Iron deficiency is amongst the most prevalent nutrient deficiencies worldwide, with approximately 25-30% of the global population affected; more than one billion people. Women are especially susceptible as they lose iron through menstruation. Symptoms of low iron include:
- Extreme fatigue that doesn’t improve with rest
- Pale skin along the lower eyelids and palms
- Shortness of breath or chest pain when doing simple, rudimentary tasks
- Fast or irregular heart beats as the heart works harder to pump oxygen. If this happens seek your doctor for evaluation.
- Dizziness, lightheadedness, or frequent headaches. Poor concentration.
- Pica. Craving ice, dirt, clay, or starch.
- Brittle nails and hair thinning.
- Cracks in the corner of your mouth; swollen or sore tongue.
- Restless leg syndrome.
If you suspect iron deficiency, check with a doctor. Ferritin testing is a relatively straightforward blood test to estimate iron content and confirm if you’re good or not.
Why You Need Iron
Iron has a few critical roles in your body. 70% of your body’s iron is bound to hemoglobin (red blood cells), functioning to carry and deliver oxygen to the tissues that need it. Oxygen is required to energy metabolism; without it your body wouldn’t make enough energy to keep you alive.
Iron also produces myoglobin, a protein that stores oxygen in your muscles as a reliable supply for exercise/emergency energy. Iron plays a role in metabolism converting the food you eat into energy.
Iron supports proper brain development. Neurotransmitters such as dopamine, serotonin, and norepinephrine require iron for production so they can properly regulate mood, awareness, and behavior. Furthermore, iron helps create myelin, a sort of insulating sheath around your nerve fibers to speed up and contain brain signals. Myelin is akin to the rubber sheath around electrical wire; it keeps the signal contained and directed to where it needs to go.
Your immune system requires iron to create T cells which fight off infection and pathogens. And iron is required for creating DNA so your cells can divide, repair, and grow normally.
Iron performs a variety of important functions though the most important is ensuring your body has enough hemoglobin for sufficient oxygen delivery. When the body doesn’t receive enough iron through nutrition, signs of deficiency creep up, eventually culminating into iron-deficiency anemia (IDA). IDA is when hemoglobin drops below ideal levels and symptoms become clear. Therefore, ensuring you get sufficient iron via your food is paramount for optimal health.
Men aged 19+ need 8mg of iron a day. Women aged 19-50 need 18mg of iron per day then 8mg per day after the age of 51 or menopause. Pregnant women need 27mg iron per day and 9-10mg per day if breastfeeding.
Iron-Rich Food
There are 2 types of dietary iron: heme iron found in animal sources and non-heme iron found in plant sources.
Heme Iron Food Sources (mg per 100 gram serving):
- Canned Clams: 24-28
- Pork Liver: 18
- Fresh Clams: 14
- Chicken Liver: 9-11
- Lamb Liver: 10.2-11
- Octopus: 9.5
- Oysters: 8.3
- Mussels: 7.1
- Beef Liver: 6.5
- Venison: 5
- Chicken Gizzard: 3.2-4.6
- Anchovies: 3.9
- Canned Sardines: 2.9
- Beef (lean cuts): 2.5
- Duck 2.5
- Lamb: 2.3
- Dark Turkey Meat: 2.3
- Dark Chicken Meat: 1.3
- Pork: 1-1.2
- Salmon 0.8
Non-Heme Food Sources (mg per 100 gram serving)
- Dried Spirulina: 28.5
- Fortified Breakfast Cereal: 8-20
- Sesame Seeds: 14.6
- Unsweetened Cocoa Powder: 13.9
- Dark Chocolate: 3.6-11.9
- Pumpkin seeds 8.07
- Hemp Seeds: 7.95
- Chia Seeds: 7.7
- Cashews: 6.7
- Flaxseeds: 5.7
- Tofu: 1.2-5.4
- Cooked Soybeans: 5.14
- Cooked Black Beans: 2.1-3.6
- Cooked Spinach: 3.6
- Cooked Lentils: 3.3
- Cooked White Kidney Beans: 2.9-3
- Cooked Chickpeas: 2.9
- Cooked Swiss Chard: 2.3-2.8
- Cooked Tempeh: 2.1-2.7
- Cooked Quinoa: 1.5
A few patterns stand out when analyzing these lists. On the heme side, organ meats provide much more iron than muscle meat. Shellfish and mollusks provide the most iron amongst seafood. On the non-heme side, seeds are the prominent contributors.
Cooking and food processing affects iron levels, as some foods lose iron compared to the raw counterparts (beans and lentils), and some foods become more concentrated through dehydration at the 100 gram level (spinach, Swiss chard, spirulina, cocoa powder).
The foods that people eat most regularly tend to gravitate to the middle and lower ends of the list. A varied diet consisting of these food sources accumulate to sufficient iron.
Increasing Bioavailability
The iron amounts listed in each food above illustrates total iron content. The actual percent of that overall iron your body absorbs depends on several factors.
Heme iron is much more bioavailable than non-heme. Your body absorbs ~15-35% of the total iron from heme sources compared to ~2-20% from non-heme sources. Heme absorption remains fairly consistent while non-heme absorption can vary greatly based on what’s present in the rest of the meal. Some constituents inhibit iron absorption while others promote.
A few dietary inhibitors of non-heme iron absorption are actually present within high-iron foods, thus explaining why non-heme iron bioavailability can range so low. Phytates in grains, beans, and lentils, certain proteins in soy, and oxalates in spinach, kale, beets, and berries all inhibit iron absorption. However, if you soak, sprout. or ferment phytate foods, and boil oxalate foods, they won’t curtail iron absorption as much, therefore increase bioavailability.
Calcium competes with iron absorption therefore separate your dairy, fortified plant milk, or calcium supplement meals at least an hour or two from your iron meals.
Plant compounds found in teas and coffee can reduce iron absorption by 90%, so again, protect your iron absorption from tea/coffee by at least 1-2 hours.
Vitamin C is the most powerful promoter of iron absorption, doubling and even tripling absorption. Vitamin C is present in many fruits and vegetables so it’s best to pair your iron foods with fruits and veggies.
Cooking with cast-iron cookware for acidic (tomato and citrus), moist (soups, stews, and sauces), and long-cooked (30-45+ minutes) foods can meaningfully increase iron content in food.
If all else fails, and you’ve been presented with a confirmed diagnosis of deficiency with supplementation prescribed, then the best way to take your supplement is on an empty stomach with vitamin C. Keep away from the inhibitors
Conclusion
Education, awareness, and knowledge of iron-rich foods can help stop deficiency before it occurs and meaningfully replenish your body’s iron requirements through healthy eating.