Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University
As an endurance athlete, you are accustomed to learning about how consuming an adequate amount of carbohydrates is necessary to fuel your skeletal muscles during activity, and that protein in your diet helps to rebuild skeletal muscle tissue after it is damaged from activity. But another area of performance nutrition that often goes overlooked by athletes is the role vitamins and minerals play in a healthy balanced diet. I would like to discuss the importance of vitamins and minerals, for both overall health and athletic performance, and also offer advice to help you get the essential vitamins and minerals that we all need every day.
All vitamins are actually biochemical substances that our bodies require everyday in small amounts for both health and optimal athletic performance. Carbohydrate consumption each day may total more than a pound and protein consumption is measured in grams, but our bodies need for vitamins is calculated in milligrams or even micrograms. That is why you will read that carbohydrate, fat, and protein are termed macronutrients and vitamins and minerals are known as micronutrients. Vitamins are often also called essential because your body does not have the ability make them, but you need them to be healthy. Ideally, vitamins should be obtained from whole healthy foodstuffs, but a once daily multivitamin supplement is a very good idea even if you believe your diet is healthy.
Vitamins are classified based on their solubility. For example, the fat-soluble vitamins are A, D, E, and K. These four do not dissolve well in water, but they are soluble in fats and can be stored and for extended periods of time in various body tissues. Water-soluble vitamins include vitamin C and the eight vitamin complex known as the B vitamins: thiamin, riboflavin, B6, niacin, folic acid, B12, biotin, and pantothenic acid. These nutrients dissolve easily in water and since they are water-soluble they also tend to be excreted more readily from the body. Lastly, minerals are substances found naturally in the earth (primarily on the crust), and some of them, like vitamins, are essential to your health and can only be obtained from what you eat and drink. The essential minerals have two subclasses: Major minerals that your body requires every day in 100 mg amounts or more include sodium, potassium, calcium, phosphorus, and magnesium. Trace minerals that your body requires every day in smaller amounts, usually less than 20 mg daily, include iron, zinc, copper, selenium, and chromium.
In spite of what you often read and hear in the popular media, vitamins and minerals do not provide you with energy for activity. However, they do have essential roles in the breakdown of carbohydrates and fats, which are the primary fuel sources your skeletal muscles utilize during exercise. Vitamins are also involved in the repair and building of muscle protein in response to training. Both energy metabolism (the breakdown of carbohydrate and fat) and protein synthesis (repair of damaged skeletal muscle from activity) are driven by biochemical regulators in the body known as metabolic enzymes. However, the enzymes often require coenzymes (think of them as helpers) in order to function properly. Many of the B vitamins serve as these “helpers” or coenzymes for these important metabolic enzymes. This is why the B vitamins in particular are so critical. If B vitamins are in adequate supply in your diet, then the metabolic enzymes are able do their respective jobs. But if a particular B vitamin is lacking or not included in the diet the enzyme it works with will be unable to function properly, and ultimately this deficit in enzyme function will have a negative influence on your performance as an athlete.
One area that I believe is very important to address is the idea of overconsumption of vitamins and minerals. Vitamins and minerals are intimately involved in many vital body functions and many individuals might be tempted to think that if getting some of these micronutrients is good, consuming more is even better. This is simply wrong. Here I think the analogy with calories works well. If you consistently do not consume enough calories, your health and athletic performance will eventually suffer. Conversely, if you consume calories in excess on a regular basis (even from good healthy food sources), you will eventually gain excess weight, and your ability to train and compete will decline. But if you consistently consume the calories your body needs, you will strike the correct energy balance that allows you to train and compete at your best. Vitamin and mineral intake is the same. If your intake is chronically too low, your body will not function very well metabolically or athletically. Conversely, if you consume too much of these micronutrients, you can develop toxicity symptoms that can impair athletic performance, and even worse, put your health at risk. But if you consistently consume vitamins and minerals in amounts that your body needs, you develop a solid micronutrient foundation that allows you to be healthy, train hard, and compete at the highest level you can achieve.
So the question of how much does an individual need when it comes to vitamins and minerals must be addressed. The daily requirements set for vitamins and minerals includes some amount of built in “wiggle room”. This buffer zone recognizes that micronutrient needs vary from one individual to the next, and that the daily requirements are determined so as to meet the needs of virtually all healthy individuals. So while your need for certain nutrients may be a bit higher here and there because you are an athlete, current research indicates that you can follow the daily requirements established for all healthy adults. Said another way, inadequate intake of vitamins and minerals will likely impair both your health and your athletic performance. However, and I want to be clear, if your micrfonutrient intake is already adequate there is no good scientific evidence that supports the idea that supplementing your diet with additional vitamins and minerals (over and above the recommended levels) will make you stronger, faster, quicker, more skilled, or better at your sport by any other performance measure.
While consuming greater amounts of vitamins and minerals than you need will not confer a performance benefit, there are a few micronutrients that warrant a bit of extra attention for two different reasons. First, there are four vitamins and minerals that are commonly under consumed by athletes (e.g., calcium, vitamin D, iron, and vitamin C). Second, there is one mineral (sodium) when consumed during exercise can make a performance difference. Lets take a more detailed look at each one.
