We often hear about the five food groups and their functions. One group that is of particular importance is the vegetable and fruit group. As all nutrition education will highlight, this is the group that we get most micronutrients from. What are these micronutrients we are referring to and why do we need them?
WHAT ARE MICRONUTRIENTS
Micronutrients are only needed in small amounts by the body but they perform vital functions. They enabled the body to produce enzymes, hormones and other substances necessary for proper growth and development1.There are two main categories of micronutrients mainly vitamin and minerals.
There are two types of vitamins, mainly fat soluble and water soluble. The fat-soluble vitamins are vitamin A, D, E, and K. They dissolve in fat and can be stored in your body. They also require fat to be absorbed. The water-soluble vitamins are the 8 B-complex vitamins and vitamin C. These vitamins dissolve in water and are not stored in the body. The body takes what it needs from food and then excretes what is not needed as waste1, 2.
Minerals are different from vitamins because they are not made by plants or animals but are elements from the soil and water that is absorbed by plants or eaten by animals. There are two types of minerals needed by the body based on the amount. Macro-minerals such as calcium are needed in large amounts while micro-minerals or trace minerals such as iron and zinc are needed in smaller amounts2.
Some vitamins such as vitamin C and E and minerals such as selenium act as antioxidants. Antioxidants protect the body from free radicals. Free radicals can damage the body’s cells and lead to health problems like cancer1.
Micronutrient deficiency is usually the long term for the lack of intake of certain vitamins or minerals. Micronutrient deficiencies affect more than two billion people of all ages in both developing and industrialized countries. Micronutrient deficiencies can cause some diseases or make other diseases worse.
Micronutrient deficiencies can be either primary or secondary. Primary deficiency is caused by too little intake while secondary deficiency can be because of other underlying factors such as malabsorption or infection. Other causes can be lifestyle such as smoking and alcohol intake3.
Some of the more commonly known micronutrient deficiencies are:
- Vitamin A deficiency causes night blindness
- Thiamine (vitamin B1) deficiency causes beriberi
- Niacin (vitamin B3) deficiency causes pellagra.
- Vitamin B12 (cobalamin) deficiency can lead to different types of anemia
- Vitamin C deficiency leads to scurvy
- Vitamin D deficiency leads to rickets in children
- Iron deficiency leads to anaemia
- Iodine deficiency leads to goitre
- Zinc deficiency can cause poor brain function3, 4
Some micronutrients can be dangerous if you take in too much of them. The fat soluble vitamins A, D and E, are prone to cause toxicity because they are stored easily in the fat cells, unlike their water soluble counterparts where excess of these is often lost in urine. But some of the water soluble vitamins can have toxicity, mainly vitamin B3 (niacin), B6, vitamin C and folate.
Some of the more commonly known vitamin toxicities are:
- Vitamin A toxicity can cause birth defects, liver abnormalities and reduced bone density
- Vitamin D toxicity can cause a calcium balance that can lead to calcium deposits in your soft tissues
- Vitamin E toxicity can cause bleeding problems
- Niacin toxicity can lead to liver damage and impaired glucose intolerance
- Vitamin B6 toxicity can cause skin lesions and nerve degeneration
- Vitamin C toxicity diarrhoea and other GI disturbance
- Folate toxicity can hide vitamin B12 deficiency4, 5
Minerals can also accumulate to toxic levels and cause problems. For instance, excess dietary calcium may lead to kidney stones. High sodium intake can impact your cardiovascular system. An excess in copper can cause liver damage and excess manganese can result in neurotoxicity.
PREVENTION IS BETTER THAN CURE
The best way to prevent micronutrient deficiencies is to eat a balanced diet that includes the correct amount of fruit and vegetables. The South African Food Based Dietary Guideline states: “eat plenty of vegetables and fruit every day”. Other guidelines recommend to have about 5 portions of fruit and vegetables daily6.
If you consider taking a micronutrient supplement it’s important to understand NRVs. NRVs are the Nutrient Reference Values. They are recommended amounts of micronutrients to be taken daily for good health as determined by scientific research. Sometimes some vitamins and minerals have an Upper Limit, or UL. This is the total amount of a vitamin or mineral that can be taken in a day before toxicity is reached and adverse reactions take place7. Try to stay within these NRVs if taking any supplement.
Micronutrients are essential for our survival. It’s important to eat the right amount of fruit and vegetables to get in the needed micronutrients. Watch out for deficiencies and make sure to correct any by taking a multivitamin supplement and correcting your eating habits. Remember if you are eating the correct amounts of fruit and vegetables then avoid taking supplements as that just leads to expensive urine because your body will excrete the ones it doesn’t need and too much of a good thing can also be bad if you get toxicity.
- Krause’s Food & the Nutrition Care Process 13th Edition L. Kathleen Mahan, Sylvia Escott-Stump, et al
- Understanding Nutrition (International Edition). Eleanor N. Whitney and Sharon Rady Rolfes