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You may have been told many times to “remember to take your vitamins,” but what’s the science behind vitamin supplementation? Our bodies function great when we eat a balanced, healthy, and varied diet. However, when we don’t eat well or our diet is lacking in food groups such as dairy or protein, we are often told to take a supplement to make up for those nutrients. There are many kinds of supplements, from energy bars to herbs to digestive enzymes. In this article, we will focus on vitamin and mineral supplements and explore the role vitamins and minerals play in managing deficiencies. (Source)

What Are Vitamins and Minerals?

Vitamins and minerals are types of micronutrients that play important roles in our bodies. 


The term “vitamin,” a mashup of “vital” (necessary for life) and “amine” (nitrogen-based chemical structure) was coined in 1912 by biochemist Casimir Funk. Funk was the first to identify individual vitamins and to understand how vitamin deficiencies can cause disease. (Source)

Vitamins are organic, or carbon-containing, micronutrients and are either water soluble or fat soluble. (Source)

Water-soluble vitamins, as the name suggests, dissolve in water, and any excess amounts that aren’t immediately used are excreted in the urine. Since these vitamins are not stored in the body, it’s important to consume them regularly. (Source)

Fat-soluble vitamins, on the other hand, are stored by the body for long-term use and may not be needed as often as water-soluble vitamins. (Source)

Vitamins are involved in energy metabolism, the process by which cells convert food to energy. Vitamins B1 and B2, for example, do this by supporting mitochondria, important structures inside cells. The mitochondria are commonly known as the “powerhouses of the cell” because they supply the energy needed to power our cells. If your body doesn’t have enough of these vitamins, you may experience fatigue because your metabolism is hindered. (Source)


Minerals, on the other hand, are inorganic micronutrients. They generally do not contain carbon atoms, and the way their molecules are bonded makes them dissolve easily in water, affecting which minerals our bodies can use.

Minerals also play an important role in energy metabolism. Studies have found that minerals such as chromium, zinc, and magnesium help our bodies harness the energy produced by the mitochondria to work efficiently. A helpful tip to remembering which micronutrients are minerals and which are vitamins is that minerals are generally elements shown on the periodic table. (Source)

What Is a Nutrient Deficiency?

Vitamins and minerals play critical roles in many biological processes, and getting insufficient amounts of any one of them can cause symptoms ranging from minor discomfort to serious illness.

If you consume a balanced and healthy diet, your body is usually able to get all the nutrients it needs through food. However, if you have a poor diet that lacks nutrients, you are at risk of developing a deficiency. It is also possible for chronic illnesses such as inflammatory bowel disease or celiac disease to impair your ability to absorb needed nutrients.

And certain groups of otherwise healthy people may also be at risk of developing a nutrient deficiency. For example, pregnant women, infants, and adolescents may need to take vitamin or mineral supplements to supplement for periods of growth and development. (Source, Source, Source)

There are many kinds of dietary supplements in a variety of forms, such as pills and powders. These dietary supplements can add nutrients that you may be lacking in your diet, or be taken to lower the risk of disease. 

Types of Vitamins 

Vitamins are either water soluble or fat soluble. Our bodies are mostly water, and the water-soluble B and C vitamins are easily dissolved and distributed to tissues where they are needed. Water-soluble vitamins can be ingested in massive quantities without being toxic, because any excess amounts are excreted in the urine.

Fat-soluble vitamins, on the other hand, can be stored in body fat and in the liver, so they don’t necessarily need to be replenished as regularly as water-soluble vitamins. It is at least theoretically possible for them to build up to toxic amounts in the body, although this very rarely happens. (Source, Source)

Water-Soluble Vitamins

Although there are many important water-soluble vitamins, we will focus on a few common vitamins and their deficiencies. 

Vitamin B1

Vitamin B1 is also known as thiamine, and a vitamin B1 deficiency is known as a thiamine deficiency. 

