On top of the macronutrients (protein, fats and carbohydrates) we also consume a range of micronutrients (vitamins and minerals) in our diet.
Just as ‘macro’ was given to the term to suggest the majority, ‘micro’ is given to this set of nutrients to suggest a much lower quantity.
To show this, typically the macronutrients are measured in grams, where the micros are measured in milligrams. However, it’s important to note that this is only related to quantity, as the micronutrients are also vital in terms of optimal body composition, health and performance.
Most vitamins and minerals are classified as essential, as the body cannot synthesize them on its own, so they must be obtained from the diet.
Needless to say, despite their name they are vital for life. In this article you will learn about all of the important micronutrients functions, including all of the recommended daily intakes, deficiency symptoms, and toxicity issues.
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Micronutrients Functions - Vitamins
Vitamins are potent, indispensable compounds that perform various bodily functions promoting growth, reproduction and maintain health.
Essentially vitamins make people’s bodies work properly.
Although we receive these nutrients from most of the foods we eat, some foods have more vitamins and minerals than others.
Most of the time, the micronutrients will be consumed within the macros we eat, as they are important within the metabolism of the macronutrients to produce energy.
Also, many of the micronutrients are involved in endogenous antioxidant defence mechanisms, meaning they are involved in the oxidation-reduction balance of the body.
There are two classifications of vitamins: water-soluble and fat-soluble.
Water-soluble Vitamins
Fat-soluble Vitamins
There are a number of key characteristics that separate the water-soluble and fat-soluble vitamins, these are shown below:
Water-soluble Vitamins
Dietary intake: Excess intake usually detected and excreted by the kidneys.
Body stores: Only a short-term supply available, with little storage, daily intake recommended.
Deficiency: Symptoms appear relatively quickly.
Toxicity: Lower risk of toxicity.
Absorption & transportation: Easily absorbed into blood and travel freely in blood
Solubility: Dissolves in water
Stability in food and handling: Less stable.
Fat-soluble Vitamins
Dietary intake: Excess intake tends to be stored in fat-storage sites.
Body stores: Long-term storage available in body tissues; regular intake recommended.
Deficiency: Symptoms are slow to develop.
Toxicity: Higher risk of toxicity.
Absorption & transportation: Like lipids, absorbed into lymph, many require protein carriers if they are to travel in the blood.
Solubility: Dissolves in lipid.
Stability in food and handling: Stable.
Summarizing this information, the vitamins have 3 key characteristics:
- They are all natural compounds found in food.
- They are essential nutrients to the body for physiological functions such as growth, repair, protection and reproduction etc.
- Deficiency can occur when consumed in reduced or limited amounts.
Over the last decade scientists have investigated the possibility that large doses of certain vitamins and minerals will help stave off chronic diseases such as cancer and heart disease, which rank as major killers today.
In fact, the study of vitamins, particularly a class known as the ‘antioxidant vitamins’, is one of the most widely published areas in current nutrition research.
What we do know is that where there is a deficiency of micronutrients, athletic performance in addition to normal physiologic function will suffer.
It’s important as nutrition coaches to therefore to be aware of and understand the steady stream of controversial and other claims regarding vitamins, so below we will look at their roles, key sources, deficiency & toxicity symptoms and how we can incorporate this information into potential advice for our clients.
A Guide to Water-soluble Vitamins
Thiamin
Best sources: Meat, pork, liver, fish, poultry, whole grain and enriched breads, cereals and grain products, nuts & legumes.
Chief roles: Helps enzymes release energy from carbohydrates – supports normal appetite and nervous system function.
Deficiency symptoms: Beriberi: oedema, heart irregularity, mental confusion, muscle weakness, apathy, impaired growth.
Toxicity symptoms: None reported.
Research: Theoretically, thiamin supplementation could increase aerobic performance given that it is required for energy production in the Krebs cycle and pentose phosphate pathway. Deficiency in this vitamin is uncommon and research does not show a direct increase in aerobic or strength performance with further supplementation. (1)
Riboflavin
Best sources: Milk, leafy greens, yogurt, cottage cheese, liver, meat, whole grain or enriched breads, cereals and grain products.
