Brief Answer:
Soy

Detailed Answer:
There is no known direct effect of soy on hypothyroidism or Hashimoto's thyroiditis.
I am not aware of any published study in world medical literature that has shown a direct negative interaction of Herbalife formula 1 meal replacement with thyroid medications.

So both are ok to take with Hashimoto's / hypothyroidism as long as they are consumed 30 to 60 minutes after your thyroid medication is taken.

Regarding whether herballife formula 1 can be taken with soy milk, you will have to see the product label by the manufacturer. But I understand that herballife itself has soy, and you are probably worried if you would get too much soy if you took it with soy milk.
As far as the thyroid is concerned, do not be worried at all.

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Brief Answer:
Follow up

Detailed Answer:
Soy and soybean infant formula are known to interfere with the absorption of levothyroxine, as are dozens of other things which include
Calcium
Iron
ingestion of any meal with levothyroxine
Certain medications


There is no published evidence to the best of my knowledge that has studied exactly how much daily soy intake is safe in terms of not impacting levothyroxine absorption enough to cause significant problems.

So the general guidance I give to my patients is to eat soy and everything else for that matter in moderation, but take it at a different time than the levothyroxine tablet.

Even a high fiber diet and espresso coffee reduce the absorption of levothyroxne but I do not even mention this to my patients because it does not make sense stopping a good habit like fiber intake, when the alternative solution of adjusting the levothyroxine dose works just fine

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