What is iron and how does our body absorb it?
Iron is involved in body functions such as energy production, growth and development, immune function, red blood cell formation, reproduction, wound healing. An iron deficiency can result in the impairment of these functions and is associated with lethargy, difficulty concentrating, and poor immune function. Obesity, calorie restriction, and greater intake of processed energy-dense, micronutrient-poor foods and beverages are associated with low iron status. An iron deficiency is most common in children, women of childbearing age, and during pregnancy. Approximately 75% of Singaporean women in the third trimester of pregnancy may be iron deficient.
Dietary iron is present in the form of heme iron from animal foods and non-heme iron from plant and animal foods. Heme iron is more bioavailable than non-heme iron. The absorption rate of heme iron is approx. 25% while the absorption rate from non-heme iron is approx. 17%. Omnivores typically get 10–15% of their dietary iron from heme iron but it contributes to 40% or more of total iron absorption. Heme iron is not affected by factors that inhibit absorption. Despite the differences between plant and animal iron, vegetarians and vegans can easily meet their iron needs. The body stores iron when stores are low and increases excretion when stores are high.
- Factors that enhance the absorption of iron include vitamin C (ascorbic acid) and other acids (citric and lactic).
- Factors that inhibit iron absorption include calcium (milk), phytates (legumes, grains, nuts, seeds), vegetable proteins (soybeans, legumes, nuts), and tannic acid (polyphenol in tea and coffee). Phytates are sometimes called “anti-nutrients” but they are also powerful antioxidants, so they are not all bad!
Where to Find it?
The iron you consume quickly adds up. The Recommended Dietary Allowance (RDA) can easily be met by consuming a healthy varied diet if there are no underlying health conditions or genetic abnormalities. For example, iron absorption can be as low as 2% in those with GI disease. Meat like chicken and beef are potent sources but so are many plant-based sources that have no saturated fat. As a bonus, they are also full of fiber and phytonutrients.
How much iron do we need per day?
The recommended daily allowance (RDA) for iron in Singapore is per the chart below.
How can I get more iron into my diet?
1. Do not take a calcium supplement at meals
2. Eat an adequate amount of calories
3. Focus on weight loss if obese
4. Consume the RDA which is 1.8 times higher for vegans / vegetarians than omnivores
- Example: 19-50 years old- 8mg (male) and 18mg (female not pregnant) omnivore
- 19-50 years old- 14.4 (male) and 32.4mg (female not pregnant) vegan
5. Consume a low sugar whole grain fortified breakfast cereal if diet not adequate
6. Optimize iron enhancers
- Vitamin C: citrus fruits, red pepper, watermelon, broccoli, tomato juice, brussels sprouts etc.
- Citric acid: Lemon or lime
- Sulphur-rich allium species: onion, garlic, red and black pepper, ginger, and black pepper
- Consider using amchur (mango powder) in cooking
7. Reduce iron inhibitors
- Avoid drinking some types of tea and coffee with meals.
8. Consider food preparation techniques that enhance iron absorption although not required
- Soaking and sprouting beans, grains, and seeds, and the leavening of bread.
- Eat foods such as miso and tempeh (fermentation may improve iron bioavailability)
9. Eat a varied plant-based diet or lean unprocessed meats
- Green leafy vegetables, such as spinach, kale, swiss chard, and beet greens
- Legumes such as chickpeas, white beans, lentils, peas, and kidney beans
- Grains such as whole wheat bread and brown rice
- Tree nuts such as cashews and pistachios
- Protein-rich food such as tofu and tempeh
- Perhaps some surprising sources, such as chocolate, potato, tomato, and raisins
Iron and a Balanced Diet
Iron is vital for optimal body function but don’t forget that too much of any nutrient can have adverse effects. Interactions between nutrients can lead to imbalances. A surplus of one nutrient can lead to a deficiency of another. For example, too much manganese can aggravate an iron deficiency. A deficiency of a nutrient like iron may also leave the body vulnerable to a contaminant mineral like lead.
Another consideration is that iron is a pro-oxidant and high iron stores and heme iron have been linked to chronic diseases such as heart disease. Nutrients like vitamin C (antioxidant) can quench iron (pro-oxidant) to mitigate negative effects. Supplementation can easily create imbalances so make sure to take supplements as directed from a healthcare provider to determine the correct dosage and type.