Essential Nutrients

The more intense your activity level, the greater your nutrient requirements. This article lists the top 10 essential nutrients for the endurance athlete, such as middle to long-distance triathletes. We also list which real-foods sources provide these essential nutrients.

The Top 10 Nutrients


Early signs of deficiency are cramps, joint pains, heart palpitations, increased cholesterol levels, slow pulse rates, insomnia, impaired growth, excessive irritability or nerves, brittle nails, eczema and numbness or tingling in arms/legs; however long term deficiency can result in irreversable osteoporosis (fragile/porous bones).

Good sources of calcium are:- Dairy foods are regarded your best source of calcium, such as milk, yoghurt, cheese and buttermilk however some people are either unable to tolerate the lactose in dairy or choose to restrict their dairy food intake. Such people may choose calcium fortified products such as soymilk. They should also focus on calcium intake from leafy green vegetables, soy, tofu, sardines or salmon (with bones), brazil nuts, almonds, tahini (sesame seed paste).


Whilst the major signs of iron deficiency are fatigue, tiredness, difficulty maintaining body temperature, glossitis (inflamed tongue), decreased work performance, and decreased immunity, these are also common symptoms of over-training, which is not the same as a true iron-deficiency. Before you self-diagnose yourself with an iron deficiency you must have a blood test. In fact, it is possible to overdose the body on iron supplements, which are toxic in large amounts and can even be fatal.

Good sources of iron are::- Iron consumed from animal sources is absorbed 2-3 times more efficiently than iron from plant foods, so meat, poultry and fish are the ideal sources of dietry iron. Some people (such as vegetarians) restrict their intake of these foods, and will therefore need to eat iron-rich foods from other sources, such as dark green leafy vegetables, raisins, nuts, seeds, beans, peas, wholegrain cereals, brown rice, breads and pastas. Iron is sometimes difficult to absorb, so be aware that Vitamin C enhances iron absorbtion when eaten at the same meal. Tannins in tea and coffee can interfere with iron absorption.


Early signs of magnesium deficiency can be subtle and seen as cramps, foot pain or muscle twitches but if combined with insomnia, and migrane could definately indicate that magnesium stores are low. For athletes, a serious magnesium deficiency will affect endurance performance because this essential mineral is critical to the metabolism of food into energy. Because magnesium is lost through heavy sweating, or even diarrhea or (just loose stools), athletes must consider magnesium deficiency if they experience any of these symptoms.

Good sources of magnesium are::- Consumption of green vegetables and whole grains will help you meet your daily dietry needs for magnesium. Food rich in magnesium include all green vegetables, some beans (eg. soy, pinto, lentils, kidney beans), nuts (brazil, almonds, pine), seeds (pumpkin, sunflower, sesame) and whole unrefined grains (ie. wholemeal flour, not white flour) especially quinoa, wheat germ and bran, oats and brown rice. Avocados, potatoes, bananas, raisins and artichokes are other good plant based sources of magnesium, whilst oysters, salmon, tuna, haddock, scallops are also good animal sources of magnesium.


Because potassium is one of the key electrolytes that affects the cells and also electrical impulse functions of the body, the symptoms of a deficiency are widespread including muscular weakness, fatigue, temporary memory loss, unusual anxiety and confusion, improper digestion leading to constipation, hypertension, excessive thirst, dry skin, heart palpitations, etc. A deficiency will increase blood acid levels, causing a lowering of pH levels. People who lose excessive fluids through sweating, such as athletes, need to consistently consider potassium replacement.

Good sources of potassium are::- Many foods are rich in potassium and in particular fruits and vegetables. The best sources are found in button or portobello mushrooms, spinach (or chard), but fennel, kale, brussel sprouts, broccoli, eggplant, rockmelon, celery, romaine lettuce, cauliflower, tomatoes, asparagus, carrots, beets, and green beans are also very good sources. It may come as some surprise to learn that bananas are not amongst the top sources of potassium but certainly do contain potassium. Just as good as bananas in terms of potassium supply, are strawberries, tuna, avocado, cabbage, cucumber and even ginger root, and tumeric.


