Following on from my Essential Guide to Vitamins, here is my guide to minerals; substances equally as important to the body.
Like vitamins, minerals must be consumed in the diet. There are many different minerals, a number, known as trace elements, are only found in tiny quantities, and their functions in the body are still somewhat unknown. However, there are a number of key minerals which I will highlight below, which are well known to be essential to human health.
As with vitamins, DIETARY intake is key, and it is important not to rely on supplements to make sure you get adequate quantities (although administered correctly, mineral supplementation can be very powerful in supporting health). As with the fat soluble vitamins, you can have too much of a good thing, and excess levels of some minerals can be toxic. It is also worth noting that a number of minerals compete with one another for absorption into the body, so an excess of one, can in fact cause a deficiency of another. Copper and zinc are two good examples of this.
As with vitamins, the UK gives reference intake guidelines for minimum, and in some cases maximum, quantities most people require. It is worth remembering however, that everyone is different, and many factors such as gender, age, genetic predispositions and diseases all play a part in determining requirements. Minerals are also all stored in the body in some form, so intake of the full reference amount every day is not necessary- more important is the average amount ingested over a longer period.
Key minerals for human health:
Iron: most people are aware that iron is very important in the body, and an important constituent of blood; it attaches to oxygen to carry it round the body, which is why low iron levels can make you feel tired. However, it is not a good idea to take iron supplements unless you have had blood tests to check your iron levels are low. This is because iron is very toxic to the body in too high quantities. It is pro-inflammatory and is required for bacteria to survive in the body. Iron is lost from the body in blood (which is why women of menstrual age need far higher iron intakes than men and pre/post-menopausal women), and a very small amount in stools, but the body actually has no active physiological way of excreting iron if stores get too high. In fact, did you know that it can be a good idea for healthy individuals, especially men, who eat a lot of red meat/a high iron diet, to give blood regularly to manage the body’s iron levels?!
There are two types of iron, one (haem iron) is found only in ‘flesh foods’ (meat, fish and poultry) and this form is best absorbed. The other type (non-haem iron) is found in both plant and flesh foods (despite some popular opinion, research has shown that vegetarians have similar levels of iron in their blood to meat eaters, and are no more likely to suffer from iron deficiency anaemia). Non haem iron makes up most of our diet, and although it is not as well absorbed as haem iron, absorption can increase up to six times when vitamin C is consumed at the same time. Some of the best sources of iron are: meat, dark green leafy vegetables, apricots and sunflower and pumpkin seeds.
It is also worth noting a number of substances decrease absorption of iron. These include oxalates (particularly high in spinach and rhubarb), large quantities of calcium (this is particularly relevant for infants who have a high milk/calcium diet, so it is key that they get enough iron in their diet when weaning begins), phytates (found in wholegrains, legumes, nuts and seeds), and polyphenols (high in tea, coffee and some spices).
Calcium is the most abundant mineral in the body and is imperative for bone health. It is mainly found in dairy, as well as in vegetables, although the latter is a less concentrated source. Many non-dairy milks are also calcium fortified. Calcium is also very important for muscles; it works with magnesium, with calcium enabling muscles to contract, and magnesium needed for them to relax. It is why you will often see calcium and magnesium sold as a combined supplement. Excess calcium can cause constipation, while excess magnesium can have a laxative effect.
Magnesium is necessary for 100s of enzyme reactions in the body, particularly in relation to energy production, muscle relaxation and nerve impulses. It is widely available in whole foods and fruit and vegetables, particularly the dark green leafy kinds. Magnesium must be bound to something, so if you are taking supplements you should be aware of the form it is in. Magnesium oxide is generally the most common, but is one of the least absorbable forms. Magnesium citrate has higher absorption and is used in some laxatives, while amino acid chelated or magnesium glycinate are well absorbable forms for muscle relaxation.
Phosphorus is the second most abundant mineral in the body. It is important for energy, bone formation and is even a component of DNA. It is a constituent of all plant and animal tissues, so deficiency is largely unknown.
Zinc is important for cell growth and immunity (which is why zinc is often recommended when you start to get a cold). It is found in protein rich foods (meats, seafood, legumes) and wholegrains, as well as vegetables, but like iron, its absorption is decreased by phytates and oxalates. Zinc competes with a number of other minerals for absorption, so long term supplementation is not recommended as it can in fact cause a deficiency of other minerals, in particular copper.
Please note this is a very simplified guide. I am not a medical practitioner, and this should not be taken as medical advice. Always consult a health professional if you have any health concerns.
Osieki, H. (2014) The Nutrient Bible, 9th Edition
Haas, E. (2006) Staying Healthy with Nutrition
Pizzorno, J. and Murray, M. (2013) The Textbook of Natural Medicine, 4th Edition
British Nutrition Foundation DRVs