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What is it?
Iron is an essential
mineral and an important component of proteins involved in oxygen
transport and metabolism.
Functions
- what does it do?
Haemoglobin
and Myoglobin. Iron
forms part of the haemoglobin in red blood cells and myoglobin
in muscle cells. Haemoglobin is used to transport oxygen from
the lungs to the cells via the bloodstream. It also assists
in the return of some carbon dioxide from the cells to the lungs
to be breathed out. Myoglobin carries the oxygen in the
muscle, and thereby facilitates physical work.
Other
functions. Iron
forms part of many enzymes, some proteins, and other compounds
used by the cells in energy production. Iron is also thought
to be important for optimal brain function and development as
well as immune function.
Requirements
- How much do we need?
|
|
| |
Recommended
Dietary Allowance*
(µg/day RAE) |
| Life-Stage
(years) |
Males |
Females |
| 0
- 0.5 |
0.27a |
0.27a |
| 0.5
- 1 |
11 |
11 |
| 1
- 3 |
7 |
7 |
| 4
- 8 |
10 |
10 |
| 9
- 13 |
8 |
8 |
| 14
- 18 |
11 |
15 |
| 19
- 50 |
8 |
18 |
| Ages
51+ |
8 |
8 |
| Life-Stage
(years) |
Pregnancy |
Lactation |
| 18
and younger |
27 |
10 |
| 19
- 30 |
27 |
9 |
| Ages
31 - 50 |
27 |
9 |
*The
Recommended Dietary Allowance (RDA) is the average daily
dietary intake level that is sufficient to meet the nutrient
requirements of nearly all (97-98%) healthy individuals
in each life-stage and gender group.
aAdequate Intakes (AI) are used as no RDA is established.
The AI is a recommended daily intake
level based on observed or experimentally determined approximations
of nutrient intake by a group of healthy people who are
assumed to be maintaining an adequate nutritional state. |
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Sources
- Where is it found?
| There
are two forms of dietary iron: haeme and non-haeme. Haeme
iron is found in meat, fish, and poultry, and is absorbed
more efficiently by your body than non-haeme iron, which
has a different structure. Non-haeme iron is provided mainly
by foods of plant origin such as vegetables, grains,
and other plant foods. Flours, cereals, and grain products
that are enriched or fortified with iron are good dietary
sources of non-haeme iron. Consuming
haeme and non-haeme iron together increases non-haeme
iron absorption. Vitamin C can modestly increase non-haeme
absorption; therefore, consuming vitamin C rich foods
is particularly desirable, if dietary intake of iron is
inadequate or the blood iron is low.
Several factors
interfere with iron absorption.
- Phytic
acid and other compounds in grain fibres
- Oxalic
acid in vegetables
- Polyphenols
(tannins) found in tea
- Zinc,
and high-dose calcium supplements
|
|
|
|
| Food
Groups |
Food
Sources |
| Nutrient
Density |
| High |
Medium |
Low |
|
| Meat,
poultry, fish, dry beans, eggs, and nuts |
Beef,
Beans, Seafood, Organ Meats, Tofu |
| Bread,
cereals, rice and pasta |
Whole
grains, Enriched grains, Wheat germ, Oatmeal |
| Vegetables |
Spinach,
Peas, Potatoes, Green beans, Broccoli |
| Fruit |
Peaches,
Prune juice, Dried apricots |
| Fats,
oils, and sweets |
Enriched
pastas |
| Milk,
yoghurt and cheese |
|
|
|
Deficiency
- When you have
too little
The World Health
Organization (WHO) considers iron deficiency to be the most
common nutritional disorder in the world. The WHO estimates
66-80% of the world’s population (as many as 4-5 billion people),
may be iron deficient. Over 30% (2 billion people) of the world’s
population is anaemic, mainly due to iron deficiency, and, in
developing countries, iron deficiency may be aggravated by malaria
and worm infestations.
Iron deficiency
occurs when blood and storage levels of iron are low, and the
blood haemoglobin level falls below normal. It may
result from a low dietary intake, inadequate intestinal absorption,
excessive blood loss, and/or increased needs. Women of childbearing
age, pregnant women, older infants and toddlers, and teenage
girls are at greatest risk of developing iron deficiency anaemia
because they have the greatest needs.
| Anaemia.
Generally refers
to a decrease in the oxygen-carrying capacity of the blood
caused by a deficiency in red blood cells. |
Toxicity
-
When you have too much
Iron overload can
be serious because it can easily lead to toxic symptoms. A large
single dose of iron of 60 milligrams can be life-threatening
to a 1-year old. Doses greater than the RDA, over an long period
should be taken under the supervision of a doctor. Individuals
with blood disorders who require frequent blood transfusions
are also at risk of iron overload and should not take iron supplements.
Haemochromatosis.
Iron overload is also the underlying cause of haemochromatosis,
a genetic disease. Individuals with haemochromatosis absorb
iron very efficiently, which can result in a build up of excess
iron in organs and can cause organ damage especially of the
liver, pancreas and the heart.
Ideally, consultation
with a doctor should precede any use of iron supplements, with
adequate follow-up so that iron overload does not occur.
|
Upper
Limit+
(mg/day) |
| Life-Stage
(years) |
Males |
Females |
| 0
- 0.5 |
40 |
40 |
| 0.5
- 1 |
40 |
40 |
| 1
- 3 |
40 |
40 |
| 4
- 8 |
40 |
40 |
| 9
- 13 |
40 |
40 |
| 14
- 18 |
45 |
45 |
| 19
- 50 |
45 |
45 |
| Ages
51+ |
45 |
45 |
| Life-Stage
(years) |
Pregnancy |
Lactation |
| 18
and younger |
45 |
45 |
| 19
- 30 |
45 |
45 |
| Ages
31 - 50 |
45 |
45 |
| +Upper
Limits (UL) = The maximum level of daily nutrient intake
that is likely to pose no risk of adverse effects. Unless
otherwise specified, the UL represents total intake from
food, water, and supplements.
ND = Not
determinable due to lack of data of adverse effects in
this age group and concern with regard to lack of ability
to handle excess amounts. Source of intake should be from
food only to prevent high levels of intake. |
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