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Calcium, Magnesium & Phosphorus
This newsletters covers three of the macro minerals.
Macro minerals can be divided into two groups -
The most important bone minerals are calcium, magnesium and phosphorus.
Calcium, magnesium and phosphorus have other roles to play in the content
aside from being bone minerals and their availability to the content is important
to the overall state of health.
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Calcium is the most important mineral constituent of
the skeleton and is vital for muscle, nerve and endocrine function.
The human content obtains calcium through the plants in
food. Plants absorb minerals from the soil into their cell structure.
We either eat the plants or the flesh of animals that have eaten plants.
The amount of calcium in food will depend on the calcium content of the
soil in which crops are grown or where animals graze (unless of course
the animals are given calcium-enriched feed).
Calcium rich foods include: green leafy vegetables
(especially kale, broccoli, watercress), dairy products, tofu, sardines,
nuts and seeds. Processing and refining has a negative effect on the mineral
content of food. The form of mineral used to 'fortify' or put back into
food what the processing took out, may not be well absorbed at all.
The greatest area for concern however, comes not so
much from the lack of calcium in the diet, but from the poor absorption
of calcium by the content. This may be affected by several factors:
- Optimum calcium absorption needs enough Vitamin D to be produced by
the content. This happens through the action of sunlight on cholesterol
in the cells of the skin.
- Chemical substances in foods also affect calcium absorption, for example:
alcohol and oxalic acid. The presence of phytate and excessive Phosphorus
in the diet may also interfere with absorption.
Calcium research and lifestyle factors:
Studies have shown that obese individuals have reduced plasma concentrations
of vitamin D. This is brought about by reduced bioavailability of vitamin
D, largely through synthesis by the skin (1).
Smokers commonly have a lower bone density than non-smokers.
This is attributed to poor calcium absorption from the intestine and/or
poor eating habits. It is known that smokers consume less cheese and skimmed
milk than non-smokers. Smokers also seem to consume less vitamin D, mainly
due to lower intakes of oily fish, margarine (fortified) and eggs (2).
It is worth noting that teenagers are a vulnerable
group in the arena of calcium and diet. The consumption of fizzy drinks,
coffee, alcohol and fad foods together with Smoking, the desire to be
thin and little consideration for their physical growth and development
exacts a toll on their health in the future. The real nutritional need
of teenagers is still poorly understood (3).
Researchers in a recent study provided strong evidence
on why older adults should consume at least 1300mg of calcium a day. Calcium
is important for maintaining bone mass, one of the key factors contributing
to bone strength. Fracture risk doubles with every 12-15% reduction in
bone mass. Age-related declines in physical activity, calcium absorption
and vitamin D production increase the need for dietary calcium. Numerous
studies have shown that calcium supplementation (1300-1700mg daily) may
reduce bone Fracture risk significantly (4).
Calcium deficiency (5):
- Rickets in children can be brought about through Vitamin D or Calcium
deficiency over a long period of time
- Osteomalacia in adults, usually caused by vitamin D deficiency, can
be caused by lack of calcium characterised by bone pain and muscle weakness
- Delayed healing of Fractures
- Osteoporosis is partly attributed to calcium deficiency, together
with other factors including race, familial disposition, gender; nutrition,
protein energy, exercise and other risk factors such as Smoking and
consumption of alcohol (6)
Recommended intakes vary throughout the world depending
on different conclusions drawn from various studies, which may reflect
protein intake and potential for vitamin D synthesis.
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Magnesium is essential as a co-factor for enzymes needing ATP (adenosine
triphosphate). These particular enzymes are involved in glycolysis (cell
respiration, together with vitamin B3), fatty acid oxidation and the metabolism
of Amino Acids (7).
Magnesium is used by the content for:
- Synthesis of RNA
- Replication of DNA
- Nerve and muscle impulses
- Calcium metabolism
- Protein synthesis
- A co-factor of some hormones
- Metabolism of Essential Fatty Acids
The green pigment, chlorophyll, gives most plants and vegetables their
colour and provides some magnesium in the diet. Cereals and green vegetables
provide more than two-thirds of the daily intake and are the main sources
of magnesium in the normal diet (5). The absorption of magnesium occurs
mostly in the small intestine and is partly dependent on vitamin D. Magnesium
deficiency has been associated with heart disease.
