Large intake of fluoride may stain and even weaken your teeth
Iron toxicity is also common, even small amount over RDA can cause gastrointestinal upset, nausea and black bowel actions.
Higher level of magnesium can cause diarrhea at doses above 400mg/d.
It can cause diarrhea at doses above 750mg/d and mild nausea and vomiting at lower does.
Over does of iodine can cause goiter, the mineral stimulate thyroid gland, which swell in a furious attempt to step up its production of thyroid hormones.
Doses as high as 5 milligram of selenium a day to thickened but fragile nails, hair loss, and perspiration with garlicky odor
It can cause nausea and vomiting, immunosuppression and impaired copper uptake. Selenium at doses above 0.91mg/d can cause brittle nails and hairs, peripheral neuropathies and gastrointestinal upset.