Vitamin D occurs in two forms. One is produced by the action of sunlight on skin (D 3 or cholecalciferol)
and the other is found in a limited range of foods (D 2 or ergocalciferol).
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Vitamin B 12 can be stored in the liver
for many years.
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Copper is widely distributed in foods with nuts and seeds being major
contributors. Wheat bran cereals and whole grain products are also good sources.
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With current food supplies
and patterns of eating, it is almost impossible to obtain sufficient vitamin D from the diet alone.
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Wernicke's encephalopathy is one of two distinct major diseases from deficiency of thiamin. It is usually seen in people who have been drinking alcohol heavily and eating very little. (Alcohol requires thiamin for its metabolism). The characteristic feature is paralysis of one or more of the external
movements of the eyes.
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The major dietary sources
of vitamin K are green leafy vegetables such as kale, spinach, salad greens, cabbage, broccoli and
brussel sprouts and certain plant oils such as soybean and canola oils.
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Processing of food (cutting up,
cooking etc) greatly improves availability and thus absorption of carotenoids from foods.
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Chromium is involved in potentiating the action of insulin. Chromium deficiency is relatively rare.
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Sodium is important for maintaining the membrane
potential of cells and for active transport of molecules across cell membranes.
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Protein occurs in all living cells and has both functional and structural properties. Amino acids,
assembled in long chains, are the building blocks of protein.
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Zinc is a component of various enzymes that help maintain structural integrity of proteins and
regulate gene expression. The biological function of zinc can
be catalytic, structural or regulatory.
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Magnesium is widely distributed in the food supply in both plant and animal foods. Most green
vegetables, legumes, peas, beans and nuts are rich in magnesium, as are some shellfish and spices.
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Deficiency of Vitamin D results in inadequate mineralisation or demineralisation of the skeleton.
This can lead to rickets in young children, causing bowed legs and knocked knees. In adults, deficiency can lead to
increased bone turnover and osteoporosis.
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The best-known role for vitamin
K is the maintenance of normal blood coagulation. The vitamin K-dependent coagulation proteins that are made in the liver have both coagulant and anticoagulant properties.
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The retinal form of vitamin A is required by the eye to change light to neural signals for vision
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Recommended carbohydrate intake in adults and children is 45-65% of
dietary energy intake. There is believed to be an increased risk for Coronary Heart Disease at high carbohydrate intakes (>65%) and increased risk of obesity with low carbohydrate, high fat intakes (<45%).
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Zinc is widely distributed in foods. Meats, fish and poultry are the major contributors to the diet
but cereals and dairy foods also contribute substantial amounts.
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Vitamin B6 is found in a wide range of foods including organ meats, muscle meats, breakfast cereals,
vegetables and fruits.
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Vitamin C, in addition to providing its own benefits, interacts with other nutrients. It aids in the absorption of iron and copper, the maintenance of glutathione in the reduced form, the regeneration, or sparing, of alpha-tocopherol and the
stabilisation of folate.
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Pantothenic acid is
involved in fatty acid metabolism. It is essential to almost all forms of life
and is widely distributed in foods. Chicken, beef, potatoes, oat-based cereals, tomato products, liver,
kidney, egg yolks and whole grains are major sources in western diets.
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Calcium intake throughout life is a major factor affecting the
incidence of osteoporosis, however other factors, notably adequate vitamin D status and exercise, also
play a role.
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Because of its role in energy metabolism, niacin
requirements are, to some extent, related to energy requirements.
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People with hypertension, diabetes and chronic kidney disease and greater age tend to be more
sensitive to the blood pressure raising effects of sodium chloride intake. Being overweight also appears to
increase susceptibility.
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Retinoic acid plays an important role in
embryonic development, particularly in the development of the spinal cord and vertebrae, limbs, heart,
eye and ears
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Magnesium is required for mitochondria to carry out oxidative phosphorylation. It plays a role in regulating potassium fluxes and in the metabolism of calcium.
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Dehydration of as little as 2% loss of body weight results in impaired physiological responses and
performance.
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Phosphorus is widely distributed in natural foods and also found in food additives as phosphate salts,
used in processing for retaining moisture, smoothness and binding.