First, calcium and vitamin D work hand in hand when it comes to supporting bone development and strength. Both calcium and vitamin D are typically under consumed in the diets of both athletes and nonathletes, and particularly in the diets of females. As an athlete, training and competing puts a consistent compressive stress on the bones. Although you do not perceive it, your bones are constantly undergoing a remodeling process, where bone mineral is being dissolved away and then replaced. By having enough calcium in your diet, you help to ensure that you have enough calcium available to fully support the bone remodeling process. And having enough vitamin D helps to promote the absorption of calcium from your gut. This why milk is almost always supplemented with vitamin D. Importantly, if your diet is low in calcium and vitamin D, you increase your risk of exercise-related stress fractures. These injuries are common in endurance athletes due to the repetitive nature of the activities. Female athletes are particularly at risk for stress fractures, since many often limit their calorie intake in order to achieve a lower level of body fat. While the reduced body fat may help in the short-term with athletic performance it is ultimately a losing proposition. The inadequate number of calories coupled with too little calcium and vitamin D is devastating to bones. The solution is to consume enough calories every day, and to make sure that you are also meeting your needs for calcium and vitamin D.
Good vitamin D sources include vitamin D-fortified milk (approximately 100 IU vitamin D per cup), salmon (approximately 360 IU per 3.5 oz serving), and fortified healthy ready-to-eat cereals (approximately 40 IU per cup). Solid calcium sources include milk (approximately 300 mg per cup), cottage cheese (approximately 150 mg per cup), yogurt (approximately 300 mg per cup), green leafy vegetables ( approximately 200 mg per cup cooked), and calcium-fortified orange juice (approximately 300 mg per cup).
Second, if your diet is low in iron your athletic performance may also suffer because iron is a component of a protein found in red blood cells called hemoglobin. Hemoglobin carries the oxygen that you breathe in through your lungs, and holds onto it as red blood cells transport the oxygen to your muscles and other tissues during exercise. Hemoglobin also transports carbon dioxide back to the lungs so it can be exhaled. Inadequate iron in the diet can result in iron-deficiency anemia, as well as an impaired oxygen and carbon dioxide transport system. This, in turn, will directly impair your ability to train and compete.
The scientific literature is not completely clear on the amount of iron-deficiency anemia people suffer from. Some reports indicate that approximately 5% of all individuals, both athletes and non-athletes, while other reports contend that iron-deficient anemia occurs in as many as a third to even half of athletes. We do know for certain that iron deficient anemia is more common for female athletes, especially female endurance athletes. Women are particularly at risk because of the monthly menstrual cycle induced blood losses. Athletes who are still growing, as well as vegetarian athletes, may also be at higher risk for iron deficiency. Clearly iron is an essential nutrient in your diet. Strategies for ensuring that you get adequate dietary iron include consuming lean cuts of red meat or dark-meat poultry, iron-fortified, healthy ready-to-eat breakfast cereals, vitamin C rich fruits or fruit juices, 100% whole grain products, and many vegetables. A balanced multivitamin supplement will generally provide your daily requirement for iron. Only consume a higher dose iron supplement if your physician instructs you to do so.
Third, vitamin C is important not because it will improve athletic performance, but because it may help to reduce the incidence of upper respiratory tract infections, which seem to occur more frequently in athletes following endurance events such as half marathons, marathons, and triathlons. The benefit is not guaranteed. In some studies, vitamin C has not made a difference, but in others, approximately 500 mg/day of vitamin C, a week or two prior to and after an extended endurance competition, reduced the chance of coming down with a chest colds after the competition.
Fourth and finally, sodium is very important because it is the major electrolyte lost in sweat. Although you lose electrolytes and other minerals when you sweat, sodium is the electrolyte lost in greatest concentration. If you are exercising for less than an hour in moderate temperature conditions, you do not need to be concerned about sodium intake during exercise itself. However, if you are exercising in high heat and humidity, or exercising for more than an hour at a time, it pays to include sodium in your hydration beverage. The most efficient way to get fluids and sodium together is with a sports drink, such as Gatorade. By rehydrating with both fluid and sodium, you do a better job of replacing what you are losing when you sweat. The benefit is more effective hydration, which allows you to perform at your best and avoid the potential adverse health effects of dehydration.
In conclusion, when it comes to essential vitamins and minerals the bottom line is get what is required for your body, but more is not better. Vitamins and minerals are important to your good health and your ability to succeed in training and during competitions so get enough of these micronutrients, but remember that getting more than you need offers no performance benefit and could prove harmful. Healthy, whole, food sources for vitamins and minerals are always best, so try to eat a wide variety of foods in your diet. To many of us tend to eat the exact same things day after day, and vitamins and minerals do not just come from a few foods. You receive many different micronutrients that you need by eating a wide variety of foods. For most people the addition of a multivitamin is a good idea. Purchase a well-balanced, one-a-day type multivitamin and mineral supplement. In general, steer clear of single supplements, However, there may be legitimate circumstances for getting a little extra calcium and vitamin D in supplement form. Work with your physician on this. Extra vitamin C a week or two before and after an extended endurance event may help reduce your risk of catching a chest cold. And finally, include sodium when rehydrating if exercising in the high heat or for longer than 60 minutes.