Vitamins are organic materials that are required in small amounts for optimal metabolism in humans. Most vitamins can’t be made in the body and must be obtained from the diet or additional supplements.  

What are Vitamins?

Vitamins are organic materials that are required in small amounts for optimal metabolism in humans. Most vitamins can’t be made in the body and must be obtained from the diet or additional supplements.  

Are vitamins good for our body and health? 

Overall, vitamins are beneficial for humans; however, moderation is key. Some vitamins are necessary for our wellbeing; however, others can cause harm if consumed in excessive amounts.  

There are numerous vitamins; only 13 vitamins are categorized as essential because they cannot be created by humans and must be provided through diet. This emphasizes that having a balanced diet is an essential first step before you start taking vitamin supplements.

The 13 essential vitamins are: Vitamin A, Vitamin C, Vitamin D, Vitamin E, Vitamin K, Vitamin B1 (thiamine), Vitamin B2 (riboflavin), Vitamin B3 (niacin), Pantothenic acid (B5), Vitamin B6, Biotin (B7), Folate (folic acid and B9), Vitamin B12 (cyanocobalamin).  

Two Categories of Vitamin 

1. Water-Soluble Vitamins

Thiamin (Vitamin B1) is one of the water-soluble B vitamins. Thiamin is naturally present in foods and also available as a dietary supplement.  

Vitamin B1, or thiamin, involves cellular metabolism of the brain, muscle, heart, stomach, and intestines.  It is also involved in the process of balancing electrolytes among muscle and nerve cells. Moreover, it helps prevent diseases (i.e., beriberi, which involves disorders of the heart, nerves, and digestive system).  

Daily Requirement: 1.2 mg for men, 1.1 mg for women, and 1.4 mg during pregnancy and lactation 

Foods that contain thiamin include: 

Cereals Bread Fish
Meat (Beef, Pork) Liver Whole grain
Fruit and vegetables

Fruits and vegetables include: cauliflower, oranges, potatoes, asparagus, and kale.

Breakfast cereals and products made with white flour or white rice are usually enriched with vitamin B. In the United States, around half of their vitamin B1 intake comes from naturally occurring foods, although it can be fortified in various food items. 

Vit B1 Deficiency 

B1 deficiency could lead to a condition called beriberi which can be categorized into wet beriberi and dry beriberi. 

Wet beriberi affects the heart and circulatory system, while dry beriberi affects the nervous system resulting in numbness of the hands and feet, confusion, trouble moving the legs, and pain. 

Riboflavin (also known as vitamin B2) is one of the B vitamins and water-soluble one. Riboflavin is naturally present in some foods, added to some food products and available as a dietary supplement.  

This vitamin is an essential component of two significant coenzymes, flavin mononucleotide (FMN; also known as riboflavin-5′-phosphate) and flavin adenine dinucleotide (FAD). These coenzymes play significant roles in energy production, cellular function, growth and development, and metabolism of fats, drugs, and steroids.  

Daily Requirement: 

RDA for Vit B2 is 1.3 mg for adult males and 1.1 mg for adult females, 1.4 mg during pregnancy, and 1.6 mg during lactation.  

Foods that are particularly rich in riboflavin: eggs, organ meats (kidneys and liver), lean meats, milk, Green vegetables, Artichokes, Avocados, Cayenne, Currants, Fortified cereals, Kelp, Mushrooms, Nuts, Parsley, pumpkins, Sweet potatoes, Whole-grain bread, enriched bread, and wheat bran.

Vit B2 Insufficiency 

Two types of Vit B2 deficiency:  

  1. Primary: Occurs due to inadequate Vit B2 dietary source. 
  2. Secondary: Inability to absorb Vit B2 via the intestine

Features due to B2 insufficiency:

  • Dry skin  
  • Cracked lips 
  • Mouth ulcers 
  • Dermatitis 

Vit B3, called Niacin, is the generic name for nicotinic acid (pyridine-3-carboxylic acid), nicotinamide (niacinamide or pyridine-3-carboxamide), and related derivatives, such as nicotinamide riboside.  