Chief roles: Helps enzymes release energy from carbohydrates, fat and protein – promotes healthy skin and normal vision.
Deficiency symptoms: Eye problems, skin disorders around nose and mouth, magenta tongue, hypersensitivity to light. Toxicity symptoms: None reported.
Research: Overall, riboflavin can function as an antioxidant, however deficiencies are not common and supplementation does not improve aerobic performance (2).
Niacin
Best sources: Meat, eggs, poultry, fish, milk, whole grain and enriched breads, cereals and grain products, nuts, legumes and peanuts.
Chief roles: Helps enzymes release energy from carbohydrates, fat and protein – promotes healthy skin, nerves and digestive system.
Deficiency symptoms: Pellagra – flaky skin rash on parts exposed to sun, loss of appetite, dizziness, weakness, irritability, fatigue, mental confusion, indigestion, delirium.
Toxicity symptoms: Flushing, nausea, headaches, cramps, ulcer irritation, heartburn, abnormal liver function, rapid heartbeat with doses above 500mg per day.
Research: The attenuated release of free fatty acids and carbohydrate oxidation could result in an increase in aerobic performance, however this has not been scientifically proved. (3)
Vitamin B6
Best sources: Meat, poultry, fish, shellfish, legumes, fruits, soy products, whole grain products, green leafy vegetables.
Chief roles: Protein and fat metabolism – formation of antibodies and red blood cells – helps convert tryptophan to niacin.
Deficiency symptoms: Nervous disorders, skin rash, muscle weakness, anaemia, convulsions, kidney stones. Toxicity symptoms: Depression, fatigue, irritability, headaches, numbness, damage to nerves, difficulty walking.
Research: Supplementation with Vitamin B6 may increase the use of muscle glycogen and a decrease in free fatty acids, however supplementation does not seem to improve aerobic performance. (4)
Folate
Best sources: Green leafy vegetables, liver, legumes, seeds, citrus fruits, melons, enriched breads, cereals and grain products.
Chief roles: Red blood cell formation – protein metabolism – new cell division.
Deficiency symptoms: Anaemia, heartburn, diarrhoea, depression, poor growth, neural tube defects, increased risk of heart disease, stroke and certain cancers.
Toxicity symptoms: Diarrhoea, insomnia, irritability, may mask a vitamin B12 deficiency
Research: The recommended daily allowance for folate should be sufficient and no research currently supports extra supplementation to improve athletic performance. (5)
Vitamin B12
Best sources: Animal products – meat, fish, poultry, shellfish, milk, cheese, eggs, fortified cereals.
Chief roles: Helps maintain nerve cells – red blood cell formation – synthesis of genetic material.
Deficiency symptoms: Anaemia, fatigue, and nerve degeneration progressing to paralysis.
Toxicity symptoms: None reported.
Research: The recommended daily allowance for vitamin B12 should be sufficient and no research currently supports extra supplementation to improve athletic performance. (6)
Pantothenic Acid
Best sources: Widespread in foods.
Chief roles: Coenzyme in energy metabolism.
Deficiency symptoms: Rare – sleep disturbances – nausea – fatigue.
Toxicity symptoms: None reported.
Research: The recommended daily allowance for pantothenic acid should be sufficient and no research currently supports extra supplementation to improve athletic performance. (7)
Biotin
Best sources: Widespread in foods.
Chief roles: Coenzyme in energy metabolism and fat synthesis.
Deficiency symptoms: Loss of appetite, nausea, depression, muscle pain.
Toxicity symptoms: None reported.
Research: Studies have not been conducted to date on the effects of biotin alone and its effect on athletic performance. (8)
Vitamin C
Best sources: Citrus fruits, cabbage-type vegetables, tomatoes, potatoes, dark green vegetables, peppers, lettuce, strawberries, mangoes, papayas.