  • symptoms of deficiency: irritability, anorexia, elevated heart rate, poor reflexes, swollen feet and legs, memory loss
  • treatment: vitamin B1 repletion, consuming foods rich in vitamin B1
  • food sources: meat such as pork and beef, whole grains, nuts, legumes
  • potential causes: consuming a diet high in processed grains and polished rice (such as white rice), malnutrition, alcoholism, use of diuretics (drugs that increase the amount of water the body excretes) 
  • prognosis: A vitamin B1 deficiency is easily treatable and symptoms generally improve quickly. (Source)

Vitamin B2

Vitamin B2 is also known as riboflavin, and a vitamin B2 deficiency is known as a riboflavin deficiency. 

  • symptoms of deficiency: anemia, fatigue, itchy eyes, migraines, swelling of the throat, depression, night blindness (difficulty seeing well at night) 
  • treatment: vitamin B2 supplements, consuming foods rich in vitamin B2
  • food sources: dairy products, eggs, grains, green leafy vegetables, meat
  • potential causes: Vitamin B2 deficiencies are rare in the U.S., but elderly individuals, alcoholics, vegans, and pregnant women have a higher risk of developing a vitamin B2 deficiency. 
  • prognosis: A vitamin B2 deficiency is generally reversible. However, some conditions that may be related to riboflavin deficiency, such as cataracts, are not reversible. (Source)

Vitamin B3

Vitamin B3 is also known as niacin. Niacin deficiency causes a serious condition known as pellagra. 

  • symptoms of deficiency: dermatitis, hyperpigmentation (brown discoloration of skin), diarrhea, dementia 
  • treatment: consuming a balanced diet and taking a form of B3 called nicotinamide
  • food sources: fish, meat, bread, cereal, legumes
  • potential causes: excessive alcohol intake, malabsorptive conditions such as chronic diarrhea, consuming a diet low in vitamin B3
  • prognosis: Vitamin B3 deficiencies are uncommon in industrialized nations, but if pellagra is left untreated over many years it can lead to death. (Source)

Vitamin B6

Vitamin B6 is also known as pyridoxine. 

  • symptoms of deficiency: seizures, depression, itchy skin, inflammation of the tongue and lips, normocytic anemia (a condition in which red blood cells are normal in size but few in number) 
  • treatment: vitamin B6 supplements
  • food sources: organ meats, vegetables, grains, fruits, fish, nuts, legumes, potatoes
  • potential causes: poor gastrointestinal absorption, liver failure, consumption of a diet low in protein and calories, use of medications that reduce levels of B6 in the body
  • prognosis: A vitamin B6 deficiency is effectively treated with vitamin B6 supplements. (Source)

Vitamin B12

Vitamin B12 is also known as cobalamin. 

  • symptoms of deficiency: infertility, anemia, inflammation of the tongue, weight loss, fatigue, dementia, pale skin
  • treatment: Vitamin B12 injections are generally used to treat a vitamin B12 deficiency.
  • food sources: beef, clams, fish, milk, breakfast cereals, yogurt
  • potential causes: gastrointestinal tract surgery, poor absorption of vitamin B12 due to a disorder such as pernicious anemia, extended use of specific medications such as proton pump inhibitors
  • prognosis: It can take years for symptoms of a vitamin B12 deficiency to occur, but once spotted, a deficiency can be treated with vitamin B12 injections. (Source)

Vitamin C

Vitamin C is also known as L-ascorbic acid. 

  • symptoms of deficiency: fatigue, inflamed and bleeding gums, joint pain, depression, discolored spots on the skin, body hair growing in a corkscrew shape
  • treatment: Vitamin C supplements, along with eating a nutritious diet, can reverse a vitamin C deficiency. 
  • food sources: red pepper, oranges, cantaloupe, kiwi, broccoli, strawberries, juices, tomatoes, potatoes
  • potential causes: undernutrition (poor health due to an insufficient intake of nutrients)
  • prognosis: A condition called scurvy can result from a vitamin C deficiency. Scurvy is rare in developed countries, but is fatal if left untreated. (Source, Source)

Fat-Soluble Vitamins

Vitamin A

Vitamin A is an important vitamin that helps our eyes detect light and see at night. 

