Vitamin E May Not Improve Diabetic Peripheral Neuropathy-Associated Symptoms

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Patients presenting with hyperhomocysteinemia received 5 mg oral folic acid once daily and 500 μg methylcobalamin 3 times per day.
Patients presenting with hyperhomocysteinemia received 5 mg oral folic acid once daily and 500 μg methylcobalamin 3 times per day.

Oral vitamin E supplementation consisting of 400 mg/day mixed tocotrienols for 1 year may not result in improved neuropathic pain symptoms in patients with diabetic peripheral neuropathy (DPN), according to a randomized trial published in JAMA Neurology.

In this double-blind placebo-controlled trial, investigators randomly assigned patients with DPN (mean age, 57.6±8.9 years; mean duration of diabetes, 11.4 ±7.8 years) to receive 200 mg mixed tocotrienols (n=111) twice daily or placebo (n=118) for 12 months.

In addition, patients presenting with hyperhomocysteinemia (homocysteine level ≥2.03 mg/L) received 5 mg oral folic acid once daily and 500 μg methylcobalamin 3 times per day.

The primary outcome was change in patient-reported neuropathy Total Symptoms Score (TSS), which included asleep numbness, burning pain, lancinating pain, and paresthesia; the Neuropathy Impairment Score (NIS) and nerve conduction were secondary outcomes.

At 12-month follow-up, the TSS and NIS were comparable in both groups (TSS: –0.30-point difference; 95% CI, –1.16 to 0.56; P =.49; NIS: 0.60-point difference; 95% CI, –1.37 to 2.65; P =.53). In patients with hemoglobin A1c levels >8%, oral tocotrienols resulted in greater reductions in lancinating pain (P =.03) and normohomocysteinemia (P =.008) compared with placebo. Although a greater percentage of patients receiving vitamin E vs placebo experienced infections (6.7% vs 0.7%, respectively; P =.04), there were no differences between the 2 groups in terms of serious adverse events (P =.16).

Because diagnosis and evaluation of DPN symptoms were determined by self-report, the study was limited, as it lacked an objective test for overall assessment. In addition, participants were recruited from hospitals in Malaysia and the results may not be generalizable to other populations.

The preliminary findings from this trial should be observed. “We interpret these preliminary observations with caution because the cutoff to define a clinically meaningful change in a TSS subscale is lacking.”

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Reference

Vitamin E in Neuroprotection Study (VENUS) Investigators; Hor CP, Fung WY, Ang HA, et al. Efficacy of oral mixed tocotrienols in diabetic peripheral neuropathy: a randomized clinical trial [published online January 29, 2018]. JAMA Neurol. doi: 10.1001/jamaneurol.2017.4609

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