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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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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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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Phosphorus is the second most abundant inorganic element in the body and is a part of many important
compounds. Phosphorus as phosphate is a major buffer of acid in urine by
virtue of its monovalent, divalent and trivalent forms.
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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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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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In teeth that have erupted, ingestion of fluoride reduces caries due
to reduced acid production by bacteria and increased enamel remineralisation in acidogenic challenge.
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Calcium is required for the normal development and maintenance of the skeleton as well as for the
proper functioning of neuromuscular and cardiac function.
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The main source of vitamin E is fats and oils. It is also found in some vegetables, in the fats of meat,
poultry and fish and, to lesser degrees, in cereals and dairy foods.
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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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Fluoride has a unique ability to stimulate new
bone formation and as such has been used as an experimental drug for the treatment of osteoporosis
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Vitamin B 12 deficiency can produce haematological, neurological or gut symptoms. The underlying problem is interference with DNA synthesis leading to production of
abnormally large erythrocytes.
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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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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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Haem iron is more bioavailable to humans than the non-haem. The presence of other nutrients such as vitamin C and organic acids such as citric, lactic or malic acid
can increase the absorption of non-haem iron.
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In Australia, the National Nutrition Survey of 1995 indicated that 45% of dietary fibre comes from breads
and other cereal foods, 10% from fruit and 30% from vegetables.
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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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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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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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In general, zinc absorption from a diet high in animal protein will be greater than from a diet rich in plant
derived proteins. The requirement for dietary zinc may be as much as 50% greater
for vegetarians, particularly strict vegetarians whose major staples are grains and legumes.
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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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Vitamin K deficiency causes a bleeding tendency through a lack of activity of the procoagulant
proteins.
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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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Niacin is involved in energy metabolism,
DNA repair and calcium mobilisation. It functions as part of the intracellular respiration system and with
enzymes involved in oxidation of fuel substrates.
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Vitamin B 12 is required for the
synthesis of fatty acids in myelin and, in conjunction with folate, for DNA synthesis.
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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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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.
|
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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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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Because of its role in energy metabolism, niacin
requirements are, to some extent, related to energy requirements.
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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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Osteoporosis is one of the major causes of morbidity amongst older Australians and New Zealanders,
particularly postmenopausal women.
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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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Magnesium is a cofactor for more than 300 enzyme systems and is involved in
both aerobic and anaerobic energy generation and in glycolysis.
|
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.
|
Alcohol intakes
below about 5% of dietary energy are recommended.
|
Folic
acid supplementation in pregnancy can reduce both the occurrence and recurrence of neural tube
defects in the newborn.
|
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.
|
The retinal form of vitamin A is required by the eye to change light to neural signals for vision
|
Sodium is found in most foods as sodium chloride, generally known as 'salt'. Sodium is a cation needed to maintain extracellular volume and serum osmolality.
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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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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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To achieve iron balance, adult
men need to absorb about 1 mg/day and adult menstruating women about 1.5 mg/day, although
this is highly variable. Towards the end of pregnancy, the absorption of 4-5 mg/day of iron is necessary.
Requirements are higher during periods of rapid growth in early childhood and adolescence
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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.
|
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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Functional indicators of iron deficiency may include reduced physical work capacity, delayed
psychomotor development in infants, impaired cognitive function, impaired immunity and adverse
pregnancy outcomes.
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The main monounsaturated fatty acid is oleic acid with one double bond. Olive, canola and peanut oils
are rich in oleic acid. The monounsaturates are synthesised by the body and are thus not required
in the diet.
|
Phosphorus is so widespread in the food supply that
dietary phosphorus deficiency is extremely rare, the exception being long-term, severe food restriction.
|
Dehydration of as little as 2% loss of body weight results in impaired physiological responses and
performance.
|
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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The parent fatty acid of the
n-3 series is alpha-linolenic acid (ALA). ALA primarily functions as a precursor for the synthesis of EPA, which in turn forms DHA (EPA and DHA are Long-Chain n-3 fatty acids)
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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.
|
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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Beri beri is one of two distinct major diseases from deficiency of thiamin. In acute
beri beri there is a high output cardiac failure, warm extremities, bounding pulse, oedema and cardiac
enlargement.
|
In excess, Manganese can interfere with iron absorption.
Manganese is excreted rapidly into the gut through bile and lost primarily in faeces. Low bile excretion can therefore increase the potential for manganese toxicity
|
The amount of energy needed for the internal bodily functions necessary for life (eg cell metabolism, synthesis and metabolism of enzymes and hormones) is called the basal metabolic rate (BMR). BMR represents about 45-70% of daily energy expenditure.
|
Choline is widely distributed throughout the food supply. Milk, liver, eggs and peanuts are particularly good sources. Wheat germ and
dried soybeans are good sources of choline for vegetarians.
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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.
|
Molybdenum is involved in catabolism of sulphur amino acids and heterocyclic compounds
including purines and pyridines.
|
High intakes of n-6 polyunsaturated fats have been associated with blood lipid profiles
associated with a lower risk of coronary heart disease.
|
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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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.
|
The primary role of dietary carbohydrate is the provision of energy to cells, particularly the brain that
requires glucose for its metabolism.
|
Inadequate folate intake leads to changes in bone marrow and other rapidly dividing tissues. As depletion progresses, eventually, full-blown anaemia results in weakness, fatigue, irritability and palpitations.
|
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.
|
Vitamin B6 acts as a coenzyme in the metabolism of amino acids, glycogen
and sphingoid bases.
|
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.
|
Although there is a lack of direct evidence, it is thought that a relationship exists between thiamin
requirement, energy supply and energy expenditure.
|
Manganese is an essential element involved in formation of bone. It is also involved in the metabolism
of carbohydrate, cholesterol and amino acids.
|
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.
|
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.
|
Retinoic acid plays an important role in
embryonic development, particularly in the development of the spinal cord and vertebrae, limbs, heart,
eye and ears
|
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.
|
It has been hypothesised that poor
chromium status contributes to the incidence of impaired glucose tolerance and type II diabetes which
has led to interest in a potential role for chromium supplements in type II diabetes.
|
Clinical deficiency of Vitamin B6 is rare. The symptoms of deficiency include seborrhaeic dermatitis, microcytic anaemia, convulsions, and
depression and confusion
|
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
|
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.
|
Copper is widely distributed in foods with nuts and seeds being major
contributors. Wheat bran cereals and whole grain products are also good sources.
|
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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Dietary intake of iron at levels found in some supplements can decrease zinc absorption, which is
of particular concern in the management of pregnancy and lactation.
|
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.
|
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.
|
Magnesium is required for mitochondria to carry out oxidative phosphorylation. It plays a role in regulating potassium fluxes and in the metabolism of calcium.
|
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.
|
Iron is a component of a number of proteins including haemoglobin. Haemoglobin is important for transport of oxygen to tissues
throughout the body.
|
Processing of food (cutting up,
cooking etc) greatly improves availability and thus absorption of carotenoids from foods.
|
An increase in saturated fat intake leads to an increase in harmful LDL (Low Density Lipoprotein) cholesterol, which leads to a greater risk of Coronary Heart Disease.
|
Omega-3 fatty acids are so named due to a double chemical bond at the n-3 position in the molecule. Humans are unable to insert a double
bond at the n-3 position of a fatty acid and thus require a dietary source.
|
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.
|
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.
|
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.
|
Calcium is stored in the teeth and bones, where it
provides structure and strength.
|
Frank copper deficiency is rare in humans but has been
seen in certain circumstances in infants.
|
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.
|
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.
|
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.
|
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.
|
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.
|
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
|
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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