Since ancient times Nutrition branched as a field related to health, it ́s importance in the last 30 years is the consequence of research trying to understand the physiological role of foods and the chemistry once ingested, the findings of metabolic research led to the discovery of vitamins and minerals, micronutrients.

Nowadays knowledge of human micronutrient requirements has greatly improved, which is a crucial step in understanding the public health significance of malnutrition and identifying the most appropriate measures to prevent them.

Organizations such as the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) have provided up-to-date knowledge and defining standards for micronutrient requirements since 19731. In recognition of this rapidly developing field and the substantial new advances that have been made in the area of Nutrition, we have come up with the ultimate guide for you to understand every single micronutrient in human health.

In a series of post we’re going to cover 7 chapters, in each of them we’ll cover the basics of all micronutrients (vitamins and minerals) such as Function (its role in the body), Sources (where can you find them in food), RDI (Reference Daily Intake), Deficiency (main health causes because of diet inadequacy) and Toxicity (main health because of diet excess). 

One thing to note is that the RDI is only as its name implies, a reference of how much in average a healthy adult should ingest, in Nutrition these markers changes depending the age, sex and specific situations like pregnancy or clinical restrictions, nevertheless the RDI is considered to be sufficient to meet the requirements of 97–98% of healthy individuals in every demographic around the world.



There are 4 fat-soluble vitamins (A, D. E and K) they are absorbed and transported along with dietary lipids, therefore intake or supplementation of these vitamins are best when taken with a fat food source, other factors to highlight is that these vitamins being fat-soluble are stored in the body in certain tissues, mostly the liver.

Vitamin A

Vitamin A is an essential fat-soluble vitamin, it ́s necessary for the normal functioning of the visual system, especially night vision; it also aids in the maintenance of skin cellular integrity, immune function, and reproduction. It also promotes bone development and influences the formation of teeth.

Best Sources: eggs, carrots, broccoli, and watermelon.

RDI: 5,000 – 10,000 UI



The most common symptom of vitamin A deficiency is present in young children and pregnant women is an eye disease called Xerophthalmia that it is the inability to see in low light and without treatment can cause blindness.


Because vitamin A is fat-soluble and can be stored, primarily in the liver, routine consumption of large amounts of vitamin A over a period of time can result in toxic symptoms, including liver damage, bone abnormalities and joint pain, loss of hair, headaches, vomiting, skin peeling and in some cases a change in skin color to orange.

Vitamin D

Vitamin D is required to maintain normal blood levels of key minerals like calcium and phosphate, which are in turn needed for optimal bone health, muscle contraction, nerve conduction, and also possess immune properties that may alter responses to infections.

Best Sources: eggs, milk, salmon, and tuna.

RDI: 600 UI


In children, vitamin D deficiency causes Rickets, a disease in which bones weaken and deform. In adults, vitamin D deficiency causes bone pain and muscle weakness.


Intoxication includes high levels of calcium in the blood and in urine, also it can cause nausea, vomiting, thirst, very abundant excretion of urine, muscle weakness, joint pain, and general disorientation.

Vitamin E

Vitamin E is the major lipid-soluble antioxidant in the cell antioxidant defense system and is exclusively obtained from the diet, it also protects red blood cells from hemolysis (destruction of red blood cells), participates in the maintenance of epithelial tissue and in the synthesis of prostaglandins (fatty acids). 

Best Sources: eggs, wheat, green leafy vegetables, and dried fruits.

RDI: 11 – 19 mg


Poor neuromuscular and reproductive system development, in adults, symptoms of deficiency can be reflected until after 5 or 10 years, it manifests clinically as a loss of reflexes, impaired sensitivity, and poor balance. 


High doses may increase the risk of bleeding, reduced coagulation capacity, and severe hemorrhagic stroke.

Vitamin K

It helps in the synthesis of prothrombin, a compound necessary for normal blood clotting, it also participates in bone metabolism for bone health.

Best Sources: liver, soybean oil, green leafy vegetables, and wheat.

RDI: 90 - 120 mcg



It could be associated with gastrointestinal diseases that cause malabsorption of fats such as obstruction of the bile ducts, inflammatory bowel disease, chronic pancreatitis, and liver disease.


No toxicity has been proven, even when administered in large quantities. However, daily doses greater than 5 mg of synthetic Vitamin K (Menadione) caused hemolytic anemia, hyperbilirubinemia and kernicterus (bilirubin in the brain) in infants.

REFERENCES - Written by Antonio Reyes RDN
  • Food and Nutrition Board. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC, National Academy Press, 2002.
  • Blomhoff R et al. Vitamin A metabolism: new perspectives on absorption, transport, and storage. Physiological Reviews, 1991.
  • Sommer A. Vitamin A deficiency and its consequences: a field guide to detection and control, 3rd ed. Geneva, World Health Organization, 1994.
  • Feldman D, Glorieux FH, Pike JW. Vitamin D. New York, NY, Academic Press, 1997.
  • Mawer EB, Davies M. Vitamin D deficiency, rickets and osteomalacia, a returning problem worldwide. In: Norman AW, Bouillon R, Thomasset M, eds. Vitamin D. Chemistry, biology and clinical applications of the steroid hormone. Riverside, CA, University of California, 1997.
  • Traber MG. Regulation of human plasma vitamin E. In: Sies H, ed. Antioxidants in disease mechanisms and therapeutic strategies. San Diego, CA, Academic Press, 1996.
  • Dutta-Roy AK et al. Vitamin E requirements, transport, and metabolism: role of a-tocopherol-binding proteins. Journal of Nutritional Biochemistry, 1994.
  • Ferland G. The vitamin K-dependent proteins: an update. Nutrition Reviews, 1998.
  • Vermeer C, Jie K-S, Knapen MHJ. Role of vitamin K in bone metabolism. Annual Review of Nutrition, 1995.
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