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Goiter, in countries such as Africa, is many times caused by very little Iodine in your diet. An increase in intake may help reduce the growth of the goiter.
Cod fish, tuna fish, yogurt, cow's milk, eggs, cheese, and strawberries are very good sources of iodine. If you have iodized salt available to you or can have it made available to you, then please use it for cooking.
Foods that should be AVOIDED include: cabbage, turnips, brussel sprouts, seaweed, and millet because they inhibit production of thyroid hormone.
If you feel like you are having difficulty breathing due to the enlarging goiter, please see a doctor or health provider as soon as possible. Because of your pregnancy, treatment may be limited but stopping the goiter from further enlargement is crucial.
Please read more information on Goiter here: https://www.empowher.com/condition/goiter/treatments