  • symptoms of deficiency: poor night vision, dry eyes and skin, increased infections
  • treatment: Vitamin A supplements, taken at a high dose followed by lower doses, are used to reverse vitamin A deficiencies.
  • food sources: eggs, cream, butter, fish liver, leafy vegetables and fruits, fortified milk
  • potential causes: consuming a diet low in vitamin A, absorption disorders such as celiac disease and chronic diarrhea, liver disorders
  • prognosis: Vitamin A supplements can reverse a vitamin A deficiency and improve vision and skin. (Source)

Vitamin D

Our bodies are able to synthesize vitamin D, also known as the sunshine vitamin, using the sun’s UV rays. We can also get vitamin D in our diet, but usually in small amounts.

  • symptoms of deficiency: Most people with vitamin D deficiency are asymptomatic, but disorders affecting the parathyroid glands such as hyperparathyroidism and chronic hypocalcemia (low calcium levels) can result from chronic vitamin D deficiency. Children with vitamin D deficiency can experience bone fractures, lethargy, and developmental delays. 
  • treatment: Vitamin D supplements are used to treat vitamin D deficiencies.
  • food sources: tuna, salmon, trout, mackerel, mushrooms, fortified milk
  • potential causes: limited exposure to sunlight, poor absorption of vitamin D, poor kidney function
  • prognosis: Vitamin D supplements are able to reverse vitamin D deficiencies. (Source, Source)

Vitamin K

Vitamin K deficiency can cause problems with blood clotting. Vitamin K deficiency bleeding (VKDB) may occur in newborns, who are deficient in the vitamin at birth. As a result, it is recommended that all newborns receive a dose of vitamin K. 

  • symptoms of deficiency: oozing gums or nose, excessive wound bleeding, easy bruising, gastrointestinal tract bleeding, bloody urine or stools, heavy menstrual periods
  • treatment: Vitamin K deficiencies are generally treated with vitamin K supplements, but if an individual has an underlying chronic condition such as alcoholism, they may require long-term vitamin K supplementation.
  • food sources: kale, spinach, broccoli, brussels sprouts, cereals, soybeans, fermented foods
  • potential causes: liver disease, consuming a diet low in vitamin K, malabsorption
  • prognosis: Vitamin K deficiency has a good prognosis if treated in time, but a complication such as late-stage VKDB has a poor prognosis. (Source, Source)

Types of Minerals

Minerals can be divided into two categories: macrominerals, also known as major minerals, and trace minerals. We need thousands of milligrams per day of most macrominerals. On the other hand, we may need just a few micrograms per day of the trace minerals. (Source)


Although there are many macromolecules that your body needs to function properly, we will only focus on a few common macrominerals.


Calcium helps build and maintain the strength of bones and teeth.

  • symptoms of deficiency: A calcium deficiency causes no symptoms in the short term, but can increase risk of fractures and osteoporosis in the long term. 
  • treatment: A deficiency can be treated with calcium supplements or by consuming foods high in calcium.
  • food sources: milk, kale, broccoli, salmon, yogurt, cheese (Source)


Magnesium regulates nerve and muscle function. Magnesium deficiencies are uncommon.

  • symptoms of deficiency: fatigue, vomiting, tingling, muscle cramps, weakness
  • treatment: Magnesium supplements can be taken to reverse a magnesium deficiency.
  • food sources: spinach, whole grains, pumpkin seeds, chia seeds, peanuts, cashews (Source)


Potassium maintains cell homeostasis, or equilibrium, and is important for normal cell function. 

  • symptoms of deficiency: fatigue, constipation, muscle weakness
  • treatment: A potassium deficiency can be treated with potassium supplements.
  • food sources: lentils, apricots, coffee, milk, prunes, potato, soybeans, bananas (Source)


Sodium is also important in maintaining cell homeostasis. A low blood sodium level is known as hyponatremia. 

  • symptoms of deficiency: lethargy, confusion, seizures in severe cases
  • treatment: Hyponatremia can be treated by restricting fluid intake and, in severe cases, giving a sodium solution intravenously. 
  • food sources: bread, cured meats, chicken, cheese (Source, Source)
cheese and pomegranate

Trace Minerals

As with macromolecules, there are many trace minerals but we will focus on the most common trace minerals and their deficiencies. 


Copper deficiencies are uncommon, but there are steps you can take to avoid one.

