A variety of vitamins, minerals, amino acids, and other supplements may help with symptoms and deficiencies associated with diabetes.

Multiple Vitamin–Mineral Supplement
In a double-blind study, supplementation of middle-aged and elderly diabetics with a multiple vitamin and mineral preparation for one year reduced the risk of infection by more than 80%, compared with a placebo.

Chromium
Medical reports dating back to 1853, as well as modern research, indicate that chromium-rich brewer’s yeast (9 grams per day) can be useful in treating diabetes. In recent years, chromium has been shown to improve glucose and related variables in people with glucose intolerance and type 1, type 2, gestational, and steroid-induced diabetes. Improved glucose tolerance with lower or similar levels of insulin have been reported in more than ten trials of chromium supplementation in people with varying degrees of glucose intolerance. Chromium supplements improve glucose tolerance in people with both type 2 and type 1 diabetes, apparently by increasing sensitivity to insulin. Chromium improves the processing of glucose in people with prediabetic glucose intolerance and in women with diabetes associated with pregnancy. Chromium even helps healthy people, although one such report found chromium useful only when accompanied by 100 mg of niacin. Chromium may also lower total cholesterol, LDL cholesterol, and triglycerides (risk factors in heart disease).

A few trials have reported no beneficial effects from chromium supplementation. All of these trials used 200 mcg or less of supplemental chromium, which is often not adequate for people with diabetes, especially if it is in a form that is poorly absorbed. The typical amount of chromium used in research trials is 200 mcg per day, although as much as 1,000 mcg per day has been used. Many doctors recommend up to 1,000 mcg per day for people with diabetes.

Supplementation with chromium or brewer’s yeast could potentially enhance the effects of drugs for diabetes (e.g., insulin or other blood sugar-lowering agents) and possibly lead to hypoglycemia. Therefore, people with diabetes taking these medications should supplement chromium or brewer’s yeast only under the supervision of a doctor.

Magnesium
People with diabetes tend to have low magnesium levels. Double-blind research indicates that supplementing with magnesium overcomes this problem. Magnesium supplementation has improved insulin production in elderly people with type 2 diabetes. However, one double-blind trial found no effect from 500 mg magnesium per day in people with type 2 diabetes, although twice that amount led to some improvement. Elders without diabetes can also produce more insulin as a result of magnesium supplements, according to some, but not all, trials. In some trials, insulin requirements are lower in people with type 1 diabetes who supplement with magnesium. However, in people with type 2 diabetes who nonetheless require insulin, Dutch researchers have reported no improvement in blood sugar levels.

Diabetes-induced damage to the eyes is more likely to occur in magnesium-deficient people with type 1 diabetes. In magnesium-deficient pregnant women with type 1 diabetes, the lack of magnesium may even account for the high rate of spontaneous abortion and birth defects associated with type 1 diabetes. The American Diabetes Association admits “strong associations…between magnesium deficiency and insulin resistance” but will not say magnesium deficiency is a risk factor. Many doctors, however, recommend that people with diabetes and normal kidney function supplement with 200–600 mg of magnesium per day.

Alpha lipoic acid
Alpha lipoic acid is a powerful natural antioxidant. Preliminary and double-blind trials have found that supplementing 600–1,200 mg of lipoic acid per day improves insulin sensitivity and the symptoms of diabetic neuropathy. In a preliminary study, supplementation with 600 mg of alpha-lipoic acid per day for 18 months slowed the progression of kidney damage in patients with type 1 and type 2 diabetes.

Evening primrose oil
Supplementing with 4 grams of evening primrose oil per day for six months has been found in double-blind research to improve nerve function and to relieve pain symptoms of diabetic neuropathy.

Glucomannan
Glucomannan is a water-soluble dietary fiber that is derived from konjac root (Amorphophallus konjac). Glucomannan delays stomach emptying, leading to a more gradual absorption of dietary sugar. This effect can reduce the elevation of blood sugar levels that is typical after a meal. After-meal blood sugar levels are lower in people with diabetes given glucomannan in their food, and overall diabetic control is improved with glucomannan-enriched diets, according to preliminary and controlled clinical trials. One preliminary report suggested that glucomannan may also be helpful in pregnancy-related diabetes. For controlling blood sugar, 500–700 mg of glucomannan per 100 calories in the diet has been used successfully in controlled research.