Niacin plays a role in keeping skin, hair, and nervous system healthy. 

Niacin is naturally present in many foods, added to some food products and available as a dietary supplement. 

Daily Requirement: 

The National Institutes of Health (NIH) recommend 16 mg for adult males and 14 mg for adult females, 18 mg during pregnancy and 17 mg during lactation. 

Foods that contain B3: 

  • Chicken 
  • Turkey 
  • Salmon 
  • Brown rice 
  • Dry roasted peanuts 
  • Beef liver 
  • Deficiency 

If you don’t consume enough Vit B3, deficiency of Vit B3 can cause Pellagra that consists of various skin symptoms, fatigue, diarrhea, and memory loss.  

Vitamin B5, known as pantothenic acid, helps turn the food you eat into the energy that you need. It’s crucial for many functions in the body, especially making and breaking down fats. It also supports healthy skin, eyes, and liver.

Daily Requirement: 

The recommended dosage is 5 mg for adults, 6 mg for pregnant females, and 7 mg for breastfeeding females.  

Foods that contain Vit B5: 

  • Beef
  • Poultry 
  • Seafood 
  • Organ meats 
  • Eggs and milk 
  • Vegetables such as mushrooms (especially shiitakes) 
  • Avocados 
  • Potatoes 
  • Broccoli 
  • Whole grains 

    Vit B5 Deficiency 

    Although Vit B5 deficiency can happen theoretically, it is rare in daily clinical practice as Vit B5 is found in various foods that we consume daily.  

    Features that associated with Vit B5 deficiency 

    • Mood changes (depression, irritability, apathy) 
    • Various GI symptoms (Nausea, vomiting, stomach pain) 
    • Numbness and burning feet 

    Vitamin B6 performs a wide variety of functions in the body and is highly versatile, with more than 100 enzyme reactions.  

    Vitamin B6 also plays a role in cognitive development through neurotransmitters’ biosynthesis, glucose metabolism, immune function, and hemoglobin formation.  

    Daily Requirement: 

    RDA for Vitamin B6 is 1.3 mg for adult males and 1.3 mcg for adult females, 1.9 mg during pregnancy, and 2.0 mg during lactation.  

    Foods that contain Vit B6: 

    • Fish 
    • Beef liver and other organ meats 
    • Turkey 
    • Banana 
    • Tofu 
    • Nuts 
    • Potatoes and other starchy vegetables 
    • Rice 
    • Onion, Squash, Spinach 
    • Watermelon 

    Sign and symptoms of Vit B6 Deficiency: 

    • Anemia 
    • Depression 
    • Higher risk of infection due to decreased immunity 
    • Peripheral neuropathy 
    • Confusion 

      However, most Americans get enough vit B6 from their diet.  

      Vitamin B7, known as Biotin, a B vitamin, is an essential nutrient involved in the metabolism of fatty acids, glucose, and amino acids. It helps to maintain the health of hair, nails, and fetal health during pregnancy.  

      Daily Requirement: 

      RDA for Biotin is 30 mcg for adult males and 30 mcg for adult females, 30 mcg during pregnancy, and 35 mcg during lactation.  

      Foods that contain the most Biotin include: 

      • Organ meats
      • Eggs and cheese 
      • Fish 
      • Seeds and nuts 
      • Leafy Greens 
      • Cauliflower 
      • Mushrooms 
      • Sunflower seeds and almonds 

      Biotin deficiency 

      Biotin deficiency is relatively rare. However, eating only raw eggs may cause biotin deficiency. 

      Biotin deficiency can be associated with various skin, hair, and nail problems.  

      Folate, known as Vitamin B9, acts as a coenzyme to synthesize genetic material such as DNA and amino acids metabolism. Folate is crucial for cellular metabolisms as well as prenatal health.  

      Moreover, folate is one of the main ingredients of red cell production. Hence, folate deficiency can lead to megaloblastic anemia, resulting in fatigue and weakness.  