  • symptoms of deficiency: anemia, connective tissue disorders, bone defects, hypopigmentation (loss of pigment, or lighter patches of skin) 
  • treatment: Copper deficiencies are treated with specific copper supplements or general multivitamin-mineral supplements.
  • food sources: beef, oysters, potatoes, mushrooms, cashews (Source)


An iron deficiency can cause a condition known as iron deficiency anemia, or reduced number of red blood cells. 

  • symptoms of deficiency: fatigue, pale skin, chest pain, inflamed tongue, dizziness
  • treatment: Iron supplements can be taken to treat iron deficiency anemia.
  • food sources: red meat, beans, cereals, raisins, spinach (Source)


Zinc is an important mineral needed for proper immune function and processes such as wound repair.

  • symptoms of deficiency: diarrhea, changes in mental health, inflamed cuticles, brittle hair, lesions on the elbows and knees
  • treatment: Zinc supplements are generally prescribed for zinc deficiencies. 
  • food sources: meat, legumes, fish (Source)


Should I Take Supplements?

Although mineral and vitamin supplements can help replace important nutrients, supplements can also be harmful. Taking too much of a single-vitamin supplement, such as vitamin D, can be toxic. Individual supplements may also interfere with some medications, so if you are on any regular medications you should consult with a health care professional before starting supplements.

In general, it is important to remember that supplements don’t make up for an unhealthy diet. It’s best to get the nutrients your body needs primarily through your diet. (Source)

Multivitamin and Mineral Supplements

Multivitamin and mineral (MVM) supplements may be better tolerated than single-vitamin supplements. MVM supplements are defined as supplements containing three or more nutrients at low dosages. 

There is some evidence suggesting MVM supplements can lower the risk of developing certain chronic diseases, such as cardiovascular disease and cancer. However, research is limited and inconsistent. 

Overall, MVM supplements have potential, but an MVM supplement should not be taken as a substitute for healthy foods. It is helpful to consult a health care professional before taking a MVM supplement to take into consideration your medical history, use of medications, and diet. (Source)

smiling women in towel head wrap

Holistic Approach to Nutrient Supplements

A balanced, nutritious diet is the first step to avoiding a nutritional deficiency. Consider incorporating more healthy fats, proteins, vegetables, fruits, and whole grains into your diet. These food groups will ensure your body is given the vitamins and minerals it needs to function and will save you the hassle of taking MVM supplements. Your diet also plays a large role in preventing chronic diseases. (Source)

In addition to eating well, it may be possible to get nutrients from other sources. For example, vitamin D is commonly known as the sunshine vitamin because a safe level of sun exposure may fuel your body with all the vitamin D it needs. (Source)

When Should I See a Doctor About Vitamin or Mineral Supplements?

It is helpful to see a doctor about supplements when: 

  • You are experiencing abnormal symptoms and want to check if you have a nutrient deficiency. 
  • You are curious about taking MVM supplements, single-vitamin supplements, or single-mineral supplements, but want to be sure they won’t interfere with your medications. 
  • You are unable to get the nutrients your body needs because of dietary restrictions or poor nutrient absorption.

Where Can I Find the Best Resources About Vitamin and Minerals?

Outside of WellTheory’s Ultimate Guide to Vitamins and Minerals, we recommend looking at:

  • National Center for Complementary and Integrative Health (NIH) to learn about the benefits of MVM supplements and safety information to keep in mind when taking MVM supplements.
  • Nutrition.gov to learn about the vitamins and minerals your body needs, what roles these nutrients play in your body, and foods that are rich in each nutrient.
  • Springer Nature’s research articles to weigh the pros and cons of MVM supplements.

What’s the Bottom Line on Vitamins and Mineral Supplements?

Mineral and vitamin supplements can be great solutions if you have dietary restrictions, are at risk for a nutrient deficiency, or are part of a group that requires additional nutrients. However, it’s important to consult a health care professional before taking a supplement. For single-vitamin supplements, it’s important to check toxicity guidelines to ensure you are consuming a safe amount of that vitamin. MVM supplements, however, may be a safer supplement alternative. Overall, a healthy and balanced diet is critical to fueling your body with nutrients and is a great way to lower your risk of a nutrient deficiency.

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