Four essential micronutrients to boost your performance

As a runner, certain micronutrients are particularly important for your exercise performance and health. Your requirement for vitamins C and D, as well as iron and zinc, may well be higher than that of non-runners. Therefore not only is it important to understand the relevant role that these micronutrients play, but also where they can be sourced from the diet and when additional help from supplements may be needed.

Vitamin C

This antioxidant vitamin is beneficial to runners for three main reasons. Firstly, vitamin C helps to counteract potentially damaging free radicals which are generated during activity and may otherwise contribute to delayed onset muscle soreness, as well as adversely affecting your risk of blood vessel damage and the development of cancerous cells. Vitamin C also helps to support your immune system, which strenuous exercise can make less effective, leaving you more vulnerable to infections, which can themselves hinder your training and performance. Lastly, this vitamin aids the absorption of iron from non-meat sources, helping to reduce the risk of anaemia that can otherwise hold you back.

A diet rich in fruit and vegetables will help to ensure that you receive a good intake of this vitamin, particularly if you focus on those items richest in vitamin C, which include citrus fruits, kiwis, berries, bell peppers, tomatoes, dark green leafy vegetables and broccoli. You will however have higher vitamin C requirements if you smoke, as the vitamin helps to neutralise some of the chemicals found in tobacco. If you are concerned that you are not getting enough vitamin C or you have an infection, you may wish to take a vitamin C supplement. However, although it is a water-soluble vitamin and your body excretes excess amounts, mega-dose supplements of vitamin C (more than 2000mg) are not advised as they are associated with the formation of kidney stones.

Vitamin D

Although this vitamin is traditionally linked to promoting strong bones and may help to reduce the risk of fractures among runners, it is now believed to offer wider benefits. As the muscles have vitamin D receptors, an adequate intake may boost muscle performance and reduce muscle injury, and a deficiency is known to cause muscle weakness and pain. There is also evidence that vitamin D may enhance immune function, which as already mentioned is beneficial to athletes.

The best source of vitamin D is from exposing your skin to sunlight, though sunscreen largely blocks its production. However, owing to our latitude in the UK, we are only able to produce vitamin D between April and October. During the spring, summer and early autumn it is advisable to spend 10 to 15 minutes daily outdoors where the skin on your face, lower arms and legs are exposed to sunlight without the use of sun cream. A small number of foods are rich in vitamin D – oily fish, egg yolks and liver – but certain products such as breakfast cereals, margarine and milk powders also have added vitamin D, so try to include at least one of these foods daily to help top up your levels. As vitamin D deficiency is becoming more common in the UK and not everyone has symptoms, a blood test will reveal whether or not you have a deficiency. However, if you would rather err on the side of caution and take a vitamin D supplement routinely, it is useful to bear in mind that the recommended daily intake is 10μg and that high dose formulations are best avoided, as these may be damaging to the body.

Iron

Iron is essential for the formation of haemoglobin for the transport of oxygen to all the tissues, including the muscles, for the release of energy. It’s therefore no wonder that depleted iron stores can impair endurance and this may even occur when haemoglobin levels are normal but ferritin levels (a marker of iron stores) are low. Iron deficiency is relatively common among female athletes, with the iron losses in sweat and urine, as well as those from gastrointestinal bleeding and the breakdown of red blood cells that can all occur during training, contributing to this. However, these aren’t the only reason for low iron stores. If you follow a vegetarian diet this may also place you at risk of iron deficiency, as non-heme iron is not as effectively absorbed as the iron from meat and phytates that are present in pulses and grains can further impair its uptake by the body. Equally, overly restricting your dietary intake to prevent weight gain can leave you short of this mineral, particularly if you avoid all animal produce. However, no matter what foods you include in your diet, when calorie intake is low it is difficult to obtain sufficient micronutrients.

Although red meat and offal are among the richest sources of iron in the diet, poultry and fish – particularly when the darker flesh is eaten – are also a useful source of heme iron that is easily absorbed by the body. Alternative sources of iron include egg yolk, fortified cereals, pulses, dried fruit, wholegrains and green leafy vegetables. However, it is important to include a source of vitamin C at all meals and to avoid caffeine near mealtimes to aid the absorption of non-heme iron. If you feel lethargic or breathless, this could be a sign of iron deficiency, so a blood test from your GP would be advisable to identify whether you require iron supplements.

Zinc

As it forms part of the enzymes that play a role in energy release, adequate zinc helps to support your running performance. That’s not all though, as zinc is also needed for a healthy immune system and to enable your recovery from injuries that you may develop through training; frequent colds and poor wound healing is usually the first signs of deficiency. However, as zinc is lost in sweat and after exercise you excrete more zinc in your urine, training hard increases your risk of deficiency if you don’t ensure you have an adequate supply in your diet. This is especially the case if you follow a high carbohydrate training diet that includes predominantly plant-based foods.

As the body cannot store zinc it must be sourced from the diet each day. Animal sources of protein – particularly meat and fish – are the best options for zinc in the diet, but pulses, wholegrains and nuts offer a helpful source for vegetarians.