A lack of iron in your diet can lead to iron deficiency anemia — leaving you lethargic and exhausted. Even a lack of iron without anemia can wear you out.
This guide tells you everything you need to know about iron intake, iron deficiency and iron deficiency anemia.
And what you can do to make sure there’s plenty of this vital nutrient in your diet.
Iron deficiency and anemia — the big picture
Iron is the 4th most common element on earth. You’d think we’d have no trouble getting enough in our diet. But lack of iron is the most common nutrient deficiency in the world (1). And low iron intake is common in the UK — with women at the highest risk.
Iron deficiency anemia is a global problem and the most frequent type of anemia worldwide (2).
What does it mean if your iron deficient?
Without enough iron-rich foods in your diet, you can develop an iron deficiency.
Iron deficiency means you have low iron stores. The main iron storage protein in your body is ferritin. Measuring the ferritin levels in your blood can be used to test your iron stores.
Without the iron stores it needs, your body will struggle to cope. You may have no obvious symptoms. But if you have a busy lifestyle iron deficiency may leave you feeling constantly worn out.
As iron deficiency becomes more severe it progresses to anemia.
But iron has multiple functions in your body. And even a mild iron deficiency without anemia can still cause problems.
What is iron deficiency anemia?
Red blood cells only live for about four months and your body is constantly replacing them. Iron is vital for red blood cell production. If your iron stores drop too low your body struggles to keep up. Eventually, you become anaemic.
The definition of anemia is having less red blood cells or haemoglobin in your blood than normal. But producing too few red blood cells is only one cause for anemia. Two others are heavy bleeding and too many of your red blood cells dying.
So anemia can be caused to one or more of three blood problems.
- too few red blood cells being produced
- persistent or heavy bleeding
- too many red blood cells dying
Conditions that cause anemia include illness, inherited conditions and nutritional deficiencies. And worldwide, iron deficiency anemia is the most common type.
Other nutritional causes of anemia
Two other common nutritional causes of anemia are
- Low intake or absorption of vitamin B12 (pernicious anemia)
- Insufficient folate (folate deficiency anemia)
Like iron deficiency, they both cause anemia by lowering red blood cell production.
Not enough of vitamin A or vitamin C in your diet can also contribute to anemia. Vitamin C because it helps iron absorption in your gut. And vitamin A because it’s involved in red blood cell growth and iron store mobilisation.
But lack of iron is the most common nutritional cause of anemia (3).
4 crucial functions of iron in your body
1. Oxygen transport
Red blood cells transport oxygen from your lungs to the tissues of your body that need it.
Iron is an essential part of the haemoglobin protein that red blood cells use to carry oxygen. Haemoglobin also carries waste carbon dioxide back to your lungs so you can breathe it out.
Two-thirds of your body’s iron is used in haemoglobin
2. Oxygen storage
Haemoglobin transports oxygen to your muscles. But a different iron-dependent protein stores it and moves it around your muscle cells. This protein is myoglobin and it gives meat its red colour.
Muscles designed to work harder contain more myoglobin making the meat darker. Ever wondered why chicken breast meat is pale and the leg meat is brown? Because chickens use their legs more than their wings.
Your metabolism is the millions of complex chemical processes that keep you alive. Enzymes are proteins that speed up these chemical reactions in your body. Without enzymes, life couldn’t exist as we know it.
Many of the enzymes that keep your metabolism functioning need iron to work.
People with an iron deficiency or overload have a higher risk of infectious disease.
The relationship between iron and immunity is complex and we don’t understand it completely. But what’s clear is an iron imbalance can compromise your immunity.
How much iron is in the human body?
There’s 3–5g of iron in your body (4). That’s about 38mg/kg body weight for women and 50mg/body weight for men.
The breakdown is roughly
- 2–3g haemoglobin in your red blood cells.
- 0.4–0.8g iron stores (mostly in the liver)
- 0.2–0.4g myoglobin
- 0.1–0.2g enzymes co-factor
- <0.05mg blood plasma
Symptoms of iron deficiency
Many iron deficiency anemia symptoms are non-specific — they’re also symptoms of other illnesses.
If you think you may be iron deficient or could have iron deficiency anemia speak to your doctor and ask for a blood test.
Always feeling tired and exhausted
Fatigue is a common symptom of iron deficiency. Without enough iron your everyday activities are more effort, you’re easily out of breath and you tire quickly (5).
