Alcohol (ethanol) is a common dietary constituent that impacts health. Although moderate alcohol consumption has a protective effect on heart disease and appears to also have other health benefits, heavy drinking increases mortality by escalating the risk of multi-system diseases in peripheral organs as well as psychiatric and neurological disorders in the central nervous system. The mechanisms of alcohol induced benefits or increased risk of morbidity are not well understood.
"There are probably no levels of drinking that give you any health benefits, but up to one to two drinks per day is not harmful, just neutral. Don't drink to protect yourself from heart disease risk. Drink modestly, up to one to two drinks per day maximum, if you enjoy alcohol, but don't kid yourself that it is protecting your heart," said Dr Rod Jackson of the University of Auckland.
But Dr David L Katz of the Yale University School of Medicine was skeptical about Dr Jackson's claims. "I think Jackson and colleagues are likely to be wrong. While we don't have randomized trials of alcohol intake and heart attacks, we do have studies of the effects of alcohol, and especially red wine, on blood lipids, blood pressure, platelet stickiness, and even the ability of blood vessels to dilate. In all instances, moderate alcohol intake produces clear and quantifiable benefits," he said.
Generally, alcohol abuse is associated with disruption of immune defenses against infections, increased incidence of bacterial pneumonias, higher rates of chronic hepatitis C infection, and increased susceptibility to HIV infection. In humans, chronic alcohol consumption is associated with increases in serum proinflammatory cytokines including TNF-α(a cytokine that induces either cell proliferation or cell death) and other cytokines. Cytokines are signalling protein molecules lying at the heart of the chronic autoimmune/inflammatory disease process.
Ethanol induced alterations in cytokines might contribute to both the health benefits and increased risk for poor health associated with alcohol consumption.
Liver, serum and brain respond differently to exposure to ethanol. In brain, ethanol induced a long lasting increase in cytokines which cause inflammation (proinflammatory cytokines) and caused multiple brain LPS (toxins) proinflammatory cytokine responses while decreasing the anti-inflammatory cytokine. Brain inflammation probably plays an important role in the development of chronic disorders like Alzheimer dementia (AD) and Parkinson's disease. Neurodegeneration caused by inflammation involves activation of the brain's immune cells, the microglia, which produce a large number of proinflammatory factors. Also, acute brain diseases, e.g., stroke and
status epilepticus (SE), are linked to inflammation.
Researchers have suggested that the abrupt disruption of the normal cytokine production process caused by alcohol intake increases risk for cardiovascular, liver, respiratory, infectious, mental and neurological diseases as well as certain cancers. Additional studies will be needed to understand the role of systemic proinflammatory cytokines in chronic diseases and how prolonged increases in proinflammatory cytokines in brain contribute to neurodegeneration and other CNS pathologies.