Iron is tricky: it’s essential for health, but ferrous sulfate (the typical supplement kind) can be corrosive and is hard to eliminate from the body. Men and postmenopausal women are especially at risk for iron overload unless they regularly donate blood. Too much iron can increase your risk for type 2 diabetes, liver problems, or even neurodegenerative diseases like Alzheimer’s or Parkinson’s.
Skip iron-fortified foods and supplements, especially if you’re not iron deficient. If you do need more iron, choose foods like liver and red meat.
7. Magnesium Oxide
Magnesium is vital for muscle relaxation, sleep, and heart health. Sounds good, right? But magnesium oxide, which is dirt-cheap and common in supplements, is absorbed so poorly (only about 3%!) you get almost none of the benefit—plus, it can cause diarrhea as you take more, flushing out essential electrolytes.
Instead, opt for magnesium glycinate, which is highly absorbable (up to 85%), gentle on the stomach, and actually works.
8. Synthetic Vitamin D (Ergocalciferol, or D2)
Vitamin D is a must for immunity, bones, and mood. The bad news? Vitamin D2 (ergocalciferol), still commonly prescribed or added to supplements, is made by irradiating fungus or yeast. It doesn’t convert well to the active form in your body and doesn’t bind as strongly to the proteins that deliver vitamin D to where you need it.
Choose vitamin D3 (cholecalciferol) from fish, cod liver oil, egg yolks, or high-quality supplements for the real deal.
