Vitamin and nutritional deficiencies

Vitamin and nutritional deficiencies

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Katie Stone - Naturopath

Written By:

Katie Stone - Naturopath
Dr. Nare Simonyan - PhD Pharmaceutical Science

Medical Reviewer:

Dr. Nare Simonyan - PhD Pharmaceutical Science
Kari Asadorian - BSN, RN

Edited By:

Kari Asadorian - BSN, RN

Updated On:

June 18, 2025

What is a nutritional deficiency?

A ‘nutritional deficiency’ is defined as severely reduced levels of one or more nutrients, resulting in the body being unable to function normally and potentially increasing the risk of certain health conditions.1 Micronutrient deficiencies lead to clinically evident symptoms.2
This is not quite the same as a nutritional inadequacy, which is a suboptimal intake of one or more nutrients but doesn’t yet cause disease or a health condition.


Micronutrient intake is essential for maintaining health and preventing illness at every stage in life. Although they are only required in trace amounts, they play critical roles in many biochemical processes such as gene transcription (turning genes on and off), enzymatic reactions, and protection against oxidative stress.3
For example, methylfolate, vitamin B12, and vitamin B6 are required for the methylation cycle, in which they assist with homocysteine metabolism and the repair of DNA. Zinc and selenium are essential for protecting against oxidative stress.


Worldwide, the most common deficiencies include vitamin A, folate, iodine, iron, and zinc.4

Deficiencies in these nutrients can lead to cognitive impairment, poor growth, perinatal complications, degenerative diseases associated with aging, and higher risk of several diseases.

Who is at risk of a nutritional deficiency?

People at higher risk of nutrition deficiencies are often those in specific life stages - such as rapid growth or development - in which the body has higher demand for certain nutrients. This includes pregnant women (and the fetus), young children, adolescents, and the elderly.


Nutritional deficiencies can be caused by environmental factors, such as lack of food. 

They can also result from digestive health conditions, such as intestinal malabsorption, diarrhea, problems with chewing or swallowing, and/or persistent vomiting.
Other causes can include poor diet, eating disorders or fasting, increased physiological demand, drug interference, or chronic diseases in which eating is affected. Genetics may also play a role.


Diseases linked to deficiencies include cardiovascular diseases, hypertension, diabetes or mellitus, cancer, inherited metabolic disorders, developmental abnormalities, food intolerances and allergies.5 Certain genetic mutations can also impair the absorption or metabolism of some nutrients, leading to deficiency.6

Micronutrient deficiencies are also prevalent in people who are morbidly obese, despite high intake of macronutrients (protein, fat, carbs). These deficiencies are often worse after bariatric surgery.7

What is a vitamin deficiency?

A vitamin deficiency occurs when the body doesn't get enough of a specific vitamin, either due to inadequate intake, enzymatic conversion or impaired absorption.

Vitamins are classified as ‘essential’ because the body cannot make them itself, so they must be obtained through the diet or supplements. Vitamins are required for catalyzing numerous biochemical reactions that are necessary for life.8

Symptoms of nutrient deficiency

Deficiency symptoms vary significantly depending on the biochemical processes affected.

For example, folate and B12 are both involved in healthy red blood cell development, and deficiency in either vitamin can lead to megaloblastic anemia (abnormally large red blood cells). Symptoms include weakness, fatigue, difficulty concentrating, irritability, headache, heart palpitations, and shortness of breath.


Folate and B12 are also vital components of homocysteine conversion and neurotransmitter production, and  cofactors for enzymes involved in the synthesis of DNA, fatty acids, and myelin. Deficiency in folate is associated with depression, anxiety, cognitive decline, and heart disease or stroke, and peripheral neuropathy.9,10 In pregnant women, folate deficiency can lead to neural tube defects.11


Vitamin B12 deficiency has been described as “a major public health problem worldwide”.12 It is linked to increased risk of adverse pregnancy outcomes and impaired cognitive development, as well as higher risk of dementia in older adults.13/sup> Symptoms can include anemia, peripheral neuropathy, glossitis, diarrhea, headaches, low energy, and mood disorders.14


Iron deficiency can lead to microcytic anemia, decreased capacity for work, and impaired immune and endocrine function. 

Iodine deficiency can lead to goiter (enlarged thyroid), impaired mental development, or reduced cognitive function. Zinc deficiency is associated with impaired immune function, increased incidence of diarrhea, and acute respiratory infections.

Vitamin A deficiency is the leading cause of blindness worldwide and also impairs immune function and cell differentiation.