Chief roles: Synthesis of collagen (helps heal wounds, maintains bone and teeth, strengthens blood vessel walls), antioxidant, strengthens resistance to infection, helps body absorb iron.
Deficiency symptoms: Scurvy – anaemia, depression, frequent infections, bleeding gums, loosened teeth, pinpoint haemorrhages, muscle degeneration, rough skin, bone fragility, poor wound healing.
Toxicity symptoms: Intakes of more than 1g per day may cause nausea, abdominal cramps, diarrhoea and increased risk for kidney stones.
Research: Vitamin C supplementation has resulted in improvements in exercise-induced damage, providing you meet the recommended daily allowance. It has not been shown to increase athletic performance and taking above the RDA may actually act as a pro-oxidant, thus inducing further damage. (9)
A Guide to Water-soluble Vitamins
Vitamin A
Best sources: Retinol – fortified milk and margarine, cream, cheese, butter, eggs and liver. Beta-carotene – spinach, broccoli, deep orange fruits (apricots, peaches, cantaloupe), and vegetables (squash, carrots, sweet potatoes, pumpkin).
Chief roles: Vision – growth and repair of body tissues – maintenance of mucous membranes, reproduction – bone and tooth formation, immunity – hormone synthesis, antioxidant.
Deficiency symptoms: Night blindness, rough skin, susceptibility to infection, impaired bone growth, abnormal tooth and jaw alignment, eye problems leading to blindness, impaired growth.
Toxicity symptoms: Red blood cell breakage, nosebleeds, abdominal cramps, nausea, diarrhoea, weight loss, blurred vision, loss of appetite, bone pain dry skin, rashes, hair loss, cessation of menstruation, liver disease, birth defects.
Research: The recommended daily allowance for vitamin A should besufficient and no research currently supports extra supplementation to improve athletic performance. (11)
Vitamin D
Best sources: Self-synthesis with sunlight – fortified milk, fortified margarine, eggs, liver, fish.
Chief roles: Calcium and phosphorus metabolism (bone and tooth formation), aids the body’s absorption of calcium.
Deficiency symptoms: Rickets in children, osteomalacia in adults, abnormal growth, joint pain and soft bones.
Toxicity symptoms: Deposits of calcium in organs such as kidneys, liver, or heart, mental retardation, abnormal bone growth.
Research: The latest research appears to show that many of us would in fact be deficient in this vitamin, thus making supplementation a good option. See www.vitamindcouncil.org for more information.
Vitamin E
Best sources: Vegetable oils, green leafy vegetables, wheat germ, whole grain products, liver, egg yolks, salad dressings, nuts, seeds.
Chief roles: Vision – Protects red blood cells, antioxidant, stabilization of cell membranes.
Deficiency symptoms: Muscle wasting, weakness, red blood cell breakage, anaemia, haemorrhaging.
Toxicity symptoms: Doses over 800IU/day may increase bleeding (blood clotting time).
Research: The recommended daily allowance for vitamin E should be sufficient and no research currently supports extra supplementation to improve athletic performance. (12)
Vitamin K
Best sources: Bacterial synthesis in digestive tract, liver, green leafy and cabbage-type vegetables, soybeans, milk, vegetable oils.
Chief roles: Synthesis of blood clotting proteins that regulates blood calcium.
Deficiency symptoms: Haemorrhaging, decreased calcium in bones.
Toxicity symptoms: Interference with anticlotting medication, synthetic forms may cause jaundice.
Research: The latest research appears to show that many of us would in fact be deficient in this vitamin, thus making supplementation a good option.
Micronutrients Functions - Minerals
TRACE MINERALS
Iodine
Best sources: Iodized salt, seafood, bread.
Chief roles: Part element of hormone thyroxin, which regulates metabolism.
Deficiency symptoms: Goiter, cretinism;
Toxicity symptoms: Depressed thyroid activity.
