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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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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Amino acids are used for the
synthesis of body proteins and other metabolites, and can also be used as a source of dietary energy.
The proteins of the body are continually being broken down and resynthesised in a process called
protein turnover.
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Pellagra, a disease caused by niacin deficiency, was a major problem in the Southern states
of the US in poor Blacks and Whites whose diet consisted of maize (American corn) and little else.
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Alcohol intakes
below about 5% of dietary energy are recommended.
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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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The major adverse effect of increased sodium chloride intake is elevated blood pressure, a risk factor
for cardiovascular and renal diseases.
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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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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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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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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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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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Frank copper deficiency is rare in humans but has been
seen in certain circumstances in infants.
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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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Unlike most animals, humans and primates lack a key enzyme necessary for the biosynthesis of
vitamin C. We therefore require a dietary source.
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The main sources of folate in Australia and New Zealand are cereals, cereal
products and dishes based on cereals (about 27%) and vegetables and legumes (about 29%). Fruit
provides about 8-10%. Orange juice is contributing a greater amount than in the past due to the recent
introduction of fortification with folate.
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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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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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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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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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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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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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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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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.
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All of the necessary amino acids can be provided in the amounts needed from plant
sources.
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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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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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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 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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Amino acids are the building blocks of proteins. The essential amino acids are those that we cannot synthesise within the body, and so need to be included in the diet.
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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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Manganese is an essential element involved in formation of bone. It is also involved in the metabolism
of carbohydrate, cholesterol and amino acids.
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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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Chronically high levels of alcohol ingestion can negatively affect vitamin A status through an effect on
the liver.
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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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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.
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Chromium is involved in potentiating the action of insulin. Chromium deficiency is relatively rare.
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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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Processing of food (cutting up,
cooking etc) greatly improves availability and thus absorption of carotenoids from foods.
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Vitamin B6 acts as a coenzyme in the metabolism of amino acids, glycogen
and sphingoid bases.
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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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Osteoporosis is one of the major causes of morbidity amongst older Australians and New Zealanders,
particularly postmenopausal women.
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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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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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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.
|
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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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.
|
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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If sunlight exposure is adequate, dietary vitamin D can
be considered unnecessary.
|
Folic
acid supplementation in pregnancy can reduce both the occurrence and recurrence of neural tube
defects in the newborn.
|
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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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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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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Iron is a component of a number of proteins including haemoglobin. Haemoglobin is important for transport of oxygen to tissues
throughout the body.
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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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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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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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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.
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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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Calcium is stored in the teeth and bones, where it
provides structure and strength.
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Adequate intake of
vitamin B 12 is essential for normal blood function and neurological function.
|
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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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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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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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.
|
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 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 K deficiency causes a bleeding tendency through a lack of activity of the procoagulant
proteins.
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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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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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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.
|
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.
|
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.
|
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.
|
Thiamin is a water-soluble substance that occurs in free or phosphorylated forms in most plant and
animal tissue.
|
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.
|
Saturated fatty
acids have both physiological and structural functions. They can be synthesised by the body so are not
required in the diet.
|
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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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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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.
|
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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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.
|
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
|
The reported health effects of chronic mild dehydration and poor fluid intake include
increased risk of kidney stones, urinary tract cancers, colon
cancer as well as diminished physical
and mental performance.
|
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.
|
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.
|
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.
|
The major sources of Riboflavin are milk and milk products and fortified breads and cereals.
|
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.
|
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.
|
Clinical deficiency of Vitamin B6 is rare. The symptoms of deficiency include seborrhaeic dermatitis, microcytic anaemia, convulsions, and
depression and confusion
|
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
|
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.
|
Magnesium is required for mitochondria to carry out oxidative phosphorylation. It plays a role in regulating potassium fluxes and in the metabolism of calcium.
|
Dental caries is often identified
as the limiting factor in terms of an upper intake of cariogenic sweeteners, even in an era of fluoride
exposure.
|
Because of its role in energy metabolism, niacin
requirements are, to some extent, related to energy requirements.
|
The amount of protein in the diet is a
factor contributing to the efficiency of zinc absorption as zinc binds to protein.
|
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.
|
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
|
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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