing the risk for coronary heart disease. Folic acid is important for one carbon metabolism and for the synthesis of certain amino acids and DNA. Folic acid exists in a number of derivatives collectively known as folates. The active form of folic acid is tetrahydrofolate (TDH).

Structure

It consists of three components: pteridine ring, PABA, and glutamic acid. Most commonly, folic acid has one glutamic acid residue called pteroyl-glutamic acid (PGA). It will destroy rapidly when exposed to sunlight.

Food Sources of Folic acid

Non-vegetarian sources: Liver, kidney, eggs.

Vegetarian sources: legumes, green leafy vegetables, cereals, whole grains, pulses, sunflower seeds, peanuts, and peas.

It is also present in milk and yeast. Although, milk is a poor source of folic acid.

Daily recommended dose of Folic acid

The daily requirement of folic acid is around 400 mcg/day. Pregnant women require a daily dose of 600mcg while lactating women require 500 mcg/day.

Daily recommended Intake of Folic acid Table

	Age	Recommended Intake (mcg/day)
INFANTS	0-6 M	65
	7-12 M	80
CHILDREN	1-3 Yr	150
	4-8 Yr	200
	9-13 Yr	300
FEMALE	18+ Yr	400
MALE	18+ Yr	400
PREGNANCY		600
LACTATION		500

Folic acid Deficiency

Folic acid deficiency is most common in pregnant women throughout the world. Nursing women, alcoholics, women on oral contraceptives are also susceptible to folic acid deficiency. It may develop due to poor dietary intake, defective absorption, use of certain drugs, and increase in demands (such as pregnancy). Some of the folic acid deficiencies are:

1. Homocysteinemia: The deficiency may increase homocysteine levels in blood. Plasma homocysteine levels above 15 micromoles/L can increase the risk of coronary artery diseases. Folic acid supplementation with adequate dose of B6 and B7 may reduce the risk of Homocysteinemia.
2. Birth defects: Folic acid deficiency in pregnancy may cause homocysteinemia and neural tube defects in the growing baby. Folic acid prevents birth defects. So, folic acid is reccomended from early pregnancy to prevent such defects.
3. Poor DNA synthesis: In folic acid deficiency, production of purines and dTMP will decrease which impairs DNA synthesis.
4. Macrocytic Anemia: Due to a block in DNA synthesis, the maturation of RBCs will slow down that results in macrocytic RBC (abnormally large RBC). As a result, bone marrow cells (rapidly dividing) are seriously affected.

Toxixity of folic acid

Doses over 1 mg may cause aggravation of vitamin B12 deficiency and may precipitate nerve damage. Since solubility
of folic acid is low, large doses should not be given parenterally, as there is a danger of crystallization in kidney tubules leading to renal damage.

8. Vitamin B12

Chemical Name: Cyanocobalamin, hydroxocobalamin, methylcobalamin

Other Name: Anti-pernicious anaemia vitamin.

This vitamin is essential for a healthy nervous system and the production of normal red blood cells.

Structure

It is a water-soluble vitamin and red in colour. It consists of a corrin ring with a central cobalt atom. This ring is almost similar to the tetrapyrrole ring structure present in other porphyrin compounds (heme and chlorophyll). The cobalt atom also has a sixth substituent group present above the plane of the corrin ring. The substituent group may be cyanide (Cyanocobalamin), a hydroxyl (hydroxycobalamin), or a nitrite group (nitrocobalamin).

Food Sources of Vitamin B12

Non-vegetarian sources: liver, kidney, eggs, fish, pork, and chicken.

Vegetarian sources: foods of animal origin are the only sources of vitamin B12 because vitamin B12 is not present in vegetables.

Milk and curd are also a source of vitamin B12. Although, the curd is a better source than milk due to the synthesize of B12 by lactobacillus.

Daily recommended dose of Vitamin B12

A daily intake of about  2.4 mcg/day is adequate to meet the adult requirements. During pregnancy, the requirement is 2.6 mcg/day while for lactation, it is 2.8 mcg/day.

