Alzheimer's disease: here's how DHA fights the disease in the early stages

The positive effects that omega-3 exerts on Alzheimer's patients depend on the stage of disease progression: treatment in the early stages would ensure better results. In particular, DHA, according to numerous studies, acts through diverse 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 performed over the past 25 years on cells and animals. The results of this review work have been published in The Journal of Nutritional Biochemistry.

Alzheimer's disease: a widespread enemy after age 65

Alzheimer's disease is a progressive and irreversible neurodegenerative disease that commonly affects the elderly population. An estimated 47 million people worldwide are affected; 1 in 10 elderly people in Italy. The disease is characterized by the presence among brain cells of protein deposits, called amyloid plaques, and intracellular tangles consisting of a protein, called hyperphosphorylated tau, which cause neuronal 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, which is associated with such disorders as difficulty in performing even the simplest daily activities, language problems, spatial and temporal disorientation, and alterations in personality and behavior.

DHA and its role in cognitive decline

DHA (docosahexaenoic acid) is an omega-3 found mainly in fish products. About 60 percent of the polyunsaturated fatty acids in neuronal membranes are DHA. It can be formed in our bodies from its precursor, α-linolenic acid, but such synthesis is not very efficient in humans. Most DHA is therefore supplied to the body from fish products, especially fatty fish, introduced through the diet. Once introduced, circulating DHA is able to easily cross the blood-brain barrier (a structure interposed between the blood and the brain that selectively regulates the passage of substances) 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 the membranes of neurons. DHA therefore is considered to be essential for the functioning of the human brain. Decreased memory and loss of cognitive function are normal consequences of aging, and age has been shown to induce alterations in lipid composition in the brain. In addition, normal aging and neurodegenerative diseases is characterized by cognitive decline that correlates with DHA deficiency in blood and brain tissue. 

These deficiencies may result from low fish consumption and/or omega-3 oxidation. High levels of dietary DHA and that found in the bloodstream have been associated with decreased risk of dementia and Alzheimer's disease. In most in vivo studies, cognitive effects were examined in subjects without dementia or in individuals with mild cognitive dysfunction. Therefore, the researchers suggested that omega-3s might be effective only when consumed before the onset of the disease or in cases of mild symptoms.

The consumption of fish or DHA in the prevention of Alzheimer's disease

In evaluating in vitro and animal studies, researchers identified a number of neuroprotective effects of DHA, which appears to act on different mechanisms involved in the disease. In addition to the presence of amyloid plaques, the key feature of Alzheimer's disease, the link between the disease and cholesterol emerged.High levels of plasma cholesterol and in brain cells were found to be associated with the disease, while increased production of amyloid plaques was observed in animals after consumption of large amounts of cholesterol. 

Protein-induced inflammation has also been shown to actively contribute to the onset and progression of Alzheimer's disease. Similarly, antioxidant effects in the brain are a mechanism that appears to be involved in the onset of Alzheimer's, particularly with increased free radical production and subsequent lipid degradation. Finally, synapse loss and neuron death (especially in the limbic and cortical regions) is thought to be one of the key processes responsible for the degeneration associated with cognitive impairment in Alzheimer's disease. 

It is precisely on these processes that DHA would act: numerous research activities have demonstrated DHA's ability to protect against oxidative stress that initiates neuronal death, just as the anti-inflammatory action of omega-3 has been well established. Early mechanisms of Alzheimer's thus represent targets for treatments, according to the scientists who conducted the review. In addition to DHA, the oxidative damage that appears 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 the formation of amyloid plaques, together with the antioxidant, anti-inflammatory, and cholesterol-lowering effects of DHA contribute to the protective action of this fatty acid. The effects are even more pronounced in genetically predisposed individuals, according to findings from studies on proteins involved in cholesterol transport.

Early intervention for better results

According to the authors of the publication,these findings provide strong evidence that cognitive abilities with advancing age can be preserved with omega-3s, and this supports the important role that consumption of fish or DHA-based supplements may have in preventing Alzheimer's disease. DHA, may protect against age-related dementia or lower the progression of Alzheimer's, and therefore, in the years to come, it will be important to develop nutritional strategies to optimize the nature and amount of lipids in the brain. Understanding how and why DHA levels change during aging and Alzheimer's is therefore one of the most important goals to be achieved.

Are DHA supplements useful?

Based on these observations, the use of supplements with DHA, which has become a popular and effective way to ensure adequate intake, could offer an alternative strategy to slow the progression of dementia and preserve cognitive abilities. In this regard, Omegor Vita DHA 1000 has a high content of DHA, which contributes to the maintenance of normal brain and visual function. In fact, 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.