FACTS YOU NEED TO KNOW ABOUT VITAMINS

Vitamins are micronutrients that have physiological effects on various biological responses, including host immunity. Therefore, vitamin deficiency leads to increased risk of developing infectious, allergic, and inflammatory diseases. Since B vitamins are synthesized by plants, yeasts, and bacteria, but not by mammals, mammals must acquire B vitamins from food or microbial sources, such as the intestinal microbiota. Similarly, some intestinal bacteria are unable to synthesize B vitamins and must acquire them from the host diet or from other intestinal bacteria for their growth and survival.

Nutrients are essential for the development, maintenance, and function of the immune system in the body. Vitamins can as well be said to be an essential micronutrients that are synthesized by bacteria, yeasts, and plants, but not by mammals. Therefore, mammals must obtain vitamins from the diet or rely on their synthesis by commensal bacteria in the gastrointestinal tract. Some vitamins are water-soluble (e.g., vitamin B family and vitamin C), whereas others are fat-soluble (e.g., vitamins A, D, E, and K). Water-soluble vitamins are not stored by the body and any excess is excreted in the urine; therefore, it is important to consume a diet containing the necessary amounts of these vitamins. Vitamin deficiency associated with insufficient dietary(food) intake occurs not only in developing countries but also in developed countries as a result of increased use of unbalanced diet.

A,D,E and K Vitamins

Fat Soluble vitamins are vitamins that can dissolve in fats and oils. Fat-soluble vitamins are absorbed along with fats in the diet and can be stored in the body's fatty tissue. They come from plant and animals foods or dietary supplements.

The B-family and C Vitamins

Water soluble vitamins are vitamins that can dissolve in water. It can as well be call the B-family and C Vitamins. It is called the B-family because it comprises B1, B2,B3,B5,B6,B7,B9 and B12. And then the vitamin C otherwise known as ascorbic acid.

Absorption of vitamins

Water soluble vitamins

In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine. Supplements and fortified foods contain B12 in its free form, so they may be more easily absorbed.

Absorption of vitamin C

The intestines have a limited ability to absorb vitamin C. Vitamin C is an acidrhat need to get rid off from the body through excretion. They can confiscate ulcer. The absorption of vitamin C take place in the small intestine. Part of the vitamin C is also absorb in small intestine. Megadoses of vitamin C are not toxic because as the body's tissue get saturated, absorption decreases and excess amount will be excreted in urine.

Food sources of vitamins 

Fat Soluble vitamins:

Vitamin A: liver,fish,liver oil, butter,carrots, spinach,fish.

Vitamin D: fatty fish, mushrooms,salmon, egg yolk,meat,fish liver oil,offal,diary.

Vitamin E: snails, crayfish,goose meat,avocados,almonds,spinach.

Vitamin K: meat,liver,fish,cheese,tomato, egg yolk, cabbage, cauliflower.

Water Soluble Vitamins

B-vitamins: Chicken ,egg,fish,liver,shell fish, legumes,leafy vegetables,meat,oysters,milk mushroom,nuts, wholegrains sunflower seeds, potatoes,bananas, diary products.

Vitamin C: Eggs,meat,fish,raw liver.

Note: As you can see,all of the above food sources of various vitamins are somewhat thesame. However,you need to consume varieties of meal and not feed on one type of food group,as this would deter your adequate healthiness. All of these vitamins has a specific role in human health. For instance, deficiency of folic acid (B9) can cause neural tube defect.

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Reference 

https://www.frontiersin.org/articles/10.3389/fnut.2019.00048/full#B4