      Daily Requirement: 

      RDA for folate is 400 mcg DFE for adult males and 400 DFE mcg for adult females, 600 mcg DFE during pregnancy, and 500 mcg DFE during lactation.  

      Sources of Folate: fruits and fruit juices, nuts, beans, peas, avocado, broccoli, seafood, eggs and dairy products, meat, poultry, Beef liver, Grains, Spinach, asparagus, and brussels sprouts, banana, papaya.     

      Features due to folate deficiency 

      • Fatigue 
      • weakness 
      • Mouth sores 
      • heart palpitation 
      • Anemia 

      Individuals that are at risk: 

      • Chronic alcohol user 
      • Pregnant women 
      • Intestine problems affecting vitamin absorption 
      • Other genetic diseases 


      Vitamin B12, also known as cobalamin, is an essential nutrient and involves various cellular metabolisms. It plays a significant role in keeping nerve tissues, as well as blood cells healthy.   

      Daily Requirement: 

      RDA for Vit B12 is 2.4 mcg for adult males and females, 2.6 mcg during pregnancy, and 2.8 mcg during lactation. The human body can store extra fat b12 for up to four years, and any excess fat B12 is removed via the urine.  

      Vit B12 is usually found in various animal and dairy products whereas not in plant foods.

      Foods that contain Vit B12: 

      • Fish 
      • Pork 
      • Poultry 
      • Lamb 
      • Beef 
      • Eggs 
      • Milk and milk products 

      Features that associated with Vit B12 Deficiency: 

      • Neurological problems (depression, confusion, memory problems) 
      • Fatigue 
      • Loss of appetite and weight loss 
      • Anemia 

      Risk of Vit B12 Deficiency: 

      Individuals who primarily eat a plant-based diet are at risk of Vit B12 deficiency and people with pernicious anemia, gastrointestinal disease, chronic alcoholism, and older adults.   


      Treatment of Vit B12 deficiency includes B12 injection and oral supplements.  

      Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that maintains skin, bones, and blood vessels. Humans, unlike most animals, are unable to synthesize vitamin C by themselves, so it is an essential dietary component. 

      Our body needs Vitamin C for various functions: 

      • biosynthesis of collagen 
      • important physiological antioxidant  
      • enhance immune system 
      • improve wound healing 
      • Iron absorption 

      Moreover, ongoing research is being performed to determine if Vitamin C might help prevent or delay the development of certain cancers, cardiovascular disease, and other diseases. 

      Daily Requirement 

      RDA for Vitamin C is 90 mg for adult males and 75 mg for adult females, 85 mg during pregnancy, and 120 mg during lactation.  

      Foods that contain Vit C 

      • citrus fruits 
      • tomatoes and tomato juice 
      • potatoes 
      • red and green peppers 
      • kiwifruit 
      • broccoli 
      • strawberries 
      • brussels sprouts, and cantaloupe 

      Vitamin C deficiency 

      Deficiency of Vit C can cause a condition called scurvy. Scurvy can manifest with various symptoms such as  

      • bruising, bleeding gums 
      • weakness and fatigue 
      • skin rash and red spots 
      • loss of appetite and muscle pain 

      2. Fat-Soluble Vitamins 

      Vitamin A is a fat-soluble vitamin and is involved in immune function, vision, reproduction, and cellular communication.  

      Vitamin A is essential for vision as it is a necessary component of rhodopsin, a protein that absorbs light in the eye’s retinal receptors.  

      Moreover, Vitamin A supports cell growth and differentiation, playing a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs.  

      Daily Requirement:  

      The Recommended Dietary Allowance for adults 19 years and older is 900 mcg RAE for men (equivalent to 3,000 IU) and 700 mcg RAE for women (equivalent to 2,333 IU).  

      Foods that contain Vit A 

      • Liver 
      • Fish Oils
      • Milk 
      • Eggs 
      • Dairy products 
      • Fortified cereals 

      Moreover, provitamin A can be found in leafy green vegetables, orange and yellow vegetables, tomato products, fruits, and some vegetable oils.  

