Vitamin and Mineral Nutrition: Signs of Deficiency and Toxicity


Vitamins are classified as “micronutrients” are necessary components to basic functions, but are also required in the optimal balance to achieve overall health and wellness. Our personal training 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.

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

Going More VitamIn-Depth

Certain vitamins and nutrients may garner more attention than others due to their roles in specific functions relevant to health and fitness.

Vitamin B6 Basics

Vitamin B6 has an innate ability to protect our organs and prevent the aging process. The cell membrane is composed of phospholipids, protein, and cholesterol. The phospholipids and protein in the cell membrane are highly vulnerable to toxic glycation reactions.

Glycation is the pathological binding of glucose to proteins in our body. Proteins are the body’s primary structural component. Glycation causes our proteins to cross-link and become non-functional. These non-functional proteins are referred to as Advanced Glycation End-Products, or commonly known as AGEs. No pun intended, but this is the basic process of aging.

Glucose that does not get into cells and stays in the blood will ‘gunk’ up the proteins in the body. “When extra glucose latches onto another molecule outside the cell, glucose will handcuff the molecule which prevents the molecule from doing its intended function.” (Life Extension Foundation (LEF), July 2009) AGEs affect arteries, blood pressure, nerves, connective tissue, lungs; to name a few, (LEF, July 2009). Within the arteries are endothelial cells which are tightly held together.

AGEs weakens the endothelial cells causing gaps, which in turn, are plugged with cholesterol. This causes plaque in the arterial wall. Further, AGEs disrupt auto-regulation of blood pressure. Auto-regulation is the body’s inherent process of compensating high blood pressure around a specific organ, e.g. heart by opening arteries around another organ, e.g. kidney. The lung connective tissue stiffens by glycation causing the effects of recoil impacting respiration and expiration.

Likewise, glycation of collagen impacts the joints. Glycation has been shown to cause peripheral neuropathy, which is numbness, burning, tingling in the extremities of the body.

The effects of AGEs and aging are remarkably similar. The negative changes common to aging are, gradual loss of elasticity of the blood vessels, wrinkled skin (loss of collagen elasticity), degradation of lens of the eye, delaying wound healing, age-induced decline of kidney function.

What can we do to counter AGEs? The good news is that AGEs have receptors (RAGE) that are now the target of new drug research. This research is designed to prevent the damage secondary to the AGEs. The better news for you is that vitamers of pyridoxine (B6) have been shown to trap AGEs and chaperone them out of cells. (LEF, July 2009).

The ingestion of B6 will result in its ultimate active form pyridoxal-5′-phospahte. It was thought that pyridoxal-5′-phospahte was degraded in the digestive tract. However, pyridoxal-5′-phosphate is bioavailable and inhibits protein and glycation, demonstrating potential systemic benefits, including vital kidney structures.

B12 Vitamin Basics

Water-soluble vitamin B12, also known as cobalamin, plays a key role in many biological functions, such as the immune system response, mitochondrial processes, production of myelin and red blood cells, and the synthesis of the neurotransmitters serotonin and dopamine.

Several characteristics set B12 apart from other B vitamins, namely the fact that it contains a metal ion. The presence of cobalt accounts for the name cobalamin.

A water-soluble vitamin will rarely reach the point of excess in the body. Our renal system (kidneys) filters the vitamin from blood and eliminates it along with water. Even if an occasional transient excess builds up, the ramifications remain largely innocuous: the body can store sufficient B12 in the liver, meaning those whose bodies contain a slight abundance can go years without needing to purposefully consume it.

B12 Deficiency

In spite of the body’s capacity to store B12 in the liver, some individuals consistently present with low (often dangerously so) circulating levels in their blood. The serious effects of vitamin B12 deficiency include anemia, depression, dementia, and hallucinations. Tingling in the lower limbs often sets in, along with neuropathy, fatigue, and an accelerated heart rate. Irritability also ranks highly on the list of reported symptoms.F

Many factors exist to explain why some individuals have low B12 stores. Since the primary sources of the vitamin B complex group include animal-derived protein – beef, chicken, dairy, and fish – both vegans and vegetarians must find other B12-rich food sources. Fortified cereals and breads, along with plant-based milk substitutes and healthful seaweed can help to fulfill B12 requirements.

