Vegans Should Consider Taking DHA Supplements

We are all fatheads.

Indeed, about half the dry weight of our brain is fat. Lower levels of the long-chain omega-3 fat DHA in some areas of Alzheimer’s brains got people thinking that perhaps DHA is protective. Since the level of DHA in the brain tends to correlate with the level of DHA in the blood, cross-sectional studies of dementia and pre-dementia patients have been done. The result? The dementia and pre-dementia subjects do tend to have lower levels of both long-chain omega-3s, EPA and DHA, circulating in their bloodstream. This doesn’t necessarily mean that lower omega-3 levels cause cognitive impairment, however. It was just a snapshot in time, so we don’t know which came first. As I discuss in my video Should Vegans Take DHA to Preserve Brain Function?, maybe the dementia led to a dietary deficiency, rather than a dietary deficiency leading to dementia.

What we need is to measure long-chain omega-3 levels at the beginning and then follow people over time, and, indeed, there may be a slower rate of cognitive decline in those who start out with higher levels. We can actually see the difference on MRI. Thousands of older men and women had their levels checked and were scanned and then re-scanned. The brains of those with higher levels looked noticeably healthier five years later.

The size of our brain actually shrinks as we get older, starting around age 20. Between ages 16 and 80, our brain loses about 1 percent of its volume every two to three years, such that by the time we’re in our 70s, our brain has lost 26 percent of its size and ends up smaller than that of 2- to 3-year-old children.

As we age, our ability to make long-chain omega-3s like DHA from short-chain omega-3s in plant foods, such as flaxseeds, chia seeds, walnuts, and greens, may decline. Researchers compared DHA levels to brain volumes in the famed Framingham Study and found that lower DHA levels were associated with smaller brain volumes, but this was just from a snapshot in time, so more information was needed. A subsequent study was published that found that higher EPA and DHA levels correlated with larger brain volume eight years later. While normal aging results in overall brain shrinkage, having lower levels of long-chain omega-3s may signal increased risk. The only thing we’d now need to prove cause and effect is a randomized controlled trial showing we can actually slow brain loss by giving people extra long-chain omega-3s, but the trials to date showed no cognitive benefits from supplementation…until now.

A “double-blind randomized interventional study provide[d] first-time evidence that [extra long-chain omega-3s] exert positive effects on brain functions in healthy older adults,” a significant improvement in executive function after six and a half months of supplementation, and significantly less brain shrinkage compared to placebo. This kind of gray matter shrinkage in the placebo might be considered just normal brain aging, but it was significantly slowed in the supplementation group. The researchers also described changes in the white matter of the brain, increased fractional anisotropy, and decreases in mean and radial diffusivity—terms I’ve never heard before but evidently imply greater structural integrity.

So, we know that having sufficient long-chain omega-3s EPA and DHA may be important for preserving brain function and structure, but what’s “sufficient” and how do we get there? The Framingham Study found what appears to be a threshold value around an omega-3 index of 4.4, which is a measure of our EPA and DHA levels. Having more or much more than 4.4 didn’t seem to matter, but having less was associated with accelerated brain loss equivalent to about an extra two years of brain aging, which comes out to about a teaspoon less of brain matter, so it’s probably good to have an omega-3 index over 4.4.

The problem is that people who don’t eat fish may be under 4.4. Nearly two-thirds of vegans may fall below 4.0, suggesting a substantial number of vegans have an omega-3 status associated with accelerated brain aging. The average American just exceeds the threshold at about 4.5, though if we age- and gender-match with the vegans, ironically, the omnivores do just as bad. There aren’t a lot of long-chain omega-3s in Big Macs either, but having a nutrient status no worse than those eating the Standard American Diet is not saying much.

