‘Tiny but mighty’
The diet of human beings needs to consist of both macronutrients (carbohydrates, protein, and fat), and micronutrients (vitamins & minerals). As macronutrients make up the larger portion ratios of our food consumption, do not be misguided in to believing that because of their name that micronutrients are less important than their larger macro-counterparts. Micronutrients are as essential as all other nutrients, yet are needed in much smaller quantities. In current research literature, it is hypothesised that it is the increased energy expenditure and muscle damage during training which calls for an increase in the consumption of vitamins & minerals in athletes (1), but not forgetting that the need for micronutrients is also vital for optimal health in sedentary individuals too.
Vitamins & minerals are essential for several functions throughout the body including, metabolizing energy, building body tissue, maintaining intracellular fluid balance, and carrying oxygen in the body. They also play an active role in the reduction of oxidative stress which is induced via endurance training (2).
During bouts of physical exertion, an excess production of a number of reactive oxygen species (ROS) and free-radical’s build-up in the body where they attack, and begin oxidising various components of our cells, such as lipids, proteins, and nucleic acids (1). The defence of our cells from ROS and free-radicals is where the consumption of micronutrients can come to the rescue, especially antioxidants such as vitamins C & E!
Currently, there are 13 different vitamins, all which play separate and vital roles in the body (see Table 1). Vitamins are catalysts that are required for metabolic processes, yet do not provide direct energy, as the macronutrients do.
Vitamins are categorised into two sub-groups; water-soluble and fat-soluble. Water-soluble vitamins are found in the fluid portion of our body’s and basically only need water to be absorbed, and they do not accumulate in large numbers. The fat-soluble vitamins on the other hand, do accumulate to significant amounts, and are typically stored in the lipid portions of our body’s. Fat-soluble vitamins need dietary fat to be absorbed and can build up to toxic levels if taken in excess levels.
Water-soluble vitamins include all 8 B vitamins and vitamin C, whereas the fat-soluble vitamins include A, D, E and vitamin K, and excluding vitamin D, can be stored in our body reasonably well if an adequate diet is consumed. However, along with vitamin D, water-soluble vitamins are not stored well in the body. As our primary source of vitamin D comes from sun exposure, if exposure levels are low, then levels of vitamin D will also be low.
Minerals are elements which combine in various ways to form structures of the body and regulate body processes (3), such as energy metabolism, building body tissue, maintaining & strengthening the skeleton, muscle contraction, oxygen transportation, maintaining acid-base pH levels, and regulating a normal heart rhythm (2), which are all important processes with regards to exercise performance (see Table 2).
Minerals also play a vital role in the metabolism of macronutrients and in obtaining energy from an important fuel source such as phosphocreatine.
Minerals themselves are sub-divided; macrominerals including (calcium, phosphorus, and magnesium) and microminerals including (iron, zinc, chromium, copper, and selenium) and are both important elements and are classed due to their size and presence within the body.
Several minerals also function as electrolytes (watch out for the separate article on this topic!!) and play vital roles in fluid balance.
Three minerals which are super important for endurance athletes are; calcium (maintaining healthy bone structure), iron (oxygen transportation), and sodium (sweat loss and potential negative performance thereafter).
Table 1: Vitamins
|Vitamin||Major Function||Food Source|
|A||Vision, immunity, reproduction & growth||Fish, Kale, dark-green cabbage, yellow & orange peppers|
|D||Bone growth & maintenance, absorption of calcium||Sunlight, fortified milks and cereals, supplements|
|E||Antioxidant, protects cell membranes||Vegetable/Nut oils, seeds & nuts, whole grains|
|K||Blood clotting, bone health||Dark-leafy greens, margarine, plant-oils|
|B1, 2, & 3||Energy metabolism||Organ meats, whole and enriched grains, leafy-greens|
|B5, 6, & 7||Macronutrient metabolism||Almost all food especially avocado, beef, broccoli, cereals, oats, & potatoes|
|B9||Maintenance of red blood cells||Asparagus, beans, Lentils, Liver, Orange juice, Spinach|
|B12||Helps make DNA for new cells, protects nerve cells||Fortified cereals, fish, meat and milks|
|C||Antioxidant, collagen synthesis, immune function||Fruits and vegetables|
Table 2: Minerals
|Mineral||Major Function||Food Source|
|Calcium||Makes up bone/teeth, muscle contraction, blood clotting, nerve function||Tofu, greens, legumes, fortified cereals and milks|
|Iron||Part of haemoglobin-carries oxygen in the blood, myoglobin carries oxygen in the muscle||Dried fruit, legumes, fortified foods, meats & poultry|
|Magnesium||Mineralization of bones and teeth, enzymatic function, muscle contraction, nerve transmission||Nuts, legumes, whole grains, greens, cocoa, meat|
|Phosphorus||Bones and teeth, DNA||Nuts, seeds, soya, beans & lentils, milk, ice-cream|
|Potassium||Fluid and electrolyte balance, nerve impulse transmission, muscle contraction||All whole foods, fruits and vegetables, grains|
|Selenium||Enzyme function, and may help to stimulate the production of antibodies after vaccination||Organ meats, sea-food, and plants depending on soil content|
|Sodium||Fluid and electrolyte balance, nerve impulse transmission, muscle contraction||Table salt, soy sauce, all processed foods, MSG|
|Zinc||Part of insulin, enzymatic function, DNA repair, taste perception, immune function, wound healing, sperm||Protein-containing foods, some grains and vegetables, red meats|
Recommendations & Deficiencies:
I guess it’s impossible to write an article on micronutrients, even a basic one, and not mention recommendations (see Table 3) and deficiencies, as many people, especially athletes do seem to be, well not necessarily deficient, but low in one micronutrient or another at least, and this may well be causing an adverse effect on their training and/or competition. However, if you have been diagnosed with a vitamin and/or mineral deficiency then your GP or sports dietician will probably suggest a supplement of some kind to help increase vitamin and mineral consumption until a balance is found through your diet once again.
