Mild form of vitamin deficiency may remain asymptomatic or have non-specific symptoms like malaise, lethargy, loss of appetite, poor weight gain and tachypnea. Many of them may present with increased history of infections like diarrhea. Specific symptoms of deficiency depend on the type of vitamin.

• Vitmain A – nyctalopia, bitot spots, dry skin, dry hair, brittle finger nails, corneal perforation and xerophthalmia
• Vitamin B1 – neurologic symptoms like poor memory, Korsakoff syndrome, muscle cramps, muscle atrophy, paresthesia, and cardiovascular symptoms like tachycardia, chest pain, hypotension, and shock. 
• Vitamin B 12 – neuropathy and myelopathy resulting in impaired vibration sense, ataxia and paresthesia, depression, paranoid psychosis, optic atrophy, nystagmus, and chiasmatic lesion.
• Vitamin C – Irritability, pain and tenderness in legs, pseudoparalysis, hemorrhage, jaundice, shortness of breath, bone pain and scurvy. 
• Vitamin D – bowing of legs in children, periosteal bone pain and osteomalacia in adults.
• Vitamin E – hyporeflexia, limb ataxia, muscle weakness, dissociated nystagmus, areflexia, dysphagia, and dysarthria. 
• Vitamin K – ecchymosis, petechiae, hematomas, and bleeding at the site of puncture or surgery. 

The initial test for the diagnosis of suspected vitamin deficiency is serum levels of specific vitamin. Imaging studies are used for evaluating the growth of the bones or for checking excessive deposition of periosteal bone. Urinary excretion of some vitamins, for example thiamine, may be useful. Deficiency may be assessed using radioassay and non-radioisotopic assay as well. Other procedures like dark adaptation test may be adopted for a particular vitamin.

Treatment modality depends on the severity of vitamin deficiency. Replenishment of the deficient vitamin is the first step in treatment. In most of the cases restoration of body stores helps to resolve the symptoms. The daily maintenance dose varies with the type of vitamin, age and severity of the condition. Parenteral administration of the vitamin is recommended in severe cases of deficiency. Duration of therapy depends on the symptoms and is usually continued till the symptoms improve. Comorbid conditions, if any, should be identified and treated appropriately. During recovery care should be taken to provide a balanced and liberal diet. Long term supplementation may be needed in some cases. If the deficiency affects gait, balance or functions of any of the organs, physical and occupational therapy may be helpful. Follow-up is very important to confirm that the levels are well within the acceptable range. Most of the cases can be treated on an outpatient basis, unless there is a serious associated condition. Support for cardiac function may be necessary in some cases, particularly wet beriberi. Some patients may need neuropsychological intervention to improve cognition and social functioning.

Timely diagnosis and treatment can help in early recovery. Most of the deficiencies are easily treatable, provided that it is subclinical and has not progressed much. Most of the manifestations resolve considerably when treated appropriately. In vitamin A deficiency, morbidity may increase with infection or when blindness has progressed. Corneal perforation, keratomalacia and punctate keratopathy are irreversible even with standard treatment modalities. Korsakoff syndrome is a poor prognostic factor in thiamine deficiency. Neurologic deficit in vitamin B12 deficiency improves considerably with vitamin B12 therapy. Outcome is generally better in younger patients.

Poverty and food faddism are some of the common causes of vitamin deficiency in developed countries. In developing countries, dietary deficiency and malabsorption are the main causes of vitamin deficiency. Malabsorption is the main cause for the deficiency of fat soluble vitamins [3]. Diseases and conditions may also result in specific vitamin deficiency.
Some of the major etiological factors of vitamin deficiency include:

• Vitamin A – Fat malabsorption, Cystic fibrosis, pancreatic insufficiency, and inflammatory bowel disease may result in vitamin A deficiency. The risk of deficiency of this vitamin is more in vegans, refugees, immigrant population, alcohol dependency, and in children from economically underprivileged population. 
• Vitamin B – Lack of adequate intake and malabsorption are the most common causes of deficiency of vitamin B complex. Celiac disease, enteritis, exudative enteropathy, intestinal resection, atrophic gastritis, pancreatic deficiency, certain medications like proton pump inhibitors and colchicine result in vitamin B12 deficiency. Conditions like hyperthyroidism, severe infection, increased physical exercise, and diets high in carbohydrate or saturated fat, lead to thiamine deficiency [4]. Diarrhea, diuretic therapy, peritoneal dialysis, and hemodialysis increase the rate of thiamine depletion in the body leading to deficiency [5]. 
• Vitamin C – Prolonged deficiency of the vitamin in the diet is the major cause of vitamin C deficiency. Alcoholism, smoking, anorexia nervosa, type I diabetes, Crohn’s disease and overload disorders increase the risk of this vitamin deficiency. 
• Vitamin D – Inadequate exposure to sunlight, malabsorption, and use of certain medications are the major cause of vitamin D deficiency. 
• Vitamin E – Malabsorption, cystic fibrosis, abetalipoproteinemia, cholestatic hepatobiliary disease, and short bowel syndrome may all lead to vitamin E deficiency. 
• Vitamin K – Vitamin K deficiency is caused by chronic illness, malnutrition, alcoholism, multiple surgeries in the abdomen, cholestatic disease, cystic fibrosis, inflammatory bowel disease, chronic kidney disease and parenchymal liver disease [6]. 