What we need is a study that gives those with such low levels some pollutant-free EPA and DHA, and then sees how much it takes to push people past the threshold…and here we go: Phase 2 of the study gave algae-derived EPA and DHA to those eating vegan diets with levels under 4.0. About 250mg a day took them from an average of 3.1 over the threshold to 4.8 within four months. This is why I recommend everyone consider eating a plant-based diet along with contaminant-free EPA and DHA to get the best of both worlds—omega-3 levels associated with brain preservation while minimizing exposure to toxic pollutants.


A list of my recommendations can be found here: Optimum Nutrition Recommendations.

Why not just eat fish or take fish oil? I explain why in these videos:

How else can we protect our brains? See, for example:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

The Purported Benefits of Eating Fish

In the landmark Global Burden of Disease study, researchers compiled the top 20 causes of death and disability. Number one on the list was high blood pressure, two and three was smoke, and the fourth leading cause of loss of life and health was not eating enough fruit. Lack of exercise was number 10, followed by too much sodium, not enough nuts and seeds, not enough whole grains, and then not enough vegetables. Number 18 on the top 20 list was not getting enough long-chain omega-3 fatty acids like DHA and EPA found in seafood, due to their purported protective effect against heart disease. As I discuss in my video Is Fish “Brain Food” for Older Adults?, even years ago when the study was published, researchers were already questioning the benefits of these fish fats, as more and more randomized controlled trials put them to the test and they failed, culminating in the meta-analysis I profiled in my video Is Fish Oil Just Snake Oil? that appeared to put the issue to rest.

Consumption of fish and fish oil wasn’t only hyped for cardiovascular protection, though. Omega-3s have also been touted to treat depression. However, after taking into account all the negative results that went unpublished, there appears to be no benefit for major depression or for preventing suicide, as I explored in my video Fish Consumption and Suicide.

What about omega-3s for the prevention of cognitive decline or dementia? The available randomized controlled trials show no benefit for cognitive function with omega-3 supplementation in studies lasting from 6 to 40 months among healthy older adults.

It may sometimes even make things worse. “Higher current fish consumption predicted worse performance on several cognitive speed constructs. Greater fish consumption in childhood predicted slower perceptual speed and simple/choice reaction time.” This may be due to neurotoxic contaminants, such as mercury, in seafood. We’ve known that the developing brain is particularly sensitive to the damaging effects of mercury, but maybe the aging brain is as well.

This would explain results that have shown higher omega-3 levels to be associated with high levels of cognitive impairment and dementia. More EPA (eicosapentanoic acid) was found in the cognitively impaired, and more DHA (docosahexanoic acid) was found in the demented, presumably because of pollutants like mercury and polychlorinated biphenyls (PCBs) in seafood that have been related to cognitive impairment and Alzheimer’s disease.

The same cognitive “functions disrupted in adults, namely attention, fine-motor function and verbal memory, are similar to some of those previously reported in children with prenatal exposures,” that is, exposed in the womb. And, the adults exposed to mercury through fish consumption didn’t have only subtle EEG brain wave changes, but “observable deficits in neurobehavioral performance measures,” such as poorer performance on tests of fine motor speed and dexterity, as well as concentration, for example. “Some aspects of verbal learning and memory were also disrupted by mercury exposure,” and the greater the mercury levels, the worse they did.

That study, however, was done downstream of a gold mining operation, which uses a process that uses lots of mercury. Other such studies were done on people eating fish next to chemical plants or toxic spills, or eating whale meat. What about a more mainstream population? An “elite group of well-educated participants”—most were corporate executives like CEOs and CFOs––all living in Florida and wealthy enough to afford so much seafood that at least 43 percent exceeded the U.S. Environmental Protection Agency’s safety limit for mercury were studied. Researchers found that excessive seafood intake, which they defined as more than three to four servings per month of large-mouth fish like tuna, snapper, and bass, elevates mercury levels and causes cognitive dysfunction, resulting in about a 5 percent drop in cognitive performance. This may not seem like much, but it’s “a decrement that no one, let alone a health-conscious and achievement-oriented person, is likely to welcome.”