Research: The recommended daily allowance for iodine should be sufficient and no research currently supports extra supplementation to improve athletic performance. (13)
Iron
Best sources: Red meats, fish, poultry, shellfish, eggs, legumes, dried fruits, fortified cereals.
Chief roles: Haemoglobin formation –part of myoglobin, energy utilization.
Deficiency symptoms: Anaemia, reduced immunity, inability to concentrate, cold intolerance.
Toxicity symptoms: Iron overload – infections, liver injury, acidosis, shock.
Research: Clients with low iron levels are recommended to supplements with the RDA to seek improved athletic performance (14).
Zinc
Best sources: Protein containing foods, meats, fish, shellfish, poultry, grains, and vegetables.
Chief roles: Part of insulin and many enzymes involved in making genetic material and proteins, immunity, vitamin A transport, taste, wound healing, making sperm, foetal development.
Deficiency symptoms: Growth failure in children, delayed development of sexual organs, loss of taste, poor wound healing.
Toxicity symptoms: Fever, nausea, vomiting, diarrhoea, kidney failure.
Research: Zinc is not usually a concern for non-athletes, but is excreted in higher amounts when a person sweats to a higher degree. In instances of high mineral excretion from sweating, zinc supplementation would be useful.
Copper
Best sources: Meats, seafoods, nuts, drinking water.
Chief roles: Helps make heamoglobin, part of several enzymes.
Deficiency symptoms: Anaemia, bone changes.
Toxicity symptoms: Nausea, vomiting, diarrhoea.
Research: The recommended daily allowance for copper should be sufficient and no research currently supports extra supplementation to improve athletic performance. (14)
Fluoride
Best sources: Drinking water (if added), tea, seafood.
Chief roles: Formation of bones and teeth, helps make teeth resistant to decay.
Deficiency symptoms: Susceptibility to tooth decay.
Toxicity symptoms: Fluorosis (discolouring of teeth), nausea, vomiting.
Research: The recommended daily allowance for fluoride should be sufficient and no research currently supports extra supplementation to improve athletic performance. (14)
Selenium
Best sources: Seafood, meats, grains, vegetables.
Chief roles: Helps protect body compounds from oxidation, works with vitamin E.
Deficiency symptoms: Fragile red blood cells, cataracts, growth failure, heart damage.
Toxicity symptoms: Nausea, abdominal pain, nail and hair changes, liver and nerve damage.
Research: The recommended daily allowance for selenium should be sufficient and no research currently supports extra supplementation to improve athletic performance. (15)
Chromium
Best sources: Meats, unrefined foods, vegetable oils.
Chief roles: Associated with insulin needed for release of energy from glucose.
Deficiency symptoms: Abnormal glucose metabolism.
Toxicity symptoms: Occupational exposures damage skin and kidneys.
Research: The recommended daily allowance for chromium should be sufficient and no research currently supports extra supplementation to improve athletic performance. (16)
Molybdenum
Best sources: Legumes, cereals, and organ meats e.g. liver, kidneys.
Chief roles: In conjunction with enzymes, facilitates many cell processes.
Deficiency symptoms: Unknown
Toxicity symptoms: Enzyme inhibition.
Research: The recommended daily allowance for molybdenum should be sufficient and no research currently supports extra supplementation to improve athletic performance. (17)
Manganese
Best sources: Widely distributed in foods.
Chief roles: In conjunction with enzymes, facilitates many cell processes.
Deficiency symptoms: Unknown
Toxicity symptoms: Poisoning, nervous system disorders.
Research: The recommended daily allowance for manganese should be sufficient and no research currently supports extra supplementation to improve athletic performance. (18)
MAJOR MINERALS
Calcium
Best sources: Milk and milk products.
Chief roles: Principal mineral of bones and teeth, involved in muscle contraction and relaxation, nerve function, blood clotting, blood pressure.
Deficiency symptoms: Stunted growth in children, bone loss in adults. Toxicity symptoms: Excess calcium is usually excreted.
