A recent review found three of 12 magnesium supplements selected by researchers at ConsumerLab.org for testing failed to meet minimum quality standards. Two of the products identified contained less than 50 percent of the magnesium spelled out on the labeling and a third was contaminated with lead.
Among the name brands tested by ConsumerLab.org were ones produced by Life Extension, Nature's Bounty, Equaline, Puritan's Pride and Vitamin World.
Also compared in the report are variances among such chemical forms as magnesium oxide, amino acid chelates, magnesium hydroxide, magnesium gluconate and magnesium citrate.
You can read more about supplement quality issues here.
ConsumerLab.com May 19, 2009
NPI Center May 20, 2009