Is Spinach a Good Source of Iron?
For years the public have widely associated spinach with Popeye and it is considered the powerhouse of leafy greens. Not only is it known for giving Popeye his strength but it is also recommended as a good source of iron.
Iron is an essential mineral required for growth and development and is required to make proteins, hemoglobin and hormones. The two type of iron found in food are haem (found in animal products) and non-haem (found in plants). This article explores the iron content of spinach and other plant foods that promote and inhibit the absorption of iron in the context of bioavailability.
SO WHAT IS BIOAVAILABILITY?
Bioavailability refers to the amount of nutrients that we can absorb from foods in the diet for metabolic use. The iron found in the majority of plant foods isn’t always fully absorbed due to the presence and influence of other dietary constituents. These dietary cofounders that inhibit iron uptake are phytic acid, (found in cereals & legumes), oxalic acid (found predominantly in vegetables) and polyphenols (which can be found in tea, coffee and vegetables).
IS SPINACH REALLY JUSTIFIED OF ITS GLORY?
Spinach contains high levels of oxalic acid, which binds with iron and blocks absorption in the gut. The oxalic acid found in spinach appears to be higher than most other green vegetables, such as kale and broccoli. The majority of iron in spinach is not usable for the body and studies have shown that as little as 2% of iron from spinach is actually absorbed by the body! Other examples of foods that inhibit iron absorption include, peas, lentils and chickpeas due to the high phytic acid content.
WHICH GREENS ARE CONSIDERED TO BE GOOD SOURCES OF IRON?
One of the vegetables that came out on top for iron content was watercress, owing to its rich vitamin C content. Vitamin C helps to promote iron absorption, therefore eating vegetables rich in vitamin C is a good place to start. Some examples include, broccoli, cabbage and cauliflower.
It is important to note that if you have been instructed to take an iron supplement for deficiency, it is beneficial to consume the tablet alongside iron promoters, for instance orange juice, due to the citric acid content. Avoid taking it with dietary inhibitors, such as tea.
SHOULD WE GIVE UP ON SPINACH AS A SOURCE OF IRON?
It is possible to reduce the oxalic acid content of spinach through cooking - boiling spinach for around 15 minutes reduces the concentration of acid. Both cooked and raw spinach have plentiful nutritional benefits, including its rich fiber, vitamin, folic acid and calcium content. Understanding which foods to eat in combination with spinach can help promote the absorption of iron.
It is good to keep in mind that other green vegetables might be better contenders of iron if it’s a mineral you are looking to boost this Winter. Here at The Be Well we recommend incorporating lots of spinach and enjoying it both cooked and raw as part of a balanced diet.
SOURCES
Nutritics Research Edition, v4.097
Muhammad Muhammad Shoaib Akhtar , Beenish Israr , Nighat Bhatty & Amanat Ali (2011) Effect of Cooking on Soluble and Insoluble Oxalate Contents in Selected Pakistani Vegetables and Beans, International Journal of Food Properties, 14:1, 241-249
Scrimshaw NS. (1991). Iron deficiency. Sci Am. 265(4):46-52
Paul Sharp (King’s College London, 2021)
