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From the Townsend Letter
May 2007


Nutritional Influences on Illness
Treating Diabetes Mellitus with Minerals, Part One
by Melvyn R. Werbach, MD

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Calcium intake is significantly related to insulin sensitivity.1 Moreover, in a study of almost 85,000 women, calcium intake was inversely related to the risk of non-insulin-dependent (type 2) diabetes. Women in the highest quintile had 70% of the risk of those in the lowest quintile.2

Fourteen years later, an equally large study of female nurses found that women who consumed at least 1200 mg of calcium daily had a 21% lower risk of type 2 diabetes than women who consumed less than 600 mg a day. In fact, a combined daily intake of at least 1200 mg calcium and at least 800 IU vitamin D daily was associated with a 33% lower risk of type 2 diabetes compared to an intake of less than 600 mg calcium and 400 IU vitamin D.3

The hypothesis that low calcium intake causes insulin resistance was tested on 20 non-diabetics with essential hypertension. They were placed on a four-week trial of a low calcium diet (500 mg daily) and then randomly assigned to receive 1,500 mg of calcium daily or placebo. Only in the supplemented group, mean fasting plasma insulin levels went down, and the insulin sensitivity index increased.4

In a small open trial, an oral calcium load augmented glucose-induced insulin secretion in diabetics but not in normals.5 Controlled trials are needed to better evaluate the efficacy of high-dosage calcium supplementation, although calcium deficiency should clearly be repleted.

Epidemiologic studies suggest that diabetics have reduced tissue chromium levels, especially those with existing cardiovascular disease.6 In fact, glucose intolerance is one of the first signs of chromium deficiency.7 Moreover, serum chromium levels are positively correlated with serum insulin levels.8

Several double-blind studies have provided evidence that chromium supplementation – especially in the form of chromium picolinate – may improve insulin sensitivity and glucose metabolism in patients with glucose intolerance and type 1, type 2, gestational, and steroid-induced diabetes.6 The picture is not entirely clear, however, as some double-blind studies have failed to find evidence of chromium's efficacy. For example, 1000 µg chromium daily in the form of chromium picolinate failed to improve HgA1c after six months in a group of poorly controlled insulin-treated type 2 diabetics.9 In addition to the effects of chromium on glycemic response, case reports suggest that peripheral neuropathy may respond to supplementation in chromium-deficient diabetics.10 Controlled trials are needed to confirm this observation.

The beneficial effects of chromium are usually attributed to its role as a component of glucose tolerance factor.11 However, the essentiality of chromium to GTF has come into question following studies in which fractions of extracts of brewer's yeast were purified and GTF activity was found in fractions that contained no chromium.12

Magnesium intake appears to be inversely related to the risk of type 2 diabetes.13 Moreover, a study of 50 non-insulin-dependent diabetics found that only 20% of them met the RDA for magnesium.14 Magnesium nutriture is frequently depressed in diabetics,15 especially those with coronary heart disease16 or proliferative retinopathy.17 Hypomagnesemia may result from increased urinary magnesium excretion as a consequence of glycosuria.18 Reduced erythrocyte and platelet magnesium concentrations are also common.19

A consensus panel of the American Diabetes Association has suggested that "magnesium deficiency may play a role in insulin resistance, carbohydrate intolerance, and hypertension."20 While insulin enhances magnesium uptake,24 when a dietary magnesium deficiency was induced in normal male volunteers, they developed insulin resistance.22

There is evidence that magnesium activates the key enzymes of glycolysis,23 and results of controlled studies suggest that chronic magnesium supplementation may improve glycoregulation by improving insulin response and action.24

Another consensus panel of the American Diabetes Association has suggested that diabetic patients with documented magnesium deficiency should receive "oral magnesium chloride of dependable potency and bioavailability."25 No matter which magnesium salt is provided, it may take a minimum of three months to correct hypomagnesemia.26

Dr. Werbach cautions that physicians or practitioners whose training prepares them to recognize serious illness and to integrate nutritional interventions safely into the treatment plan should supervise the nutritional treatment of illness.