Iron deficiency reduces how efficiently your body uses energy. You need to burn more to get the same amount of work done, increasing the effort to do everyday tasks.
Anemia makes it harder for your blood to carry oxygen from your lungs to your muscles. Without enough haemoglobin rich red blood cells your cardiovascular system struggles.
Your lungs and heart work harder to supply the oxygen your body needs. Even moderate physical effort has you out of breath and your heart beating fast. If you’re an athlete, the first sign you’ll notice could be a drop in your VO2 max.
Iron deficiency anemia reduces the oxygen getting to your muscles. Plus, low iron in your muscles reduces their ability to use the oxygen that does reach them.
This combination can cause a drop in your endurance and ability to maintain effort. But even in the absence of anemia, iron deficiency can lower your endurance.
More frequent and prolonged infections
Your iron status has a complex relationship with your immune function. Here’s what we know.
Both iron deficiency anemia and iron overload can impair your immune response (6).
And even a mild iron deficiency can slow the production and activation of your immune cells to combat infections (7).
Plus, your body lowers iron availability to combat infections by depriving infectious bacteria of the iron they need.
Studies have linked iron deficiency and iron deficiency anemia to hair loss.
There still isn’t enough evidence to say for sure that iron deficiency causes hair loss. But the two appear to be related (8).
Nails that dip in the middle to form a spoon shape is a condition known as koilonychia. A classic symptom of iron deficiency anemia (9).
Typically, the dip is large enough that you could hold a drop of water on the back of your fingernail.
A vitamin C, riboflavin or niacin deficiency can also cause koilonychia.
Onycholysis is the separation of your nail from the nail bed of your finger. Sometimes it’s related to iron deficiency but is more often linked to trauma or a reaction to an external irritant.
Pica — strange cravings
Pica is the craving for and eating or chewing non-food substances like soil, coal and ice. It’s known as a strong indicator of iron deficiency (10).
Restless leg syndrome
An unceasing urge to move your legs to relieve an unpleasant itching, creeping, crawling or aching feeling. It’s known as restless leg syndrome and is most common at night.
It’s normally a nervous system disorder but can be caused by an iron deficiency (11)
Pallor — a paler than usual complexion
There are many possible reasons for pallor. And pallor on its own is not enough to indicate iron deficiency. But a lack of pallor can be used to rule out severe anemia (12).
It’s difficult to judge your own complexion. The easiest place to accurately check your pallor is the inside of your lower eyelid (13). It should be pink close to the edge and paler close to the eye. If it is uniformly pale that’s a sign of pallor.
Dry mouth and smooth tongue
Prolonged iron deficiency causes your tongue to lose its papillae -the bumps that house your taste buds.
Other oral symptoms include a dry mouth, a burning sensation, numbness and loss of taste.
The symptoms are more severe for anemia than iron deficiency alone (14).
The 3 stages of Iron Deficiency
Stage 1 — depleted iron stores
You may have no obvious symptoms.
But an early sign is often a drop in exercise performance and recovery. Without a reserve of iron, adapting to physical challenges is more exhausting.
A blood test will show low levels of ferritin (the principal iron storage complex).
And without enough iron in your diet, low iron stores advance to iron-deficient erythropoiesis.
Stage 2 — iron-deficient erythropoiesis
Blood ferritin levels continue to fall.
Free transferrin (the iron transport protein in the blood) increases as less iron circulates around your body.
Your exhausted iron stores iron stores can’t support normal red blood cell production. So your body struggles to replace blood cells.
And without more iron intake, iron-deficient erythropoiesis advances to anemia.
Stage 3 — iron deficiency anemia
Without iron, haemoglobin production falls and you can’t produce enough healthy red blood cells.
Your red blood cell volume shrinks and the cells produced are smaller. Because each red blood cell has less haemoglobin, they’re a paler in colour too.
Iron deficiency and early iron-deficient erythropoiesis can be symptomless. And any symptoms you have are likely to be subtle and difficult to identify.
Even mild iron-deficiency anemia can be asymptomatic. Some people only develop symptoms when the anemia becomes severe.
Who’s at higher risk of iron deficiency anemia?
Anyone can be iron deficient but some of us have a higher risk than others. In the UK the people with the most chance of iron deficiency are:
9–11% of premenopausal women in the UK could be iron deficient (15)
Women need to consume more iron than men because of blood lost during menstruation. And women with menorrhagia — unusually heavy periods — have a higher risk of iron deficiency.
