Ways to increase iron absorption from food

​Some people may find they are always low in iron, despite eating plenty of iron-rich foods. There can be a few key interferences to iron absorption, so if you’re running low, here are some tips to maximise absorption.

Why do we need iron?^​1​

When we’re about five months old, our need or iron rises drastically, and between ages 1-6, the body’s iron content is doubled. Kids and teens have the greatest need for iron, especially during growth spurts.

Girls have a growth spurt before puberty, while boys have it during puberty, with iron need at this time above what an adult woman getting regular periods needs – that to say, a lot.

The body stores 1000-3000mg of iron, and this is tightly regulated, a delicate balance between what we take in from food and what we lose every day through mucosal surfaces, such as the digestive tract and vagina. We naturally lose about 1mg of iron each day. During menstrual bleeding, this loss increases to 2mg per day.

Even mild to moderate forms of iron deficiency can be linked with functional impairments. Less than optimal levels of iron can affect cognitive development, the immune system (important in vaginal and urinary tract infections), and our capacity to get out of bed and go about our lives.

Iron deficiency during pregnancy is a known issue for baby and mother, with greater risk of sepsis, low birth weight and other more serious outcomes including learning disabilities.

Plant and animal forms of iron

There are two forms of iron – heme (from meat) and non-heme (from plants). Plant iron is harder to absorb compared with meat iron. Some elements in food inhibit both heme and non-heme iron at the site of uptake, such as calcium, while others only inhibit non-heme plant iron, such as polyphenols.^​2​

Animal proteins such as casein (in dairy products like milk, cheese and yoghurt), whey, egg whites and plant proteins like soy inhibit iron absorption in humans. Oxalates, found in spinach, chard, beans and nuts also binds and inhibits iron absorption.^​2​

Orange juice or vitamin C with food – increases^​3–8​

Orange juice and vitamin C both increase uptake of iron, and vitamin C can overcome the effects of all dietary iron-absorption blockers when it’s included in a diet rich in non-heme (plant-based) iron.

Ascorbic acid (vitamin C) forms a bind with iron in the acidic stomach, which continues to hold as the pair make their way to the alkaline environment further down in the intestine, where it can be absorbed.^​2​

In this sense, promoting stomach acidity while eating is very useful, for example, don’t drink with meals (except a little orange juice!) and don’t overfill your stomach. Both cause stomach acid to be diluted, thus less effective.

Orange juice was found to increase iron absorption even more than vitamin C, so drink a small amount of good quality fresh orange juice with meals, especially meals containing high-iron foods, to increase uptake.

If you take an iron supplement, drink some orange juice or take vitamin C at the same time as your supplement. Vitamin C works well, 500mg is enough, but more won’t hurt.

Black tea – reduces^​9–11​

Black tea inhibits iron absorption by about 80-90%, so to maximise iron absorption, drink black tea away from food by at least one hour. 

Coffee – reduces^​9–11​

Coffee inhibits iron absorption, by about 40%, if consumed during or after a meal containing iron for about an hour. Stronger coffee has a stronger impact, and drinking coffee before your meal doesn’t affect absorption.

Polyphenols – reduce^​9–15​

Polyphenols found in plants inhibit iron absorption to varying degrees, so for example, peppermint tea inhibits iron absorption by 84%, while chamomile tea by 47%.

Polyphenols are healthy plant compounds and we need them, so the idea is not to cut them out, but to tweak your ingestion so as to maximise iron absorption. To increase non-heme (plant-based) iron absorption, use the orange juice or vitamin C trick.

Coffee and tea are high in polyphenols, as are berries, herbs and spices, cocoa, nuts, cereals, flaxseeds, wine, legumes, fruit and vegetables. 

Use this searchable list of high polyphenol foods. Don’t skimp on polyphenols – they are excellent for your health and are not to be avoided, however, if you’re eating foods high in iron, consider what is in the meal and it’s ability to inhibit iron absorption.

Genetic mutations

If you have certain genetic mutations that impact how your body absorbs iron. The iron-related genetic mutations are TF, HFE, TFR2, TMPRSS6, and SLC40A1. Some are related to haemochromatosis (excessive iron absorption), while others are related to insufficient iron uptake and distribution in tissues.^​8​

Zinc – take at different times

Take zinc and other supplements away from any meal containing iron, as zinc can compete for absorption with other nutrients, including iron.^{​16–19​}

Tips for supplementation with iron

If you are taking an iron supplement, take minimal doses and only every three days, as this will improve absorption. Uptake receptors become full and the excess iron that is not absorbed travels through the digestive system, creating disruptions to gut flora and therefore the digestive process.^{​20–22​}

Bacteria utilise iron, therefore having an excess in the digestive system can create an imbalanced ratio of microbes.^{​23–27​}

If you are eating enough red meat, skip the iron supplement, and work on these other factors instead, as a large load of iron can have the opposite effect, and cause a reduction in uptake, in some people.

References^{​3,28–30​}

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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

• International Society for the Study of Vulvovaginal Disease (ISSVD)
• International Society for the Study of Women's Sexual Health (ISSWSH)
• National Vulvodynia Association (NVA) Australia
• New Zealand Vulvovaginal Society (ANZVS)
• Australian Traditional Medicine Society (ATMS)