Evidence That Niacin Can Cause Diabetes, and Can Damage Eyesight

by Nils Osmar. October 3, 2022. Medical Disclaimer

I take NMN (and sometimes NR) to raise NAD+ levels. (I take them every day, about an hour before my workouts.) I sometimes also take niacin (later in the day) because it greatly improves my ratio of triglycerides to HDL. (It lowers my TG and raises my HDL).

It’s important to be aware that taking niacin can come with some risks.

What’s (possibly) wrong with niacin?

  1. Niacin raises blood glucose. (For this reason I usually take it along with berberine, which lowers BG) (When I was taking niacin every day, my blood sugar shot up alarmingly.) Incidentally, berberine also lowers LDL and raises HDL.
  2. There is evidence that niacin can under some circumstances cause diabetes in previously non-diabetic individuals.
  3. Niacin can damage our eyesight, at least temporarily. (I’ve experienced badly blurred vision when taking large amounts of it; I become unable to read fine print for several hours.)

From a study entitled “Niacin therapy and the risk of new-onset diabetes: a meta-analysis of randomised controlled trials“:

Of those treated with niacin, 725 (5.53%) out of 13 121 participants developed diabetes while, on control treatment, 646 (4.89%) out of 13 219 developed diabetes. This represents a RR of 1.34 (95% CI 1.21 to 1.49) (see figure 2). Expressed in absolute terms, treating 43 (95% CI 30 to 70) initially non-diabetic individuals with niacin for 5 years would result in one additional case of diabetes being diagnosed compared with no treatment.

From a 2015 study entitled “Ocular Effects of Niacin: A Review of the Literature”:

Many authors reported ocular side effect after therapy with niacin. Fraunfelder et al. (5) reported that 3 g or more per day of nicotinic acid, could cause blurred vision, eyelid edema, toxic amblyopia, proptosis, loss of eyelashes or eyebrow, superficial punctate keratitis and CME.

Some cases of blurred vision were reported in the literature (73), and 18 cases were reported to the National Registry or the FDA spontaneous reporting system.

In these cases, the average dose of niacin was 1.5–2 g per day, with a duration of therapy varying from 6 weeks to 1 year.

Follow-up reported complete resolution of visual symptoms after discontinuing niacin.

Dry eye was explained because this vitamin may be secreted and concentrated in human tears, thereby irritating an already dry eye. Niacin can cause ocular signs and symptoms reversible dose related, so if the patient wishes to continue this therapy, it may be feasible to reduce the dose of the drug (6).

Cases of niacin related maculopathy there is a 10:1 male: female ratio. Most cases were in their third to fifth decade of life and were being treated with an average dose of 3–6 g of niacin per day.

In summary, I’ve become more cautious about niacin. I do take it, but keep the dose low and only take it if I can do so along with a compound known to lower blood glucose..

What about the cost? DoNotAge’s NMN costs about $1 for a gram (or $1 a day) if you buy their bulk powder and use the discount.

This article is not intended as, and should not be taken as, medical advice.

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