Introduction

Minerals are naturally occurring substances which are essential to the functioning of human body. Examples of minerals are calcium, chromium, copper, iodine, iron, magnesium, manganese, phosphorus, selenium and zinc. Minerals can be obtained from food. However, some people may not get sufficient minerals from the diet alone due to reasons such as on low-calorie diets, poor appetite, or avoid intake of certain foods. Such individuals may consider taking health supplement products with adequate amount of minerals to meet the daily requirement.This article provides information on the roles of the most common minerals in our body, the symptoms or health problems related to mineral deficiency, and the recommended daily values for the maintenance of good health.

1. Calcium

   Calcium is the most abundant mineral in our body and 99% of the body’s calcium is stored in bone and teeth. The main dietary sources of calcium are milk, dairy products (e.g. yogurt and cheese), fish with edible bones (e.g. canned sardines) and bean products (e.g. tofu). Many people do not get the recommended amount of calcium from dietary sources alone due to several factors. Certain components in food such as phytic acid and oxalic acid, found naturally in some plants may inhibit absorption of calcium. For example, eating spinach and milk at the same time may reduce the absorption of the calcium in milk. Additionally, calcium absorption decreases for elderly people. The lack of vitamin D intake (e.g. lack of sunlight exposure) may also decrease calcium absorption. Calcium plays important role in the development and maintenance of bones and teeth. Long-term deficiency of calcium may cause low bone mass and increases the risks of osteoporosis and bone fractures. The following is the Daily Value of calcium recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	600
   Children < 4 years old	800
   Adults and children ? 4 years old	1000
   Pregnant and Lactating Women	1300

    

2. Phosphorus

   Phosphorus is the second most abundant mineral in the human body. 80% of phosphorus can be found in the skeleton and the remaining 20% involve in the cell metabolism. Phosphorus works together with calcium to provide strength and rigidity in bones and teeth. It is also an integral part of phospholipids, which is a component of all cellular membranes. Additionally, phosphorus is essential in energy storage and production processes, enzymatic reactions and protein synthesis in human body. The main dietary source of phosphorus is animal protein foods, such as meat, fish and eggs. Individuals with excessive alcohol consumption, intestinal problems and renal failure might be at risk of phosphorus depletion. Deficiency of phosphorus may lead to fragile bone and teeth, fatigue, loss of appetite and stiff joint. The following is the Daily Value of phosphorus recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	500
   Children < 4 years old	800
   Adults and children ? 4 years old	1000
   Pregnant and Lactating Women	1300

    

3. Magnesium

   Magnesium is an important nutrient that is involved in many processes in human body, such as maintaining proper muscle functions (including heart muscle), nerve functions, blood pressure, blood sugar levels, energy metabolism, tissue formation, bone and teeth development, and protein synthesis. Good dietary sources of magnesium include dark green leafy vegetables (e.g. spinach), nuts, legumes, cereal grains, milk and milk products. Some groups of people are more likely to have insufficient daily intake of magnesium, such as elderly people, alcoholics, patients with type 2 diabetes and gastrointestinal diseases. Magnesium deficiency for a long period of time may cause muscle cramps, fatigue, weakness, loss of appetite, osteoporosis and personality changes. Low magnesium states are also associated with serious diseases such as heart diseases, high blood pressure and diabetes mellitus. The following is the Daily Value of magnesium recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	70
   Children < 4 years old	200
   Adults and children ? 4 years old	400
   Pregnant and Lactating Women	450

    

4. Iron

   Approximately 80% of Iron can be found in our blood. Iron is a mineral that plays crucial roles in oxygen transport and storage in human body. It is used to make hemoglobin, a protein in red blood cells which carries oxygen from the lungs to other parts of the body. It is also used to produce myoglobin, a protein which carries oxygen to muscles. Iron deficiency anemia will occur if the levels of iron storage in the body become too low because the red blood cells contain less hemoglobin, hence carry less oxygen from the lungs to other parts of body. This may cause symptoms such as fatigue, weakness, headache, poor concentration and more susceptible to infections. Pregnant women also require more iron due to the increase of the amount of blood in the body. The following is the Daily Value of iron recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	15
   Children < 4 years old	10
   Adults and children ? 4 years old	18
   Pregnant and Lactating Women	18

    

5. Iodine

   Iodine salts can be found naturally in marine sediment. Hence, this trace element is rich in seafood such as fishes, seaweed, kelp and shrimp. Iodine is required for proper functioning of the thyroid gland, which contains around 70-80% of iodine of human body. Our body uses iodine to make thyroid hormones, which influence body’s metabolism, brain development (e.g. infant and during pregnancy) and other important functions such as protein synthesis and enzymatic activities in the organs such as muscle, heart, pituitary and kidney. Inadequate intake of iodine-rich food may eventually lead to the enlargement of thyroid gland (easily visible as a mass in the neck), which is known as goiter. Severe iodine deficiency in pregnant women and children may cause physical and mental retardation of the infant and children. The following is the Daily Value of iodine recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	45
   Children < 4 years old	70
   Adults and children ? 4 years old	150
   Pregnant and Lactating Women	150

    