Additionally, certain gastrointestinal issues can lead to malabsorption of nutrients, including B12. Celiac disease, Crohn’s, leaky gut, and atrophic gastritis will all affect gut-related absorption. Age contributes to this problem as well; older individuals lose the ability to effectively absorb vitamin B as time goes on.

Rare Excess of B12

The human body rarely accumulates an excess of circulating B12, certainly not to any degree of toxicity. Thus, when a consistently high value of vitamin B12 in one’s body presents itself, this generally indicates the presence of underlying illnesses, some of which need immediate medical attention. A damaged liver/liver disease, kidney failure, and a unique subset of blood cancers known as myeloproliferative disorders (most notably, myelocytic leukemia) can cause an excess build-up of this micronutrient.

In their very early stages, illnesses associated with high vitamin B12 often present with generally common symptoms, such as persistent fatigue and loss of appetite.  A blood test will confirm a dangerous excess of vitamin B, and considering the potentially life-threatening nature of some of these illnesses, an early diagnosis makes all the difference.

One research study attempted to draw a correlation between levels of vitamin B12 in one’s system and death rates. The scientists observed that among the participants studied, those whose blood showed the highest levels of B12 also had a higher death rate. Science has yet to determine any definitive reason for this outcome.

Senior author Dr. Stephan J.L. Bakker, a professor of internal medicine at the University Medical Center Groningen in the Netherlands, refers to the data as “only an association, not a cause-and-effect relationship.” He adds, “High amounts of vitamin B12 are often taken without a medical indication.” Dr. Bakker goes on to say how excessive levels of B12 “might change the gut microbiota in ways that could be harmful — but no one really knows.”

When an individual presents with greatly elevated circulating levels of B12, and physicians have ruled out any serious underlying comorbidity, several easy steps can help return the level to a normal range.

Engage in regular moderate exercise. The resulting heat generated by the body causes sweating, a natural mechanism for shedding water (and with it, water-soluble vitamin B12). Exercise also lends itself to an increase in water consumption which, in turn, will boost renal activity. Water remains the beverage of choice, since a majority of “sports drinks” contain added vitamins, including B12.

*With the growing popularity of intramuscular and intravenous high vitamin doses to restore “energy” clients who subscribe to these practices need to be reminded that movement and nutrient-dense diet is still necessary.

Consume a natural mild diuretic, such as coffee or tea. Once again, this causes a positive impact on the body’s renal system, thereby helping to filter out excess quantities of vitamin B12.

Shift meal planning to include more plant-based sources of protein. Reduce consumption of animal-derived foods, as they serve as a generous provider of B12.

Vitamin D

Perhaps best known for its ability to shore up bone health, vitamin D also plays an important role in immune function and inflammation.

Vitamin D deficiencies abound worldwide, notably among individuals whose darker skin pigmentation makes absorbing the vitamin through sunlight all the more challenging. In addition, this D deficiency tends to affect older adults, obese individuals and those living in nursing home– people with the most vulnerable immune systems. According to the Third National Health and Nutrition Examination Survey, 61% of white and 91% of black Americans suffer from severe vitamin D deficiency.

Dr. David Meltzer, Chief of Hospital Medicine at the University of Chicago, has explored the potential impact of diminished vitamin D levels on contracting the novel COVID-19 virus. A serious COVID-19 infection often plunges one’s immune system into overdrive, resulting in rampant lung inflammation and concomitant shortness of breath, which can thwart or halt workouts.

A recent study analyzing over 200 patients hospitalized with a COVID-19 infection revealed that those with sufficient serum levels of vitamin D exhibited a reduction in the severity of the illness, lower levels of C-reactive protein (a marker for inflammation), an increase in the immune system’s lymphocytes, and a decreased risk of death. This combination strongly suggests an association between appropriate vitamin D stores and a properly functioning immune system.

If a client suffers from Inflammatory Bowel Syndrome (IBS), note that they may have impaired D signaling within the intestines, perhaps contributing to the host of comorbidities typically associated with IBS. Such a client might benefit from a reminder to get plenty of D, through food sources or regular sunshine exposure.

The Tandem Effect of Calcium/Vitamin D

A tremendous amount of scientific data exists linking low concentrations of serum vitamin D to an increased incidence of cardiovascular disease and mortality, among other things. Despite this alarming fact, most clinical trials have failed to find a positive link between vitamin D supplements and cardiovascular disease.