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The major role of vitamin E is to protect polyunsaturated fatty acids from oxidation. It acts as
an anti-oxidant in the lipid phase of cell membranes.
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Phosphate helps to protect blood systemic acid/base balance, acts as a temporary store and transport mechanism for energy and helps in activating
catalytic proteins.
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Symptoms of biotin deficiency include dermatitis, conjunctivitis,
alopecia and Central Nervous System (CNS) abnormalities, including developmental delay in infants. People with
genetic biotinidase deficiency will have increased requirements.
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Calcium is stored in the teeth and bones, where it
provides structure and strength.
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All of the necessary amino acids can be provided in the amounts needed from plant
sources.
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Water is defined as an essential nutrient because it is required in amounts that exceed the body's ability
to produce it. All biochemical reactions occur in water.
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The primary role of dietary carbohydrate is the provision of energy to cells, particularly the brain that
requires glucose for its metabolism.
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Thiamin plays an essential role in the supply of energy to the tissue, in carbohydrate metabolism
and in the metabolic links between carbohydrate, protein and fat metabolism.
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In the last decade, there has been
an exponential rise in publications on health benefits of omega-3 polyunsaturated fatty acids, particularly the longer chain
omega-3s, EPA, DPA and DHA.
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Phosphorus is so widespread in the food supply that
dietary phosphorus deficiency is extremely rare, the exception being long-term, severe food restriction.
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Manganese deficiency in animals is associated with impaired growth, reproductive function and
glucose tolerance as well as changes in carbohydrate and lipid metabolism. Manganese deficiency also interferes with
skeletal development.
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Frank copper deficiency is rare in humans but has been
seen in certain circumstances in infants.
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Potassium blunts the effect of sodium chloride on blood pressure, mitigating salt sensitivity and lowering urinary calcium excretion.It has been hypothesised that high protein-low potassium diets could induce a low-grade metabolic acidosis that could induce demineralisation of bone, osteoporosis and kidney stones.
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Low intakes of calcium have been associated with a condition of low
bone density called osteoporosis which is quite common in western cultures and which often results in
bone fracture.
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Vitamin E deficiency symptoms have never been described. Deficiency occurs only as a result of genetic abnormalities, fat malabsorption syndrome, or protein-energy malnutrition.
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Copper deficiency results in defects in connective tissue that lead to vascular and skeletal problems, and
anaemia related to defective iron metabolism. It can also affect the central nervous system and the immune and cardiovascular systems, notably in infants.
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Potassium is the major cation of intracellular fluid and an almost constant component of lean body
tissues. Potassium requirements can be affected by climate and physical activity, the use of diuretics, and the
intake of other electrolytes, notably sodium.
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There is some evidence that choline may improve cognitive function and memory at all ages and,
by extension, choline deficiency has been implicated in poor performance for groups such as the
institutionalised elderly.
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The potential role of selenium in cancer prevention has been assessed in humans. One prospective
study of 34,000 men using a nested case-control study design showed that high selenium intakes were
protective against prostate cancer.
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Avidin, a
protein found in raw egg white, binds biotin in the gut and prevents its absorption. Although rare, biotin deficiency has been seen in people who consume raw egg white over long
periods.
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Chronically high levels of alcohol ingestion can negatively affect vitamin A status through an effect on
the liver.
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Iron in foods can come in two general forms - as
haem or non-haem iron. Iron from animal food sources such as meat, fish and poultry may be either
haem or non-haem whereas the iron in plant sources such grains and vegetables is non-haem.
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Magnesium is a cofactor for more than 300 enzyme systems and is involved in
both aerobic and anaerobic energy generation and in glycolysis.
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Calcium balance deteriorates at menopause. In post menopausal women, there is evidence that a high
calcium intake will slow the rate of bone loss and may reduce the risk of fracture.
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If sunlight exposure is adequate, dietary vitamin D can
be considered unnecessary.
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Molybdenum is involved in catabolism of sulphur amino acids and heterocyclic compounds
including purines and pyridines.
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Folate is essential for DNA synthesis. Without folate,
living cells cannot divide. The need for folate is higher when cell turnover is increased, such as in fetal
development. It is also involved in amino acid interconversions.
