Dietary Prevention of Glaucoma:

Nutrition & Cellular Health
Written By Kevin Wallace

Leafy Greens, Nicotinamide, and What the Evidence Actually Shows

Can your diet help prevent glaucoma? For primary open-angle glaucoma, the honest answer is a qualified yes on risk, and a careful maybe on slowing early functional change. It does not replace pressure-lowering drops, laser, or surgery.

The 2018 video this article comes from was not a lecture I planned. It was an answer to a viewer who had just had eye surgery and was being sold a vision smoothie. I get questions like that. I answer them as well as I can. I am not an ophthalmologist. I am a retired small-animal internist. The eye anatomy I use here is the same basic physiology I learned in veterinary school, plus whatever the current papers actually say when I go look them up. That is the limit of what I am offering.

Where the skeptics are right

Most of the food data are observational. People who eat more kale also tend to do other healthy things. The black-currant trials are small. Nicotinamide looks interesting in short human studies and in one large real-world cohort, but it is not an approved glaucoma drug. At the doses used in trials, about 1.5 to 3 grams a day, two participants developed drug-induced liver injury. The American Glaucoma Society and the American Academy of Ophthalmology said in 2025 that doses of 3 grams a day or more should stay inside monitored trials, and that people with liver disease should not take it. (1)

Niacin, the other common form of vitamin B3, is not a substitute. It flushes, and at high doses it is known to injure the liver. Do not swap one for the other.

If a website tells you a smoothie will restore sight, that is a sales claim. I could not find a trial that supports it in 2018, and I still cannot.

What the stronger studies show

Leafy greens and nitrate. In the Nurses’ Health Study and the Health Professionals Follow-up Study, more than 100,000 adults followed for decades, people in the highest fifth of dietary nitrate intake had about a 21 percent lower risk of primary open-angle glaucoma than people in the lowest fifth. The link was stronger for the subtype with early paracentral visual-field loss, the pattern tied more to blood-flow problems than to pressure alone. Green leafy vegetables supplied most of that nitrate. Kale and collards stood out. A generic green salad did not. (2)

Black currants. Japanese trials gave people with open-angle glaucoma 50 mg a day of black-currant anthocyanins for up to two years, on top of their drops. Visual-field loss slowed a little compared with placebo, and optic-nerve blood flow improved. Eye pressure itself barely moved. These are small studies. They are a signal, not a prescription. (3)

Nicotinamide. This is the compound Rhonda Patrick highlighted in 2017, after Williams and colleagues showed that oral nicotinamide protected retinal ganglion cells in a glaucoma-prone mouse. At the highest dose, 93 percent of treated eyes did not develop optic-nerve damage. The mechanism is mitochondrial: retinal NAD+ falls with age, and nicotinamide is a precursor that restores it. (4)

A note on the name, because it gets mixed up. Nicotinamide is a form of vitamin B3. Neonicotinoids are insecticides. They are not the same molecule, they are not what those reviews were about, and they have no documented role as a glaucoma treatment.

Short human trials followed the mouse work. A U.S. crossover study of nicotinamide plus pyruvate improved the number of visual-field locations that tested better. An Australian crossover study improved inner-retinal electrical function. A 2025 Korean crossover trial in normal-tension glaucoma, 1 gram a day for six weeks then 2 grams a day for six weeks, improved photopic negative response and B-wave amplitude versus placebo. These are functional signals over weeks, not proof that vision is saved over years. (5)

The largest human dataset so far is a 2026 JAMA Ophthalmology cohort of 2,920 matched patients with ocular hypertension. Over about 3.7 years, 3.5 percent of nicotinamide users were diagnosed with primary open-angle glaucoma, versus 9.0 percent of matched controls (hazard ratio 0.34). They also started drops and laser less often. This is real-world exposure, not a randomized trial, so it cannot prove cause. Phase 3 trials are running in the United Kingdom, Singapore, and the United States. Results are not in yet. (6)

Caffeine and genes. Habitual caffeine is not linked to glaucoma in the population as a whole. In UK Biobank data, people in the top quarter of genetic risk for higher eye pressure who also drank a lot of caffeine (roughly three or more cups of coffee a day) had higher pressure and higher glaucoma prevalence. For most people this is a non-issue. (7)

StudyWhat it looked atKey findingKang et al., JAMA Ophthalmol 2016NHS + HPFS, nitrate and leafy greensHighest vs lowest intake: about 21% lower POAG risk; stronger for paracentral lossOhguro et al., Ophthalmologica 201238 patients, black-currant anthocyanins 50 mg/day, 2 yearsSlower visual-field loss and better optic-nerve blood flow vs placeboWilliams et al., Science 2017Glaucoma-prone miceNicotinamide protected the optic nerve; high dose protected 93% of eyesHa et al., Br J Ophthalmol 202553 normal-tension glaucoma patients, crossover1–2 g/day nicotinamide improved retinal electrical signals over 12 weeksAhmed et al., JAMA Ophthalmol 20262,920 matched ocular-hypertension patientsNicotinamide exposure: 3.5% vs 9.0% progressed to POAG

Honest caveats

I am reading the papers and telling you what they say. I am not your eye doctor, and I am not diagnosing or treating anyone from a garden in Oswego County.

Diet does not treat established glaucoma. Pressure control still does the heavy lifting. Food-level nicotinamide, from poultry, fish, peanuts, mushrooms, and fortified grains, will not reach the gram doses used in trials. Those doses are far above the usual daily allowance and need a doctor and liver tests. Black-currant jam is not the extract used in the Japanese trials. The 2026 cohort can be confounded by who chooses to take a supplement.

Where we land

  1. Eat the greens that grow here. Kale and collards handle an Oswego County winter under a row cover. A few servings a week is the pattern tied to the nitrate data. Spinach and chard count too.

  2. If you already have ocular hypertension or glaucoma, keep the drops and the visits. Ask for the pressure numbers and the visual-field printout. Bring someone with you, or record the visit if the doctor allows it. That was my practical advice in 2018, and it still is.

  3. Do not start gram-dose nicotinamide on your own. If you and your ophthalmologist want to discuss it, loop in your primary doctor and get liver enzymes checked. Skip it entirely if you have liver disease. Do not use niacin in its place.

  4. If glaucoma runs in your family and you drink a lot of coffee, cut back toward one or two cups. For everyone else the caffeine data do not demand a change.

  5. Ignore any product that promises to restore sight. That was the claim in the viewer’s question, and it is still not supported.

The original video, answering that viewer, is here: Dietary prevention and treatment of Glaucoma.

Further Reading

The nitrate paper is still the cleanest food study. The nicotinamide story is the one that has moved since 2018, and the 2025 AGS/AAO statement is the safety line I would read before anyone buys a bottle. Patrick’s 2017 note points at the mouse paper on nicotinamide, not at an insecticide.

On Our Website

The same greens that show up in the glaucoma data are the ones we keep in the ground here for the table and for the soil. The carbohydrate piece is the companion if you want the gut side of that plate.

Kevin Wallace
Previous

Beyond the Anecdotes: Old Drugs, New Questions in Cancer
Next

Growing Turmeric and Ginger in Zone 5