But the average woman in the UK only consumes 76% of their daily recommended iron intake (16).
During pregnancy red blood cell production skyrockets to cope with a growing baby. This puts a strain on the mother’s iron stores.
An iron deficiency increases the risk of maternal and infant mortality, premature birth, and low birthweight.
Having good iron stores before conception and eating an iron-rich diet when pregnant lower the risks.
If you’re planning a pregnancy ask your doctor to check your iron levels.
Infants and young children
Around 6% of infants under 24 months are iron deficient (17)
A mother’s milk contains little iron but by design, it’s enough for the first few months of life. By around 4–6 months babies have outgrown the iron their mother’s milk can supply. They start to need iron from other sources.
Careful timing of weaning and thoughtful selection of early foods are important to ensure adequate iron to support baby’s growth.
Rapid growth and rising blood volume make pre-school children vulnerable to iron deficiency. 3% of kids below to school age are iron deficient (18).
Iron deficiency may harm the cognitive, motor and behavioural development of young children (19).
No toddler eats perfectly. But smuggling lots of iron-rich foods into their diet will help the development of your child.
Regular blood donors
Replacing donated blood puts a strain on your body’s iron stores. It’s important to allow your body time replenish. How long it takes depends on your body size and your iron stores before you donate.
In the UK, a woman can give blood every 16 weeks and a man every 12 weeks. But less than 6 months between donations increases your risk of iron deficiency.
Blood donations are vital to our health service, but giving too often can lead to iron deficiency.
Vegetarians and Vegans
A vegetarian or vegan diet contains as much and often more iron than a typical omnivore diet. But that doesn’t tell us anything about how easily you can take up the iron.
There is only non-haem iron in vegetarian and vegan diets. And so relatively less of the iron can be absorbed from your food.
Avoiding iron deficiency is not difficult. It just takes a little more planning. If you’re vegetarian or vegan, combine high iron foods and high vitamin C foods to boost absorption. And eat foods that inhibit iron absorption, like dairy as snacks or with meals that are low in iron.
There are lots of varied vegetarian and vegan foods available in the UK. Keeping your iron levels healthy and eating a vegetarian or vegan diet has never been easier.
And it’s hypothesized that the slightly lower iron stores of vegan and vegetarians may reduce the risk of chronic diseases.
Even so, some vegan and vegetarians, especially premenopausal women, struggle to meet the recommended iron intake. And iron supplementation hasn’t been shown to help their iron status.
People who are unwell
Major surgery or trauma, chronic diseases and many medical treatments can cause iron deficiency.
The role of a dietician is to manage iron and other nutrient deficiencies related to the patient’s illness.
Medication, underlying disease and reduced appetite all contribute to iron deficiency in the elderly.
People with a poor diet
Food is plentiful in the UK. The rising obesity rates suggest we’re eating too much as a nation.
We consume plenty of fats, carbs, protein and calories. But poor food quality leaves many undernourished in vitamins and minerals, including iron.
People on fad and restrictive diets or poorly thought out weight loss regimes are even more vulnerable to iron deficiency.
How much Iron do you need?
Too much iron causes free radical damage and encourages the growth of infectious bacteria. Too little causes anemia.
To maintain safe levels your body tightly controls iron uptake. It only absorbs what it needs to replace daily losses.
This loss amounts to a tiny 1–2mg/day — only one or two-thousandths of a gram! (20). But your body can only absorb a small percentage of the iron in food. So, the recommendations are much higher.
The recommended daily iron intakes are (21):
- 4–6-month-old babies — 4.3mg/day
- 7–12-month-old infants — 7.8mg/day
- toddlers 1–3 years old — 6.9mg/day
- children 4–6 years old — 6.1mg/day
- children 7–10 years old 8.7mg/day
- adolescent boys — 11.3mg/day
- adolescent girls — 14.8mg/day
- women between puberty and menopause — 14.8mg/day
- adult men — 8.7mg/day
- post-menopausal women — 8.7mg/day
What affects iron absorption?
Consuming enough iron in the diet is the first step. But there are four other factors that significantly affect iron absorption:
- Your iron stores
- The type of iron in you eat
- Iron absorption inhibitors
- Iron absorption enhancers
How your body controls iron stores
Your body recycles iron and only tiny amounts are lost with shed skin and mucosal cells. It has no mechanism of iron excretion.