About 250 million children worldwide are at risk of developing vitamin deficiency. The majority of them are malnourished and develop complications like measles and diarrhea that often lead to death. Vitamin A deficiency is the most common and every year about 500,000 children become blind due to the same. Accurate statistics on the prevalence and incidence of other vitamin deficiencies are not available. Difficulty in estimation may arise due to differences in etiologies and assays. Approximately 3 million people are affected by vitamin B12 deficiency in United States. Prevalence of vitamin C was found to be more among men, particularly those older than 60 years. Prevalence of vitamin C was reported as 8.2% in men and 6% in women [7]. Vitamin D deficiency is more prevalent among elderly and hospitalized patients. About 60% of the patients in nursing homes are reported to have deficiency of vitamin D [8]. Healthy adults also may have vitamin D deficiency. About 10.3% of the general population have this and the prevalence is greater among dark-skinned people. As the production of vitamin D declines with age, elderly population is at a higher risk of this deficiency. Although it may occur at any age, vitamin K deficiency is more common among infants. The prevalence varies according to geographic region in US [9].

Deficiency of vitamins are caused by decreased intake, malabsorption, and increased requirements or due to altered metabolism. In most of the cases, the body stores vitamins to last for some time even when the diet has inadequate amounts when compared to daily requirements. This lasts for few weeks but once this reserve is over the serum levels of the vitamin drops. The concentration of the vitamin in the serum may also be affected by other factors like infection, nutritional status, and presence of other nutrients. When thiamine stores are depleted, it results in weakness, tachycardia and deep tendon reflexes. Vitamin C deficiency affects collagen synthesis leading to poor wound healing. Impaired collagen synthesis results in gum hemorrhage, defective dentine formation, and also loss of teeth. When the circulating level of vitamin D is lower, parathyroid hormone levels increase, resulting in decreased mineralization of bones. Vitamin E plays an important role as antioxidant, and also has an immunomodulator and antiplatelet effect [10]. Deficiency of this vitamin results in ataxia, hyporeflexia, and muscle weakness.

Having a well-balanced diet is the most important preventive measure for vitamin deficiency. Having a variety of foods, like cereals, breads, crackers, vegetables, fruits and fortified foods help to provide the recommended doses of these nutrients. Those who have associated conditions like gastrectomy, pancreatectomy, or atrophic gastritis should undergo periodic testing to check for deficiencies. Vegetarians should supplement the amount of vitamin B12 in their diet as they are at an increased risk of developing deficiency.

Micronutrient deficiencies, including vitamins and mineral deficiencies, are one of the major contributors to the global disease burden [1]. About 2 million people all over the world are considered to be deficient in vitamins and other minerals. The most important nutrients among them are vitamin A, iodine, iron and zinc. Vitamin deficiencies increase the risk of infections and also cause premature death, poor health, blindness, stunted growth, mental retardation, learning disability and low work capacity. It also increases the mortality rate due to associated conditions like measles, malaria, pneumonia and diarrhea. These conditions are some of the leading causes of death in the world [2]. Vitamin deficiencies may also result in overt clinical syndromes like osteomalacia, peripheral neuropathy, night blindness and beriberi.

Vitamin and mineral deficiencies, called as micronutrient deficiencies, are one of the most important cause of diseases and death. Vitamin A, iron, zinc and iodine are the major deficiencies noted worldwide. These deficiencies cause diseases and also increase the risk of blindness, poor health, stunted growth and learning disability. Poverty, malnourishment, and fad diets are the most common causes of vitamin deficiency. It may also be caused by difficulty in absorbing the nutrients due to diseases or conditions. Inadequate exposure to sunlight is the major cause of deficiency of vitamin D. About 250 million children worldwide are at risk of developing different kinds of vitamin deficiency. Many of them develop measles and diarrhea which may lead to death.
In all these cases, the body uses up the vitamin stores when there is inadequate amounts of vitamins in the diet. When the body reserves are over, serum levels drop and start affecting metabolism. It results in signs and symptoms specific of different vitamins. Mild forms may remain asymptomatic for long time. Most common symptoms of vitamin deficiency are non-specific like tiredness, poor appetite, and lethargy. Each vitamin is associated with a specific set of symptoms like

• Vitamin A – night blindness, dry skin and hair, and dry eyes
• Vitamin B – beriberi, anemia, depression and poor memory
• Vitamin C – scurvy
• Vitamin D – bowing of legs in children, osteomalacia in adults
• Vitamin E – muscle weakness, neuromuscular problems, anemia
• Vitamin K – Bleeding at the site of surgery or puncture

Testing the levels of vitamin in the blood is the first way to assess deficiency of vitamin. Imaging techniques may be used to assess damage caused to the internal organs. Treatment suggested depends on the severity of the symptoms. Replenishing the deficient vitamins is the first step in the treatment. The dose and route of administration varies with the type of vitamin and severity of deficiency. Treatment is usually continued till the symptoms resolve. Having a well-balanced diet with lots of vegetables, fruits, whole grains and fortified foods go a long way in preventing and controlling the symptoms of vitamin deficiency. Those who have diseases that increase the risk of vitamin deficiency should monitor the levels to prevent complications. Timely diagnosis and treatment is the most important step in recovery. Most of the deficiencies are easily treatable.

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