In Foundations of Nutritional Medicine, one of Dr. Werbach's internationally acclaimed Sourcebooks of Clinical Research, health practitioners concerned with nutritional influences on illness will find valuable information which will improve the quality of their practices. A free brochure describing all Dr. Werbach's books is available from Third Line Press, 4751 Viviana Drive, Tarzana, California 91356; 800-916-0076; 818-996-0076 ; Fax: 818-774-1575; E-mail:; Internet:

1. Ma B, et al. Dairy, magnesium, and calcium intake in relation to insulin sensitivity: Approaches to modeling a dose-dependent association. Am J Epidemiol. 2006; 165(5):449-58.
2. Colditz GA, et al. Diet and risk of clinical diabetes in women. Am J Clin Nutr. 1992; 55:1018-23.
3. Pittas AG, et al. Vitamin D and calcium intake in relation to type 2 diabetes in women. Diabetes Care. 2006; 29(3):650-56.
4. Sanchez M. Oral calcium supplementation reduces intraplatelet free calcium concentration and insulin resistance in essential hypertensive patients. Hypertension. 1992; 29(2):531-6.
5. Fujita T, et al. Insulin secretion after oral calcium load. Endocrinol Jpn. 1978; 25(6):645-8.
6. Cefalu WT, Hu FB. Role of chromium in human health and in diabetes. Diabetes Care. 2004; 27(11):2741-49.
7. Freund H, et al. Chromium deficiency during total parenteral nutrition. JAMA. 1979; 241(5): 496-8.
8. Liu VJ, Abernathy RP. Chromium and insulin in young subjects with normal glucose tolerance. Am J Clin Nutr. 1982; 25(4):661-7.
9. Kleefstra N, et al. Chromium treatment has no effect in patients with poorly-controlled, insulin-treated type 2 diabetes in an obese Western population: A randomized, double-blind, placebo-controlled trial. Diabetes Care. 2006; 29(3):521-25.
10. Jeejeebhoy KN, et al. Chromium deficiency, glucose tolerance, and neuropathy reversed by chromium supplementation, in a patient receiving long-term parenteral nutrition. Am J Clin Nutr. 1977; 30(4):531-8.
11. Haylock SJ, et al. Separation of biologically active chromium-containing complexes from yeast extracts and other sources of glucose tolerance factor (GTF) activity. J Inorg Biochem. 1983; 18(3):195-211.
12. Simonoff M, et al. The isolation of glucose tolerance factors from brewer's yeast and their relation to chromium. Biol Trace Elem Res. 1992; 32:25-8.
13. vanDam RM et al. Dietary calcium and magnesium, major food sources, and risk of type 2 diabetes in US black women. Diabetes Care. 2006; 29:2238-43.
14. Schmidt LE, et al. Evaluation of nutrient intake in subjects with non-insulin-dependent diabetes mellitus. J Am Diet Assoc. 1994; 94(7):773-4.
15. Durlach J, Collery P. Magnesium and potassium in diabetes and carbohydrate metabolism. Review of the present status and recent results. Magnesium. 1984; 3(4-6):315-23.
16. Wen-gang Z, et al. Hypomagnesemia and heart complications in diabetes mellitus. Chin Med J. 1987; 100:719-22.
17. McNair P, et al. Hypomagnesemia, a risk factor for diabetic retinopathy. Diabetes. 1978; 27:1075-7.
18. Tosiello L. Hypomagnesemia and diabetes mellitus. Arch Intern Med. 1996; 156:1143-8.
19. Corica F, et al. Magnesium levels in plasma, erythrocyte, and platelets in hypertensive and normotensive patients with non-insulin-dependent diabetes mellitus. Biol Trace Elem Res. 1996; 51:130-2.
20. American Diabetes Association. Consensus statement. Magnesium supplementation in the treatment of diabetes. Diabetes Care. 1992; 15(8):1065-7.
21. Lostroh AJ, Krahl. Magnesium, a second messenger for insulin: Ion translocation coupled to transport activity. Adv Enz Regul. 1974; 12:73-81.
22. Nadler JL, et al. Magnesium deficiency produces insulin resistance and increased thromboxane synthesis. Hypertension. 1993; 21:1024-9.
23. Elamin A, Tuvemo T. Magnesium and insulin-dependent diabetes mellitus. Diabetes Res Clin Pract. 1990;10:203-9.
24. Paolisso G, et al. Improved insulin response and action by chronic magnesium administration in aged NIDDM subjects. Diabetes Care. 1989;12:265-69.
25. American Diabetes Association. Consensus panel. Magnesium supplementation in the treatment of diabetes. Diabetes Care. 1995; 18(Suppl 1):83-5.
26. Eibl NL, et al. Hypomagnesemia in non-insulin-dependent diabetes: effect of a 3-month replacement therapy. Diabetes Care. 1995; 18(2):188-92.


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