How to find out if you have any nutritional deficiencies

Doctors will usually test for a deficiency by examining blood, saliva, and urine-based biomarkers. These biomarkers can detect particular nutrient deficiencies at an early stage, before symptoms develop.15

However, there is no single way to test for a specific nutrient because different deficiencies can have similar symptoms, and can affect people differently.16 The most accurate approach is a comprehensive nutritional assessment involving patient history and physical examination, along with diagnostic tests and dietary assessments.17

Vitamin and nutritional deficiencies

Key takeaways:

  • Icon Nutritional deficiencies occur when severely reduced levels of one or more nutrients lead to clinical symptoms.
  • Icon The most common nutritional deficiencies are folate, iron, iodine, vitamin A, zinc, and magnesium.
  • Icon Health conditions linked to deficiencies can be physiological or neurological.

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  • Fully Bioactive L-Methylfolate & Vitamin B12 Supplement
  • Cofactors Supporting Methylation, Cognition & Wellbeing
  • Superior-Absorbing Magnesium, Proven in Human Study
  • 3rd-Party Tested for Purity & Safety, Non-GMO, Gluten-Free

Frequently Asked Questions about nutritional deficiencies

What are the most common nutritional deficiencies?

Iron, iodine, folate, vitamin A, and zinc deficiencies are the most common nutritional deficiencies globally, all of which contribute to poor growth, impaired cognitive development, perinatal complications, and increased risk of chronic illness.18

What are 10 signs of poor nutrition?

The top 10 most common signs of poor nutrition may include:

1. Fatigue and low energy, even after adequate sleep
2. Unintentional weight loss
3. Pale skin (pallor) due to low iron levels
4. Slow wound healing
5. Brittle hair and nails
6. Bleeding gums
7. Dry, flaky skin
8. Mouth ulcers
9. Frequent infections and slow recovery time
10. Difficulty concentrating

How do you find out what you are deficient in?

Blood tests are usually recommended when a nutritional deficiency is suspected, but these only measure nutrient levels in the bloodstream, which may not accurately reflect the body's utilization or storage of those nutrients.19
The most accurate way to measure a deficiency is with a comprehensive assessment of a patient’s symptoms, diet, health history, other health conditions, and other relevant information. This is usually best done by a holistic health practitioner such as a naturopathic doctor or nutritionist.

What is the most common vitamin deficiency?

Vitamin A is the most common vitamin deficiency around the world. Other common micronutrient deficiencies include iron, iodine, folate, and zinc.20

What diseases are caused by vitamin deficiency?

Deficiency-related diseases depend on the specific vitamin that an individual is deficient in.
The most commonly known diseases related to specific vitamins include:
↪ anemia (iron deficiency)
↪ scurvy (vitamin C deficiency)
↪ rickets (vitamin D deficiency)
↪ pellagra (niacin deficiency)21
↪ megaloblastic anemia (folate deficiency)
↪ depression (folate and B12 deficiency)

References

  1. Aysha Karim Kiani, Kristjana Dhuli, Kevin Donato, Barbara Aquilanti, Valeria Velluti, Giuseppina Matera, Amerigo Iaconelli, Stephen Thaddeus Connelly, Francesco Bellinato, Paolo Gisondi, Matteo Bertelli; "Main nutritional deficiencies"; Journal of preventive medicine and hygiene; 2022 Oct

    https://pubmed.ncbi.nlm.nih.gov/36479498/

  2. AYSHA KARIM KIANI, KRISTJANA DHULI, KEVIN DONATO, BARBARA AQUILANTI, VALERIA VELLUTI, GIUSEPPINA MATERA, AMERIGO IACONELLI, STEPHEN THADDEUS CONNELLY, FRANCESCO BELLINATO, PAOLO GISONDI, MATTEO BERTELLI; "Main nutritional deficiencies"; Journal of preventive medicine and hygiene; 2022 Oct

    https://pmc.ncbi.nlm.nih.gov/articles/PMC9710417

  3. Hellas Cena, Philip C Calder; "Defining a Healthy Diet: Evidence for The Role of Contemporary Dietary Patterns in Health and Disease"; Nutrients; 2020 Jan

    https://pubmed.ncbi.nlm.nih.gov/32012681/

  4. Santiago Espinosa-Salas, Mauricio Gonzalez-Arias; "Nutrition: Micronutrient Intake, Imbalances, and Interventions"; StatPearls [Internet]; 2023 Sept

    https://www.ncbi.nlm.nih.gov/books/NBK597352/

  5. AYSHA KARIM KIANI, KRISTJANA DHULI, KEVIN DONATO, BARBARA AQUILANTI, VALERIA VELLUTI, GIUSEPPINA MATERA, AMERIGO IACONELLI, STEPHEN THADDEUS CONNELLY, FRANCESCO BELLINATO, PAOLO GISONDI, MATTEO BERTELLI; "Main nutritional deficiencies"; Journal of preventive medicine and hygiene; 2022 Oct

