Iron Containing Foods: A Practical Guide
What does iron do in your body?
Iron is an essential component of hemoglobin (i.e. the substance in red blood cells that carries oxygen from your lungs to transport it throughout your body).
Hemoglobin makes up about two-thirds of your body’s iron stores.
If you don’t have enough iron, your body can’t make enough oxygen-carrying red blood cells. This means your tissues and muscles won’t get enough oxygen to function optimally.
Along with iodine, iron is required to make thyroid-stimulating hormone (TSH). Inadequate iron can cause hypothyroidism.
Iron is also critical to maintaining strong bones, detoxification, immune function, skin and nail formation as well as the synthesis of neurotransmitters in your brain.
Factors affecting iron absorption
Your gut will absorb more iron in your intestines if you need more of it, but let it pass through if you have adequate amounts in your system.
Phytates in grains, vegetable protein, legumes and green leafy vegetables will decrease the absorption of iron, as do tannins in red wine and coffee.
Vitamin C, fructose and sodium increase the absorption of dietary iron. If you are getting less vitamin C, sodium or fructose, you may not be absorbing as much iron as you otherwise would.
Iron supplements are commonly combined with vitamin C to assist with absorption.
Factors increasing iron demand
You may need more iron in your diet if you:
- are anemic and have low blood levels of ferritin,
- consume excess calcium (e.g. from a lot of dairy products),
- consume a large amounts of phytates (i.e. from grains, green vegetables and legumes),
- experience heavy menstrual periods,
- donate blood on a regular basis,
- are particularly cold-sensitive,
- suffer constipation,
- have pale skin (i.e. you look “anemic”),
- are experiencing slow growth,
- have a poor appetite, or
- are pregnant.
If you are female and have low energy levels, you should watch for lower ferritin levels on your standard blood tests.
Practical steps you can take to increase your iron levels include:
- modifying your diet to improve your iron intake,
- taking iron supplements,
- ensuring you are getting adequate vitamin C (which assists iron adsorption), and
- reducing phytates (e.g. from grains and legumes).
Can you get too much iron?
Iron is one nutrient that women of childbearing age require significantly more of. However, men, who tend to not bleed much in modern times, can get excessive amounts of iron (haemochromatosis or iron overload). One in three hundred people have hemochromatosis.
While adequate iron helps you manage oxidation, excess iron can become bound to proteins and acts as a pro-oxidant, literally causing your tissues to rust.
If left untreated, the excess iron can increase your risk of diabetes, cirrhosis of the liver and a host of other chronic diseases.
Symptoms of iron overload
Symptoms of iron overload include:
Iron toxicity and its symptoms can be improved by ensuring you are getting adequate niacin, tryptophan, zinc, manganese and lipoic acid. You should also avoid excessive levels of vitamin C supplementation.
If you are male, you should watch for elevated ferritin levels and consider regular blood donations if they are high. Blood donation is not just good for you. It could be a matter of life or death for someone in need.
Heme iron vs non-heme iron
Iron in our diet comes in two forms:
- heme iron (from animal-based foods), and
- non-heme iron (from plant-based foods).
You will absorb 15 to 35% of animal-based iron while you will only absorb 2% of plant-based iron. Hence, you may be at risk of anemia if you are a strict vegan.
However, while some people like to make a big deal of the bioavailability of iron in plants vs animal products, super high iron absorption is not always a good thing for the reasons above.
If you are consuming an omnivorous diet you are unlikely to have significant issues with low iron levels unless you have digestive problems, consume a lot of grains or minimal vitamin C (all of which will affect the absorption).
Availability of iron in the food system
As shown in the chart below, the availability of dietary iron has increased with the introduction of iron-enriched foods, particularly breakfast cereals.
Ironically, iron absorption is also negatively affected by the phytates in the grains that the cereals are made from.
The form of iron used in fortification is also not ideal as it may cause constipation, feed pathogenic gut flora and contribute to oxidative stress that damages the intestines.
Excess iron intake can affect zinc absorption. If your dietary ratio of iron:zinc is greater than 2:1 then your absorption of zinc will be reduced.
How much iron do you require per day?
Our satiety analysis of people using Nutrient Optimiser shows a moderate satiety response when people consume food that contains higher levels of iron. People consuming food that contain more iron tend to eat around 20% fewer calories than those who consume less iron-rich foods.
How much iron is too much?
The average iron intake of Optimisers is 18mg/day with an 85th percentile intake of 25 mg per 2000 calories. This is more than the Estimated Average Requirement for iron of 6 mg and the Recommended Daily Intake for iron of 8 mg/day but less than the Upper Limit of 45 mg/day which is set to prevent gastrointestinal issues.
Optimal iron target
Based on this analysis, we have set a stretch target of 30 mg/day for both men and women.
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Foods that contain more iron are listed below (note: plant-based forms are less bioavailable).
- chicken liver
- lamb liver
- beef liver
- whole egg
- ground beef
- green peppers
- flax seeds
- sweet potato
The nutrient fingerprint below shows the micronutrient profile of the foods that contain the most iron. We can see that iron is easy to obtain in adequate quantities from a nutrient-dense diet.
Nutritious meals to boost your iron intake naturally
If you are experiencing any of the symptoms of iron deficiency or your current vitamin A intake is low (e.g. due to a heavily grain-based diet) then you may be interested in our lists of iron-rich foods and meals.
What you will get:
- Our Nutritional Optimisation Kickstart Guide,
- A list of the most popular 50 foods that contain more iron,
- A longer list of popular 100 foods that contain iron, and
- A longer list of the 150 common foods that contain more iron to allow you to expand your nutrient-dense repertoire further.