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Iodine is an integral component of a key thyroid hormone. The thyroid hormones are required for normal growth and development of tissues such as the central nervous system and have a broader role in maturation of the
body as a whole. They are important for energy production and oxygen consumption in cells thereby helping to maintain the body's metabolic rate.
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Folic
acid supplementation in pregnancy can reduce both the occurrence and recurrence of neural tube
defects in the newborn.
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Various expert groups have made consensus recommendations for
consumption of ALA and/or the very long chain omega-3s.
The evidence is strongest for reduction of Cardio Vascular Disease risk by EPA and DHA.
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Pantothenic acid deficiency is very rare. Symptoms of a deficiency of Pantothenic acid include irritability, restlessness, fatigue, apathy, malaise, sleep disturbance, nausea,
vomiting and cramping, numbness and staggering gait, as well as hypoglycaemia and increased insulin
sensitivity.
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Adequate dietary fibre is essential for proper functioning of the gut and has also been related to risk
reduction for a number of chronic diseases including heart disease, certain cancers and diabetes.
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Alcohol intakes
below about 5% of dietary energy are recommended.
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Vitamin C is found in high concentrations in gastric juices where it may prevent the formation of N-nitroso-compounds, which are potential
mutagens.
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Deficiency of niacin causes the disease pellagra which is associated with inflammation of the skin on
exposure to sunlight, resembling severe sunburn except that the affected skin is sharply demarcated. Pellagra is the disease of 'three Ds', namely dermatitis, diarrhoea and (in
severe cases) delirium or dementia.
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For infants, breast-feeding is recommended, as the iron in formula is much less bioavailable
(generally only 10-20% as available as that in breast milk)
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Selenium functions as an antioxidant and in redox reactions and thyroid metabolism. It is thought to have a role in cellular antioxidant systems.
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Riboflavin and its derivatives are
important for the body's handling of some other nutrients including conversion of vitamin B-6 to its
bioactive form, and conversion of tryptophan to niacin.
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Ingestion of fluoride in the pre-eruptive development of teeth has the effect of reducing caries due to
uptake of fluoride by enamel crystallites and formation of fluorohydroxyapatite.
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Molybdenum is found in plant foods and reflects the soil content in which they grow. Legumes are
major contributors of molybdenum in the western diet, as are grain products and nuts.
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Saturated fatty
acids have both physiological and structural functions. They can be synthesised by the body so are not
required in the diet.
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The parent n-3 fatty acid, ALA, aids in the formation of EPA and DHA, but the conversion of ALA to EPA and DHA is limited, creating the need for a dietary source
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The environment within the gastrointestinal
tract, which can be affected by other dietary constituents, markedly influences the solubility and
absorptive efficiency of zinc.
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Cholesterol comes in 2 main forms: LDL (Low Density Lipoprotein) Cholesterol and HDL (High Density Lipoprotein) Cholesterol. LDL Cholesterol is harmful, and is associated with an increased risk of Coronary Heart Disease(CHD). HDL Cholesterol is beneficial, and reduces the risk of CHD.
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Molybdenum is absorbed very efficiently over a wide range of
intakes. No clear deficiency syndrome has been seen in animals even with
major reductions in molybdoenzymes.
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Selenium is found in a range of foods, the content of which varies with geographic sources of the
food. Soil concentrations can range from <0.01 μg/g to >1,000 μg/g with plant food content reflecting
this range.
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Fluoride is a normal constituent of the human body, involved in the mineralisation of both teeth and
bones. Because of its role in the prevention of dental caries, fluoride
has been classified as essential to human health.
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Riboflavin deficiency can
result in raised plasma levels of homocysteine that are associated with increased cardiovascular risk. The classic disease of riboflavin deficiency is ariboflavinosis, which manifests in growth disturbances, seborrhaeic dermatitis, inflammation of the oral mucosa and tongue, cracks at the corner of the mouth
and normocytic anaemia.
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Saturated fats are found mainly in animal-based foods. They are the
main type of fatty acids found in milk, cream, butter and cheese, meats from most of the land animals,
palm oil and coconut oil as well as in products such as pies, biscuits, cakes and pastries.
