People’s Pharmacy: Can a supplement relieve neuropathy pain?

Q. I’ve suffered from neuropathy in my feet for a couple years. It mostly caused numbness rather than pain, but recently it became very painful, like someone stabbing me with a fork.

A friend recommended a supplement for healthy feet and nerves. When I take it, the pain disappears and the numbness is reduced. Have you ever heard of this?

I tried stopping the supplement at one point, and the pain quickly returned. So I resumed it, and the pain is gone. Do you know how this works?

Are there any dangers from taking it long term? What ingredients might help?

A. The supplement you describe contains many B vitamins along with zinc, chromium, alpha lipoic acid, Boswellia extract and benfotiamine. Boswellia has anti-inflammatory activity, but we suspect that alpha lipoic acid and benfotiamine might be the key ingredients for treating neuropathy. Doctors recommend both compounds for diabetic neuropathy (Minerva Medica, October 2017).

The usual dose for benfotiamine is 300 mg twice a day. Alpha lipoic acid, as well as vitamin B complex, L-acetylcarnitine, vitamin E and Coenzyme Q, might ease neuropathy pain (Current Drug Metabolism, May 2018). Although these treatments were less effective for numbness or tingling, all of these compounds are considered relatively safe.

Oncologists have used alpha lipoic acid in combination with DHA (docosahexaenoic acid, an omega-3 fatty acid from fish oil) to prevent chemotherapy-induced peripheral neuropathy (Integrative Cancer Therapies, Dec. 22).

Scientists don’t often study supplements with an eye to long-term safety, but we have seen no indication that you would develop difficulties as a result of using these supplements for months.

Q. In a recent article, a person said having a scan with iodine led to signs of hyperthyroidism. A thyroid doctor found antithyroid antibodies in the patient’s blood. You replied that some people react to iodine exposure by developing thyroid problems.

I have been considering using decolorized (white) iodine on my fingernails, which are weak and brittle. Painting iodine on nails every day for a week and then weekly after that is supposed to strengthen the nails.

Now I wonder if that is safe. Although my thyroid levels have always been normal, there are thyroid problems in my family (sibling, aunts and uncles are on Synthroid).

A. We have heard from a number of readers that decolorized iodine can be helpful against nail fungus. It does have antifungal activity. We do not know whether it could strengthen nails that are simply brittle but not infected. Occasionally, brittle nails signal an underactive thyroid gland, though.

Consequently, if you have other symptoms (fatigue, constipation, dry skin, mental fogginess, hair loss), you should see your doctor.

It is unlikely that putting iodine on your nails will affect your thyroid gland. When povidone iodine is used as a disinfectant, the skin absorbs it, and urinary excretion increases significantly (Thyroid, June 2005). This returns to normal within three to five days.

So far as we can tell, no one has measured iodine absorption through fingernails or toenails. However, nails do not absorb minerals very well. As a result, these surfaces seem less likely to absorb large quantities of the mineral than skin.

We would be very surprised if putting white iodine on nails led to enough iodine absorption to make a difference for thyroid function. Even dietary iodine through multivitamin pills does not appear to increase the chance of thyroid cancer or other thyroid problems (Cancer Epidemiology, Biomarkers & Prevention, September 2001).

On the other hand, the dose of iodine used in contrast material during a medical scan is huge, more than 30 times the minimum daily allowance for this mineral (JAMA Otolaryngology-Head & Neck Surgery, May 2013).

In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email them via their website peoplespharmacy.com. Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”