Daily recommended dose of Vitamin B12

	Age	Recommended Intake (mcg/day)
INFANTS	0-6 M	0.2
	7-12 M	0.4
CHILDREN	1-3 Yr	0.9
	4-8 Yr	1.2
	9-13 Yr	1.8
FEMALE	14-18 Yr	2.4
	19+ Yr	2.4
MALE	18+Yr	2.4
PREGNANCY		2.6
LACTATION		2.8

Vitamin B12 Deficiency

Nutritional vitamin B12 deficiency is very common in India, especially among vegetarians of low socio-economic groups. The deficiency may also develop in older people. Symptoms of deficiency may include anaemia and neurological changes, such as numbness and tingling in the hands and feet. 

1. Pernicious Anaemia: It is characterized by low hemoglobin level, decreased number of erythrocytes and neurological manifestations. There are vaious causes of Pernicious Anaemia. For example, hereditary malabsorption of vitamin B12, partial or total gastrectomy, automimmune destruction of gastric parietal cells tha secreteintrinsic factor, etc.

Toxicity of Vitamin B12

No adverse effects have been known with overconsumption of vitamin B12.

9. Vitamin C

Chemical Name: Ascorbic Acid.

Other Name: no other name

It is a water-soluble vitamin that plays an important role in human health and disease. It provides collagen production, wound healing, and bone formation. Vitamin C also strengthens blood vessels and helps the body absorb iron.

Interesting point: Vitamin C will rapidly oxidize in the presence of copper. Hence, vitamin C becomes inactive if we cook food in copper utensils.

Structure

Vitamin C is a hexose derivative and closely resembles carbohydrates in structure. Vitamin C is acidic because of the presence of enolic hydroxyl groups. Further, the strong reducing property of vitamin C depends on the double-bonded (enediol) carbons. Both ascorbic acid and dehydroascorbic acid are biologically active. However, D-ascorbic acid has no activity.

Food Sources of Vitamin C

Non-vegetarian sources: Very low amount of vitamin C is present in animal sources such as raw liver, eggs, fish roe.

Vegetarian Sources: Citrus fruits, gooseberry, green vegetables, tomatoes, guava, kiwi, strawberry, potatoes, cabbage and spinach.

High content of vitamin C is present in adrenal glands and gonads. However, milk is a poor source of vitamin C.

Daily recommended dose of Vitamin C

About 90 mg/day for adult males and 75 mg/day for adult females of vitamin C is required. Additional intakes are suggested for pregnant and lactating women.

Daily recommended dose of Vitamin C Table

	Age	Recommended Intake (mg/day)
INFANTS	0-6 M	40
	7-12 M	50
CHILDREN	1-3 Yr	15
	4-8 Yr	25
	9-13 Yr	45
FEMALE	14-18 Yr	65
	19+ Yr	75
MALE	14-18 Yr	75
	19+ Yr	90
PREGNANCY		80-85
LACTATION		115-120

Vitamin C Deficiency

1. Vitamin C deficiency results in Scurvy. The symptoms of Scurvy are sore and spongy gums,loose teeth, anaemia, fatigue, fragile blood vessels, delayed wound healing, etc. Most of these symptoms are related to impairment in the synthesize of collagen and the antioxidant preoperty of Vitamin C.

Toxicity of Vitamin C

Ascorbic acid has not been found to be toxic but dehydroascorbic acid is toxic.

Most people can tolerate high doses of ascorbic acid without any adverse effects. However, very high doses exceeding 3 gm/day cause diarrhoea, nausea and abdominal cramps. This is because only a limited amount of vitamin C can be absorbed from a single dose.

Sources and External Links

Biochemistry, 4th edition by Dr U. Satyanarayana, Section one: chemical constituents of life, chapter no. 7: Vitamins, page no. 132-156

Textbook of Biochemistry For Medical Students, Sixth Edition by DM Vasudevan, chapter no. 34: water-soluble vitamins, page no. 291-410.

Medical Biochemistry, 4th edition, John W. Baynes, PhD, chapter number 11: Vitamins and minerals.

Harper’s Illustrated Biochemistry, 28th edition, Robert K. Murray, David A Bender, Kathleen M. Botham, Peter J. Kennelly, Victor W. Rodwell, P. Anthony Weil, chapter number 44: Micronutrients- Vitamins and Minerals.

https://www.uofmhealth.org/health-library/ta3868

https://www.medicalnewstoday.com/articles/195878#the-13-vitamins

https://www.healthline.com/nutrition/water-soluble-vitamins#b1

Cheilosis: Causes, Symptoms and Treatment

https://en.wikipedia.org/wiki/Corneal_neovascularization