Vitamins are essential nutrients that are required for various biochemical and physiological processes in the body. Humans are unable to synthesize vitamin C and are dependent on dietary sources, mainly fruit and vegetables. Adult women (who aren't pregnant or breastfeeding) need 75 milligrams of vitamin C per day; men, 90 milligrams. A mere 3/4 cup of orange juice will do it, while 1/2 cup cooked broccoli gets you at least halfway there. Even in high income countries population-based studies have reported blood levels of vitamin C in the range indicating deficiency in around 1 in 5 men and 1 in 9 women in low income groups.

The body requires vitamin C for normal physiological functions. It helps in the synthesis and metabolism of tyrosine, folic acid and tryptophan, hydroxylation of glycine, proline, lysine carnitine and catecholamine. It facilitates the conversion of cholesterol into bile acids and hence lowers blood cholesterol levels. It also increases the absorption of iron in the gut by reducing ferric to ferrous state. 

Deficiency:

The most likely people include those with an overall poor diet, with kidney disease who get dialysis, heavy drinkers, and smokers. You'll need an extra 35 milligrams of vitamin C per day to help repair the damage caused by free radicals that form when you smoke. Tobacco use is common in India with a third of adults smoking or chewing tobacco . These factors: Smoking or chewing tobacco and cooking with fuels such as wood crops suggest that vitamin C deficiency might be high in the Indian population but currently no studies have investigated all age groups of population in India.

Symptoms of a vitamin C deficiency include:

Bleeding Gums

Sometimes a rough tooth brushing technique is at the root of bleeding gums, but a diet lacking in vitamin C can also be to blame. Vitamin C plays an important role in wound healing and immunity, and it even acts as an antioxidant, helping prevent cell damage.

Weight Gain

Early research has found a link between low levels of vitamin C and higher amounts of body fat, especially belly fat. This vitamin may also play a role in how well your body burns fat for energy.

Weak Immune System

 According to a 2017 report published in the scientific journal Nutrients and shared by the U.S. National Library of Medicine, vitamin C, also known as ascorbic acid, supports both innate and adaptive immune function, positively affecting how well cells involved in this complex and multifaceted system perform. Research indicates a lack of vitamin C, therefore, negatively impacts immune system strength.

Dry skin

Vitamin C is good for your skin health. You will notice almost every skin product contains vitamin C. High content of antioxidants makes vitamin C beneficial for the skin. Poor intake of vitamin C results in dry and damaged skin. You can also notice wrinkles on your skin in many places.

Slow healing of wounds

Vitamin C deficiency can lead to a slow rate of collagen formation which results in slow healing of wounds. Lack of vitamin C will also increase the spread of infections. This sign is usually visible when there is severe vitamin C deficiency.

Tired and Cranky

In a very small study, 6 of the 7 men who had low levels of vitamin C said they felt tired and irritable. That suggests a link, though other things could be playing a role. 

Scurvy

Before the 1700s, this potentially deadly disease used to be a huge problem for sailors. Today, it's relatively rare but possible if you get only 10 mg/day of vitamin C or less. People with scurvy also have problems such as loose teeth, cracked fingernails, joint pain, brittle bones, and corkscrew body hair. When you boost vitamin C, symptoms start getting better in a day, and usually it's cured within 3 months.

Source: Ravindran et al.,. https://doi.org/10.1371/journal.pone.0028588,  Chambial et al., 2013 10.1007/s12291-013-0375-3, northportwellnesscenter.com, healthline.com, webmd.com,