Several vitamin D–dependent calcium transport proteins regulate intestinal calcium absorption. Once absorbed into the small intestine, calcium and phosphorus can begin to form hydroxyapatite crystals which serve to strengthen/mineralize bones. Such knowledge substantiates the need for a diet rich in vitamin D as well as calcium for proper bone mineralization.

As one can imagine, such insufficiency can certainly lead to calcium malabsorption and further deficiencies. Without adequate vitamin D, the body can absorb no more than 10% to 15% of dietary calcium. Even intestinal calcium absorption only approaches 30% to 40%.

Overdosing of Vitamin D

Only a blood test can reveal genuine vitamin D deficiencies or rare excesses. While toxicologists feel that 4000 IU (International Units) of the sunshine vitamin in one’s bloodstream serves as a tolerable upper limit, this might only prove useful if one’s body already possesses adequate amounts of stored D.

The CDC extolls the virtues of vitamin D in maintaining a healthy immune system, advocating a reasonable degree of supplementation along with vitamin C and zinc, also well-established infection fighters.

Many pro-supplement individuals prefer to leave no room for error, unnecessarily ingesting large excesses of many vitamins.

Such a practice may backfire, however, as “overdosing” on vitamin D can lead to a host of health problems. Hypercalcemia, the main consequence of D toxicity, results in a buildup of calcium in the blood. If left unchecked, such a situation leaves one prone to nausea, vomiting, frequent urination, and an overall sense of weakness, further complicated by bone pain, kidney problems, and the development of calcium-based kidney stones. Once health issues related to toxicity have occurred, reversing them takes time.

It’s also worth noting that a synergistic relationship has been identified between vitamins D and K. You’ll find that many supplements on the market today combine Vitamin D3 (a more absorbable form than D2) and K2.

Mood and Memory Impact

Recently the medical world noted a link between vitamin D deficiency and an increased risk for many mental health issues, among them depression, Alzheimer disease, epilepsy, and generalized neurocognitive decline. Possibilities for drawing such conclusions may relate to vitamin D’s role in increasing serotonin levels in the brain, or perhaps the work of macrophages/phagocytosis of amyloid-β plaques in Alzheimer patients.


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Analysis of Intake

Data from the U.S. Preventive Services Task Force (USPSTF), published in The Annals of Internal Medicine, highlighted the controversy over what constitutes a diminished level of vitamin D. Some laboratories define deficiency as below 20 nanograms per milliliter (ng/mL), whereas others more generously list below 50 ng/mL as problematic. This gets further compounded by the fact that tests for vitamin D have poor reliability.

Dietitians and doctors typically cite the following yet confusing guidelines:

  • Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of 97%–98% of healthy individuals; often used to plan nutritionally adequate diets.
  • Adequate Intake (AI): Intake level assumed to ensure nutritional adequacy; sometimes established in lieu of RDA.
  • Estimated Average Requirement (EAR): Approximate daily intake level that meets the requirements of 50% of healthy individuals.
  • Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.

One major national study revealed that roughly 94% of Americans ingested less than the 4000 International Units (IU) EAR vitamin D from food/beverage sources or supplements.

Cell-Specific Autoimmune Response

In healthy populations, T cells play a crucial role in fighting infection. For individuals living with autoimmune diseases, however, T cells can attack the body’s own tissues. A research team at the University of Edinburgh focused on how D affects a specific mechanism within the immune system – the ability of dendritic cells to activate T cells.

Professor Richard Mellanby, of the University of Edinburgh’s Centre for Inflammation Research, says that “Low vitamin D status has long been implicated as a significant risk factor for the development of several autoimmune diseases. Our study reveals one way in which vitamin D metabolites can dramatically influence the immune system.”

Since our scope of practice prohibits the dispensing of specific medical advice, suggesting food sources and sunshine, and referring your clients to a medical provider for advice on supplementation is the most prudent approach.



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

Ann NY Acad Sci. 2005 Jun; 1043: 759-66; Biochemistry. 2006 Dec 26; 45(51): 15756-67.

Nephrol Dial Transplant. 2007 Aug; 22(8): 2165-74

Biochem Med. 1983 Dec; 30(3): 333-41; Ophthalmic Res. 2006 38(5): 294-302; Kidney Int. 2002 Mar; 61(3); 939-50,risk%20of%20colds%20and%20flu—MCTRL-051421-F1-5465479&ET_CID=5465479&ET_RID=26367137&encparam=F9QBWGplorQZt59zKIjwfOXfUJt6K5CL5t8rI2eeqWY%3d


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