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Multi-Vitamins, Iron supplements, Selenium...Does my client need them? [article]

Micro-nutrients and the case for supplementation

A regular commercial screening on NZ television advertising a multi-vitamin product asks the viewers whether they are felling ‘tired and run-down’, and leads them to believe that this could be due to a vitamin deficiency.  It doesn’t consider the possibility that being tired is a completely normal consequence of a busy day, skipping meals due to time constraints or being dehydrated. 


If you know your macro-nutrients you’ll know that carbohydrates are the body’s preferred source of energy. One of the best sources of good carbohydrate is fruit and vegetables and the average kiwi isn’t getting enough.  So being ‘tired’ and run down’ is more likely to be due to poor intakes of fresh fruit, vegetables and other good sources of carbohydrates such as wholegrain breads and cereals than vitamin deficiency.


As the name suggests ‘micro’-nutrients are nutrients the body needs in very small amounts.  Vitamins and minerals are micronutrients and just like carbohydrates, fats and proteins they are not food groups, rather they are nutrients that are found in the various food groups.  Food groups are; fruits and vegetables, breads and cereals, milk and milk products and lean meats, poultry, seafood, eggs, nuts, seeds and legumes.


Vitamins are divided into two groups; the water soluble vitamins (B-Complex & C) and the fat soluble vitamins (A, D, E & K). The fat soluble vitamins are absorbed with fats and well stored in fatty tissue. Reserves of these vitamins can last a long time and daily intake is not essential.  The water soluble vitamins cannot be stored and are easily excreted, making deficiency more likely and daily intake more important.  The following table summarises the functions of the major vitamins and the food groups that provide these




Common Sources

Vitamin A

Important in growth, bone and teeth formation, cell structure and night vision


Yellow & green vegetables, liver, cheese, eggs, oily fish

Vitamin B Complex

Important in digestion, development of a healthy immune system, and body maintenance

Wholegrain breads & cereals, rice, pasta, meat & poultry, seafood, milk, eggs, nuts, legumes


Vitamin C

Important in manufacture of collagen, gums, teeth, blood vessels, growth and maintenance of healthy bones and ligaments.  Is also a powerful antioxidant


Fresh fruit and green leafy vegetables

Vitamin D

Regulates calcium and phosphate, critical for nerve function, aids absorption of calcium, is required for strong bones and teeth


Fish, liver oils, egg yolk

Vitamin E

Important for cell structure, maintaining the activities of enzymes, protecting the lungs against pollutants, and protecting against aging

Wholegrain breads & cereals, nuts, most green vegetables


If followed, the Ministry of Health (MoH) guidelines for daily consumption of the major food groups should ensure that micro-nutrient requirements are easily met. Their information suggests that vitamin deficiency in the NZ diet is actually very rare.


Vitamins however can be ‘temperamental’!  Some, such as vitamin c can be easily destroyed by cooking.  The MoH estimates that boiling vegetables can destroy 50-80% of vitamin c content.  It recommends cooking with minimal water (steaming) or using the microwave.  And where possible fresh is best and raw is great.


Minerals are absorbed from the soil by plants.  They come into our diet through the plants we eat and/or the animals we eat that have eaten the plants.  New Zealand soils do tend to be deficient in iodine and selenium but the MoH has not determined that these soil deficiencies have actually resulted in deficiencies in our diet.  They recommend the use of iodised table salt if possible but advise people to be wary of adding salt to the diet as our intake of sodium is actually considered excessive and excessive sodium levels are linked to high blood pressure. 


There has been an increase in the use of supplemental selenium in animal feeds and the importation of wheat and other products from Australia where selenium in the soil is higher, to counter the low selenium levels in NZ soils. 


In both cases the MoH does not recommend the use of supplements unless under the supervision of a doctor.  The table below highlights some of the major minerals, their functions and common food sources.  