“It is worth noting the irony in the situation; that is, the fact that corporate executives who chose to overconsume seafood for health reasons sustained a drop in their executive functions. Yet, if a 4.8% drop in executive function due to excessive seafood intake occurs in highly functioning, healthy adults with ample cognitive reserve, the major concern for further study is whether similar [mercury] level elevations in individuals already suffering from cognitive decline might result in substantially greater declines,” particularly with cognitive decline, dementia, and seafood consumption on the rise.


Fruit deficiency is the number-one dietary risk factor? For more, see Inhibiting Platelet Aggregation with Berries.

But what about th Inuit? See Omega-3s and the Eskimo Fish Tale.

For more on the shift of the evidence on fish and heart disease, see my Is Fish Oil Just Snake Oil? video.

The greatest danger of mercury exposure may be for children, as I discuss in Mercury vs. Omega-3s for Brain Development and How Long to Detox from Fish Before Pregnancy?.

Other videos on the effect of fish contaminants and health among adults include Fish and Diabetes and Fish Consumption and Suicide.

Mercury is not the only neurotoxic contaminant of seafood, though. See Diet and Amyotrophic Lateral Sclerosis (ALS) and ALS (Lou Gehrig’s Disease): Fishing for Answers.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Diet Can Trump the Alzheimer’s Gene ApoE

Back in the 1990s, a major susceptibility gene was discovered for Alzheimer’s, called ApoE4. If we have one ApoE4 gene, either from our mom or dad, like about 15 percent of the U.S. population does, our risk of getting Alzheimer’s is tripled. If we’re like the 1-in-50 folks who have ApoE4 genes from both parents, we may be at nine times the risk. But there are ways to minimize that risk, which is the focus of my video The Alzheimer’s Gene: Controlling ApoE.

The highest frequency of ApoE4 in the world is in Nigeria, but Nigerians also have some of the lowest Alzheimer’s rates. To understand this paradox, one has to understand the role of ApoE. What does the ApoE gene do? ApoE is “the principal cholesterol carrier in the brain.” So, the Nigerians’ diet appeared to have trumped their genes, with their low cholesterol levels from their low intake of animal fat from living off of mainly grains and vegetables.

Indeed, Nigerians have high ApoE4, but Alzheimer’s is a rarity, thanks, perhaps, to low cholesterol levels, which any of us can achieve by eating healthfully. These findings suggest that “long-term changes in plasma cholesterol…can lead to changes in brain ApoE expression.”

Just because we may have been dealt some bad genetic cards doesn’t mean we can’t reshuffle the deck with diet.

We cannot change our genetic makeup, but we can “reduce or prevent high cholesterol.” In a study of a thousand people for more than 20 years, ApoE4 doubled the odds of Alzheimer’s, but high cholesterol nearly tripled the threat. So, the “risk for Alzheimer disease from treatable factors—elevated total cholesterol level and blood pressure—appears to be greater” than that from the dreaded Alzheimer’s susceptibility gene. In fact, projecting from their data, controlling lifestyle factors could reduce a person’s risk for Alzheimer’s disease from nine or ten times the odds down to just two—even if they have the double barrel ApoE4 gene from both parents.

“People tend to have a fatalistic view toward developing Alzheimer disease,” as though it’s going to happen if it’s going to happen, but such a view has been undermined. We just need to emphasize the need for preventing and treating high blood pressure and cholesterol in the first place to reduce our risks for heart disease, stroke, and Alzheimer’s disease, and, “as a result, potentially enhance quantity and quality of life….Of equal importance, these data should be comforting to anyone interested in attempting to reduce the risk for and future burden of Alzheimer disease.”


So what are these dietary changes that help lower our risk? See some of my latest videos on preventing Alzheimer’s disease:

If you’d like to learn more about the exciting world of epigenetics and this concept of switching genes on and off, see BRCA Breast Cancer Genes and Soy and Cancer Reversal Through Diet?.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: