Alzheimer's Disease: How DHA Fights the Disease in Its Early Stages

The positive effects that omega-3 exert on patients affected by Alzheimer’s depend on the stage of disease progression: treatment in the early stages would guarantee better results. In particular, DHA, according to numerous studies, acts through different and interactive processes and its effectiveness depends on the mechanisms by which it exerts its neuroprotective effects: anti-amyloid, antioxidant, anti-inflammatory, and cholesterol-lowering.

These are the conclusions reached by a group of researchers from the University of Lyon (France), who evaluated a series of studies conducted over the past 25 years on cells and animals. The results of this review work were published in the journal The Journal of Nutritional Biochemistry.

Alzheimer’s Disease: A Common Enemy After Age 65

Alzheimer’s disease is a progressive and irreversible neurodegenerative disorder commonly affecting the elderly population. It is estimated that about 47 million people worldwide are affected; in Italy, 1 in 10 elderly individuals. The disease is characterized by the presence of protein deposits between brain cells, called amyloid plaques, and intracellular tangles made up of a protein called hyperphosphorylated Tau, which cause neuron death. In addition to these neurological phenomena, there is growing evidence that inflammatory processes and oxidative stress are involved in the progression of the disease. The most common and early symptom of Alzheimer’s is memory loss, associated with difficulties in performing even the simplest daily activities, language problems, spatial and temporal disorientation, and personality and behavioral changes.

DHA and Its Role in Cognitive Decline

DHA (docosahexaenoic acid) is an omega-3 found mainly in fish products. About 60% of the polyunsaturated fatty acids in neuronal membranes are represented by DHA. It can be formed in our body from its precursor, alpha-linolenic acid, but this synthesis is not very efficient in humans. Therefore, most DHA is supplied to the body by fish products, especially fatty fish, introduced through diet. Once introduced, circulating DHA can easily cross the blood-brain barrier (a structure between blood and brain that selectively regulates substance passage) and become part of the nervous system. 

Overall, DHA has several biological effects: it is essential for the growth and development of the brain and synapses and is involved in maintaining the fluidity of neuron membranes. DHA is therefore considered an essential element for human brain function. Memory decline and loss of cognitive function are normal consequences of aging, and it has been shown that age induces changes in the lipid composition of the brain. Moreover, normal aging and neurodegenerative diseases are characterized by cognitive decline correlated with low DHA levels in blood and brain tissue. 

These deficiencies may result from low fish consumption and/or omega-3 oxidation. High dietary and circulating DHA levels have been associated with decreased risk of dementia and Alzheimer’s disease. Most in vivo studies have examined cognitive effects in subjects without dementia or with mild cognitive impairment. For this reason, researchers have suggested that omega-3s may be effective only when consumed before disease onset or in cases of mild symptoms.

Fish or DHA Consumption in Alzheimer’s Prevention

In evaluating in vitro and animal studies, researchers identified several neuroprotective effects of DHA, which appears to act on different mechanisms involved in the disease. In addition to amyloid plaques, a key feature of Alzheimer’s disease, a link between the disease and cholesterol has emerged. High plasma and brain cell cholesterol levels have been associated with the disease, while increased amyloid plaque production was observed in animals after consuming large amounts of cholesterol. 

It has also been shown that protein-induced inflammation actively contributes to the onset and progression of Alzheimer’s disease. Similarly, antioxidant effects in the brain seem to be involved in Alzheimer’s onset, particularly with increased free radical production and resulting lipid degradation. Finally, synapse loss and neuron death (especially in limbic and cortical regions) are considered key processes responsible for degeneration associated with cognitive decline in Alzheimer’s disease. 

DHA would act precisely on these processes: numerous research activities have demonstrated DHA’s ability to protect against oxidative stress that initiates neuron death, as well as the well-established anti-inflammatory action of omega-3s. Early mechanisms of Alzheimer’s are therefore the targets of treatments, according to the scientists who conducted the review. In addition to DHA, oxidative damage appearing in the early stages of Alzheimer’s disease increases the demand for certain micronutrients, particularly antioxidants such as vitamins C and E and polyphenolic compounds, which could be useful in reducing the risk of dementia progression. Overall, the ability to counteract amyloid plaque formation, together with DHA’s antioxidant, anti-inflammatory, and cholesterol-lowering actions, contributes to the protective effect of this fatty acid. Effects are even more pronounced in genetically predisposed individuals, according to some studies on proteins involved in cholesterol transport.

Early Intervention for Better Results

According to the authors of the publication, these results provide strong evidence that cognitive abilities with advancing age can be preserved with omega-3s, supporting the important role that fish consumption or DHA-based supplements can have in preventing Alzheimer’s disease. DHA could protect against age-related dementia or slow Alzheimer’s progression, and thus, in the coming years, it will be important to develop nutritional strategies aimed at optimizing the nature and amount of lipids present in the brain. Understanding how and why DHA levels change during aging and Alzheimer’s is therefore one of the most important goals to achieve.

Are DHA Supplements Useful?

Based on these observations, the use of DHA supplements, which has become a popular and effective way to ensure adequate intake, could offer an alternative strategy to slow dementia progression and preserve cognitive abilities. In this regard, Omegor Vita DHA 1000 contains a high amount of DHA, which contributes to the maintenance of normal brain and visual function. One capsule of this product contains as much as 470 mg of DHA and 100 mg of EPA. 

Source: Mounir Belkouch, Mayssa Hachem, Abdeljalil Elgot, Amanda Lo Van, Madeleine Picq, Michel Guichardant, Michel Lagarde, Nathalie Bernoud-Hubac.  “The pleiotropic effects of omega-3 docosahexaenoic acid on the hallmarks of Alzheimer's disease.” The Journal of Nutritional Biochemistry.