IRON – MICRONUTRIENT ONE:

THE ROLE OF IRON IN THE HUMAN BODY

Iron is an essential mineral found in the human body (Spatone, 2019). The body is incapable of producing iron independently so intake through dietary sources is required. It is found in both animal and plant-based foods in two different forms. Dietary sources of heme iron include meat, poultry and fish, which produce highly bioavailable iron sources (15-35%) (Nazanin Abbaspour, 2019). Non-heme iron, the other variety of dietary iron, is found in plant-based foods such as cereals, legumes, fruits and vegetables and has a low bioavailability (2-20%) compared to heme iron (Nazanin Abbaspour, 2019). Iron has the key function of facilitating oxygen transported by haemoglobin, as well as assisting the body with contribution to enzyme systems and immunity (Spatone, 2019). Around 70% of iron in the body is found within the haemoglobin and myoglobin in the blood and muscles (UCSF Health, 2019). Iron is used by the body to convert blood sugar to energy as well boost haemoglobin production which increases overall transportation of oxygen, reducing symptoms of tiredness and fatigue (Spatone, 2019).

DIETARY SOURCES

Heme-iron and non-heme iron are found is opposing dietary sources. Heme iron is found in animal-based foods, such as; red meat, offal (liver), chicken, duck, pork, turkey, eggs and fish (Healthdirect, 2019). Non-heme iron on the other hand is found primarily in plant-based foods. The best dietary sources of non-heme iron include; green vegetable (spinach, silverbeet and broccoli) as well as lentils, beans, nuts, seeds, grains (whole wheat, brown rice etc.) and dried fruit (Healthdirect, 2019). Because of the significantly low bio-avaliablitlity of non-heme iron, there is a high dependence on the presence of other foods (Nazanin Abbaspour, 2019). For example, foods high in vitamin C can significantly help the body absorb iron (UCSF Health, 2019).

RECOMMENDED DAILY INTAKE AND THERAPEUTIC DOSES

The recommended daily intake (RDI) of iron varies across stages of life. A child, requires between 9mg/day to 15mg/day dependence of age, as seen in figure one. The RDI was set by observing iron requirements and estimating the requirement for absorbed iron at the 97.5th centile, using an upper limit of 10% absorption and rounding (Nrv, 2019). The RDI for adults also varies based on age, gender stage of life, between 8mg/day and 18mg/day, as seen in figure two. In setting the RDI for adults, it is assumed women over 50 years do not menstruate (Nrv, 2019). Supplementation of iron is not recommended unless instructed by a medical professional 

 DEFICIENCY AND EXCESS

DEFICIENCY

Iron deficiency is as a condition where there are no mobilizable iron stores and in which signs of a compromised supply of iron to tissues (Nazanin Abbaspour, 2019). Iron deficiency and depletion occurs in several stages1 (Nazanin Abbaspour, 2019), and can lead to significant health complications2. The most common cause of iron deficiency is blood loss (UCSF Health, 2019), therefore, menstruating women need to be wary of their iron levels. Other symptoms3 of iron deficiency can be observed to prevent diseases such as anemia4. Deficiencies can be treated through iron supplementation.

EXCESS

Just like deficiency, excess consumption of iron can cause harm to our health and life threatening conditions5. Iron can form free radicals in the body and can lead to tissue damage in excess amounts6 (Nazanin Abbaspour, 2019). Excessive consumption of iron can occur when intake exceeds the upper intake level, which is 45mg/day7 (Micronutrients, 2019). Symptoms of over consumption of iron include; joint pain, weakness, fatigue, loss of sex drive and abdominal pain (Mayo Clinic, 2019). Excess iron can be treated via the removal of blood, to lower iron levels.

REQUIREMENT ACROSS THE HUMAN LIFESPAN

Certain people are of an increased risk of iron deficiency and therefore need to consciously consume enough. Some of these people include; babies that are given cow’s milk rather than breastmilk or formula, menstruating women, people with poor diets, athletes in training, regular blood donors, people with chronic disease and many more8 (Betterhealth, 2019). A human’s need for iron increase’s over the lifespan, with substantial increase during pregnancy, lactation and menstruation. As seen in figure three (Nrv, 2019), an adult women’s RDI for iron when pregnant increases to 27mg/day. This need is crucial for the healthy development of a baby as well as to ensure health of the mother.

VITAMIN A – MICRONUTRIENT TWO:

THE ROLE OF VITAMIN A IN THE HUMAN BODY

Vitamin A is the name of a group of fat-soluble retinoids; retinol, retinal and retinyl esters (ODS, 2019). Vitamin A is crucial for vision8, healthy skin and support of the the immune system (Healthdirect, 2019). The body cannot create vitamin A therefore it must be supplied through dietary sources. Most Australian’s are able to receive enough vitamin A to avoid deficiency through a varied, healthy diet (Healthdirect, 2019) so supplementation is not necessary. There are two types of vitamin A; fully formed, found in meat, poultry, fish and dairy products as well as precursor, which is found in plant-based products (Healthdirect, 2019).  Because vitamin A is fat soluble, it is stored in the body’s tissue for later use10 (Healthline, 2019).

