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-   -   Do Fiber supplements interfere with Synthroid absorption? (http://www.lowcarbfriends.com/bbs/general-health-medical-issues/804046-do-fiber-supplements-interfere-synthroid-absorption.html)

Ronnie51 05-13-2013 08:39 AM

Do Fiber supplements interfere with Synthroid absorption?
My gastroenterologist told me I need to increase my fiber and water intake, which I've done to good results. However, I recently read that fiber supplements can interfere with the absorption of Synthroid, which I also take. The Synthroid bottle says to take it four hours apart from iron, calcium and antacids, but nothing about fiber. I've been taking a teaspoon of fiber powder in my morning coffee which is approximately an hour after taking my synthroid. Should I increase it to four hours apart? Thank you!

Leo41 05-13-2013 09:34 AM

Where did you read about fiber interfering with Synthroid? Everything on the internet isn't reliable.

The reason I ask is that I, too, take thyroid Rx, and I've read almost everything about the interference issues, and I've never seen fiber mentioned as a problem.

I'd be curious to see your source for this info because I've recently increased my fiber intake myself.

Ronnie51 05-13-2013 02:28 PM

Hi Leo,
I just did a search to see if I could find where I read that fiber interferes with Synthroid. I couldn't find my orginal "source", but I found something similar on thyroid.about.com. I've cut and pasted it below:

"Important Note for Thyroid Patients:
Increasing the fiber in your diet can affect your absorption of thyroid hormone. Be sure to take your thyroid medication at least two to three hours apart from fiber-rich foods and supplements if possible.

You should have your thyroid function retested about eight weeks after you start a fiber-rich diet or supplements--you may need an increased drug dosage to account for absorption changes due to the fiber."

So, now that's two places I've read it. I think the first one was at ehow.com but I can't find it now. What do you think?

Ronnie51 05-13-2013 02:32 PM

I found a website called synthroid.com and found this under "Tips for Taking Synthroid":

"Take Synthroid alone. Do not take Synthroid within 4 hours of ingesting medications, supplements, or foods that may interact with Synthroid. Antacids, iron, and calcium supplements, dietary fiber, soy, and even walnuts can affect your body's absorption of Synthroid. Talk to your doctor to learn more."

Right out of the horse's mouth...so I guess it's true. Hmmm....I almost always have an Atkins bar within 1-2 hours of taking my Synthroid. Not only does that contain fiber, it also contains soy. But I've been doing it for years and I'm not about to stop.

Leo41 05-13-2013 05:07 PM


I went to synthroid.com, and I think you'll see that if you read carefully, they are 'suggesting' that fiber and certain foods 'may' interfere with Synthroid absorption, but I think they're unnecessarily alarmist--based on having spoken to both my endo and pharmacist about exactly this issue.

There are always warnings about soy and walnuts, and raw spinach and all sorts of other food. My endo says that unless one particular food is a staple of my diet--i.e., I eat it every day, I should not be concerned. My pharmacist not only agrees, he says that the only things to be concerned about are calcium, iron, and antacids--with any thyroid Rx. They should be taken 4 hours away if in medicinal form. But if it's some calcium-rich food, like cheese, he says 2 hours should be sufficient.

Since I not only take Synthroid but also Cytomel--and that's in 3 dosages throughout the day, I'd go crazy trying to separate all the items that are mentioned. I have enough problems just with the calcium.

Ronnie51 05-13-2013 06:18 PM

Thank you for that information, Leo! I am not going to worry about it unless my next blood test in June shows a big change in my levels, which I'm not expecting based on how I feel (i.e., I feel the same as I did before starting the fiber supplements). Thanks again.

Lokarbiebarbie 05-19-2013 12:04 PM

Fiber 'binds' the absorption of the T4...T3 is easily absorbed and it starts with saliva...not the same with T4...the stomach doesn't 'uptake to the bowel' very fast with this synthetic hormone, therefore..I'd (and I do this even taking Armour) wait an hour for that fiber...actually..you could just take that fiber at night before bed too.

It take six weeks to see any change in blood chemistry with T4...that's why you go from feeling 'a bit better' to either 'great' or 'not so great' in six weeks after a change. :0

If I were trying to lose weight, and I was getting ONLY T4, I wouldn't take the chance of it being 'bound' by fiber, or calcium or anything else. Just sayin'

Ronnie51 05-22-2013 07:29 PM

I barely weigh 105 lbs, so needing to lose weight isn't an issue for me. The issue is my thyroid is sluggish, and I don't want anything to interfere with my absorption of synthroid. Just to be safe, I'm waiting two hours between taking the fiber and the synthroid and four hours with the calcium.

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