The facts about vitamins, minerals

If we think of fat, protein and carbohydrates as the building blocks of our food, vitamins and minerals are the nuts and bolts. They work together with each other, as well as enhancing the effectiveness of the building blocks. Imagine building a car. Without the nuts and bolts, it would be little more than a pile of metal panels. 'Vita' means life, and it has been known since 1500BC that specific nutrients can treat disease. In the 18th century, a Scottish naval surgeon discovered the curative effect of citrus fruit on his sailors' scurvy. Hence the British being called 'Limeys', named after the limes used to treat scurvy at sea. It was not until the early 1900s that this was attributed specifically to vitamin C. Similarly, vitamin B1 was discovered at this time through the restorative effect of unpolished rice, a rich source of vitamin B1, on sufferers of beriberi, a wasting disease. Vitamin D was then found to cure rickets, a bone deformity disease, and so it went on until the 1930s when all thirteen of today's vitamins had been identified. Two types of vitamins Vitamins are divided into two types: water-soluble and fat-soluble. Neither is more important than the other, but they are very different in terms of what they do and where they are found. The majority of vitamins are water-soluble, namely all the B vitamins and vitamin C. Because water-soluble vitamins are dissolved in our body fluids, we are unable to store these vitamins, making a regular supply essential to our well-being. In contrast, fat-soluble vitamins A, D, E and K can be stored in the body's fat deposits, in which they are both transported and stored. Most vitamins have two names, eg. vitamin C is also known as ascorbic acid. Apart from vitamin D, which we can make from the action of sunlight on our skin, and some of both B vitamin biotin and vitamin K, made by the beneficial bacteria in our gut, the rest must be found in our food. Water-soluble vitamins and their function Vitamin B1 (Thiamin) – Releases energy from carbohydrates. Vitamin B2 (Riboflavin) – Releases energy from protein, fat and carbohydrate; promotes healthy skin and eyes. Niacin (Vitamin B3) – Releases energy from protein, fat and carbohydrate; involved in cholesterol production. Pantothenic Acid (Vitamin B5) – Releases energy from carbohydrate, fat and protein. Vitamin B6 (Pyridoxine) – Breaks down protein; helps to make red blood cells. Vitamin B12 (Cyanocobalamin) – Helps to make red blood cells, nerve cells and genetic material (DNA); breaks down carbohydrate and fat. Folate (Folic acid) – Helps to make red blood cells and enzymes and prevents neural tube defects; breaks down DNA material and reduces levels of homocysteine (high levels are a risk factor for cardiovascular disease). Biotin – Breaks down fat and protein Promotes growth and healthy nerve cells. Vitamin C (Ascorbic acid) – Forms collagen (an essential component of the skin, blood vessels, bone and teeth); acts as an antioxidant, providing resistance to infections and promoting wound healing; improves non-haem iron absorption. Fat-soluble vitamins and their function Vitamin A* (Retinol) – Maintains healthy skin and eyes, improving vision at night and in dim light; acts as an antioxidant, having a role in cancer prevention. Vitamin D (Cholecalciferol) – Promotes strong bones and teeth. Vitamin E (Tocopherols) – Maintains healthy cell membranes; acts as an antioxidant. Vitamin K (Phylloquinone) – Needed for normal blood clotting. * Vitamin A also occurs as beta-carotene in our food, being converted into retinol in the body. Minerals: Little and large Minerals form the body's backbone – literally as well as metaphorically. Some, like calcium and fluorine, are structural, whereas others are essential to the many chemical and electrical reactions occurring every second of every day within the body. As a friend once said to me, "I feel like one big chemical experiment, diluted down with a bit of water." Some minerals are needed in larger quantities than others, hence the term 'trace minerals' for those needed in minute amounts. We don't need much of each trace mineral, but what we do need is essential. Major minerals and their function Calcium – Forms the structure of bones and teeth; assists nerve function, muscle contraction, enzyme activity and blood clotting. Iron – Transports oxygen around the body via red blood cells; important part of many enzymes and muscle protein. Magnesium – Controls nerve signals and muscle contractions, and is involved in many enzyme systems; forms the structure of bones and teeth. Phosphorus – Works with calcium in forming the structure of bones and teeth; releases energy from carbohydrates, fats and protein; important part of many enzymes and DNA. Potassium – Maintains water and acid-base balance in the body and nerve impulses by working with sodium; involved with many enzyme systems. Sodium – Maintains water and acid-base balance in the body and nerve impulses by working with potassium. Trace minerals and their function Chromium – Regulates blood glucose through its action on insulin. Copper – Produces colour pigments in skin, hair and eyes; promotes nervous system function and red blood cell formation. Fluoride – Strengthens teeth and bone; reduces tooth decay. Iodine – Necessary for thyroid function, needed for normal growth. Selenium – Acts as an antioxidant; promotes a healthy immune system and resistance to disease; necessary for adequate thyroid function Zinc – Promotes normal growth, wound healing and immune system function, reproduction and sensory abilities, such as taste, smell and sight. How much is enough? It is quite easy to visualise the 'building blocks' of our food. Fat we can see as a lump of butter; protein as a piece of meat; carbohydrate as a slice of bread. Vitamins and minerals aren't so obvious because they're invisible to the naked eye. So how much do we need? And how much is enough? Earlier this year, the Ministry of Health along with the National Health and Medical Research Council of Australia published a set of tables detailing the amount of 28 vitamins and minerals we need to eat each day, based on the best available scientific evidence. You will see these amounts on food labels as the term %RDI, showing how much of the recommended amount a serving of that particular food provides. RDI stands for 'recommended dietary intake'. These amounts are set according to age and many of them differ between men and women. They are deemed to be enough for almost all of us; that is 97-98% of healthy New Zealanders. As well as preventing vitamin and mineral deficiencies, the latest recommendations also aim to combat the major killers in our society today – such as heart disease and cancers. For the first time, 'suggested dietary targets' (SDTs) have been included for the antioxidant vitamins, A, C, E and folate. These higher recommendations are based on amounts shown in research to help prevent these chronic diseases. Amazingly, we still see New Zealanders going short of some vitamins and minerals. The most common is iron, a mineral not easily absorbed by the body. Others include folate, calcium, iodine, vitamin D and selenium. The selenium content of New Zealand soil is particularly low, which is reflected in the lower amounts available in our food. Those in the North Island obtain more selenium from bread made from imported Australian wheat, but 'Mainlanders' still rely on other dietary sources, such as seafood, meat and eggs. Our soil is also low in iodine, so we rely on this important mineral being added to our table salt. This has been done since the 1920s, helping to overcome our previously high rate of goitre. The consumption of iodised salt has decreased in more recent times, as has the use of iodine in the production of dairy products, and the government is, once again, faced with considering mandatory fortification of another food.