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Tea and Iron Absorption

Iron has several vital functions in the body, it’s major role being as an Oxygen carrier in blood haemaglobin and muscle myoglobin. In addition, it is a component of many enzymes and is required for a number of metabolic processes. Deficiency in dietary
iron is the most common nutritional deficiency in the world and can ultimately result in anaemia.

Tea drinking mainly influences the absorption of non-haem iron as haem iron is relatively unaffected by tea. The inhibitory effects of tea drinking on iron absorption was first identified in a study that used test meals fed under experimental conditions.8 A few studies have attempted to quantify the effect of tea on non-haem iron absorption. These studies concluded that tea does have an inhibiting effect on iron absorption, however it has been proposed that findings from experiments using human or animal models based on test meals fed under experimental conditions may not reflect the role of tea when consumed as part of a complex, real diet.

Tea Drinking and Iron Status

It would be expected that if tea has a strong inhibitory affect on non-haem iron absorption it would be associated with a poor iron status. A number of population studies have investigated this hypothesis. Studies investigating tea drinking in children show a higher incidence of anaemia amongst tea drinkers compared to non-tea drinkers Results from studies in adults looking at the effects of tea drinking on iron status are conflicting. Mehta found a negative association between total cups of coffee and tea consumed and risk of anaemia. In contrast, Razagui, et al17 found that meal time drinking was strongly negatively associated with serum ferritin levels in a group of long stay mentally handicapped women.

Similar findings have been found in elderly subjects, where a low consumption of total iron, haem and non-haem iron and ascorbic acid, and higher intakes of calcium, dietary fibre and tea and coffee consumption was found in healthy subjects with low iron stores compared to those with good iron status. These short term studies indicate that there maybe a negative association between tea drinking and iron status in a number of different populations. However, these studies do not necessarily show cause and effect ie that negative iron status is as a result of tea drinking instead it shows that a group who had a low iron status also had a higher intake of tea. Moreover, they have not controlled adequately for other factors that are likely to affect iron status e.g. genetic factors, other dietary factors and status of an individual’s iron stores. For this reason no firm conclusions can be drawn from these results. In an attempt to address these other factors, Dr Michael Nelson from King’s College, London investigated the data from the National Diet and Nutrition Survey (NDNS) in a review on tea drinking and iron status. Information from the NDNS is collected by social class thereby showing differences in dietary intakes according to a number of parameters and therefore likely to reveal any effect of diet on iron status. He concluded that there was no clear evidence from this survey that the higher levels of tea consumption found in the manual social class households is specifically associated with poorer iron status. Further studies are required in this area before any firm conclusions can be made. In addition, because the rate of iron absorption is dependent in part on iron status, some authors have concluded that people could adapt to low iron intakes or low iron bioavailability over time and maintain good iron status.

Practical advice for tea drinking in relation to iron status

There is no evidence to suggest that tea drinking should be restricted in healthy individuals who are not at risk of iron deficiency and are consuming a well balanced, mixed diet.
People who have a poor iron status should avoid drinking tea with meals and up to at least one hour after the meal. Any adverse effects that tea may have on iron absorption are then likely to be minimized.
Certain groups are at higher risk of poor iron status, including infants and toddlers, teenage girls, premenopausal women and men aged 75 years and over. Based on the published evidence in the UK , the higher rates of poor iron status amongst these groups cannot be directly linked to tea drinking. However, it would be prudent to recommend that tea is not drunk with meals or up to one hour after the meal.
Moderate tea drinking (3-4 cups) spread throughout other times of the day is unlikely to have any adverse effect on iron status. The inhibitory effects of tea on iron absorption maybe partially overcome by the simultaneous consumption of animal tissues and Vitamin C.

Tea consumption will not result in iron deficiency for healthy individuals who are consuming a varied and balanced diet.

The absorption of iron from food is generally low and is influenced by a number of factors including the quantity of iron consumed, the chemical form (haem versus nonhaem), interaction with other dietary factors and the individual's physiological condition (status of iron stores, period of growth, menstruation or pregnancy).

Haem iron present in good amounts in meat, offal and meat products is readily absorbed and is unaffected by tea drinking. Non-haem iron found in cereals, vegetables, dried fruit, legumes and nuts is less well absorbed and its absorption is influenced by a wide variety of dietary factors which include enhancers e.g Vitamin C (present in fruit and fruit juice) and animal tissue (meat), and inhibitors e.g. phytate (bran) and tea (polyphenols).

Therefore for those who have a poor iron status or are at high risk of iron deficiency it would be prudent to avoid drinking tea with meals.

Otherwise moderate tea drinking (3-4 cups) spread throughout other times of the day is unlikely to have any adverse effect on iron status, and in fact at this level can actually bring about other health benefits thereby helping to promote overall health
and well being.