The body controls iron levels by tightly regulating the amount it absorbs from your food. This ability to keep your iron levels between narrow limits is essential for your health.
Iron deficiency compromises the body’s ability to function at its best. And iron deficiency anemia left untreated can be fatal.
But iron overload is also harmful. Because iron is a highly reactive element. Iron that isn’t bound to proteins like haemoglobin or ferritin can cause free radical damage to cells. What’s more, too much iron encourages the growth of infectious bacteria.
This tight regulation of absorption is the most significant factor affecting iron uptake (22).
But when your iron stores are high, the absorption of both non-haem and haem iron fall rapidly. So, iron overload from your diet is almost impossible.
Two types of iron — Haem and Non-haem
The iron in food comes in two forms, haem and non-haem.
Haem iron is iron bound to the animal proteins haemoglobin and myoglobin. Non-haem iron is non-organic or ferric iron.
Meat, fish and seafood contain both. Plants and fortified foods only contain non-haem iron.
How easily your gut can absorb a nutrient is known as its bioavailability.
The bioavailability of haem iron is greater than non-haem iron. Roughly 25–35% of dietary haem iron is absorbed and only 2–20% of non-haem iron.
If you follow a plant-based omnivore diet, most of the iron you consume is non-haem iron. But over a third of the iron you absorb is haem iron because it has the greater bioavailability.
Vegans and vegetarian diets contain only non-haem iron. The non-haem iron in a vegetarian or vegan diet can be more than the combined iron in an omnivore diet. This higher total iron content helps compensate for the lower absorption rate.
Iron absorption inhibitors
Inhibitors bind to the iron in your meal and prevent your gut from absorbing it.
Calcium inhibits the absorption of both haem and non-haem iron. The main sources of calcium are dairy products and fortified cereals.
Milk or cheese in a meal can inhibit uptake by as much as 50%.
Many plant foods contain oxalates. Oxalates reduce the bioavailability of non-haem iron.
Spinach is a good example. It’s high in iron, but the oxalates it contains reduce the iron’s bioavailability.
Oxalates tend to be concentrated in a plant’s leaves. That said, foods high in oxalates include; spinach, rhubarb, beetroot, parsley, nuts, chocolate, celery, wheat bran and tea.
Polyphenols are antioxidants found in most fruits, vegetables and legumes.
Many antioxidants help prevent diseases like cancer, osteoporosis and cardiovascular disease.
But some polyphenols inhibit non-haem iron absorption. The worst offenders are the tannins in tea, coffee, red wine, cocoa and some berries.
Phytates are antioxidant compounds found in nuts, seeds, whole grains, soy products and legumes.
Soaking and fermenting grains and legumes reduces phytate interference with non-haem iron absorption.
Soybeans and edamame are a great source of protein and fibre but have a very high phytate content. Removing the phytate helps. But treated soy protein still inhibits non-haem iron absorption.
Drugs that lower stomach acid to treat heartburn reduce iron absorption. Their long-term use can deplete your body’s stores and contribute to iron deficiency.
Iron absorption enhancers
Iron enhancers boost iron absorption and help overcome the effects of iron inhibitors. But it’s important to know the effect of different enhancers is not cumulative.
The best sources of vitamin C are fruits and vegetables.
Vitamin C increases iron uptake in two different ways.
It stops absorption inhibitors binding with iron and keeps it available for uptake.
And it converts ferric iron to ferrous iron. Most non-haem iron is ferric iron. An enzyme in your gut converts ferric iron is to ferrous iron to allow absorption.
Vitamin C gives your gut enzyme a helping hand.
Meat and fish
Meat and fish added to a plant-based meal increases your non-haem iron uptake by 2–3 times.
Unlike vitamin C, why meat and fish have this effect is unclear.
But meat and fish have a double iron absorption benefit. They enhance non-haem iron uptake and contain the more easily absorbed haem iron.
The best sources of carotenoids are brightly-coloured fruits and vegetables like carrots, leafy greens, red peppers, and oranges.
Carotenoids enhance non-haem iron uptake. But, like meat and fish, how they increase absorption is unclear.
The essential amino acid lysine can improve iron uptake. Fortunately, many foods rich in iron are also high in lysine. Foods like red meats, seafood and pulses.