6. Zinc

   Zinc is an essential trace element that is widely distributed in all body tissues and fluids. It is an essential component of over 300 different enzymes involved in the synthesis and degradation of carbohydrates, proteins, lipids and genetic materials (e.g. DNA) in the body. The best dietary sources of zinc are lean meat (e.g. beef, pork), organ meats (e.g. liver from beef, poultry) and shell fish (especially oysters). However, mild to moderate zinc deficiency may happen in certain groups of people, such as individuals with inadequate intake, individuals with increased need of zinc for growth and development and individuals with decreased zinc absorption. Zinc deficiency may result in impaired growth in infants, children and adolescents, impotence in men, hair loss, slow wound healing, impaired sense of taste or smell, and decreased immunity. The following is the Daily Value of zinc recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	5
   Children < 4 years old	8
   Adults and children ? 4 years old	15
   Pregnant and Lactating Women	15

    

7. Selenium

   Selenium was thought to be toxic in the past, but it is now recognized as an essential trace element when it is taken in appropriate amount. Selenium is involved in the body’s antioxidant system, thus helps to protect cells against oxidative damage caused by free radical. Selenium also plays important roles in thyroid gland function, reproduction and immune system. Foods rich in protein contain more selenium. For example, seafood, meat (especially organ meat such as liver), eggs and milk are good animal sources of selenium. Selenium is also available in breads, cereals and grains products. Selenium deficiency may cause heart disease, arthritis and reduced male fertility. The following is the Daily Value of selenium recommended by USFDA:

   Groups	Daily Value (mg)
   Adults and children ? 4 years old	70

    

8. Chromium

   Foods generally contain small amount of chromium, but the chromium content in foods vary widely due to different growing location and processing methods. Common dietary sources of chromium are Brewer’s yeast, wholegrain bread, cereals, meat and chocolate products. Intestinal absorption of chromium is low and can be enhanced by vitamin C and niacin. High sugar in the diet can increase the excretion of chromium in the urine. Other factors that may exacerbate chromium depletion include pregnancy, excessive exercise, stress, infection and trauma. Chromium can enhance the activity of insulin, which is a hormone that plays significant role in the metabolism of carbohydrate and fat in our body. Hence, chromium deficiency may be associated with the development of diabetes and obesity. The following is the Daily Value of chromium recommended by USFDA:

   Groups	Daily Value (mg)
   Adults and children ? 4 years old	120

    

9. Copper

   Copper occurs naturally in many foods, including dark green leafy vegetables, legumes, nuts, grains, shellfish and organ meats such as liver and kidney. It is a trace mineral that is used in the formation of hemoglobin in the red blood cells. It is also involved in the synthesis of collagen and elastin, hence play an important role in maintenance of bone, connective tissues and blood vessels. Copper deficiency may cause symptoms such as anemia, fatigue and loss of color in the skin and hair. The following is the Daily Value of copper recommended by USFDA:

   Groups	Daily Value (mg)
   Infants	0.6
   Children < 4 years old	1
   Adults and children ? 4 years old	2
   Pregnant and Lactating Women	2

    

10. Manganese

    Manganese is a trace element that is stored mainly in the bones, liver, kidney and pancreas. It is a constituent of several enzymes or used as activator for some enzymes in our body. It also involves in many biological activities in human body, including the maintenance of normal bone growth and maintains the body’s ability to metabolize nutrients such as carbohydrate and protein. Wholegrain, cereals, nuts, beans and vegetables are good source of manganese. Low levels of manganese in the body may lead to skeletal abnormalities, impaired glucose tolerance, altered metabolism of carbohydrate and lipid, and bone demineralization. The following is the Daily Value of manganese recommended by USFDA:

    Groups	Daily Value (mg)
    Adults and children ? 4 years old	2

     

Conclusion

Minerals are essential in the maintenance of good health in human. A balanced diet with wide variety of foods may provide most of the required amount of minerals for healthy people. However, individuals who do not get enough minerals from food alone may consider taking health supplement products formulated with minerals. It is important to note that mineral supplements are not a replacement for a healthy diet. Additionally, taking too much minerals can be unhealthy and even dangerous to our body. Consumers should only choose registered health supplement products and follow the dose and use instructions as stated on the label. Please refer to Appendix 1 for the maximum daily levels of minerals for adults allowed in health supplements. It is advisable to consult a doctor or pharmacist before taking any health supplement product if you have any health problems or if you are taking any other medications/ herbal products/ health supplement products.

Appendix 1

Maximum Daily Levels of Minerals for Adults Allowed in Health Supplements

References:

1. Braun, L., & Cohen, M. (2015). 4th Edition Herbs & Natural Supplements: An evidence-based guide. New South Wales: Elsevier Australia.
2. National Coordinating Committee on Food and Nutrition (2005).Recommended Nutrient Intakes for Malaysia. Putrajaya: Ministry of Health Malaysia.
3. National Institute of Health, Office of Dietary Supplements, U.S. Department of Health & Human Services (2013): Vitamin and Mineral Supplement Fact Sheets.
4. United States Food and Drug Administration (2013). Guidance for Industry: A Food Labeling Guide (14. Appendix F: Calculate the Percent Daily Value for the Appropriate Nutrients).
5. United States Food and Drug Administration (2013). Guidance for Industry: A Food Labeling Guide (15. Appendix G: Daily Values for Infants, Children Less Than 4 Years of Age, and Pregnant and Lactating Women).