Inhibition of tumor growth by magnesium depletion of rats.

In earlier studies tumor growth was inhibited in rats that first were made magnesium-deficient and subsequently implanted with tumors. The objective of this study was to determine if the reverse sequence is also effective. Namely, is tumor growth inhibited if tumors first are established and then a magnesium deficiency imposed? Rats with palpable mammary adenocarcinomas, or with sham implants were pair-fed either a control or magnesium-deficient diet for 32 days. Rats were then killed and tumors, plasma and several tissues analyzed. In tumors from magnesium-depleted rats, growth was inhibited 46%, magnesium concentration decreased 40% and necrosis was 50% greater. Magnesium depletion alone resulted in a 66% decrease in magnesium and a 29% increase in copper in plasma. Also, depletion caused a decrease in heart zinc and increase in kidney copper concentrations. As a result of tumor growth alone, concentrations of zinc in plasma decreased 40% and copper increased 37%. Rats with tumors also had decreased sodium and increased potassium levels in plasma. To our knowledge this is the first demonstration that the growth of an established tumor can be retarded solely by dietary magnesium depletion and thus may be significant for the nutritional management of tumor patients.