Vitamins are essential for the maintenance and function of cells, tissues, and organs of our body through their roles in the metabolism of carbohydrates, proteins, and fats. Deficiency in vitamins results in disorders and diseases such as:
- Megaloblastic anemia
- Hemolytic anemia
- Birth defects
I. Types of Vitamins and Their Function in the Body
There are two types of vitamins: water-soluble and fat-soluble vitamins.
1- Water Soluble Vitamins
Most water-soluble vitamins are used immediately by the body and any surplus is eliminated through urine; however, vitamin B12 can be stored in the liver for a prolonged period.
Vitamin B1 (Thiamine)
Vitamin B1 is required for the production of ATP (energy) and for the metabolism of glucose, proteins, and fats by our body cells. It is naturally present in food such as whole grains, legumes, and fish .
Vitamin B2 (Riboflavin, Vitamin B2)
Vitamin B2 is naturally present in food including almonds, eggs, meat, milk and dairy products, mushrooms, and green vegetables.
Vitamin B3 (Niacin, Niacinamide)
Vitamin B3 is essential for the synthesis of nicotinamide adenine dinucleotide (NAD), a coenzyme (work together with an enzyme) necessary for the metabolism of cells (e.g., redox reactions), DNA repair, and calcium mobilization within the cells of the body .
It is naturally available in food such as eggs, meat, milk, and beans.
Vitamin B5 (Pantothenic Acid)
Vitamin B1 is found in most food and is required for the synthesis of coenzyme A involved in the synthesis and oxidation of fatty acids that are necessary for the production of hormones, energy production from fats, fat storage, and the transfer of information within the cell (signaling) .
Vitamin B6 (Pyridoxine, Pyridoxamine)
Vitamin B7 (Biotin)
It is naturally available in food such as beef liver, salmon, nuts, eggs, avocadoes, pork, and sweet potatoes.
Vitamin B9 (Folic Acid, Folate, Folacin)
Vitamin B9 is required for DNA synthesis and for the activation of vitamin B12 . Many types of food contain vitamin B9; however, due to its instability (e.g., high heat cooking), it is being added to several food sources as a fortifier to prevent a vitamin B9 deficiency.
Vitamin B12 (Cyanocobalamin)
It is naturally present in foods such as meat, liver, milk, clams, fortified breakfast cereals, and eggs.
Vitamin C (Ascorbic Acid)
It is naturally available in citrus fruits, guava, kiwifruit, strawberries, brussels sprouts, broccoli, and bell peppers.
2- Fat-Soluble Vitamins
This family of vitamins requires fat and bile acids to be absorbed by the intestine through a process named micellar solubilization.
The Vitamin A Group
Vitamin A is not a single entity but is rather a group of compounds that include retinol, retinal, and carotenoids such as beta-carotene.
They are naturally found in many foods such as fish and beef liver, cod liver oil, green vegetables (e.g., kale, spinach), carrots, and dairy products (cheese and butter).
The Vitamin D (Calciferol) group
Vitamin D is also a group of compounds that include ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
They are naturally found in many foods such as beef liver, cod liver oil, eggs, salmon, tuna, mackerel, and sardines.
The Vitamin E group
Vitamin E is another example of a group of vitamin compounds that include the antioxidants tocopherols and tocotrienols that protect the body’s cells from reactive oxygen species . They are naturally available from wheat, seeds, and nuts oils.
Vitamin K (Phylloquinone, Menaquinones)
Vitamin K includes two compounds known as vitamin K1 (Phylloquinone) and vitamin K2 (Menaquinones) that are involved in blood coagulation and in the regulation of calcium attachment to the bones .
Phylloquinone is naturally found in leafy green vegetables, while menaquinones naturally exist in food such as chicken and beef meat, mollusks, and dairy products (e.g., cheese, yogurt, and milk).
II. Vitamin Deficiency
There are several conditions, diseases, and disorders due to vitamin deficiencies, and here is an overview of the most known ones.
1- Vitamin B1 Deficiency
- Beriberi is a rare genetic disease characterized by effects on the nervous and cardiovascular systems. It may manifest with increased heart rate, swellings of the legs, speech difficulty, mental confusion, and shortness of breath .