    https://pmc.ncbi.nlm.nih.gov/articles/PMC9710417/

  6. National Research Council (US) Committee on Diet and Health; "Diet and Health: Implications for Reducing Chronic Disease Risk"; National Academies Press (US); 1989

    https://www.ncbi.nlm.nih.gov/books/NBK218767/

  7. Jeanne Kochkodan, Dana A Telem, Amir A Ghaferi; "Physiologic and psychological gender differences in bariatric surgery"; Surgical endoscopy; 2018 Ma

    https://pubmed.ncbi.nlm.nih.gov/28840338/

  8. Santiago Espinosa-Salas, Mauricio Gonzalez-Arias; "Nutrition: Micronutrient Intake, Imbalances, and Interventions"; StatPearls [Internet]; 2023 Sept

    https://www.ncbi.nlm.nih.gov/books/NBK597352/

  9. --

    --

  10. Tom Taverner, Francesca L Crowe, G Neil Thomas, Krishna Gokhale, Rasiah Thayakaran, Krishnarajah Nirantharakumar, Yusuf A Rajabally; "Circulating Folate Concentrations and Risk of Peripheral Neuropathy and Mortality: A Retrospective Cohort Study in the U.K"; Nutrients; 2019 Oct

    https://pmc.ncbi.nlm.nih.gov/articles/PMC6835340/

  11. E H Reynolds; "Folic acid, ageing, depression, and dementia"; BMJ : British medical journal; 2002 Jun

    https://pmc.ncbi.nlm.nih.gov/articles/PMC1123448/

  12. Alexander J Layden, Kristos Täse, Julia L Finkelstein; "Neglected tropical diseases and vitamin B12: a review of the current evidence"; Transactions of the Royal Society of Tropical Medicine and Hygiene; 2018 Aug

    https://pmc.ncbi.nlm.nih.gov/articles/PMC6457089/

  13. Alexander J Layden, Kristos Täse, Julia L Finkelstein; "Neglected tropical diseases and vitamin B12: a review of the current evidence"; Transactions of the Royal Society of Tropical Medicine and Hygiene; 2018 Aug

    https://pmc.ncbi.nlm.nih.gov/articles/PMC6457089/

  14. Alex Ankar, Anil Kumar; "Vitamin B12 Deficiency"; StatPearls [Internet]; 2024 Sept

    https://www.ncbi.nlm.nih.gov/sites/books/NBK441923

  15. AYSHA KARIM KIANI, KRISTJANA DHULI, KEVIN DONATO, BARBARA AQUILANTI, VALERIA VELLUTI, GIUSEPPINA MATERA, AMERIGO IACONELLI, STEPHEN THADDEUS CONNELLY, FRANCESCO BELLINATO, PAOLO GISONDI, MATTEO BERTELLI; "Main nutritional deficiencies"; Journal of preventive medicine and hygiene; 2022 Oct

    https://pmc.ncbi.nlm.nih.gov/articles/PMC9710417

  16. Aditi Kesari, Julia Y. Noel; "Nutritional Assessment"; StatPearls [Internet]; 2023 Apr

    https://www.ncbi.nlm.nih.gov/books/NBK580496/

  17. Charles Mueller, Charlene Compher, Druyan Mary Ellen, American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) Board of Directors; "A.S.P.E.N. clinical guidelines: Nutrition screening, assessment, and intervention in adults"; Journal of parenteral and enteral nutrition; 2011 Jan

    https://pubmed.ncbi.nlm.nih.gov/21224430/

  18. Regan L Bailey, Keith P West Jr, Robert E Black; "The epidemiology of global micronutrient deficiencies"; Annals of nutrition & metabolism; 2015

    https://pubmed.ncbi.nlm.nih.gov/26045325

  19. Mette M. Berger, Dinesh Talwar, Alan Shenkin; "Pitfalls in the interpretation of blood tests used to assess and monitor micronutrient nutrition status"; Nutrition in Clinical Practice; 2022 Nov

    https://aspenjournals.onlinelibrary.wiley.com/doi/10.1002/ncp.10924

  20. Regan L Bailey, Keith P West Jr, Robert E Black; "The epidemiology of global micronutrient deficiencies"; Annals of nutrition & metabolism; 2015

    https://pubmed.ncbi.nlm.nih.gov/26045325

  21. Santiago Espinosa-Salas, Mauricio Gonzalez-Arias; "Nutrition: Micronutrient Intake, Imbalances, and Interventions"; StatPearls [Internet]; 2023 Sept

    https://www.ncbi.nlm.nih.gov/books/NBK597352/

Katie Stone - Naturopath

About the Author

Katie is a qualified Naturopath (BNatMed) and freelance writer from New Zealand. She specializes in all things health and wellness, particularly dietary supplements and nutrition. Katie is also a dedicated runner and has completed more half-marathons than she can count!

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