Yes. They can significantly lower the amount of thyroid hormone that gets absorbed. Because calcium is a positively charged ion, it can bind to any negatively charged chemical, including levothyroxine. Spacing the thyroid hormone at least 2 hours from calcium (including antacids such as tums), iron, multi-vitamins, and certain other meds can help keep thyroid blood levels stable.
Does high VitD3 & Calcium supplements interfere with absorption of Iron & Omega3 Fatty Acid from food for 57+ yr female?
They help each other. The do not compete directly. In fact, consuming essential fatty omega-3 fatty acids can increase vitamin D's ability to increase calcium absorption from the gut. This is especially important in improving bone mineralization and decreasing bone loss seen in osteoporosis. Vit D3 and omega-3 together can also improve the risk profile for peripheral vascular disease. Read more...