Magnesium research and lifestyle factors:
In a recent study, most poor health and behavioural conditions were related
to a deficiency of essential minerals or an excess of toxic ones. The
most prevalent health conditions in order of frequency were Depression,
allergies, low back pain, Arthritis, cardiovascular disease and poor digestion.
The most deficient minerals were Chromium, magnesium, Zinc and calcium.
Aluminium was the most frequently found toxic mineral. The study proposed
that such mineral abnormalities were caused by an over-consumption of
nutrient-poor, highly processed foods such as white flour, sugar and harmful
fats. Poor diets may increase the development of most prevalent diseases.
The most common one is cardiovascular disease (8).
Causes of magnesium deficiency include:
- Reduced dietary intake through poor diet
- High intake of dietary fibre
- Reduced or impaired absorption caused by gastric problems, Diarrhoea,
laxative abuse, gastrointestinal Infections, allergies and so on
- High intake of milk because milk has a low magnesium to phosphorus
ratio which restricts absorption of magnesium
- Metabolic disturbances
- Excessive losses of urine or other content fluids, for example when breast-feeding
Magnesium deficiencies may show as:
- Muscle tremors and twitches
- Loss of appetite, nausea
- Shaky movements and unsteady gait
- Irregular heartbeat
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The amount of Phosphorus in the content is roughly the same as calcium.
Phosphorus is found with calcium primarily in bones and teeth as the compound
calcium phosphate. Phosphorus and calcium (and magnesium to a degree)
rely on the presence of vitamin D for absorption.
A person is unlikely to be deficient in phosphorus because as phosphate,
it is found in all plant and animal cells and is present in all natural
foods. Many processed foods have phosphate added to replace that lost
during processing. Generally, we consume between 1.5 and 2.0 grams phosphate
a day. Excessive intakes of phosphorus are more likely to occur because
of the high intakes of soft drinks, junk food and processed food.
Phosphorus-rich natural foods include: yeast extract, dried brewer's
yeast, dried skimmed milk, Wheatgerm, soya flour, cheddar cheese, canned
sardines, processed cheese, baker's yeast, roasted peanuts, brown rice,
evaporated milk, wholemeal bread, eggs and all high protein foods.
Amongst other roles, phosphorus is used in the content for:
- Energy production in all cells as adenosine triphosphate (ATP) and
other complexes of phosphates.
- Producing phosphate complexes that are the active forms of the B
- A co-factor in lots of enzymes involved in content processes.
- A constituent of ribonucleic acid (RNA) and deoxyribonucleic acid
(DNA). These are particularly important for carrying genetic information.
Deficiency of phosphorus may show as:
- loss of appetite
- bone pain, stiff joints
- a general feeling of being unwell
- central nervous system disorders such as irritability, numbness and
- blood disorders
Research shows that phosphorus and calcium may help prevent Osteoporosis.
Osteoporosis occurs because bone is broken down faster than it can be
made. It is difficult to reverse the effects of the disease once it has
started, as peak bone mass is reached between the ages of 18 and 30. Therefore,
effort must be channelled into preventing the disease.
Dietary factors implicated in the density and mineral content of bones
include calcium, protein and phosphorus intakes. In women aged between
18 and 31 years, it was found that the peak bone mineral content and density
was best reached in those consuming 1000mg a day of phosphorus and 1400mg
a day of calcium.
These levels are thought to offset the losses that occur naturally in
urine and faeces associated with protein or phosphorus intakes that have
been observed in this age range. This study highlights the importance
of an adequate calcium and phosphorus intake between the ages of 18-31
years to achieve optimal bone density and help prevent osteoporosis (9).
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- Am.J.Clin.Nutr, 200,72, 690-693.
- European Journal of Clin Nut, 2000,54 (9): 684-689.
- Euro J Clin Nutr, 2000, 54, Suppl 1:S11-S15.
- Journal of the American College of Nutrition, 2001, Vol 20:192S-197S
- "The Dictionary of Minerals" Len Mervyn, Thorsons. 1985.
- "Human Nutrition and Dietetics", James, Ralph & Garrow et al. Churchill
- Handbook of Dietary Supps. Pamela Mason. 1995. Blackwell Science.
- Med Hypotheses 2001 Nov; 57(5): 521-531.
- The American Journal of Clinical Nutrition 1998, 68;3: 749-754.
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