Every runner knows that certain nutrients are essential for health and performance. Failure to consume adequate amounts of these essential nutrients--which include 13 vitamins, 22 minerals, essential fatty acids, essential amino acids and, of course, water--results in consequences that range from low energy to death, depending on the specific nutrient, the individual and the severity and duration of the deficiency.
Recently, nutrition science has brought new attention to the vitamin and mineral needs of athletes and the consequences of deficiencies. A recent study from the University of Oregon found that vitamin B deficiencies were common in athletes and that these deficiencies sabotaged athletic performance.
An even more recent article published in the pro-supplementation Journal of the International Society of Sports Nutrition concluded that it is impossible for athletes to meet their daily vitamin and mineral requirements without supplementation.
The prevailing view is that runners and athletes probably do need slightly more nutrients than non-athletes, but that these nutrients are obtained automatically in the course of eating the extra calories that are required to fuel workouts--assuming a balanced, healthy diet.
However, besides the extra calories, the typical athlete eats very much like the typical American--and in the typical American there are several common nutrient deficiencies resulting from poor diet balance. In runners these deficiencies are likely to affect health and performance. Let's take a look at each of the most common deficiencies, the consequences and how to overcome them.
The recommended daily intake of calcium is 1,000 to 1,300 mg. The average adult consumes only 500 to 700 mg daily. The major consequence of this common deficiency is weakening of the bones, which increases the risk of stress fractures in runners and other athletes. You can easily avoid a calcium deficiency by consuming three servings of dairy foods per day. (An eight-ounce glass of milk equals one serving.)
The average American consumes 12 to 15 grams of fiber daily. Unfortunately, women need at least 25 grams and men need at least 38 grams per day for optimal health. Adequate fiber is needed for healthy cholesterol levels, reduced colon cancer risk and weight control. Good sources of fiber include vegetables, legumes and whole grains.
Iodine is a trace mineral that is needed in very small amounts but is often consumed in even smaller amounts. It is naturally found almost exclusively in seafood. When iodine deficiency became widespread in the early 20th century, the U.S. government mandated that iodine be added to table salt. But as salt consumption has decreased over the past quarter century, iodine deficiency has become more widespread once again.
Iodine is essential for normal thyroid function. Iodine deficiency often leads to hypothyroidism, whose symptoms include fatigue, weight gain, cold intolerance, dry skin, constipation and depression. You can avoid iodine deficiency by eating a diet rich in seafood and by seasoning foods with iodized table salt.
The recommended daily iron intake is 10 mg per day for men and 15 mg for pre-menopausal women. Due to iron losses during menstruation, women need more iron than men. However, because they eat fewer calories, women generally take in less iron than men, often failing to meet their needs. Since iron is essential to the formation of red blood cells, iron deficiency often results in anemia, characterized by persistent fatigue.
There is evidence that anemia is more common among endurance athletes, and especially runners, than among the general population -- possibly due to iron losses incurred through sweating and other exercise-related mechanisms. Iron deficiency is easily avoided through adequate intake of iron-rich foods including tuna, chicken and beef.
Omega-3 essential Fatty Acids (EFA)
The human body is unable to produce the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which must therefore be obtained through the diet. But the average American diet contains very small amounts of these nutrients.
The recommended daily intake of omega-3 EFAs is one to three grams. The average intake is just 130 mg. Inadequate consumption of omega-3 EFAs may contribute to eczema, depression, memory loss, poor fetal development, attention deficit disorder, diabetes and bipolar disorder.
It is very important to include omega-3 EFA-rich foods in the diet. These include fatty fish such as salmon and tuna, flax seeds and flax oil, walnuts and soybean oil. Taking a daily omega-3 supplement for insurance is not a bad idea.
The recommended daily intake of vitamin B12 is two to three micrograms per day. Vitamin B12 is only found in animal foods, so strict vegetarians are at high risk of deficiency. Because vitamin B12 plays an important role in red blood cell formation, deficiency may result in anemia. Non-vegetarians can avoid a deficiency by eating three servings of meat, fish and/or eggs daily. Vegetarians require a daily vitamin B12 supplement.
Athletes who live and train in the heat are at risk for chronic dehydration due to large daily sweat losses and failure to adequately replenish these losses with fluid intake. To prevent this condition, which wreaks havoc on exercise performance, you need to not only consume a sports drink during exercise but also drink water frequently throughout the day. A simple guideline for water intake is the urine test--if your urine is consistently pale yellow or clear in color, you are consuming enough water.
Active Expert Matt Fitzgerald is the author of several books on triathlon and running, including Brain Training for Runners and Runner's World Performance Nutrition for Runners (Rodale, 2005).