ISSA Nutritionist Chapter 7: Vitamins 1

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    Chapter Goals:

    • Be able to discuss the fat-soluble and the water-soluble vitamins.
    • Know the main roles of each vitamin.
    • Be able to discuss the benefits of vitamins for health and optimal physiological performance. 
    • List the important food sources for the vitamins.


    Vitamins are micronutrients required in the diet for maintaining good health, the functioning of a normal metabolism, the growth of bone and tissue, recovery, healing, immunity, performance athletically, and much more than those. 

    We find vitamins in fruits, vegetables, grains, milk, and dairy. Vitamins are organic, so they contain carbon atoms as part of their chemical structure. 

    Vitamin Classifications

    These are organized and classified by how they will be absorbed and stored in the body. 

    The first vitamin ever discovered was vitamin A in 1911. 

    Fat-Soluble Vitamins

    The fat-soluble vitamins are A, D, E, and K. 

    The fats are fat-soluble since they are only able to dissolve inf ats and organic solvents. 

    These vitamins will be stored in large amounts in the body fat and liver. 

    Toxicity from these vitamins is rare but possible, and the use of supplements makes it easier to exceed safe intake. 

    Vitamin A (Retinol, Beta-Carotene)

    Role in the body is in the eye health and vision, the immune system, reproduction, and the development of fetus’. Carotenoids belong in a class of molecules similar to vitamin A, and they give pigments to their foods.

    Deficiencies in Vitamin A will cause dry skin, rashes, frequent infection, and night blindness or just impairments in vision generally. 

    Excess intake occurs acutely or chronically, and the symptoms include things like nausea and vomiting, yellow dry skin, loss of hair, pain in your bones, and swelling of the bones. 

    Good food sources will be things like liver, fish, eggs, crab, halibut, and whole milk products. 

    When talking about athletes, the intake of vitamin A is going to be very important for the overall health and performance. 

    Vitamin D (Calciferol)

    The roles of vitamin D are quite important. It is essential for growth and development, and some main specific functions are that of absorption and metabolism of calcium and phosphorous for the ongoing support of mineralization of bones and teeth. 

    Deficiency in vitamin D is shown through poor mineralization of bones and the associated abnormalities. 

    Vitamin D can be quite toxic when receiving excess, especially in younger adults and children. The consequences are build up in the soft tissues and irreversible damage to the kidneys and cardiovascular system. 

    Dietary sources of vitamin D are from things such as fish liver oil, buttercream, halibut, and many types of seafood.

    Vitamin E

    The major function of vitamin E is as an antioxidant that is used for preventing free radical reactions and protecting the fatty acids within the cell membranes.

    Vitamin E deficiency has been observed in other animals, but not so much in humans. But it is known that babies will have lower concentrations of the vitamin in their cells. 

    Toxic intake occurs around 1,000 mcg or more of vitamin E. it can lead to anticoagulant problems and delays in blood clots. 

    Food sources high in vitamin E include things like vegetable oils, soybeans, corn, peanuts, and safflower. 

    Vitamin K

    This is used as a coenzyme for the promotion of prothrombin and procoagulants. Essentially the roles will involve coagulation and blood clotting.

    Deficiency in vitamin K is very rare in healthy people, but if green veggies are restricted, it is possible.

    No real problems have been found with excessive intake in the long or short term with this vitamin.

    The main sources of vitamin K are green leafy vegetables.

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    Water-Soluble Vitamins

    The water-soluble vitamins include vitamin C and the whole family of B vitamins. 

    They are not going to be stored in the body in any significant amounts as they only dissolve in water and are sent out with our urine. 

    Vitamin C (Ascorbic Acid)

    Vitamin C serves many roles as both a cofactor and an enzyme. It has a role in the forming and maintaining of collagen, which is, of course, a major connective tissue. 

    Vitamin C has some various roles like: 

    • Promotion of healthy capillaries, gums, and teeth.
    • Aiding in the absorption of iron, and its transport and storage. 
    • Prevention of the oxidation of folacin.
    • Helping to heal the wounds to the body.
    • It may have some significant impact on resistance to infection.
    • Aiding in the metabolism of tyrosine and phenylalanine.
    • It works to boost the immune system.
    • Protection from damage from free radicals.

    Deficiency of vitamin C can lead to diseases like scurvy, where the connective tissues are quite weak.

    More than 2 grams of vitamin C per day has been seen to lead to some serious side effects like headache, increased urination, diarrhea, and nausea.

    Some food sources include fruits and vegetables.

    It may be quite beneficial for athletes to increase their intake of vitamin C.

    Vitamin B1 (Thiamin)

    Thiamin is converted to coenzymes and this works to help break down carbohydrates and branched-chain amino acids. 

    Deficiencies in this vitamin and have some serious effects on our carb metabolism, show signs of fatigue, a loss of appetite, depression, poor coordination, and diseases like beriberi. 

    Excess intake is cleared by the kidneys and has rarely ever been reported in healthy adults. 

    It may be possible to increase athletic performance for endurance athletes by increasing the intake of thiamin 5 days prior to competition. 

