There are two types of iron in food & supplements: heme & non-heme.   These two types of iron utilize different absorption pathways in our intestines, so the things that affect their absorption are very different.

The challenge facing those looking to improve their iron status is the fact that non-heme iron has quite a low absorption rate...and if you can’t absorb it, you can’t use it.

Despite the fact that heme iron is more effectively absorbed, a large portion of the iron found in the average diet is derived from non-heme sources.

Therefore, it is essential to understand the factors that enhance and inhibit our absorption of non-heme foods.  So let's dive into what these factors are; we'll start with what interferes with non-heme absorption.

What factors can Block or Inhibit NON-HEME Iron Absorption?

Medications: Non-heme iron requires an acidic environment for optimal absorption. Medications that reduce the amount of acid in the stomach such as antacids or proton pump inhibitors can lead to low non-heme iron absorption.

Examples: Tums, Prevacid, Nexium, Omeprazole.

Phytates and Fiber: Phytate compounds have a significant effect on the amount of non-heme iron that is absorbed from a meal, and can reduce non-heme absorption by 50-65%.

Examples: Almonds, walnuts, peas, soy, rice, cereal, whole grains, beans, lentils, wheat bran.

Oxalates: Naturally-occurring food chemicals found in numerous food sources, and may inhibit the body’s iron absorption by combining with non-heme iron to form a compound called iron oxide.

Examples: Spinach, kale, potatoes, yams, dark chocolate, raspberries, beets, nuts & seeds, oregano, basil, parsley.

Calcium: (like iron) is an essential mineral, which means the body must get this nutrient from diet. As a mineral, calcium competes for the same absorption sites as iron.

Examples: Milk, cheese, yogurt, broccoli, kale, almonds, collard greens, rhubarb, tofu.

Tannins and polyphenols: Biological compounds that can bind with iron, therefore making non-heme iron insoluble. Of the polyphenols, cocoa (chocolate) and tea demonstrates the most powerful iron absorption inhibiting capabilities, in some cases up to 90%. Coffee is high in tannin and chlorogenic acid; one cup of coffee can inhibit non-heme iron absorption by as much as 60%.

Examples: Coffee, tea, chocolate, blackberries, blueberries, tomatoes, herbs, spinach, broccoli, blackberries.

Low stomach acid: Non-heme iron requires an acidic environment for optimal absorption, so low stomach acidity can greatly decrease the amount of iron absorbed in your stomach. Elderly individuals or bariatric patients often have less acidic stomachs. Frequent use of antacids or PPIs (proton pump inhibitors) can affect your stomach’s iron absorption.

Eggs: Contain phosphoprotein, a compound with iron-binding capacity that can impair non-heme iron absorption.  Studies have shown that one hardboiled egg can reduce the absorption of iron in a meal by as much as 28%.

How can I improve HEME iron absorption?

In both food and supplementation, heme iron is considered the body’s preferred iron source, as it has a 30-45% absorption rate on average.

Heme is bioavailable in its natural state, which means it is absorbed whole and does not need to be converted to enable absorption.  While heme is naturally well absorbed, there are a couple factors that can improve its absorption as well.

Protein: In the diet, heme iron naturally accompanies the protein in meat.  This is known as the MPF (Meat Protein Factor) in iron absorption.

Collagen Peptides: Collagen is a protein with a very unique amino acid structure. These amino acids, including histidine, isoleucine, and lysine, have been shown to have a positive impact on iron absorption and red blood cell creation.  Additionally, collagen aids in reducing inflammation within the intestines, which improves gut health & nutrient absorption.