Signs of Vitamin Deficiency and Toxicity


We recently discussed vitamins and their role in supporting the body’s various metabolic processes. These are classified “micronutrients” are necessary components to basic functions, but are also required in the optimal balance to achieve overall health and wellness. Clients may often inquire about supplementation and whether taking vitamins are necessary. A healthy and balanced diet usually requires all one needs to obtain essential vitamins, but only an in-depth vitamin analysis could reveal deficiencies and even toxically high levels of a particular vitamin.

Recall that there are two types of vitamins, water-soluble and fat soluble.

Water-soluble vitamins dissolve in water and are absorbed in the GI tract and are not readily stored (like fat-soluble vitamins), are utilized quickly, and need to be replenished more frequently as a result. Vitamins C and the B complex are water-soluble. Toxicity is unlikely since these vitamins are excreted quickly and not stored.

Fat-soluble vitamins such as A, D, E, and K are mostly absorbed passively in the GI tract by binding to dietary fats and are also stored in the body’s fatty tissues making toxicity possible if an individual ingests too high a dose of one of these vitamins.

Consequences of Deficiencies and Overconsumption

Although vitamin needs, intake, and absorption will vary for each fitness client, there are some signs that will point to a deficiency or level of toxicity that requires attention and a referral to the appropriate health professionals. Here’s a simple breakdown – consider this your “cheat sheet” for a quick vitamin overview.


Fat-soluble Vitamin Food Sources Functions Deficiency Examples Toxicity Examples
(carotenoids) Red, orange, yellow fruits & veggies Synthesizing proteins, immunity, red blood cell development Dry eyes, acne; rough, dry skin; difficulty seeing in low light Nausea, headache, fatigue, dizziness, birth defects during pregnancy



Fish, mushrooms, egg yolks, fortified dairy products Cell differentiation, immunity, serum calcium levels, regulating glucose tolerance Rickets in children, low bone density in adults tooth decay Elevated blood calcium, loss of appetite, nausea, itching, calcification of soft tissues



This family includes eight antioxidants

Nuts, seeds, peanuts, dark leafy greens, avocado Scavenging free radical, expression of immune and inflammatory cells Muscle weakness, damage to red blood cells, impaired vision, acne Impaired blood clotting

(phylloquinone) – Plant-based


(menaquinone) – Animal-based

Leafy greens, asparagus, cruciferous greens, cheese, egg yolks, beef, dairy, chicken, duck, goose liver, grass-fed butter Blood clotting (both), amino acid metabolism co-factor (K2), cell signaling in bone tissue (K2 Bruising, anemia, calcium going to the wrong places Negating anti-clotting effects from blood-thinning drugs


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Water Soluble Vitamin Examples of Sources  Function in Body Signs of Deficiency Signs of Toxicity
Vitamin B1 (thiamin) Beans, legumes, whole grains Producing energy, synthesizing DNA/RNA Beriberi, Wernicke-Korsakoff syndrome (resulting from chronic deficiency in alcoholics) None known
Vitamin B2 (riboflavin) Soybeans, mushrooms, eggs, almonds, whole grains, eggs, spinach Metabolizing drugs and toxins, red blood cell production, iron metabolism Damage to mucous membranes, loss of appetite, anemia, fatigue, anxiety Not well absorbed as it is only somewhat water-soluble; none known
Vitamin B3 (niacin) Whole grains, fish, pork, chicken, canned tomato products DNA repair, maintaining health of skin, digestive system, nerves, influences lipid synthesis in liver Diarrhea, dementia Nausea, headache, liver toxicity, insulin resistance, flushing of the skin
Vitamin B5 (pantothenic acid) Mushrooms, corn, peas, potatoes, lentils, egg yolk, poultry, yogurt, seafood Forming acetyl-CoA, drug metabolism, maintaining skin health Tingling feet (only in severe malnutrition) Very rare but could include nausea, heartburn, diarrhe
Vitamin B6 (pyridoxine) Potatoes, sunflower seeds, chickpeas, spinach, fish, beef, poultry Glycogen breakdown, red blood cell metabolism, nervous and immune function, forms neurotransmitters and steroid hormones Nervous system disorders, confusion, depression, anxiety Neurological symptoms – pain
Vitamin B7 (biotin) Nuts, sweet potatoes, onions, whole grains (oats), liver, dairy, fish, pork, legumes Forming carboxylases, DNA replication and transcription Dry or rashy skin, nausea, hair loss, conjunctivitis, depress Unlikely
Vitamin B9 (folate) Beans, legumes, leafy greens, chicken liver Forming new proteins, breaking down and using B12 and C vitamins, fetal development Anemia, low white blood cells, weakness and weight loss, low birth weight, and neural tube defects Masks Vitamin B12 deficiency
Vitamin B12 (cobalamin) Fish and shellfish, beef (liver), dairy Forming and maintaining healthy nerve cells and red blood cells, DNA synthesis Neurological problems, loss of appetite, fatigue, depression, megaloblastic anemia, mouth inflammation Extremely rare
Choline (grouped with Vitamin B) Shellfish, eggs, salmon, pork, chicken, tomato products, legumes Building cell membranes, liver metabolism, nutrient transport Problems metabolizing fats, liver and/or kidney disease, muscle and nervous tissue damage, cognitive disruption Rare without supplementation but can cause hypotension
Vitamin C Most colorful fruits and veggies, organ meats Protecting cells from free radicals, improves iron absorption, regenerates vitamin E supplies, builds collagen, synthesizing norepinephrine and carnitine, metabolizing cholesterol to bile acids Poor wound healing, poor dental health diarrhea, higher risk for kidney stones


Though these organic compounds do not provide a caloric value and thus give us energy directly, they are both directly and indirectly involved in a number of metabolic processes and physiological functions. They are critical to surviving and thriving. As a fitness professional, you are not qualified to diagnose a deficiency (or toxicity) but you are qualified to review your clients’ macro and micronutrient patterns and observe changes in those patterns that may contribute to an issue later on. Remember, when in doubt, refer out.

Fitness Nutrition Coach


 Beradi, J., Andres, R., St. Pierre, B., Scott-Dixon, K., Kollias, H., DePutter, C. (2018). The Essentials of Sport and Exercise Nutrition, 3rd Edition.


Dr. Erin Nitschke, NFPT-CPT, NSCA-CPT, ACE Health Coach, Fitness Nutrition Specialist, Therapeutic Exercise Specialist, and Pn1 is a health and human performance college professor, fitness blogger, mother, and passionate fitness professional. She has over 15 years of experience in the fitness industry and college instruction. Erin believes in the power of a holistic approach to healthy living. She loves encouraging her clients and students to develop body harmony by teaching focused skill development and lifestyle balance. Erin is also the Director of Educational Partnerships & Programs for the NFPT. Erin is an editorial author for ACE, IDEA, The Sheridan Press, and the Casper Star Tribune. Visit her personal blog at