    Vitamin B2 (Riboflavin)

    This coenzyme is involved in energy production and the cellular respiration.

    Deficiency symptoms include inflammation of the lips, cracked and dryer skin, reduction in the growth rate, loss of hair, and things like cataracts. 

    There is no unsafe amount of riboflavin that exists so far.

    This vitamin comes from brewer’s yeast, meats, poultry, fish and similar products. 

    Vitamin B3 (Niacin)

    This is functionally active in the body, and there are two important coenzymes it takes the form of. They will both be present in all cells and function in vital metabolic processes.

    Deficiency in this vitamin can cause symptoms like depression, confusion, headaches, elevated levels of body fat, fatigue, and pellagra.

    Intakes over 50 mg has been seen to cause serious effects in the skin. 

    Food sources for this vitamin includes foods like liver, brewer’s yeast, leaner meats, whole grains, nuts, legumes, and potatoes. 

    Excess intake of this vitamin may cause negative effects on the athlete’s performance and should be avoided in general. 

    Vitamin B6 (Pyridoxine)

    This plays a role in the metabolization of the amino acids, glycogen, and sphingoid bases. 

    Deficiency in this vitamin will cause symptoms like depression, skin problems, poor healing from wounds, anemia, fatigue, and convulsive seizures. 

    Toxicity occurs around 1,000 mg per day and causes some serious problems. 

    Even 100 – 300 mg can be toxic and cause problems for people. 

    Food sources for this vitamin include things like chicken, kidney, liver, eggs, rice, soybeans, bananas, and walnuts.

    Endurance athletes should avoid the higher doses of this vitamin as it is seen to impair performance in general. 

    Vitamin B9 (Folate)

    This vitamin is involved in the amino acid metabolism and the synthesis of nucleic acids. It is needed as a cofactor for the formation of our DNA and RNA, for the synthesis of proteins, and the division of cells. 

    Deficiency can cause symptoms like anemia, birth defects, soreness of the tongue, problems with digestion and growth fatigue, and megaloblastic anemia. 

    Toxic levels are considered to be above the 1,000 mcg daily and may cause damage to kidneys and stimulate seizures in epileptic people. 

    Food sources include most animal meats, asparagus, whole wheat, dark leafy veggies, and yeast. 

    Endurance athletes may greatly benefit from folate and its role in the production of red blood cells and repair of tissues. 

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    Vitamin B12 (Cobalamin)

    This is absolutely essential for energy in the body. 

    Deficiency of this is not common in the diet, unless someone has a poor absorption of the vitamin. These deficiencies may cause anemia, fatigue, irritability, loss of appetite, constipation, and soreness of the tongue. 

    No adverse effects have been found with the vitamin.

    Dietary sources include many meats, and it is important to know that vegans may need to consider supplementing this vital vitamin. 

    Vitamin B7 (Biotin)

    This coenzyme is used in carboxylation reactions and has a role in the metabolism of energy, formation of urea, synthesis of protein, and metabolizing the amino acids, glucose, and fatty acids. 

    Deficiency can result from low levels in the diet but also the excessive consumption of egg whites. 

    Some common toxicity signs could be skin rashes, but there is actually no designated unsafe level.

    Food sources includes liver, egg yolk, soy flour, nuts, and legumes. 

    The role in cellular energy production could make it an interest in athlete’s and supplementation. 

    Vitamin B5 (Pantothenic Acid)

    This plays many vital roles in metabolism, the main one being as a component of Acetyl CoA.

    Deficiencies will cause weakness, irritability, burning feet, vomiting, and insomnia. 

    Toxic levels are considered to be when the intake is over 10 – 20 grams every day.

    Food sources includes potatoes, eggs, pork, beef, fish, milk, whole wheat, and vegetables. 

    This may be beneficial for athletes to focus on and supplement, more so for the endurance athletes.

    Vitamin-Like Compounds

    These are classified as neither fat nor water-soluble vitamins, and they are still quite important, mainly as parts of cellular metabolism and other bodily processes.


    This vitamin is involved in the metabolism of fatty acids, the function of the liver, and the structural integrity of the cell membranes. 

    Deficiencies have not really been observed, but it could interfere with the liver. 

    Intake greater than 2 grams per day is likely to cause toxicity and bad side effects.

    Dietary sources include things like egg yolk, soybeans, most fatty foods, and wheat germ.

    There have been some reports of advantages delaying muscle soreness and fatigue when athletes supplement this vitamin. 

    Vitamin B8 (Inositol)

    This is a lipotropic agent like the last vitamin, and it works to fill its roles in fatty acid metabolism, carb metabolism, and mobilization of intracellular calcium. 

    Deficiency has been shown to cause a buildup of fat in the liver and may affect the nervous system functioning.

    Toxic levels are shown at around 12 grams or more per day.

    Food sources include things like heart, organ meats, whole grains, fruit, milk, seeds, and vegetables. 

    ISSA Nutritionist Chapter 7: Vitamins 2
    ISSA Nutritionist Chapter 7: Vitamins 3
    ISSA Nutritionist Chapter 7: Vitamins 4

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