Vitamin C - why it's one of the most powerful vitamins?
Vitamins are essential nutrients that are required for various biochemical and physiological processes in the body. Based on their solubility we classify them as water-soluble (C and B complexes) and fat-soluble vitamins (A, D, E, K). Most of the vitamins cannot be synthesized in the body, that's why their supplementation in the diet is essential.
Vitamin C, also known as ascorbic acid (AA) exists in reduced (ascorbate) and oxidized forms as dehydroascorbic acid, which are easily interconvertible and biologically active thus it acts as an important antioxidant. Most plant and animal species can synthesize vitamin C from glucose and galactose, but humans can't.
Vitamin C deficiency
Vitamin C deficiency is often associated with anemia, infections, bleeding gums, poor wound healing, muscle degeneration. Severe and prolonged vitamin C deficiency can lead to scurvy, which is fatal if left untreated.
Whereas vitamin C deficiency is mainly caused by poor diet, several additional risk factors have been identified, including smoking, pregnancy, low socioeconomic status, genetic predisposition, old or young age, strenuous exercise, diabetes, and obesity.
For the correction of deficiency, vitamin C is often supplemented in large doses and unlike fat-soluble vitamins, toxicity is rare.
Dietary sources of vitamin C
Vitamin C is water-soluble so the body doesn't store it. To maintain adequate levels of vitamin C, people need to consume food that contains it every day. Vitamin C is found in citrus fruits, green peppers, red peppers, strawberries, tomatoes, broccoli, brussels sprouts, and other leafy vegetables. Animal sources are poor in vitamin C content that's why plants sources are important because of the high content of vitamin C, up to 5000 mg/100g. A total of 5-9 servings of fresh, minimally processed, or frozen fruit and vegetables per day is estimated to equal – 200 mg of vitamin C.
Vitamin C and health
Our body requires vitamin C for normal physiological functions:
- It helps in the synthesis and metabolism of tyrosine, folic acid, and tryptophan.
- It facilitates the conversion of cholesterol into bile acids and hence lowers blood cholesterol levels.
- It increases the absorption of iron in the gut by reducing ferric to the ferrous state.
- As an antioxidant, it protects the body from various effects of free radicals, toxins, and pollutants.
Biochemical functions of vitamin C
Vitamin C is crucial in the maintenance of collagen, which represents about 1/3 of the total body protein. Collagen is the main component of connective tissue and makes up 1-2% of muscle tissue. Synthesis & accumulation of collagen and subsequent cross-linking of the fiber is also important because it gives new tensile strength to the damaged tissue, thus it helps with wound healing.
Vitamin C is also a co-factor for the enzyme dopamine-B-hydroxylase, which catalyzes the conversion of the neurotransmitter dopamine to norepinephrine, therefore is essential for the synthesis of catecholamines. They are compounds that play major roles in the body such as regulation of physiological processes, development of neurological, mental, endocrine, and cardiovascular diseases. They also play an important part in the body's response to stress, which is a very important function in maintaining the optimal functioning of the human body.
It's also involved in the transformation of cholesterol into bile acids. The deficiency of vitamin C affects this conversion. As result, cholesterol accumulates in the liver leading to hypercholesterolemia & cholesterol gall stones formation.
Vitamin C and the common cold
The most widely known effect of vitamin C in the prevention and relief of the common cold. If we have a weak immune system, we are prone to get sick more often. Vitamin C has been shown to stimulate the immune system by enhancing T-cell proliferation in response to infection. These cells are capable of lysing infected targets by producing large quantities of cytokines and by helping B cells to synthesize immunoglobulins to control inflammatory reactions.
The role of vitamin C in skin health
Vitamin C can be also found in cosmetic products. Skincare experts from all over the world are forging it into stars. You probably wonder why. Mainly because it's extremely effective against skin aging. It also makes our skin shiny, evens out the skin tone, and at the same time smoothes out small and deep wrinkles. We all want to look young, right?
- It promotes collagen formation: Vitamin C acts as a co-factor for the proline and lysine hydroxylases that stabilize the collagen molecule structure and it also promotes collagen gene expression.
- Acts like antioxidant: It can neutralize and remove oxidants, like those from environmental pollutants and after exposure to ultraviolet radiation. This is the most important in the epidermis, where vitamin C is concentrated in the skin. However, it's the most effective at reducing oxidative damage to the skin, when it's used in conjunction with vitamin E.
- Inhibits melanogenesis: Vitamin C derivates, have been shown to decrease melanin synthesis. This is thought to be due to its ability to reduce the ortho-quinones generated by tyrosinase. Agents that decrease melanogenesis are used to treat skin hyperpigmentation in conditions such as melasma or age spots.