Vitamin E
People with low blood levels of vitamin E are more likely to develop type 1 and type 2 diabetes. Vitamin E supplementation has improved glucose tolerance in people with type 2 diabetes in most, but not all, double-blind trials. Vitamin E has also improved glucose tolerance in elderly people without diabetes. Three months or more of supplementation may be required for benefits to become apparent. The amount used is at least 900 IU of vitamin E per day.

In one of the few trials to find vitamin E supplementation ineffective for glucose intolerance in people with type 2 diabetes, damage to nerves caused by the diabetes was nonetheless partially reversed by supplementing with vitamin E for six months. Animal and preliminary human data indicate that vitamin E supplementation may protect against diabetic retinopathy and nephropathy, serious complications of diabetes involving the eyes and kidneys, respectively, though no long-term trials in humans have confirmed this preliminary evidence.

Glycosylation is an important measurement of diabetes; it refers to how much sugar attaches abnormally to proteins. Vitamin E supplementation reduces this problem in many, although not all, studies.

In one report, vitamin E was found to impair glucose tolerance in obese patients with diabetes. The reason for the discrepancy between reports is not known.

Vitamin E appears to lower the risk of cerebral infarction, a type of stroke, in people with diabetes who smoke. A review of a large Finnish study of smokers concluded that smokers with diabetes (or hypertension) represent a subset population that can benefit from small amounts of vitamin E (50 IU per day) without experiencing an increased risk of bleeding.

Vitamin C
People with type 1 diabetes appear to have low vitamin C levels. As with vitamin E, vitamin C may reduce glycosylation. Vitamin C also lowers sorbitol in people with diabetes. Sorbitol is a sugar that can accumulate and damage the eyes, nerves, and kidneys of people with diabetes. Vitamin C may improve glucose tolerance in type 2 diabetes, although not every study confirms this benefit. Vitamin C supplementation (500 mg twice daily for one year) has significantly reduced urinary protein loss in people with diabetes. Urinary protein loss (also called proteinuria) is associated with poor prognosis in diabetes. Many doctors suggest that people with diabetes supplement with 1–3 grams per day of vitamin C. Higher amounts could be problematic, however. In one person, 4.5 grams per day was reported to increase blood sugar levels.

One study examined antioxidant supplement intake, including both vitamins E and C, and the incidence of diabetic retinopathy (damage to the eyes caused by diabetes). Surprisingly, people with extensive retinopathy had a greater likelihood of having taken vitamin C and vitamin E supplements. The outcome of this trial, however, does not fit with most other published data and might simply reflect the fact that sicker people are more likely to take supplements in hopes of getting better. For the present, most doctors remain relatively unconcerned about the unexpected outcome of this isolated report.

B Vitamins
Many people with diabetes have low blood levels of vitamin B6. Levels are even lower in people with diabetes who also have nerve damage (neuropathy). Vitamin B6 supplementation has improved glucose tolerance in women with diabetes caused by pregnancy. Vitamin B6 supplementation is also effective for glucose intolerance induced by birth control pills. For other people with diabetes, 1,800 mg per day of a special form of vitamin B6—pyridoxine alpha-ketoglutarate—has improved glucose tolerance dramatically in some research. Standard vitamin B6 has helped in some, but not all, trials.

Biotin is a B vitamin needed to process glucose. When people with type 1 diabetes were given 16 mg of biotin per day for one week, their fasting glucose levels dropped by 50%. Similar results have been reported using 9 mg per day for two months in people with type 2 diabetes. Biotin may also reduce pain from diabetic nerve damage. Some doctors try 16 mg of biotin for a few weeks to see if blood sugar levels will fall.

Blood levels of vitamin B1 (thiamine) have been found to be low in people with type 1 diabetes. In the 1930s, a trial using 10 mg of vitamin B1 per day for four weeks reported reduced blood sugar levels in six of eleven people with diabetes. More recently, administration of both vitamin B1 (25 mg per day) and vitamin B6 (50 mg per day) led to significant improvement of symptoms of diabetic neuropathy after four weeks. However, this was a trial conducted among people in a vitamin B1-deficient developing country. Therefore, these improvements might not occur in other people with diabetes. Another trial found that combining vitamin B1 (in a special fat-soluble form) and vitamin B6 plus vitamin B12 in high but variable amounts led to improvement in some aspects of diabetic neuropathy in 12 weeks. As a result, some doctors recommend that people with diabetic neuropathy supplement with vitamin B1, though the optimal level of intake remains unknown.