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Choline is a precursor for a number of compounds including the neurotransmitter acetylcholine. It is also important for lipid and cholesterol transport and metabolism if methyl groups.
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Clinical deficiency of Vitamin B6 is rare. The symptoms of deficiency include seborrhaeic dermatitis, microcytic anaemia, convulsions, and
depression and confusion
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A 10-year study of skin cancer in the US initially found no effect of supplemental selenium at 200 μg/
day on basal cell or squamous cell skin cancer, but significant reduction in total cancer and cancers of
the prostate, lung and colorectum.
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Long Chain (LC) n-3 fatty acids (EPA, DHA, and DPA) are found predominantly in oily fish such as mackerel,
herrings, sardines, salmon and tuna and other seafood.
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Most of the early signs of deficiency are neurologic or neuromuscular defects that may develop with time into anorexia, nausea, muscular
weakness, lethargy, weight loss, hyper-irritability, hyper-excitability, muscular spasms, tetany and finally
convulsions.
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Vitamin K deficiency causes a bleeding tendency through a lack of activity of the procoagulant
proteins.
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Energy is not a nutrient but is required in the body for metabolic processes, physiological functions,
muscular activity, heat production, growth and synthesis of new tissues.
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Cereal products provide about one-third of the intake of manganese and beverages (tea) and vegetables
are the other major contributors.
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The nine indispensable or essential amino acids, defined as those that the body is unable to synthesise
from simpler molecules, are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine,
tryptophan and valine.
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The major function of Vitamin D in humans is to enhance the ability of the small intestine to absorb calcium from the diet. Vitamin D also plays a role
in enhancing absorption of phosphorus from the diet.
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Vitamin B6 acts as a coenzyme in the metabolism of amino acids, glycogen
and sphingoid bases.
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Dietary fibre is the most effective treatment for all forms of constipation due to its influence on faecal
bulk and consistency.
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The dietary essentiality of choline was demonstrated in a study of healthy men with
normal folate and vitamin B 12 status who developed liver damage with lower plasma choline and
phosphatidylcholine concentrations when fed a choline-deficient diet.
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Iodine was one of the first trace elements to be identified as essential. In the 1920s it was shown
to be an integral component for normal growth and metabolism. Soon after, it was recognised as a key regulator of important cell processes.
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A seasonal variation in vitamin D levels occurs in Australia. In the
Geelong Osteoporosis Study, the mean vitamin D levels for winter were 58 nmol/L compared with
70 nmol/L in summer
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Linoleic Acid, the most common Polyunsaturated fatty acid, is involved in the regulation of gene expression. Linoleic Acid is also found as a structural component of cell membranes and is important in
cell signalling.
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Iron absorption is about 18% from a mixed western diet including animal foods and about 10% from a
plant-based diet; so vegetarians and vegans need higher intakes.
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Vitamin C deficiency causes scurvy, symptoms of which include skeletal and vascular lesions with
gingival changes, pain in the extremities, haemorrhage, oedema, ulcerations and death.
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Vitamin C is a reducing agent (antioxidant). In humans, vitamin C acts as an electron donor for eight enzymes,
of which three are involved in collagen hydroxylation, and two are involved in carnitine biosynthesis.
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Vitamin A is a fat-soluble vitamin which helps maintain normal reproduction, vision and immune
function. Vitamin A intakes or requirements are generally expressed in terms of retinol equivalents (RE). Retinol is required for the integrity of epithelial cells throughout the body.
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Thiamin is a water-soluble substance that occurs in free or phosphorylated forms in most plant and
animal tissue.
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Water fills the spaces in and between cells and helps
form structures of large molecules such as protein and glycogen. Water is also required for digestion,
absorption, transportation, dissolving nutrients, elimination of waste products and thermoregulation.
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The amount of protein in the diet is a
factor contributing to the efficiency of zinc absorption as zinc binds to protein.
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Vitamin C is found widely in fruits and vegetables. Fruits such as blackcurrants, guava, citrus, and
kiwi fruit and vegetables such as broccoli and sprouts are good sources.
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