The Importance of Iron to Thyroid Patients and Links to Gut Health

Many thyroid patients struggle to keep their iron levels up to a healthy level, as a result of the effect of prolonged hypothyroidism.

The four main tests to use to determine if iron is adequate within the body are:

  1. Serum iron.
  2. Serum Ferritin.
  3. Total Iron Binding Capacity (TIBC).
  4. Transferrin Saturation %.

From patient experience thyroid patients usually feel better if:

  1. Serum iron is over 90 ug/dL and ideally closer to 100-110 ug/dL. This is based on a lab range of 65-176 ug/dL for men and 50-170 ug/dL for women.

  2. Serum ferritin is at least in the range 80-100 ng/mL for women (men do well with similar results or even a little higher). This is based on a lab range of 22-320 ng/mL for men/post menopausal women and 10-290 ng/mL for pre menopausal women.

  3. If iron supplementation is being considered, TIBC should be at or above the lower quartile. This is so that it is clear there is capacity to supplement with iron.

  4. Transferrin saturation % in the 35-45% range.

This post is not about iron itself, or about supplementing it to achieve healthy levels. It is about the digestive system, and its role in absorbing iron, and the implications of this.

The absorption of the majority of nutrients takes place in the jejunum (the middle section of the small intestine), with the following notable exceptions:

  • Iron is absorbed in the duodenum and first part of the jejunum.
  • Vitamin B12 is absorbed in the terminal ileum (the last part of the small intestine).
  • Water and lipids are absorbed throughout the small intestine.
  • Sodium bicarbonate, glucose, fructose and amino acids are also absorbed in the small intestine.

The mechanism of iron transport from the gut into the blood stream remains a mystery, despite intensive investigation.

However, the physical state of iron entering the duodenum greatly influences its absorption.

Gastric acid lowers the pH in the duodenum (makes it more acidic), enhancing the solubility and uptake of iron. When gastric acid production is impaired (for instance by acid pump inhibitors, such as the drugs Prilosec or Omeprazole), iron absorption is reduced substantially.

Heme is the name of a number of naturally occurring organic molecules that contain iron. Heme is found in meat. Interestingly, heme is absorbed by machinery completely different to that of inorganic iron. The process is more efficient and is independent of duodenal pH.

Consequently meats are excellent nutrient sources of iron. Meat is the best form of food to obtain iron from, as even when stomach acid is reduced, which it often is in hypothyroid patients, the natural form of organic iron is still absorbed extremely well. Heme iron may also be provided in supplement form.

Many people discuss the benefits of eating vegetables like spinach but this form of iron is not as well absorbed as the heme in meat (red meat, liver and kidneys especially). The shortage of meats in the diets of many of the people in the world adds to the burden of iron deficiency.

A number of dietary factors influence iron absorption. Vitamin C can often increase iron uptake (but better to take this as Whole Food Vitamin C, as sometimes the standard type can lower ferritin), in part by acting as weak chelators to help to make the iron more soluble in the duodenum.

Iron absorption is inhibited by plant phytates and tannins. These compounds also chelate iron, but prevent its uptake by the absorption machinery. Phytates are prominent in wheat and some other cereals, while tannins are prevalent in (non-herbal) teas.

So, the health of the digestive system is critical to the raising, and maintenance, of good iron levels, as it is the duodenum that absorbs iron.

Low stomach acid may also affect the absorption or iron.

It is also important to note that all iron is not equal. Iron in meat is very effectively absorbed. In addition to this, for someone with a gut that is already compromised in some way, then they often have a group of pathogenic bacteria growing in their gut. These pathogens are iron-loving bacteria, and they consume much of any inorganic iron supplements that are taken, which in turn feeds the population and creates further imbalances in the gut flora. These bacteria include: Actinomyces spp., Mycobacterium spp., strains of E.coli, Cornybacterium spp., and others.

Consequently, for someone with a compromised gut taking iron supplements may make this situation worse, and particular attention may need to be given to healing the gut.

If someone has a compromised gut then they may continue to struggle to raise iron levels, and, as a consequence, they may struggle to have effective thyroid hormone action and adrenal health. A compromised gut does not always mean that the individual has many obvious digestive system symptoms!

Sometimes, the overall health of the person, their response to thyroid hormone, laboratory test results of nutrient levels, their diet and past history (antibiotic use etc) may need to be assessed to get some idea that the gut is involved. Healing a compromised gut is often the most important action that a thyroid patient can take in order to get well.

For people who struggle to raise their iron storage, infusions or injections may be needed from their doctor.

The bottom line is that iron is critical to the function of many of our systems, including thyroid hormone action. Good iron levels are essential, but we must not ignore the digestive system. Improving the health of a thyroid patient’s digestive system may be critical to the absorption of iron and other nutrients as well as limiting the entry of other toxins into the bloodstream. Just taking iron supplements from a bottle, without dealing with digestive system health, may not be an effective approach for some thyroid patients.

Best wishes,


Paul Robinson

Paul Robinson is a British author and thyroid patient advocate. The focus of his books and work is on helping patients recover from hypothyroidism. Paul has accumulated a wealth of knowledge on thyroid and adrenal dysfunction and their treatment. His three books cover all of this.

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