      Foods that contain provitamin A 

      • Carrots
      • Broccoli 
      • Cantaloupe 
      • Squash 

      Vit A Deficiency 

      It can present eye problems and night blindness. However, if you take too much Vit A, it can lead to Vit A toxicity.  

      Symptoms are: 

      • various skin manifestations (changes in skin color, dermatitis) 
      • psoriasis 
      • dry mucosa 
      • damage to the liver and nervous systems 


      Vitamin D, known as calciferol, is a fat-soluble vitamin that the human body can produce in response to ultraviolet rays from the sun. Vitamin D enhances calcium absorption and helps to maintain bone and teeth synthesis and muscle functions.  

      Vitamin D can be described as a prohormone rather than a vitamin as it requires activation by the liver and kidneys before becoming biologically active. 

      Daily Requirement:  

      RDA for Vitamin D is 15 mcg (600 IU) for adult males and adult females (same dose during pregnancy and lactation). The dosage is 20 mcg (800 IU) for males and females over the age of 70. 

      Roles of Vitamin D  

      • Maintain bone and teeth health 
      • Support nervous system and immune function 
      • Help to manage sugar control and insulin levels 
      • Improves cardiac and lung functions 

      Vitamin D sources: 

      • fish (such as trout, salmon, tuna, and mackerel) 
      • fish liver oils  
      • fortified milk, cereals, and juices 
      • eggs 
      • cheese 
      • mushrooms 

      Vitamin D insufficiency 

      Although our body produces vit D, several conditions could lead to Vit D deficiency, such as limited sun exposure, darker skin, bariatric surgery, and infants. 


      • mood changes (low mood, fatigue) 
      • hair loss 
      • delayed wound healing 
      • bone pain 
      • muscle pain 
      • prone to get an infection 


          Vitamin E is a fat-soluble vitamin and possesses specific antioxidant activities. Although more scientific evidence is needed, it is believed that Vit E has several beneficial effects on heart health, cancer, eye health, hair health, and brain functioning.  

          Daily Requirement: 

          RDA for Vitamin E is 15 mg for adult males and 15 mg for adult females, 15 mg during pregnancy, and 19 mg during lactation.  

          Foods that contain Vitamin E: 

          Numerous foods provide vitamin E. Nuts, seeds, and vegetable oils are among the best alpha-tocopherol sources, and significant amounts are available in green leafy vegetables and fortified cereals.  

          Most vitamin E in American diets is in gamma-tocopherol from soybean, canola, corn, and other vegetable oils and food products. 

          Any other form? 

           Vitamin E is also available as a supplement form in various stores.  

          Vitamin K is a fat-soluble vitamin and can be found in two different forms. Phylloquinone, known as Vitamin K1, is found in green leafy vegetables like collard greens, kale, and spinach.  

          The other type, menaquinones, known as Vitamin K2, are found in some animal foods and fermented foods and can be produced by bacteria in the human body. 

          Vitamin K plays a significant role in blood clotting, calcium, and bone metabolism.  

          Daily Requirement: 

          RDA for Vitamin K is 120 mg for adult males and 90 mg for adult females, 90 mg during pregnancy, and 90 mg during lactation. 


          Food sources of phylloquinone include vegetables, especially green leafy vegetables, vegetable oils, and some fruits.  

          Meat, dairy foods, and eggs contain low levels of phylloquinone but modest amounts of menaquinones. Other fermented foods, such as cheese, also contain menaquinones.  

          The most common vitamin K sources in the U.S. diet are spinach; broccoli; iceberg lettuce; and fats and oils, particularly soybean and canola oil. 

          Vit K deficiency 

          • Increased risk of bleeding (under the skin, from the gut, brain) 


          Vitamin K deficiency can be treated with oral or IV injection of Vitamin K.  


          1. Johnson EJ, Russell RM. Beta-Carotene. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:115-20. 
          2. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press; 2001.