Key Topics

• • Overview of role of micronutrients
• • Water and fat soluble vitamins
• • Minerals and trace elements

Learning Objectives

• • To be able to list different vitamins and minerals
• • To be able to explain their role in human health including the oral health

Introduction

Micronutrients, such as vitamins and minerals, have an important role in maintaining general and oral health. There are several reasons why people take vitamins and minerals. These can be prescribed by doctors to treat a deficiency: vitamin B₁₂ intramuscular injections are used to manage pernicious anaemia; iron preparations are used to manage iron deficiency. They may also be used to prevent a disease, for example calcium and vitamin D supplements can be used in certain patient groups to prevent osteoporosis and folate supplements are recommended for pregnant women to prevent neural tube pathologies in the foetus.

Sometimes vitamin preparations are used to treat a disease that is not caused by underlying vitamin deficiency, for example the use of vitamin A in treatment of severe acne or psoriasis. In addition, people often take vitamin and mineral supplements obtained over-the-counter for various reasons: your patients may not think of these supplements as medications and may not mention them when you take a medical history.

Although often perceived as entirely harmless, in some situations use of these supplements may be dangerous. For example, patients on coumarin anticoagulants like warfarin, should not take vitamin K supplements. Also, pregnant women should avoid taking vitamin A supplements as this may exceed the safe recommended daily dose and cause congenital defects of the foetus.

It is recommended to have a healthy diet and lifestyle to provide the body with micronutrients. However, often diets are suboptimal and may not meet the body’s requirements.

In addition to systemic medications and supplements, vitamins and minerals can be added to topical preparations, for example fluoride in toothpastes and oral rinses.

Vitamins occur in two groups: they are classified as either water-soluble or fat-soluble. In humans, there are 13 vitamins: 4 fat-soluble (A, D, E and K) and 9 water-soluble (8 B vitamins and vitamin C). Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids (fats). Because they are likely to accumulate in the body, they are more likely to lead to hypervitaminosis. Water-soluble vitamins dissolve readily in water and are easily excreted from the body. Fat and water soluble vitamins will now be discussed in turn. This will be followed by a consideration of minerals and trace elements.

Fat-soluble vitamins

The fat-soluble vitamins will now be discussed in turn. The details relating to individual vitamins are summarized in Table 23.1.

Vitamin A

There are several compounds that have vitamin A activity – retinol, retinoic acid, retinalaldehyde and carotenoids that can be cleaved to yield retinalaldehyde and are sometimes called provitamin A.

Retinol and retinoic acid are found in animal products such as liver, egg yolk, fish liver oil, whole milk. Carotenoids are found in various vegetables and fruit, especially green, yellow and orange vegetables contain beta-carotene.

Retinol and carotene are absorbed from the small intestine and as they are fat-soluble, they require lipids to be absorbed. Low fat diets impair the absorption and can be associated with vitamin A deficiency. On the other hand, most of the dietary retinol gets absorbed and is stored in the liver. Excessive vitamin A intake can lead to hypervitaminosis, which is a serious toxic condition.

Recommended daily allowance (RDA) (or reference nutrient intake, RNI) of vitamin A for adults is 600–700 mcg/day. Vitamin A deficiency in developed countries is rare as liver stores can last 1-3 years. However, in developing countries vitamin A deficiency-related problems are common. Worldwide it is estimated each year about 10 million pre-school children and pregnant women are at risk of developing blindness due to vitamin A deficiency. Initially deficiency impairs vision’s adaptation to dim light and night blindness. This is reversible. Prolonged deficiency causes xerophthalmia – severe dryness of eyes leading to ulceration of the cornea and keratinization causing irreversible blindness. Vitamin A is also required for epithelial cell turnover and deficiency produces thickening of skin and mucosae due to hyperkeratosis.

Hypervitaminosis