Coenzyme Q10
Coenzyme Q10 (CoQ10) is needed for normal blood sugar metabolism. Animals with diabetes have been reported to be CoQ10 deficient. People with type 2 diabetes have been found to have significantly lower blood levels of CoQ10 compared with healthy people. In one trial, blood sugar levels fell substantially in 31% of people with diabetes after they supplemented with 120 mg per day of CoQ7, a substance similar to CoQ10. In people with type 1 diabetes, however, supplementation with 100 mg of CoQ10 per day for three months neither improved glucose control nor reduced the need for insulin. The importance of CoQ10 supplementation for people with diabetes remains an unresolved issue, though some doctors recommend approximately 50 mg per day as a way to protect against possible effects associated with diabetes-induced depletion.

L-carnitine
L-carnitine is an amino acid needed to properly utilize fat for energy. When people with diabetes were given L-carnitine (1 mg per 2.2 pounds of body weight), high blood levels of fats—both cholesterol and triglycerides—dropped 25–39% in just ten days in one trial. In higher amounts (1 gram per day by injection), L-carnitine has been reported to reduce pain from diabetic nerve damage as well.

Vitamin B12 is needed for normal functioning of nerve cells. Vitamin B12 taken orally, intravenously, or by injection has reduced nerve damage caused by diabetes in most people studied. In a preliminary trial, people with nerve damage due to kidney disease or to diabetes plus kidney disease received intravenous injections of 500 mcg of methylcobalamin (the main form of vitamin B12 found in the blood) three times a day for six months in addition to kidney dialysis. Nerve pain was significantly reduced and nerve function significantly improved in those who received the injections. Oral vitamin B12 up to 500 mcg three times per day is recommended by some practitioners.

The intake of large amounts of niacin (a form of vitamin B3), such as 2–3 grams per day, may impair glucose tolerance and should be used by people with diabetes only with medical supervision Smaller amounts (500–750 mg per day for one month followed by 250 mg per day) may help some people with type 2 diabetes, though this research remains preliminary.

Preliminary trials have shown that niacinamide (another form of vitamin B3) supplementation might be useful in the very early stages of type 1 diabetes, though not all trials support this claim. Although an analysis of research shows that niacinamide does help preserve some function of insulin-secreting cells in people recently diagnosed with type 1 diabetes, the amount of insulin required for those given niacinamide has remained essentially as high as for those given placebo. A controlled trial found no beneficial effect of niacinamide supplementation (700 mg three times per day in addition to intensive insulin therapy) on pancreatic function and glucose tolerance in people newly diagnosed with type 1 diabetes.

Some, but not all, reports suggest that healthy children at high risk for type 1 diabetes (such as the healthy siblings of children with type 1 diabetes) may be protected from the disease by supplementing with niacinamide. Parents of children with type 1 diabetes should consult their doctor regarding niacinamide supplementation as a way to prevent diabetes in their other children. Although the optimal amount of niacinamide is not known, recent evidence suggests that 25 mg per 2.2 pounds of body weight per day may be as effective as higher amounts.

Zinc
People with type 1 diabetes tend to be zinc-deficient, which may impair immune function. Zinc supplements have lowered blood sugar levels in people with type 1 diabetes, though some evidence indicates that zinc supplementation in people with type 2 diabetes does not improve their ability to process sugar. Nonetheless, people with type 2 diabetes also have low zinc levels, caused by excess loss of zinc in their urine. Many doctors recommend that people with type 2 diabetes supplement with moderate amounts of zinc (15–25 mg per day) as a way to correct for the deficit.

Some doctors are concerned about having people with type 1 diabetes supplement with zinc because of a report that zinc supplementation increased glycosylation, generally a sign of deterioration of the condition. This trial is hard to evaluate because zinc supplementation increases the life of blood cells and such an effect artificially increases the lab test results for glycosylation. Until this issue is resolved, those with type 1 diabetes should consult a doctor before considering supplementation with zinc.

Vitamin D
Vitamin D is needed to maintain adequate blood levels of insulin. Vitamin D receptors have been found in the pancreas where insulin is made and preliminary evidence suggests that supplementation can increase insulin levels in some people with type 2 diabetes; prolonged supplementation might also help reduce blood sugar levels. Not enough is known about optimal amounts of vitamin D for people with diabetes, and high amounts of vitamin D can be toxic. Therefore, people with diabetes considering vitamin D supplementation should talk with, and have vitamin D status assessed by, a doctor.

Inositol
Inositol is needed for normal nerve function. Diabetes can cause a type of nerve damage known as diabetic neuropathy. This condition has been reported in some, but not all, trials to improve with inositol supplementation (500 mg taken twice per day).