DIETARY SOURCES

As mentioned previously, there are two types of vitamin A. Fully formed vitamin A is found in foods such as lean meats, liver, poultry, oily fish, egg yolks butter, whole milk, yoghurt and cheese (Healthdirect, 2019).  Precursor vitamin A is found in foods such as; leafy green vegetables, as well as orange, yellow and other coloured vegetables, legumes, beans, fruit, wholegrain foods, tofu, nuts and seeds (Healthdirect, 2019). The most common type of precursor vitamin A found in foods and dietary supplements is beta-carotene.

RECOMMENDED DAILY INTAKE AND THERAPEUTIC DOSES

Just like iron, the need for vitamin A increases over the lifespan. The RDI for a child varies from 0.3mg-0.7mg (Nrv, 2019) depending on age, as shown in figure four. The RDI of vitamin A for adults is higher than that of children where for women it is set 0.7mg and for men is 0.9mg (Healthdirect, 2019).  Unlike iron however, there is no substantial increase in the need for Vitamin A during pregnancy, with only a 0.1mg increase in RDI. Vitamin A is often taken as a supplement by many people in the Australian population however, there is no good evidence to suggest benefits from this, unless suffering from a deficiency (Healthdirect, 2019). 

DEFICIENCY AND EXCESS

DEFICIENCY

Vitamin A deficiency occurs as a result of inadequate intake, liver disorder or fat malabsorption (Johnson, 2019). Vitamin A deficiency can impact your health dramatically, including deterioration of vision and inability to fight disease due to impaired immune function (Healthdirect, 2019). Deficiency is common among children in developing countries and is responsible for one to two million deaths and half a million new cases of blindness every year (Sommer, 2001). Symptoms include; dry skin and eyes, night blindness, delayed growth and acne and breakouts (Healthline, 2019). Vitamin A deficiency can be treated through Vitamin A supplementation.

EXCESS

Excess vitamin A can also cause harm and become toxic when the upper limit levels11 are exceeded. Symptoms such as; blurry vision or change in vision, swelling of bones, poor appetite, dizziness, nausea and vomiting and dry, rough skin can all indicate excess intake of vitamin A (Healthline, 2019). Vitamin A toxicity can also cause birth defects in pregnant women, orange skin colour, kidney or liver damage and inability to control body movement (Healthdirect, 2019). To cure this, an immediate halt in taking vitamin a supplements should occur.

REQUIREMENT ACROSS THE HUMAN LIFESPAN

Vitamin A is most needed in periods such as infancy, childhood, pregnancy and lactation (ODS, 2019).  Vitamin A is most needed during these times to support growth and prevent deficiency in both the mother and child during pregnancy and lactation and development and growth of the child during childhood. Deficiency during childhood can lead to increased risk of eye, chronic lung and gastrointestinal diseases (ODS, 2019) as well as blindness and poor vision. To avoid this, foods high in vitamin A should be fed to children and pregnant women to ensure adequate vitamin A levels.

CONCLUSION:

In conclusion, both vitamin A and iron are essential macronutrients in the human body. Because neither can be produced by the body itself, adequate consumption of a variety of healthy foods must be consumed to avoid deficiency and promote health. Neither vitamin A or Iron should be consumed via supplementation unless advised by a medical practitioner or when in states of deficiency. This will prevent excess consumption, avoiding toxicity in the body.

APPENDIX:

1.     Iron depletion and deficiency progresses through several stages (Nazanin Abbaspour, 2019):

·      Mild deficiency or storage iron depletion: Serum ferritin concentrations and levels of iron in bone marrow decrease.

·      Marginal deficiency, mild functional deficiency, or iron-deficient erythropoiesis (erythrocyte production): Iron stores are depleted, iron supply to erythropoietic cells and transferrin saturation decline, but haemoglobin levels are usually within the normal range.

·      IDA: Iron stores are exhausted; haematocrit and levels of haemoglobin decline; and the resulting microcytic, hypochromic anaemia is characterized by small red blood cells with low haemoglobin concentrations.

2.     Mild iron deficiency anemia usually doesn't cause complications. However, left untreated, iron deficiency anemia can become severe and lead to health problems, including the following (Mayo Clinic, 2019): Heart problems, Problems during pregnancy, Growth problems. 

3.     Iron deficiency anaemia signs and symptoms may include (Mayo Clinic, 2019): Extreme fatigue, weakness, pale skin, chest pain, fast heartbeat or shortness of breath, headache, dizziness or light-headedness, cold hands and feet, inflammation or soreness of your tongue, brittle nails, unusual cravings for non-nutritive substances, such as ice, dirt or starch, poor appetite, especially in infants and children with iron deficiency anemia

4.     Anemia is a condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body's tissues (Mayo Clinic, 2019).

5.     Excess iron is stored in your organs, especially your liver, heart and pancreas. Too much iron can lead to life-threatening conditions, such as liver disease, heart problems and diabetes (Mayo Clinic, 2019.

