Chromium status appears to be an important factor in glucose metabolism: individuals with lower chromium levels are more likely to have type 2 diabetes or pre-diabetes than those with higher levels, and low chromium status is associated with poor glycemic control and insulin resistance in people with type 2 diabetes.^26,27,28,29 Furthermore, chromium supplementation has been shown to improve glucose control, insulin sensitivity, and other metabolic variables in people with insulin resistance and type 2 diabetes.

In one placebo-controlled trial that included 64 participants with type 2 diabetes and heart disease, taking 200 mcg per day of chromium was associated with greater weight loss, lower fasting glucose and insulin levels, improved insulin sensitivity, and reduced blood pressure after four months. In addition, chromium supplementation led to lower levels of inflammatory markers and higher antioxidant capacity.³⁰ A meta-analysis of 28 other randomized controlled trials concluded that chromium supplementation, particularly chromium chloride or chromium picolinate, reduces fasting blood glucose levels, triglyceride levels, and hemoglobin A1c values, and increases HDL-cholesterol levels.³¹ Because of its ability to help regulate dopamine and serotonin activity, some researchers propose chromium may be especially beneficial in people with type 2 diabetes who also suffer from depression or binge eating.³²

Studies showing beneficial effects from chromium supplementation have generally used 200 mcg per day or more. Many doctors recommend up to 1,000 mcg per day for people with diabetes.

Folic acid, sometimes called vitamin B9, is needed along with vitamins B6 and B12 for healthy homocysteine metabolism. Elevated homocysteine levels have been associated with a range of chronic cardiovascular and neurological diseases.⁴⁸ A meta-analysis pooled findings from 18 randomized controlled trials with a combined total of over 21,000 participants with type 2 diabetes. The analysis found folic acid supplementation lowered fasting blood glucose levels and reduced insulin resistance, but had no discernible effect on HbA1c, a marker of long-term blood glucose control.⁴⁹

Meta-analyses of studies have found high homocysteine levels are correlated with increased risk of diabetic retinopathy (damage to the visual center of the eye) and nephropathy (kidney damage).^50,51 Because folic acid supplementation can lower high homocysteine levels in people with type 2 diabetes, it may be protective.⁵² In a preliminary trial, a B vitamin supplement providing 6 mg of methylfolate (the active form of folic acid), along with 70 mg of pyridoxal 5-phosphate (active vitamin B6) and 4 mg of methylcobalamin (active vitamin B12), per day improved retinal function and reduced retinal edema in participants with type 2 diabetes-related retinopathy.⁵³ Several preliminary and placebo-controlled trials using the same B vitamin supplement indicate this combination may reduce symptoms of neuropathy related to type 2 diabetes.^54,55,56

Numerous studies have shown that poor magnesium status is associated with insulin resistance and type 2 diabetes.^61,62,63,64 Furthermore, diabetes itself causes increased magnesium loss, resulting in a vicious cycle of dropping magnesium levels and worsening insulin resistance.^65,66 Low magnesium levels have also been correlated with poor blood glucose control and increased risk of complications such as heart disease, kidney disease, and nerve damage in those with type 2 diabetes.^{67,68,69,70,71} Moreover, meta-analyses of randomized controlled trials have concluded that magnesium supplementation can lower blood pressure and decrease the risk of diabetes-related cardiovascular disease in people with type 2 diabetes.^72,73

Taking 250 mg of elemental magnesium (from magnesium oxide, gluconate, and lactate) per day for three months improved glycemic control and insulin sensitivity in a randomized controlled trial with 42 participants with type 2 diabetes.⁷⁴ In a placebo-controlled trial, patients with diabetes-related kidney failure taking 250 mg of elemental magnesium (from magnesium oxide) per day for 24 weeks had improved vascular health, as well as reduced insulin, total cholesterol, LDL-cholesterol, and C-reactive protein levels, Hgb1c values, and insulin resistance scores, and increased antioxidant capacity.⁷⁵ However, another placebo-controlled trial that included people with type 2 diabetes and related kidney disease found the combination of 250 mg magnesium (from magnesium oxide) plus 47 mg calcium (from calcium carbonate) per day improved lipid profiles but had no effect on glucose control and worsened insulin resistance after 12 weeks.⁷⁶ Many doctors recommend that people with diabetes supplement with 200 to 600 mg per day of elemental magnesium from a highly bioavailable magnesium salt without added calcium.