Common Sources


Transport oxygen to body tissues and pick up CO2 for exhalation

Meat (esp. red) and poultry, seafood, wholegrain breads & cereals, some green leafy vegetables



Supports bone & teeth formation and remodelling, assists muscle contraction, blood clotting, cardiovascular health & iron metabolism


Milk & dairy products, wholegrain breads & cereals,


Helps conduct nerve impulses, is vital for muscle contraction, helps maintain normal heart rhythm and regulates fluid balance


Green leafy vegetables, lean meat, some fruits, wholegrain breads & cereals


Important for growth & neurobehavioural development, immune & sensory function and  reproduction


Lean meat and poultry, some seafood, nuts and seeds, wholegrain breads & cereals


Important for structure of bones and teeth, transmission of nerve impulses and muscle contraction

Wholegrain breads & cereals, nuts, lean meat, poultry & seafood, some fruits & vegetables



Important for energy transfer, fluid balance, nutrient uptake and the maintenance of a normal heart rhythm.


Common salt whether added to food or in processed food


Required for normal growth and development and the maintenance of normal metabolic rate

Iodised table salt, low fat milk products, eggs & seafood



Has important roles in control of thyroid hormone metabolism, reproduction and immune function


Seafood, lean meat & poultry, eggs, wholegrain breads & cereals


Has role in bone mineralisation and protects teeth from dental cavities

Fluoridated water and toothpaste


Probably the most controversial mineral is calcium. There is confusion over what the optimal intake is to achieve and maintain peak bone mass, protect from osteoporosis (brittle bones) and the subsequent risk of bone breakages. The MoH estimates that 20% of the population have an inadequate intake of calcium. Rather than encouraging supplementation, the MoH advises people to consume the recommended low fat intakes of milk & dairy products and other foods containing calcium. MoH also recommends preventing losses by minimising alcohol intake and smoking, and including regular exercise which aids calcium retention.


A mineral we in the fitness world are often interested in is iron, due to its importance in the transportation of oxygen to the body, and therefore to performance in endurance events that are largely dependant on an optimal supply of oxygenated blood to working muscles. 


According to its source, iron can be classified as ‘haem’, from meat, poultry and fish, or ‘non-haem’, from plant based foods, iron supplements and iron fortificants in food.  Approximately 20-30% of haem iron is absorbed by the body whereas only about 5% or less of non-haem iron is absorbed.  Because of this it has often been thought that vegetarians especially would be vulnerable to deficiency.  However iron deficiency is actually very low according to the MoH. 


To optimise the absorption of iron the MoH advises people to include foods high in vitamin c at mealtimes, and minimise the consumption of tea and coffee at mealtimes which hinders iron absorption.  Again the MoH only advises supplementation under medical supervision.


Supplements (as their name suggests) are only required to supplement a diet when a deficiency has been established.  As with vitamins, if the MoH’s recommendations for daily intakes of the food groups are met then so will the requirements for daily mineral intakes. 


When you read through the MoH guidelines it is very clear that supplementation (and indeed diagnosing the need for supplementation) is the domain of medical professionals and not fitness professionals. 


So what is our role in regard to micro-nutrient intakes and the use of supplements?  We should:

  • Answer our client’s questions concerning micro-nutrient intakes with sound knowledge based on MoH guidelines for healthy eating
  • Understand the MoH guidelines for daily intakes of the major food groups and help our clients to meet these guidelines
  • Where necessary work with medical professionals to ensure the nutritional needs of all our clients can be met.


I remember a prominent NZ sports doctor referring to the urine at the Olympic Games as the ‘most expensive pee in the world’; because the athletes would take every supplement available on the chance it might offer them a split second advantage.  The reality is that the body only uses what it needs and excretes the rest, hence very expensive pee!  There are probably better things to spend ones money on than unnecessary supplements, such as fresh fruit and vegetables! 


For more information on micro-nutrients, their intakes and the MoH recommendations for healthy eating follow the hyperlink to this article$File/foodandnutritionguidelines-adults.pdf

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