Taurine
Taurine is an amino acid found in protein-rich food. People with type 1 diabetes have been reported to have low blood taurine levels, a condition that increases the risk of heart disease by altering blood viscosity. Supplementing with taurine (1.5 grams per day) has restored blood taurine to normal levels and corrected the problem of blood viscosity within three months. However, in a double-blind trial, taurine supplementation (2 grams per day for 12 months) failed to improve kidney complications associated with type 2 diabetes.

Fish oil
Glucose tolerance improves in healthy and cholesterol levels in people with diabetes. people taking omega-3 fatty acid supplements. Some studies have found that fish oil supplementation improves glucose tolerance, high triglycerides, However, other studies have found that cholesterol increases and diabetes worsens with fish oil supplementation.

Until this issue is resolved, people with diabetes should feel free to increase their fish intake, but they should consult a doctor before taking fish oil supplements. Sometimes, such supplementation may be considered. In one trial, people with diabetic neuropathy and diabetic nephropathy experienced significant improvement when given 600 mg three times per day of purified EPA—one of the two major omega-3 fatty acids found in fish oil supplements—for 48 weeks.

Doctors have suggested that quercetin might help people with diabetes because of its ability to reduce levels of sorbitol—a sugar that accumulates in nerve cells, kidney cells, and cells within the eyes of people with diabetes—and has been linked to damage to those organs.233 Clinical trials have yet to explore whether quercetin actually protects people with diabetes from neuropathy, nephropathy, or retinopathy.

Vanadium
Vanadyl sulfate, a form of vanadium, may improve glucose control in people with type 2 diabetes, though it may not help people with type 1 diabetes. Over a six-week period, a small group of people with type 2 diabetes were given 75–300 mg of vanadyl sulfate per day. Only in the groups receiving 150 mg or 300 mg was glucose metabolism improved, fasting blood sugar decreased, and another marker for chronic high blood sugar reduced. At the 300 mg level, total cholesterol decreased, although not without an accompanying reduction in the protective HDL cholesterol. None of the amounts improved insulin sensitivity. Although there was no evidence of toxicity after six weeks of vanadyl sulfate supplementation, gastrointestinal side effects were experienced by some of the participants taking 150 mg per day and by all of the participants taking 300 mg per day. The long-term safety of the large amounts of vanadium needed to help people with type 2 diabetes (typically 100 mg per day) remains unknown. Many doctors expect that amounts this high may prove to be unsafe in the long term.

Fructo-oligosaccharides
In a preliminary trial, supplementation with fructo-oligosaccharides (FOS) (8 grams per day for two weeks) significantly lowered fasting blood-sugar levels and serum total-cholesterol levels in people with type 2 diabetes. However, in another trial, supplementing with FOS (15 grams per day) for 20 days had no effect on blood-glucose or lipid levels in people with type 2 diabetes. In addition, some double-blind trials showed that supplementing with FOS or galacto-oligosaccharides (GOS) for eight weeks had no effect on blood-sugar levels, insulin secretion, or blood lipids in healthy people. Because of these conflicting results, more research is needed to determine the effect of FOS and inulin on diabetes and lipid levels.

Manganese
People with diabetes may have low blood levels of manganese. Animal research suggests that manganese deficiency can contribute to glucose intolerance and may be reversed by supplementation. A young adult with insulin-dependent diabetes who received oral manganese chloride (3–5 mg per day) reportedly experienced a significant fall in blood glucose, sometimes to dangerously low levels. In four other cases, manganese supplementation had no effect on blood glucose levels. People with diabetes wishing to supplement with manganese should do so only with a doctor’s close supervision.

Medium chain triglycerides
Based on the results of a short-term clinical trial that found that medium chain triglycerides (MCT) lower blood glucose levels, a group of researchers investigated the use of MCT to treat people with type 2 diabetes mellitus. Supplementation with MCT for an average of 17.5% of their total calorie intake for 30 days failed to improve most measures of diabetic control.

Starch blockers
Starch blockers are substances that inhibit amylase, the digestive enzyme required to break down dietary starches for normal absorption. Controlled research has demonstrated that concentrated starch blocker extracts, when given with a starchy meal, can reduce the usual rise in blood sugar levels of both healthy people and diabetics. While this effect could be helpful in controlling diabetes, no research has investigated the long-term effects of taking starch blockers for this condition.

Are there any side effects or interactions with diabetes?
Refer to the individual supplement for information about any side effects or interactions.