Iron-rich foods include:
- red meat
- beans and pulses
- nuts and seeds
- leafy green vegetables
- iron-fortified flour and breakfast cereals
For more detail on the iron content of many readily available foods, take a look at this top 30 sources of iron.
You can see there’s a wide variety of naturally iron-rich foods. But most UK adults get 40% of their iron intake from fortified foods. Processed foods like white flour and breakfast cereals.
It’s a reflection of the success of the UK flour fortification strategy (a legal requirement since 1953). But it’s also a reflection of the nations high dependence on refined foods.
Yet there are questions over the benefits of flour fortification on iron status. Because the iron powders used to fortify flours have such low bioavailability (23).
A varied diet of unprocessed, healthy foods provides all the iron your body needs. And the bonus? You get all the other nutrients you need to keep feeling great too!
How to increase your iron absorption
Eating a healthy plant-based omnivore diet provides plenty of iron in your diet. And the combined effects of the absorption inhibitors and enhancers cancel each other out.
If you’re a vegan or vegetarian you may have more total iron in your diet than an omnivore. But you only have the less bioavailable non-haem iron in your diet. Carefully combining meal ingredients will help enhance the iron uptake from your food.
Vegan, vegetarian or omnivore, if you want to enhance your iron uptake, there are few simple diet tweaks you can make to help.
First, it’s essential you’re eating plenty of iron-rich foods. No amount of diet tweaking can fix your iron levels if you don’t consume enough iron in the first place.
Combine absorption enhancers and iron-rich foods in the same meal. This reduces the effect of inhibitors and increases your iron uptake.
If dairy and calcium-fortified foods are an important part of your diet, limit them to snacks or meals that already have a low iron content.
Lower phytates in legumes and grains by soaking, fermenting or sprouting them. With less iron-inhibiting phytates the bioavailability of the non-haem iron will increase.
Drinking tea and coffee with food lowers your iron absorption. Try to keep your favourite brew for between meals.
Lastly, traditional iron cookware, although not common in the UK, can increase iron intake. Because foods cooked in an iron pot absorb iron from the pan (24). Especially acidic sauces like tomato. This boosts the non-haem iron content of the meal.
Unless you are severely iron deficient supplements aren’t necessary. If you suspect you are, ask your doctor for a blood test.
All iron supplements are made from non-haem sources. The bioavailability depends on the type of non-haem iron used in the tablet. But in general, it’s more easily absorbed than the iron in a multivitamin.
Taking an iron tablet is a tempting quick and easy fix for poor iron intake. And supplements are available in most chemists, supermarkets and health shops.
But iron supplements don’t address the underlying causes of iron deficiency or anemia. And they should only be used as a short-term measure to boost low iron levels (unless prescribed by your doctor).
If you’re going to try them be careful not to overdo it. Read product information the label and never take more than indicated. The UK guidance recommends you take no more than of 17mg/day of iron from supplements.
Warning- iron supplements can interfere with your absorption of other minerals, especially zinc. So iron supplements may improve your iron status — but could lower your levels of other important minerals.
Getting the iron you need from your diet is the best and safest way to maintain your iron status. And supplements should never be used to replace a healthy diet.
The dangers of iron overload
Iron deficiency is not good for your health. But neither is iron overload.
High doses of iron supplements can cause constipation, stomach pain, nausea and vomiting.
Very high doses of iron can be fatal — especially to children. Always keep iron supplements out of reach of sticky little urchin fingers!
Even a mild iron overload lowers your immune function and increases your risk of infections. And too much iron can interfere with the absorption of other essential minerals like zinc.
Haemochromatosis is a rare inherited condition. It disrupts iron absorption and if untreated causes iron levels to rise (25). But healthy adults have an extremely low risk of iron overload from dietary iron.
Your first choice should always be to get the iron you need from your diet.
In our modern environment, we’re surrounded with an abundance of food choices. Unfortunately, most foods on offer are full of calories but empty of vital nutrients like iron.
Your busy life is busy. And you’re constantly bombarded with food marketing masquerading as health advice. It’s too easy to slip into a habit of convenient foods devoid of essential nutrients. A lack of iron or other nutrient deficiencies can sneak up on you.
It’s time to ask yourself
Is it really your busy life that’s wearing you out?
Or does your diet lack the nutrients your body needs breeze through every day?
Originally published at www.movementandnutrition.co.uk on January 27, 2019.