• Vitamin A is vital for a healthy immune system, bone growth, vision, cell recognition and reproduction. Vitamin A often works as an antioxidant, fighting cell damage, but it also has many other uses. It has a vital role in the formation of heart, lungs, and kidney.
• Other functions of vitamin A include the formation and maintenance of teeth, bones, soft tissue, white blood cells, the immune system and mucus membranes. 
• Most people get enough vitamin A from their diets. However, a doctor might suggest vitamin A supplements to people who have vitamin A deficiencies. People most likely to have vitamin A deficiency are those with diseases (such as digestive disorders) or very poor diets.

• Vitamin A is used for improving the eyesight, maintaining cells of the skin and the lining of the digestive, urinary and respiratory tracts.
• It also helps in the formation of red and white blood cells in our body that are important to carry out the various essential functions of our body.
• Topical and oral retinoids are common prescription treatments for acne and other skin conditions, including wrinkles. 
• Oral vitamin A is also used as a treatment for measles and dry eye in people with low levels of vitamin A. 
• Vitamin A is also used for a specific type of leukemia.
• Vitamin A has been studied as a treatment for many other conditions, including cancers, cataracts, and HIV. However, the results are inconclusive.

• Night blindness
• A higher risk of infections, especially in the throat, chest, and abdomen
• Follicular hyperkeratosis, leading to dry, bumpy skin.
• Fertility issues
• Delayed growth in children
• Symptoms of vitamin A toxicity include dry skin, joint pain, vomiting, headaches, confusion.

• If you take too much of Vitamin A, it can lead to birth defects, abnormalities of the liver and disorders of the central nervous system.
• It can also decrease bone mineral density, leading to an increased risk of osteoporosis.
• This is because an excess of Vitamin A suppresses the building up of bones and increases its breakdown.
• The rate of calcium absorption by Vitamin D can also get affected due to excess of Vitamin A. Therefore, it is advised to use Vitamin A only as directed by your doctor.
• Interactions. Vitamin A supplements may interact with some birth control pills, blood thinners (Coumadin), acne medicines (isotretinoin), cancer treatments, and many other drugs.
• People who drink heavily or have kidney or liver disease shouldn’t take vitamin A supplements without talking to a doctor.

• Iodine is a chemical element. The body needs iodine but cannot make it. The iodine needed by the body must come from the diet. Iodine helps convert thyroid stimulating hormone (TSH) to triiodothyronine (T3) and thyroxine (T4). This conversion is important for the thyroid to function properly.
• An iodine imbalance can lead to an overactive or underactive thyroid.

• The thyroid gland needs iodine to make hormones. Lack of iodine can cause an enlarged thyroid gland (goiter), which causes a swollen neck.
• It is also used for treating lumpy breasts (fibrocystic breast disease) and breast pain (mastalgia).
• Iodine deficiency and the resulting low levels of thyroid hormone can cause women to stop ovulating, leading to infertility. Iodine deficiency can also lead to an autoimmune disease of the thyroid and may increase the risk of getting thyroid cancer.
• Iodine is also used for radiation emergencies, to protect the thyroid gland against radioactive iodides.
• Iodine is sometimes applied to the skin for skininflammation and to kill germs and facilitate wound healing.
• It is also used prevent soreness inside the mouth or along the digestive tract, and other conditions, but there is no good scientific evidence to support these uses.
• Iodine is used in the vagina to prevent post-Cesarean swelling of the lining of the uterus. Iodine is also used for water purification.

•  burning mouth/throat, sore teeth/gums, swelling inside the mouth, increased saliva,
•  eye irritation/swollen eyelids,
•  severe headache,
•  swelling of the front of the neck/throat (goiter),
•  signs of decreased thyroid gland function (e.g., weight gain, cold intolerance, slow/irregular heartbeat, constipation, unusual tiredness), confusion,
•  numbness/tingling/pain/weakness of the hands/feet.

Excessive iodine may cause hypothyroidism by feedback inhibition of thyroid hormone production and conversion of triiodothyronine(T3) to less active thyroxine(T4). Use caution in patients with renal impairment. Iodine enters breast milk; use caution if breastfeeding

• Folic acid is the synthetic form of folate, which is a naturally occurring B vitamin. Folate helps make DNA and other genetic material. It is especially important in prenatal health.
• Folate, also called vitamin B-9, is a B vitamin that naturally occurs in certain foods. Folic acid is the form of folate that manufacturers add to vitamin supplements and fortified foods.

• It helps the body make healthy new red blood cells.
• In its deficiency a person can develop anemia, leading to fatigue, weakness, and a pale complexion.
• It leads to folate deficiency anemia.
• Folate is also important for the synthesis and repair of DNA and other genetic material.
• It is particularly important to get during pregnancy. Folate deficiency during pregnancy can lead to neural tube irregularities, such as spina bifida and anencephaly.
• Folic acid is crucial for early fetal development.
• Neural tube irregularities - Taking folic acid supplements before and during pregnancy will help prevent neural tube irregularities in the fetus.
• It may also reduce the risks of preterm birth, heart irregularities, and cleft palate, among other things.
• Depression - Taking folic acid supplements could make depression medications more effective.
• The Office on Women’s Health recommend that women who are or might become pregnant take 400–800 mcg of folic acid per day, and that people with spina bifida or a family history of neural tube irregularities take 4,000 mcg per day. Those who are breastfeeding should aim to take around 500 mcg per day.
• The body absorbs folic acid from supplements and fortified foods better than the folate from naturally occurring foods.

Skin reactions, seizures, gases problem, diarrhea, irritability, confusion, stomach upset, loss of appetite, and hypersensitivity

It is important to note that folic acid can interact with certain medications.

A person should speak to a doctor before taking folic acid if they have any of the following:

• Epilepsy
• Type 2 diabetes
• Rheumatoid arthritis
• Lupus
• Inflammatory bowel disease (ibd)
• Celiac disease

People undergoing kidney dialysis may also wish to avoid taking folic acid.