Research: Calcium is not an ergogenic aid, but supplementation should be used to prevent osteoporosis if there is a deficiency. (19)
Phosphorus
Best sources: Meat, poultry, fish, dairy, soft drinks, processed foods.
Chief roles: Part of every cell, mineralization of bones and teeth involved in buffer systems that maintain acid base balance, used in energy metabolism.
Deficiency symptoms: Muscle weakness and bone pain.
Toxicity symptoms: May cause calcium excretion, calcium deposits in soft tissues.
Research: The recommended daily allowance for phosphorus should be sufficient and no research currently supports extra supplementation to improve athletic performance. (20)
Magnesium
Best sources: Nuts, legumes, whole grains, green vegetables, seafoods, cocoa.
Chief roles: Involved in bone mineralization, protein synthesis, enzyme action, normal muscular contraction, nerve transmission.
Deficiency symptoms: Weakness, confusion, depressed pancreatic hormone secretion, growth failure, muscle spasms. Toxicity symptoms: Excess intake has caused low blood pressure, lack of co-ordination, coma and even death.
Research: Magnesium does not have a really good single food source aside from some nuts. If most of your food is from nuts then you are not likely to be deficient in this mineral, however if not, then supplementation is a good option.
Sodium
Best sources: Processed foods, whole grains, legumes, nuts, seeds.
Chief roles: Sodium is a mineral that carries an electrical charge, known as an electrolyte, which facilitates muscle contractions and nerve cell transmission.
Deficiency symptoms: Low blood sodium typically results from increased fluid retention. One may notice nausea, vomiting, headache, cramps, fatigue and disorientation.
Toxicity symptoms: Excessive intake can lead to increased fluid volume, nausea, vomiting, diarrhoea and abdominal cramps.
Research: The recommended daily allowance for sodium should be sufficient and no research currently supports extra supplementation to improve athletic performance. (21)
Potassium
Best sources: Sweet potato, tomato, green vegetables, carrots, prunes, beans, molasses, squash, fish, fruits.
Chief roles: Is essential for maintaining proper fluid balance, nerve impulse function, muscle function, and cardiac function.
Deficiency symptoms: Caused by protein wasting conditions. Diuretics can also cause excessive loss of potassium in the urine. Low potassium can result in cardiac arrest.
Toxicity symptoms: Occurs when the intake of potassium exceeds the kidneys’ capacity for elimination. Found with kidney failure and potassium sparing diuretics. Symptoms include muscle weakness, nausea, vomiting and diarrhoea.
Research: The recommended daily allowance for potassium should be sufficient and no research currently supports extra supplementation to improve athletic performance. (22)
Recommended Daily Allowances (RDA)
The below table shows the recommended daily allowances of vitamins and selected minerals for young adults.
RDA’s are set to meet the needs of 97-98% of individuals. There can be small differences in these depending on sex, and upper limits (UL) have been suggested to highlight the maximum amounts that are not likely to cause adverse effects. No data (ND) exists to support the suggested upper limits.
Summary
The micronutrients are vital for life and therefore essential components of our diet. The body cannot make any of the micronutrients (except vitamin D from the sun) so we need to intake an adequate amount from food, or supplement these if required.
There is no research to support that increasing daily dosages above the RDA levels significantly improves health or athletic ability, so supplementation is not essential.
There is evidence to suggest that vitamin C and E may enhance recovery after exercise by reducing oxidative stress and acting as strong antioxidants. Also, it has been highlighted that those with low iron levels, particularly menstruating females, would benefit from an iron supplement.
Ideally, by eating a well-balanced and complete diet, we should receive all the micronutrients in sufficient amounts, but this is not always the case with our clients.
Those with ‘poor’ diets i.e. lacking in any fruit and vegetables may suffer from deficiencies. Also, those who are following a low calorie intake for significant time periods may not be receiving sufficient micronutrients in their diet. In these cases supplementation can be warranted to ensure no deficiencies are present.
Overall, supplementation of micronutrients can be important for those who are not meeting the recommended daily intakes for each.
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