6.     The tolerable Upper Intake level for adults is 45 mg/day of iron, a level based on gastrointestinal distress as an adverse effect. (Micronutrients, 2019)

7.     Iron can form free radicals in the body, therefore it’s concentration in body tissues must be tightly regulated as excessive amounts may cause tissue damage

8.     Certain people are at increased risk of iron deficiency, including (Betterhealth, 2019): Babies given cow’s or other milk instead of breastmilk or infant formula, toddlers (particularly if they drink too much cow’s milk), teenage girls, menstruating women, especially those who have heavy periods, women using an IUD (because they generally have heavier periods), pregnant or breastfeeding women, people with poor diets such as alcoholics, ‘fad dieters’ or people with eating disorders, vegetarians or vegans, athletes in training, people with intestinal worms, Aboriginal Australians, regular blood donors, people with conditions that predispose them to bleeding, such as gum disease or stomach ulcers, polyps or cancers of the bowel, people with chronic diseases such as cancer, auto-immune diseases, heart failure or renal (kidney) disease, people taking aspirin as a regular medication and people who have a lower than normal ability to absorb or use iron, such as someone with coeliac disease.

9.     Vitamin A is critical for vision as an essential component of rhodopsin, a protein that absorbs light in the retinal receptors, and because it supports the normal differentiation and functioning of the conjunctival membranes and cornea (ODS, 2019).

10.  Most vitamin A is stored in the liver in the form of retinylesters (Healthline, 2019).

11.  Upper limit levels of vitamin A, figure five (ODS, 2019)

REFERENCES:

1.     Betterhealth. (2019). Iron. Retrieved 2 November 2019, from https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/iron

2.     Healthdirect. (2019, March). Vitamin A. Retrieved from https://www.healthdirect.gov.au/vitamin-a.

3.     Healthdirect. (2019). Foods high in iron. Retrieved 2 November 2019, from https://www.healthdirect.gov.au/foods-high-in-iron

4.     Healthline. (2019). 8 Signs and Symptoms of Vitamin A Deficiency. Retrieved 2 November 2019, from https://www.healthline.com/nutrition/vitamin-a-deficiency-symptoms

5.     Healthline. (2019). Hypervitaminosis A: Causes, Symptoms, and Diagnosis. Retrieved 2 November 2019, from https://www.healthline.com/health/hypervitaminosis-a

6.     Healthline. (2019). Vitamin A: Benefits, Deficiency, Toxicity and More. Retrieved 3 November 2019, from https://www.healthline.com/nutrition/vitamin-a#what-it-is

7.     Johnson, L. (2019). Vitamin A Deficiency - Nutritional Disorders - MSD Manual Professional Edition. Retrieved 3 November 2019, from https://www.msdmanuals.com/en-au/professional/nutritional-disorders/vitamin-deficiency,-dependency,-and-toxicity/vitamin-a-deficiency

8.     Mayo Clinic. (2019). Hemochromatosis - Symptoms and causes. Retrieved 2 November 2019, from https://www.mayoclinic.org/diseases-conditions/hemochromatosis/symptoms-causes/syc-20351443

9.     Nazanin Abbaspour, R. (2019). Review on iron and its importance for human health. Retrieved 2 November 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3999603/

10.  Nrv. (2019). Iron | Nutrient Reference Values. Retrieved 2 November 2019, from https://www.nrv.gov.au/nutrients/iron

11.  Nrv. (2019). Vitamin A | Nutrient Reference Values. Retrieved 2 November 2019, from https://www.nrv.gov.au/nutrients/vitamin-a

12.  Office of Dietary Supplements. (2019, October). Office of Dietary Supplements - Vitamin A. Retrieved from https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/.

13.  Shenkin, A. (2006, January 10). The key role of micronutrients. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0261561405002116.

14.  Sommer, A. (2001, April 19). Vitamin A Deficiency. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1038/npg.els.0002106.

15.  Spatone. (2019). The Role of Iron in the Body. Retrieved 2 November 2019, from https://www.spatone.com/en-au/about-iron/role-of-iron-in-the-body

16.  UCSF Health (2019). Hemoglobin and Functions of Iron. Retrieved 2 November 2019, from https://www.ucsfhealth.org/education/hemoglobin_and_functions_of_iron/

17.  Volpe, S. (2019). Micronutrient Requirements for Athletes. Retrieved 2 November 2019, from https://www.sportsmed.theclinics.com/article/S0278-5919(06)00079-2/abstract

18.  Micronutrients, I. (2019). Iron. Retrieved 3 November 2019, from https://www.ncbi.nlm.nih.gov/books/NBK222309/#ddd00470