About sixty to seventy percent of all people with diabetes have some form of nerve damage, called neuropathy (or more accurately, neuropathies, since there is more than one kind). High blood sugar levels over a long period of time damages nerves throughout the body, but those in the hands and feet are most often damaged. Symptoms of diabetic neuropathy can include pain and numbness, particularly in the hands and feet, or problems with digestion, the urinary tract, blood vessels, and the heart. These symptoms can range between mild and extremely painful to the point of disability.1 This article will review some information on diabetic neuropathies (DNs), then take a look at specific dietary supplements that may help in the treatment of this problem.

The Types Of Diabetic Neuropathies

According to the National Institutes of Health2, DNs are most common in those who have problems controlling their blood glucose levels, those with high blood lipid levels (i.e., cholesterol and triglycerides), those with high blood pressure and those who are overweight.

Other factors can also contribute to the cause. The risk increases with age and with the length of time a person has diabetes. Those who have had diabetes for at least 25 years have the highest rates of neuropathy.

There are different types of DNs, with their own symptoms:3

  • Peripheral neuropathy is the most common type of DN. It causes pain or loss of feeling in the toes, feet, legs, hands, and arms.
  • Changes in digestion, bowel and bladder function, sexual response, and perspiration take place in autonomic neuropathy; the nerves that serve the heart and control blood pressure, as well as nerves in the lungs and eyes, may be affected as well. Hypoglycemia unawareness, a condition in which people no longer experience the warning symptoms of low blood glucose levels, may also occur.
  • Proximal neuropathy results in thigh, hip, or buttocks pain, and leads to weakness in the legs.
  • Sudden weakness of one nerve or a group of nerves, causing muscle weakness or pain, is caused by focal neuropathy. In this case, any nerve in the body can be affected.

DIETARY SUPPLEMENTS

There are a number of dietary supplements with the potential to help in the treatment of DN. Some of the most promising are acetyl-L-carnitine, alpha lipoic acid, benfotiamin, gamma-linolenic acid and methylcobalamin.

Acetyl-L-Carnitine
Acetyl-L-carnitine (ALC) is a form of the amino acid L-carnitine. Both have similar roles in helping to transport fat into muscle cells where it can be burned for energy. Also, the “acetyl” part of ALC helps produce the acetylcholine, a brain chemical, which is required for various mental functions. ALC occurs naturally in the brain, liver and kidneys.

ALC has been shown to be deficient in diabetics.4 In double-blind research, type 1 or type 2 diabetics with peripheral neuropathy experienced improved symptoms after taking 1500–3000 mg ALC daily in divided doses for a year. ALC seems to increase nerve fibers, regenerate clusters of nerve fibers, and improve sensations. In patients who have pain as the most significant symptoms, taking ALC 1000 mg two to three times daily also decreases neuropathy-related pain within six months of beginning treatment. Lower doses (500 mg three times daily) do not seem to reduce pain. ALC also seems more likely to be effective for reducing pain in patients with a shorter duration of diabetes and patients with poorly-controlled type 2 diabetes.5,6,7,8 In research, the best response was associated with using 1,000 mg ALC, three times daily.

Orally, acetyl-L-carnitine is generally well tolerated. One gram daily of L-carnitine seems to significantly increase the anticoagulant effects of acenocoumarol.9,10 Acenocoumarol is an oral anticoagulant similar to warfarin, but shorter-acting. This interaction has only been reported with L-carnitine, but theoretically could occur with acetyl-L-carnitine.

Alpha Lipoic Acid
Alpha lipoic acid (ALA) is a natural antioxidant manufactured by the body and similar to certain vitamins. Unlike most other antioxidants, however, it has the advantage of being soluble in both fat and water, so it can provide production both inside and outside of cells.11 ALA is also found in some foods, particularly liver and yeast.

Giving 600 mg to 1200 mg oral or intravenous ALA daily reduced symptoms of peripheral neuropathy in diabetics. ALA improved symptoms such as burning, pain, numbness, and prickling of the feet and legs. It also seems to improve objective measures such as ratings of nerve function decline and disability. Symptom improvement occurs within three to five weeks with oral and intravenous dosing.12,13,14,15,16,17,18,19,20 Doses lower than 600 mg daily have not been shown to be effective.21 Furthermore, other research shows that ALA can also contribute to reducing blood sugar levels and insulin sensitivity.22,23,24,25 A daily dosage range of 600 mg to 1200 mg ALA is likely to yield positive results.

