Dr. Joel Fuhrman has spent more than four decades treating patients who follow plant-based diets. While many experience impressive improvements in cardiovascular health and longevity, he noticed a concerning pattern among some long-term vegans: higher rates of neurological disease later in life.
Recent findings from the Seventh-day Adventist Health Study 2 have raised similar questions. The study followed approximately 88,000 participants over several decades and found that older vegans experienced higher mortality from stroke, dementia and Parkinson’s disease than their non-vegan counterparts. Because Adventists generally avoid smoking and alcohol and tend to lead healthy lifestyles, researchers can more easily isolate the effects of dietary patterns.
Fuhrman believes one nutrient may help explain part of the difference: DHA.
Why DHA Matters
DHA is a long-chain omega-3 fatty acid that plays a critical role in brain structure and function. Research also suggests it may support the brain’s ability to clear waste products and environmental toxins.
Dr. Cara Fuhrman, a naturopathic doctor and researcher, explains the mechanism plainly: “In vegans specifically, we’re not eating enough DHA, and without DHA, your brain can’t filter these toxins out, which is leading to the increase in Parkinson’s disease.”
While flaxseeds, chia seeds and walnuts contain ALA, a plant-based omega-3, the body must convert ALA into DHA before it can be used by the brain. Research suggests that conversion rates vary considerably, and many individuals may not produce enough DHA from plant sources alone.
Dr. Cara explains the timeline: “What the research shows is that flax and chia are high in ALA, which can increase your levels of EPA, but it doesn’t increase your levels of DHA. That would take years and years and years.”
In 2021, researchers published a study measuring omega-3 index levels in people’s blood and tracking who lived longer.
People with an omega-3 index greater than 8 per cent lived about five years longer than those with an index below 4 per cent.
Five years doesn’t sound like much until you realize: that’s statistically equivalent to the longevity difference between smokers and non-smokers.
More recent research from 2024 analyzed every clinical trial on omega-3 supplementation and dementia prevention. Scientists from around the world spent years compiling data.
Their conclusion: People with higher omega-3 intake and higher levels of DHA and EPA in their red blood cells had a lower risk of cognitive decline.
How Plant-Based Eaters Can Close the Gap
Fuhrman’s recommendation is not to abandon plant-based eating but to ensure it is nutritionally complete.
He advocates a plant-rich diet combined with strategic supplementation for nutrients that can be difficult to obtain from plants alone, particularly DHA, EPA, vitamin B12 and zinc.
“The recommendation is to follow a plant-rich diet and supplement intelligently with the few nutrients that the plant-based diet doesn’t reliably provide,” he says.
This approach explains why he’s been ahead of the research for decades. He wasn’t pushing veganism while secretly hoping his patients would figure out the gaps. He was recommending a different approach altogether—one that combines the protective benefits of plant-based eating with the nutritional completeness that smart supplementation provides.
For strict vegans, algae-based DHA supplements provide a direct source of omega-3s without relying on fish. Fuhrman also recommends monitoring B12 and zinc status and using blood testing when appropriate to help guide supplementation.
The Bottom Line
Plant-based diets remain one of the healthiest dietary patterns for longevity and chronic disease prevention. However, Fuhrman believes that nutritional completeness matters as much as dietary philosophy.
For people following a vegan or predominantly plant-based diet, ensuring adequate DHA intake may be one of the most important steps they can take to support long-term brain health.
Don’t wait for symptoms. Don’t wait for memory problems. Don’t wait for tremors.
Get your omega-3 index tested. Get your B12 levels checked. Know your actual numbers, not your assumptions.
Then supplement accordingly.
This article is edited for length and reprinted with the permission of Dr. Fuhrman.
The Supplement Protocol: What Dr. Fuhrman Recommends
For anyone following a plant-rich diet (whether strictly vegan or not), these nutritional gaps require attention:
DHA/EPA (Omega-3 Fatty Acids)
- Use algae-based DHA, not fish or fish oil
- Keep refrigerated in dark glass to prevent oxidation
- Target omega-3 index: 6–9 per cent (get tested to know
- your actual level)
B12
- Most plant-based eaters already supplement this
- Get levels tested every few years
Zinc
- Often overlooked but critical for immune function and neurological health
- Plant-based sources have lower bioavailability
- Supplementation is likely necessary
Critical point: Don’t guess at dosages. Get tested.
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