- Wernicke Encephalopathy is caused by neurological damages that manifest with symptoms of confusion, ataxia (absence of voluntary movements coordination), and ophthalmoparesis (uncontrolled movement of the eye muscles) .
2- Vitamin B2 Deficiency
- Ariboflavinosis is characterized by lesions on the lips and around the corners of the mouth, the nose, and the eyes. In extreme cases, neurological, reproductive, hepatic, and anemic disorders are observed .
3- Vitamin B3 Deficiency
4- Vitamin B5 Deficiency
- Paraesthesia manifests with abnormal and painless sensations in the skin of arms and legs .
5- Vitamin B6 Deficiency
- Anemia, that is due to vitamin B6 deficiency, is associated with reduced synthesis of the heme, a necessary component of hemoglobin .
6- Vitamin B7 Deficiency
- Dermatitis is associated with dryness and inflammation of the skin leading to rashes and lesions on the face .
- Enteritis manifests with symptoms such as fatigue and tiredness, nausea, and vomiting.
7- Vitamin B9 Deficiency
- Birth Defects are associated with abnormal development of the embryo neural tube (brain and spinal cord development) during pregnancy .
8- Vitamin B12 Deficiency
- Megaloblastic Anemia is due to the reduction in DNA synthesis associated with the production (proliferation) of red blood cells .
9- Vitamin C Deficiency
- Scurvy manifests with symptoms of tiredness and fatigue, sore arms and legs, gum disease, and bleeding from the skin .
10 – Vitamin A Deficiency
- Night Blindness is associated with the difficulty of adaptation of the vision from day to night usually due to an anomaly with the retina .
- Keratomalacia affects the cornea and conjunctiva of the eye that looks cloudy and opaque resulting in blindness .
11- Vitamin D Deficiency
- Rickets (Osteomalacia) is characterized by soft bones in children that lead to bone deformities .
12- Vitamin E Deficiency
Hemolytic Anemia is associated with rupture or breakdown of red blood cells due to the lack of antioxidant protection from vitamin E (antioxidant effect) .
13- Vitamin K Deficiency
- Bleeding is due to a defect in the coagulation as vitamin K is required for clot formation to stop bleeding.
- Diathesis is characterized by increased bruising and bleeding.
III. Vitamin Overdose
Vitamin overdose or hypervitaminosis is associated with excessive reserves of vitamins in the body that lead to toxicity, irritability, and overexcitement.
1- Vitamin B3 Overdose
Vitamin B3 overdose can cause flushing with headache, dizziness, and sensations of burning and itching. In certain cases, it can lead to liver damage .
2- Vitamin B6 Overdose
The overdose of B6 is associated with neuropathies due to nerve damage such as sensory ataxia (absence of voluntary movements coordination), abnormal and painless sensations in the skin of arms and legs (paraesthesia), and areflexia (absence of muscle reflexes) .
3- Vitamin B9 Overdose
An overdose of this vitamin results in nerve damage resulting in neuropathies. It also causes proprioception characterized by difficulty and uncoordinated walking and clumsiness .
4- Vitamin A Overdose (Hypervitaminosis A)
Vitamin A overdose has a wide effect on mental health such as depression, dizziness, and mental dullness, and on the liver (toxicity), skin (dry skin), cheilosis (inflammation of the mouth corners), gingivitis, muscle, and joint pains, and fatigue .
5- Vitamin D (Hypervitaminosis D) overdose
An overdose of vitamin D manifests with large disorders such as hypercalcemia, hypertension, ectopic calcifications, renal stones, hyperphosphatemia, polyuria and polydipsia, anorexia, depression, nausea, vomiting, and constipation .
6- Vitamin E overdose
An overdose of this vitamin results in muscle weakness, fatigue, nausea, and diarrhea. However, higher intake can lead to hemorrhagic stroke and premature death .
7- Vitamin K Overdose
An overdose of this vitamin, when consumed orally, is not toxic; however, it can cause toxicity in infants administered with a synthetic precursor (Menadione). Toxicity includes hemolytic anemia, jaundice due to hyperbilirubinemia (increase bilirubin in the blood), and brain damage .
Vitamins are essential for the function of the body as they are involved in key metabolic pathways. Although deficiencies in vitamins are low in developed countries, other places in the world are still affected due to malnutrition.