Skin rash has been reported in some individuals after using oral doses of alpha-lipoic acid.26 Theoretically, use with other hypoglycemic drugs might cause additive blood sugar lowering effects.27

Benfotiamin
Benfotiamin is a particularly well-absorbed form of vitamin B1. Double-blind research in diabetics demonstrated that oral doses of 400 mg daily resulted in a statistically significant improvement in neuropathy score in the treatment group compared to placebo. The most significant improvement reported was pain decrease in polyneuropathy (a type of peripheral neuropathy).28 Other research has demonstrated statistically significant effectiveness in reducing diabetic neuropathy pain with daily doses ranging between 150–320 mg benfotiamin.29 In addition, studies have also shown that benfotiamin in combination with other B vitamins is effective in the treatment of DNs.30 Best results will probably be seen with 400 mg of benfotiamin daily.

Benfotiamin has a good tolerance profile without any adverse effects, and no established drug interactions.

Gamma Linolenic Acid
Gamma linolenic acid (GLA) is an omega-6 fatty acid commonly found in evening primrose oil (derived from the seeds of the evening primrose plant) as well as black currant seed oil and borage oil. The body converts GLA into an anti-inflammatory, hormone-like substance called prostaglandin E1. In addition to DN, GLA has shown benefit in the treatment of eczema31, fibrocystic breast disease32, premenstrual syndrome33 and rheumatoid arthritis.34

In double-blind research, taking oral doses of 360 to 480 mg GLA daily for six months to one year reduced symptoms and prevents nerve deterioration in peripheral neuropathy patients who have type 1 or type 2 diabetes.35,36,37,38 It seems to be more effective in patients with better glucose control compared to patients with poor glucose control.39 Take 360 to 480 mg GLA daily. It may take six months or longer for results.

Orally, gamma-linolenic acid (GLA) can cause mild gastrointestinal effects such as nausea, vomiting, soft stools, diarrhea, flatulence, and belching.40,41,42 GLA might prolong bleeding time.43 GLA appears to have anticoagulant effects.44 Theoretically, taking GLA with other anticoagulant or anti-platelet drugs might increase the risk of bruising and bleeding.

Methylcobalamin
Methylcobalamin is a well-absorbed form of vitamin B12. In double-blind research, daily oral supplementation of 1500 mcg methylcobalamin by diabetics resulted in significant improvements in autonomic neuropathy compared to placebo.45 Other research also demonstrated similar benefits and improvements in autonomic neuropathy when methylcobalamin was given orally or as an injection.46,47

Orally and intramuscularly, vitamin B12 does not usually cause adverse effects, even in large doses. Limited case reports suggest that chloramphenicol (an antimicrobial drug) can delay or interrupt the response of immature red blood cells to supplemental vitamin B12 in some patients.48 A daily dose of 1500 mcg methylcobalamin is appropriate.

Conclusion
Just in case you’re wondering, you can use any or all of these dietary supplements indicated at the same time. Other than the adverse reactions listed, there are none associated with the concurrent use of more than one supplement.

References:

  2. Diabetic Neuropathies: The Nerve Damage of Diabetes. NIH Publication No. 08–3185. Bethesda, MD: National Diabetes Information Clearinghouse, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. February 2008. Retrieved October 3, 2008 from http://diabetes.niddk.nih.gov/dm/pubs/neuropathies/
  3. Ibid. Diabetic Neuropathies.
  4. Ibid. Diabetic Neuropathies.
  5. Sima AAF, Calvani M, Mehra M, et al. Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception in patients with chronic diabetic neuropathy: An analysis of two randomized, placebo-controlled trials. Diabetes Care 2005;28:89–94.
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  28. Konrad, op. cit.
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  39. Keen H, Payan J, Allawi J, et al. Treatment of diabetic neuropathy with gamma-linolenic acid. The gamma-Linolenic Acid Multicenter Trial Group. Diabetes Care 1993;16:8–15.
  40. Ibid.
  41. Leventhal LJ, Boyce EG, Zurier RB. Treatment of rheumatoid arthritis with gammalinolenic acid. Ann Intern Med 1993;119:867-73.
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  43. Keen op. cit.
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  45. Ibid.
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  48. Ide H, Fujiya S, Asanuma Y, et al. Clinical usefulness of intrathecal injection of methylcobalamin in patients with diabetic neuropathy. Clin Ther 1987; 9:183–192.
  49. Tatro DS, ed. Drug Interactions Facts. Facts and Comparisons Inc., St. Louis, MO. 1999.