There is no better way of being confident in reaching your daily vitamin & mineral requirements than consuming a well-balanced diet including lots of fresh fruits and vegetables. Supplements may be used in conjunction with a ‘food first’ approach with athletes who have high training loads, or individuals who choose to follow a particular diet (vegetarian or vegan) and may not necessarily be able to reach daily recommendations as easily as those who consume a more rounded diet.
Unfortunately, we do not live in a perfect world where we all eat an amazingly healthy diet all of the time. Things get in the way, life gets in the way; time and convenience restraints come in to play knocking us off our ‘well-balanced healthy diet’ perch from time to time, causing us to make poor food choices which lack many of those vital micronutrients our body’s so need for optimal health & performance, therefore it so important that athletes make well-educated healthy food choices as often as possible.
Micronutrients & Performance:
Currently, there is limited data to back up any performance benefit claims from the consumption of individual vitamins or minerals, or from higher dosage intakes, and therefore any potential performance increasing claims should be taken with a ‘pinch of sodium’!
Vitamins C (5,6) and E (7,8,9) has shown potential in aiding recovery after resistance training and endurance training, due to their antioxidant properties, and their ability to decrease oxidant-induced muscle tissue damage.
Iron, is the only mineral to date which has be proven to improve performance (10,11,12), however, it is also the world’s most common mineral deficiency which may lead to anaemia, and consequently, a reduction in oxygen transport capacity and a reduction in cellular oxygen capacity, if it is not consumed to the recommended levels.
Table 3: Vitamin & Mineral Daily Recommendations
|Nutrient||*RDA (men)||RDA (woman)||**UL|
|Pantothenic acid-B5 (mg/d)||5||5||ND|
|Vitamin B6 (mg/d)||1.3||1.3||100|
|Vitamin B12 (µg/d)||2.4||2.4||ND|
|Vitamin C (mg/d)||90||75||2000|
|Vitamin E (mg/d)||15||15||1000|
|Vitamin A (µg/d)||900||700||3000|
|Vitamin D (µg/d)||5||5||50|
|Vitamin K (µg/d)||120||90||ND|
Source: Adapted from Grandjean (2003) (4)
*Recommended Daily Allowance
**Upper Limit-the maximum amounts which are likely to NOT cause any adverse effects
Next up in the series is Understanding Fats
- Micronutrients are essential for many metabolic processes such as, energy production, haemoglobin synthesis, bone maintenance, immune function, and protection from exercise induced oxidative stress
- Wherever possible, obtain recommended levels of vitamins & minerals through a ‘food first’ approach, not supplements
- Consult professional advice and guidance when contemplating taking a vitamin and/or mineral supplement, as you may not need it
- Athletes especially should pay particular attention to their consumption of calcium, iron, and zinc, and also to vitamins B, C, D, and E
- Remember! Vitamin D production is primarily based on sun exposure so get outside and train whenever you are able, however, do be ‘sunshine sensible’ and limit your time in the hottest parts of the day
- Athletes who choose to follow a plant-based diet need to be aware of potentially lower levels of vitamins B12 and D, plus the minerals iron and zinc than their meat-eating fellow human beings, so may need to top up these nutrients with a supplement-however, all micronutrient needs can generally be met through a well-balanced diet and a little ingredient knowledge
1– Van Gammeren (2013). Essentials of Sports Nutrition and Supplements: Vitamins & Minerals. NJ, USA, Humana Press
2– Ryan. M. (2012) Sports Nutrition for Endurance Athletes (3rd Ed.). Colorado, USA, Velo Press
3– Seebohar, B. (2011). Nutrition Periodization for Athletes. (Second Ed.) CO, USA, Bull Publishing Company
4– Grandjean A. Vitamin/Mineral Supplements and Athletics. Strength Cond J. 25:76-78, (2003)
5– Kaminsky M and Boal R. An Effect of Ascorbic Acid on Delayed-Onset Muscle Soreness Pain. 50:317-321, (1992)