Iron deficiency is rife, particularly among women and people who have a diet low in the nutrient. It is one of the main causes of anaemia, which leaves individuals feeling lethargic and looking pale. Symptoms, however, depend on the severity of the condition. While it is important to emphasise the right foods to avoid a deficiency, excessive consumption of certain tea could contribute to the condition.
The body needs iron to produce a substance in red blood cells that enables them to carry haemoglobin or oxygen.
Depleted oxygen levels are the reason individuals end up feeling tired and short of breath.
Iron is found predominantly in food, so the majority of deficiencies are put down to inadequate dietary intake.
But researchers have identified some molecules in herbal teas that could interfere with the absorption of the nutrient.
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A clinical case report published in 2016, found that “tea interferes with iron absorption and leads to iron deficiency anaemia when consumed in large quantities”.
The compound responsible for this is tannins, which has been shown to reduce the body’s absorption of iron from plant sources.
VeryWell Health explains: “Tannin found in black tea gives it its dark reddish-brown colour and characteristic full-bodied, astringent flavour.
“Although the amount of tannins in black tea varies depending on the variety, growing condition and processing method, black tea is considered one of the major sources of tannins in the human diet.
“Other significant sources include red wine, oak-aged white wine, chocolate and coffee.”
Alongside oxalates, the naturally-occurring tea compounds, are particularly abundant in herbal teas and can bind to iron.
This could predispose individuals to anaemia, particularly if individuals do not eat meat and other potent iron sources.
The authors of one 2016 case study noted: “The rechallenge effect of green tea on anaemia in a middle-aged man emphasises the potential causal role of this beverage.
“Lifestyle and dietary habits are important diagnostic considerations in diseases of this type.
“The fact that iron absorption can be reduced by tea consumption has been recognised for many years, with the inhibitory effects predominantly facilitated by the marked iron-binding properties of the phenolic compounds bearing catechol groups in tea.
“A review of clinical data has previously shown that haemoglobin levels rise significantly after withdrawing from tea consumption in two reported cases.”
Improvements in iron deficiency after abstinence are not necessarily an indication that tea consumption should be avoided, however.
In a 2007 study published in the American Journal of Clinical Nutrition, scientists found that tea consumed with a meal decreased iron absorption.
The findings, however, revealed that tea consumed one hour after a meal didn’t decrease absorption to the same extent.
What’s more, the findings are inconsistent with previous research published in the European Journal of Clinical Nutrition, which looked at the iron levels of 954 healthy adults and estimated their tea intake.
This time researchers did not find an association between iron levels and intake or black, green and herbal tea consumption.
There wasn’t evidence of a correlation between the strength of the tea, infusion time, time of drinking and iron levels either.