Higher magnesium intake may protect against colorectal cancer A report published in the January 5 2005 issue of the Journal of the American Medical Association revealed an association between a higher intake of the mineral magnesium and a lower incidence of colorectal cancer. Experimental studies have shown that supplementing with magnesium lowers the incidence of colon cancer in animals, but human epidemiologic evidence has been lacking.
Swedish researchers examined data obtained from the Swedish Mammography Cohort, which followed 61,433 women for 14.8 years beginning in 1987. The women were between the ages of 40 and 75, and were cancer-free upon enrollment. Analysis of food frequency questionnaires provided data on the intake of zinc and other nutrients.
Five hundred forty-seven women were diagnosed during follow-up with colon cancer; 252 developed rectal cancer, and 6 women developed both colon and rectal cancer. The researchers found that women whose magnesium intake was in the top one-fifth of subjects had a 41 percent lower risk of developing colorectal cancer than those whose intake was in the lowest fifth. Magnesium intake was inversely related to the incidence of both proximal and distal colon cancer as well as rectal cancer.
As elevations in the marker for insulin secretion known as C-peptide have been related to a greater risk of human colorectal cancer, magnesium may protect against the disease via its ability to improve insulin sensitivity and lower insulin concentrations. The mineral also plays an essential role in the maintenance of genomic stability, DNA repair, and modulation of cell proliferation, cell cycle progression and cell differentiation.
While the results of this large study indicate that increased magnesium intake could reduce colorectal cancer risk, the authors recommend the usual randomized clinical trials to verify the findings.
Colorectal Cancer The lifetime risk of developing colorectal cancer, which is higher in developed countries, appears to be 4.6% for men and 3.2% for women (Chu et al. 1994).
Obesity, particularly abdominal obesity, is associated with an increased risk (Martinez et al. 1999; Russo et al. 1998) whereas physical activity is associated with a decreased risk of colorectal cancer (Giovanucci et al. 1996). There is also an association between diabetes mellitus and colorectal cancer risk; the risk is increased with a high fasting glucose level, high insulin levels, and obesity (Ma et al. 1999; Schoen et al. 1999).
Insulin plays an active role in promoting tumor growth via angiogenesis. Insulin is a growth factor that stimulates glycolysis and the proliferation of many cancer cell lines. Insulin is thought to facilitate angiogenesis by increasing lactic acid production in hypoxic tumor cells and by stimulating the proliferation of vascular cells. In cancer patients, elevated levels of insulin are common in cancerous tissue and blood plasma. It is therefore suggested that both a low sugar and a low saturated fat diet be followed.
Natural compounds have been reported to inhibit cancer-promoting effects of insulin. For example, vitamin C has been reported to increase oxygen consumption and reduce lactic acid production in tumor cells. In addition, some natural compounds may help reduce insulin production by reducing insulin resistance. Insulin resistance occurs when cells are no longer sensitive to insulin and thus more insulin is produced in an effort to reduce glucose levels.
Insulin resistance has been implicated as a risk factor for cancer, and diets high in saturated fats and omega-6 fatty acids promote insulin resistance. Although the exact pathway is unknown, it is thought that the mechanism of action is via chronic activation of protein kinase C (PKC). Some of the known natural compounds that can reduce insulin resistance include omega-3 fatty acids, curcumin, flavonoids, selenium, and vitamin E.
A review of assimilation studies suggests that the citrate salt of magnesium is the best absorbed into the bloodstream. The major downside of using magnesium citrate, however, is that it is only 10% magnesium and the recommended intake of elemental magnesium to maintain vascular health is between 300 to 800 mg a day.
The Life Extension Buyers Club offers a magnesium supplement that provides 160 mg of elemental magnesium in each 1000 mg capsule of magnesium citrate.