What are the characteristics of water- soluble vitamins?

biochemical assessment of water- soluble vitamins;

Folate;

Folate is a generally term as vitamin B9 or petrol glutamic acid, the active from of which is known as levamisole acid or methyl tetrahydro folate. It is naturally present in many food and is also sold as supplement .

What are the characteristics of water- soluble vitamins?

Folic acid is essential in the formation of healthy blood cells and nucleic acid along with role in protein metabolism. Folic acid is also involved in the catabolism of homocysteine ; the elevated level of which exert harmful effect on the body.

Adequate folic acid consumption during pregnancy reduce the chance of neural tube defects, spina bifida and macrocytic anemia.

Deficiency of folate;

The primary reason for folate deficiency is inadequate dietary intake. Moreover, number of gastrointestinal diseases can result in folate deficiency.

Folate deficiency result in to megaloblastic anemia, a state in which fewer but enlarged red blood cells are produced. These cells are oval-shaped, not round and carry a shorter life span than normal red blood cells.

Measurements of folate status;

To get an estimate of folate concentration in blood, folate levels of either RBC or serum are tested; low levels being indicative of deficiency. Serum folate fluctuates on daily basis depending upon dietary intake and shows the absorbed dietary folate concentration.

Moreover, it only provides information about current folate intake but does not represent the tissue store; for which RBCs folate concertation is observed. Reference value for hematocrit, red cell count, mean corpuscular volume(MCV) and mean corpuscular hemoglobin (MCH)are used to confirm either of the folate, vitamin B12 and iron deficiency anemia .

Deficiency of these nutrient result in the production of abnormally large (folate and vitamin B12 ) or small RBCs (iron deficiency of anemia) . Plasma homocysteine (tHcy) level may also be checked because deficiency of folate and vitamin B12 result in its increase. However, these testes (except serum and RBC folate) are seldom performed because they indicate both folate and vitamin B12 deficiencies.

Vitamin B12

It is generally term as cobalamin and its active form is known as methylcarbylamine. Animal based foods are rich in vitamin B12 though negligible amounts are present in plants.

The human body is wholly dependent on vitamin B12 for the uptake of iron in small intestine . Vitamin B12 is also required to keep blood and nerve cell healthy. An adequate amount of vitamin B12 prevent megaloblastic anemia.

Deficiency of vitamin B12 status;

Several factor contribute to vitamin B12 deficiency including malabsorption, vegetarian diet, gastrectomy, certain medications (metformin used in type 11 diabetes) and increased demand during pregnancy or lactation.

After 40 year of age, its level start to decrease due to diminished production of intrinsic factor which is essential for its absorption.

Measurement of vitamin B12 status;

Vitamin B12 status could be assessed either by measuring cobalamin concentration in the body or by functional indicator i.e. metabolites accumulated due to inadequate vitamin B12 . Direct assessment involves the measurement of total circulating cobalamin and holo- transcobalamin(holo- -TC)in serum.

Basically holo- transcobalamin is is the carrier protein for the absorbed vitamin B12 . Apart two functional biomarker are used to measure vitamin B12 status i.e. urinary or serum methylmalonic acid (MMA) and plasma total homocysteine level. These biomarker are useful to identify the early changes in vitamin B12 status or sub-clinical deficiency .

However, many factors could limit the use of individual biomarker for determining vitamin B12 status. Advance renal diseases and renal impairment may increase the value of all four biomarker . Moreover, serum cobalamin concentration falls due to deficiency of folate . Hence, no single test could identify cobalamin deficiency , two or more tests should be performed to ascertain the level .

Vitamin B6;

Vitamin B6 found in different forms i.e. pyridoxal, pyridoxine and pyridoxamine. In liver, erythrocytes and other tissue, it exists in the form of pyridoxal 5- phosphate(PLP).

It serves as a co-factor for enzymes involved in amino acid metabolism and plays an important role in final step of heme synthesis through incorporation of iron into protoporphyrin. It is also required for the proper functioning of the brain and is part of serotonin(regular mood) and melatonin (maintain sleep)hormones.

Deficiency of vitamin B6;

Vitamin B6 deficiency is rare owing to its abundance in foods. However, it may occur due to autoimmune disorder, prolonged malabsorption and excessive alcohol consumption. Certain disease/ disorders including diabetes, autism, oxaliplatin-induced neurotoxicity, pyridoxine inactivating drug and neuropathy can lead to vitamin B6 deficiency.

Measurement of vitamin B6 status;

Vitamin B6 status cold be measured by both static and functional biomarker.

a)Plasma pyridoxal 5- phosphate(PLP);

Deficiency of vitamin B6 can be determined by plasma PLP level the most frequently test used to assess vitamin B6 status. However, its levels are decreased by increased protein intake, raised glucose level , elevated plasma volume, asthma and coronary heart diseases.

Contrarily, increased vitamin B6 intake and physical activity lead to increased PLP levels in plasma. Although PLP is a valuable test for the diagnosis of vitamin B6 deficiency, its utility is best accomplished when used in conjunction with other tests.

b) Urinary 4- pyridoxic acid;

It is a major urinary metabolite of vitamin B6 . The urinary value of 4- pyridoxic acid changes abruptly with alteration in dietary intake of vitamin B6; making it an instant indicator of vitamin B6 status. The test value is limited by the need of 24-hour urine sample collection.

c) Methionine load test;

The methionine load test is another indicator of vitamin B12 status . Since PLP is required for the metabolism of methionine, a comparison of methionine metabolism in normal and deficiency person is made following the consumption of 3 g methionine. Protein intake and 24-hour urine sample requirement could affect the test results .

indicators reference value

direct blood

plasma PLP (nmol/L) >30

plasma total vitamin B6(nmol/L) >40

urine

4-pyridoxic acid(nmol/day) >3.0