Our food provides us with the energy, vitamins and minerals we need to keep us healthy. They come in the form of macronutrients and micronutrients. Macronutrients are our largest source of energy and comprise of carbohydrates, fats and protein. We need these in large quantities and they are discussed further here.
Micronutrients are just as important but are needed in much smaller quantities, as the term ‘micro’ suggests. These are made up of vitamins and minerals. Whilst there are 26 known vitamins and minerals in total, some are especially important when it comes to our health and therefore our nutrition.
How do I know I am getting enough?
The government has provided us with RNI’s (Reference Nutrient Intake – previously RDA) and AI’s (Adequate Intake) for all microminerals but it is important to note that these are very generic and reflect the needs of a population rather than an individual. In most cases, we require more than is recommended. Fear not, however, recommended intakes are actually very easy to hit if you have a well-balanced diet that focusses on fresh food. The issue, of course, is that our current environment is laden with processed foods that challenge this. I will therefore provide you with some valuable information on where you can best source the most crucial vitamins and minerals to ensure they are in your every-day diet.
Vitamin A helps our bones to grow and maintains healthy connective, muscle and nerve tissue. It also has antioxidant properties and literally does help us see in dim light.
It is found in animal foods in the form of retinol. Good sources include liver, oily fish and whole milk. It is also found in green leafy vegetables and orange fruit (hence the saying that carrots help you see in the dark) but this is not converted effectively in the body. Combining it with a fat source can enhance its absorption.
The RNI for Vitamin A is 700 IU (International Unit) for men and 600 IU for women.
Vitamin D helps us to absorb calcium which is important to our bone health. It also improves our immune system and has been shown to reduce depression (Shaffer et al, 2014).
It is very difficult to get adequate amounts of vitamin D through diet alone as it is mainly synthesised through our skin from sunlight. It can be found in oily fish, egg yolks, butter and meat but the lack of sun in the UK does mean that many of us are deficient so it is one of the few nutrients that is generally worth supplementing. Vitamin D deficiency has been linked to cancer, cardiovascular and autoimmune disease (Hollick, 2007).
The RNI is 400 IUs but the Institute of Medicine actually recommends 4000 IUs as an upper limit.
Vitamin E is easily consumed through the diet. It has antioxidant properties that help to prevent cell damage.
It can be found in sunflower seeds, almonds and olive oil but you only need to consume small quantities to reach the RNI which is 4mg for men and 3mg for women.
Whilst Vitamin E as a supplement is not evidence-based, it has been proven to be effective in skin care (Ekanayake-Mudiyanselange et al., 2005)
Vitamin K is, again, important to our bone health and clotting of blood. Therefore babies are given a vitamin K injection soon after birth, to prevent bleeding.
It can be produced in our gut bacteria, but its main food sources are green leafy vegetables, olive oil, butter and chicken.
There is no RNI for vitamin K but an AI of 90 for women and 120 for men has been suggested.
Vitamin C is an antioxidant, is important to our immune function and helps our wounds to heal. It also helps us to absorb iron, so it is worth combining it with iron rich foods (explained further on).
It can it is found in lots of fruits and vegetables but those containing the most include broccoli, brussels sprouts, cauliflower, green and red peppers, spinach, and citrus fruits.
The RNI is 40mg for both men and women but it is worth noting that much of this essential mineral is lost when cooking and processing. You can avoid this by eating foods raw or steaming.
Vitamin B-complex is made up of Vitamin B1, B2, B3, B5, B6, B9 and B12. They are essential in helping the body convert food in to fuel and are very easy to consume through the diet, unless someone has a very heavily processed diet.
Vitamin B12 is particularly important in maintaining healthy nerve cells and helps us to produce DNA and red blood cells.
It is readily available but only in animal products i.e. shellfish, fish, red meat, dairy products etc. It is therefore easy for omnivores to get through their diet but is often deficient in vegetarians and vegans. Symptoms include headaches, fatigue and breathlessness.
The RNI is 1.5IU for both men and women.
Vitamin B9 (or Folate) plays an important role in our brain function, DNA and red blood cell production and also helps us absorb iron.
It can be found in leafy greens, avocados and citrus fruits.
The RNI is 200 IU for men and women but 300 IU is recommended for pregnant women. It is, therefore, worth supplementing during pregnancy.
Iron is used to transport oxygen around our body. It also helps produce haemoglobin and red blood cells.
There are 2 types; haem and non-haem. Haem iron is only found in meat, chicken and fish, and is easily absorbed. Non-haem iron is found in plant foods, such as vegetables, cereals, beans and lentils, but this is not absorbed well by the body which is why many vegetarians often find themselves deficient. A lack of iron can lead to anaemia.
The RNI’s are 8.7 mg for men and 14.8mg for women.
Calcium helps us to build healthy bones and teeth and our blood to clot normally.
It is very easy to get through sources such as milk, cheese, nuts, kale, tofu, broccolli and cabbage. Calcium can reduce the absorption of iron so it is worth considering this is you are iron deficient.
The RNI is 700mg.
Zinc is important in producing testosterone and helps us to digest food.
It is found in red meat and spinach and the RNI’s are 9.5mg for men and 7mg for women. Whilst this is not difficult to achieve, many of us in the UK are deficient in this important mineral.
Magnesium helps with our cell growth and reproduction. It also helps us to synthesize protein. There has been some suggestion that it can aid sleep but the evidence is not clear on this.
Most whole grains, legumes, nuts and seeds contain magnesium.
The RNI for women is 270mg and 300mg for men.
Sodium is important to our acid-base and fluid balance. It is an important electrolyte that helps our nerves to function appropriately. This means that is can help prevent muscle cramps.
It is abundant in processed foods and its negative effects are, in fact, massively over exaggerated. If a healthy individual consumes too much sodium, they more often than not will excrete it through their urine or their sweat.
The RNI for men and women is 1.6g which is the equivalent of 4g of salt.
When should you supplement?
As I have demonstrated, most micronutrients are acquired readily through food. There are, however, circumstances when a person may not be getting enough of a certain vitamin or mineral. This could be because they are pregnant, elderly or through the food choices they make. Any person who is not getting enough of a certain nutrient should, therefore, consider supplementing it. This does not necessarily mean that they need a multivitamin, it is better to supplement the vitamin or mineral they are lacking. Supplementing a micronutrient that you get enough of through your diet can have a negative effect.
A multivitamin is usually only necessary if a person lacks fresh food and variety in their diet or if they are on a calorie restricted diet as they may not be getting enough of a number of the micronutrients necessary for optimal health. If this is the case, make sure that you choose a quality vitamin as many cheap ones will not provide nutrients that your body can absorb.
The best way to make sure you are providing your body with everything it needs is through a balanced, varied diet that revolves around fresh food. A supplement is only necessary in the if your diet is lacking an essential nutrient, is very poor or is low in calories.
If you would like more information on how a typical day can meet all of your nutritional needs, please see my example day here.