Signs of deficiciency are both mental and physical because it can affect multiple bodily systems including the brain, skeleton, eyes, heart, gastrointestinal tract, and lungs. Common symtoms include sleep problems, depression, eating disorders, poor attention/concentration, slow wound healing, skin problems, mouth ulcers, white coating on tongue, poor night vision, finger nail problems including white spots, brittle, thin or peeling nails and impotence. Athletes have lower zinc levels than sedentry people and people who train without days off lose zinc more quickly. Athletes should consider increased zinc in their daily food intake as it aids in post-exertion tissue repair.

Good sources of Zinc include:- pumpkin seeds, sunflower seeds, soybeans, mushrooms, whole grains, wheat bran, animal protein including seafood, lamb, beef, liver.


For athletes, a sodium deficiency can occur quickly as it an electrolyte (and mineral) stored predominantly in the blood and prolonged excessive sweating increases the risk that an athlete's blood-sodium concentration will be altered. Sodium helps cells retain water and prevents dehydration. Hyponatremia is a condition commonly seen in events over 5 hours, especially in very hot temperatures, whereby the concentration of water in the blood becomes too high, caused from drinking too much plain water to rehydrate the body with insufficient replacement of essential sodium that is also lost during sweating. The early warning signs are nausea, muscle cramps, disorientation, which may develop into seizures, coma or even death. Athletes must drink sodium containing sports drinks (not just water) and/or salty snacks during long distance, high intensity events of more than 60-90 minutes to avoid hyponatremia.

Good sources of sodium:- during multiple hour training or race events, athletes should get some salt from snacks (crackers & pretzels seem to be the most popular) and electroyle-replacement drinks. Some ultra-endurance athletes will also take salt-tablets. It is also advisable to hydrate in the days before long distance racing by using an electrolyte drink containing sodium, rather than water alone to build the blood salt a little.


General symptoms of a deficiency of this trace mineral and antioxidant are lethargy, inability to perform basic physical tasks, hypothyrodism (leading to heart palpitations, emotional disturbance, sensitivity to light), mental fatigue, moodiness, hair loss, loose skin, and even reproductive disorders such as changes in menstruation. Widespread research has produced numerous theories with low selenium levels pointing towards various cancers and permanent cell-damage. Selenium is shown to benefit athletes immune function and repair cellular damage.

Goods sources of selenium:- plant foods are the major dietry sources of selenium, especially brazil nuts, and whole grains however there is a direct relationship to the quality of the soil in which the plants are grown. Sulphur based fertilizers can affect selenium uptake by plants. Farmers are well aware of selenium and many add it to pastures, and feed to keep their animals healthy. Selenium is also found in some meats and seafood, with good choices being tuna, cod, turkey, chicken, and even eggs. Too much selenium can be toxic so blood testing is advised before taking supplements.

Vitamin E

Whilst deficiencies are generally rare, athletes tend to experience more oxidative damage to their cells and research shows less cellular damage occurs when vitamin E intake is increased.

Good sources of Vitamin E:- Numerous foods provide vitamin E. Nuts, seeds, and vegetable oils are among the best sources, especially green leafy vegetables and fortified cereals.


The main sign of a protein deficiency in an athlete would include be wasting of muscle tissue, impaired recovery and slow wound-healing. Strict vegetarians who don't consume any animal products at all and attempt to engage in regular endurance aerobic activities are at risk at developing protein deficiency.

Good sources of protein:- meat, poultry, fish, eggs, dairy products, seeds and nuts, beans and lentils, soy products and grains (especially wheat), rice, barley and corn. Animal products contain all the essential amino acids, whilst plant proteins usually lack at least one amino acid. Vegetarians can still obtain sufficient protein from plant foods by combining a variety of foods together.


Deficiences of this amino acid in athletes may present as increased vulnerability to infection.

Good sources of glutamine are:- most high protein sources such as beef, chicken, fish, beans, dairy products and cabbage.


Hopefully, you've already recognised the connection between good health and a balanced diet. Through this article we hope to have made it apparent that whilst athletes may have specific needs to increase intake of certain essential nutrients, this is easily made possible through eating a well balanced diet consisting of a rich variety of fresh, high quality plant and animal foods - along with dairy, nuts and oils. It isn't surprising that many athletes have a tendency to become over-obsessed with the need to take supplements due to the clever marketing of pills and powders under the guise of sports nutrition and sometimes there is a place for these additional supplements, however in general most of us simply need to chuck out the rubbish in our diet and get back to simple fresh food.

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Created: February 2012
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