Low iron and hypothyroidism connection

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Iron is tricky – in excess is toxic as it increases oxidative stress and accelerates ageing. When low, it can contribute to fatigue and slow down your thyroid and lead to hypothyroidism. By low iron, I don’t mean below standard lab ranges as these are usually pretty wide. You can have everything within “normal” range but still feeling that something is a bit off or noticing certain symptoms of hypothyroidism.  By low, I mean at the suboptimal level – not dramatically deficient however not enough to perform necessary function.

What is optimal ferritin level (functional medicine range)?

In terms of thyroid, you should be really looking at ferritin status which is storage form of iron. There is strong correlation between low ferritin and low thyroid function. Again, by low I mean below 70 (while the lab range is usually 12-150 for women and 12-300 for men).

Why iron is important for thyroid function?

TPO (thyroperoxidase) is iron dependent enzyme that is involved in making thyroid hormones as well as converting T4 (inactive thyroid hormone) to T3 (active form). If the conversion is impaired you may experience symptoms like hair loss, weight gain, fatigue, depression.  It can happen even when T4 is within normal range as T3 it’s the active hormone that controls your metabolism and other processes. Also, iron is required for the utilization of T3 inside the cell. If you are looking for natural treatment for hypothyroidism – definitely check your iron levels as that’s one of the key nutrients necessary for healthy thyroid function.

Understand your thyroid blood results

Usually GP will recommend to do TSH and T4 blood test which to be honest will not tell you much. As just mentioned, the amount of T3 impacts how you feel. Moreover, T3 hormones have to enter the cell to perform it’s action. The amount of T3 in the blood serum will give you some picture of your thyroid function but it won’t tell you how much T3 is inside the cell.

Here iron comes in play again. Low iron stores can impair utilization of thyroid hormone at the receptor side, meaning you make you can make enough of T3 but T3 can’t enter the cell and because of that you can still experience low thyroid symptoms. You may also see elevated TSH if the TPO activity (iron dependent enzyme) is downregulated. As result, pituitary gland will be constantly sending signals (by producing TSH) to make more thyroid hormones as there is not enough available. Elevated TSH with low T4 could be another symptoms of hypothyroidism. Additionally, low ferritin levels can increase production of reverse T3 which is an inactive form of T3 that is ‘blocking’ action of active T3 hormones

You can see how devastating low iron stores can be on the thyroid as it can affect the production, conversion, and utilization of thyroid hormone.

Important nutrients for thyroid function

Iron is only one of many other cofactors involved in thyroid hormone synthesis. Other essential cofactors include selenium, copper, zinc, magnesium, niacin, riboflavin, B6, iodine and tyrosine. A deficiency of any one of these nutrients would result in reduced T3 production, causing you to experience hypothyroid symptoms. Vitamin A and D also play important roles in thyroid cell receptor behaviour to regulate thyroid hormone metabolism. Nevertheless, let’s focus only on iron today.

Difference between ferritin and iron

Both are important but ferritin shows overall iron status, not only blood iron levels. Ferritin is your storage iron that body is using up if not enough iron is provided with food daily. If you have normal blood iron level but low ferritin it could mean that your body is slowly using up your iron reserves to maintain blood iron level at certain level.  

Once you used up most of you iron storage, blood iron level can no longer be maintained and it will start to fall. If both ferritin and iron levels are low that probably would indicate that you are at high risk of anaemia and other low iron related issues like low energy, hair loss etc. Additionally, women are more prone to low iron/ferritin because of menstrual cycles and blood loss. 

Iron intake vs absorption

Dietary iron comes in various forms, depending what is source of the food we eat: animal vs plant sources. For example, iron from meat is more bioavailable (so called heme iron) and it’s in a form that your body can utilise. Iron from vegetable and other plant sources is a non-heme iron and is less bioavailable. From animal sources you can absorb up to 15-35% of iron in a meal, from plant sources the absorption is around 2-7%. Moreover, iron absorption from plant sources can be greatly increased or decreased by various factors.

What can impair iron absorption from plant sources?

  • Phytic acid rich foods (cereals, grains, nuts, beans), 
  • Milk, dairy and egg protein,
  • Polyphenols (tea and coffee). 
  • Tannic acid (tea)
  • Cocoa
  • Certain herbs (peppermint, chamomile)
  • Certain minerals: calcium, zinc, magnesium, copper.
  • Autoimmune diseases and leaky gut 

You may think…. so phytic acid is pretty much in most of the plant foods right? Yes… however you can decrease phytic acid content by cooking, soaking or fermenting the food. Phytates can reduce iron absorption even by 80%. The good thing is that, vitamin C rich foods (bell peppers, broccoli, papaya, kiwi, guava) can counteract the effect and enhance iron uptake

Spinach – one of the main thyroid disruptor

Spinach is known as a good source of iron however; raw spinach contains oxalic acid or oxalate. Oxalic acid naturally binds with minerals like calcium and iron, making them harder for the body to absorb. Also, spinach contain goitrogen, a molecule that slows your thyroid gland. Cooking spinach can help decrease activity of harmful oxalates and also goitrogens, making it better to consume in terms of iron absorption and thyroid health.

Iron deficiency and hypothyroidism – a vicious cycle

Low iron can be driving hypothyroidism but also hypothyroidism can lower your stomach acid which is necessary for mineral absorption including iron. It’s a bit like vicious cycle that you can break if you sort out your digestion, provide your body with essential minerals, vitamins and take care of your gut and stomach acid levels to ensure the right absorption

How to boost your iron levels with foods?

Your daily iron intake should be around 15mg a day. Here are foods highest in iron:

  • Chicken liver: 12mg/100g
  • Beef: 9mg / 6oz steak
  • Shellfish/Oysters: 8mg. 3oz serving
  • Dried apricots: 7mg/ per cup
  • Parsley: 6mg/100g
  • White beans: 6mg/ cup
  • Spinach: 6mg/ cup (cooked)
  • Quinoa: 3mg/cup (cooked)          
  • White button mushrooms: 3mg/cup (cooked)
  • Spirulina: 3mg/10g

Supplement iron or not?

The simple answer is never supplement iron without having your blood test done. This is because it’s very easy to overdose iron and there is no known mechanism to excrete iron apart from blood loss. Iron is needed but as mentioned earlier, excess iron is highly pro-inflammatory and damaging. If it comes to supplements, liquid iron is also gentler for stomach and less likely to cause constipation (very common side effect of iron supplements). Also, iron supplements should not be taken at the same time as levothyroxine  (thyroid medication). Allow at least 3-4 hours after taking iron before taking your thyroid medication.

If you are interested in finding out more about side effects and dangers of iron supplementation click here

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