Does alcohol harm or help these chronic diseases?

The effects of alcohol on chronic diseases can be either a blessing or a curse, depending on the amount consumed. 

At lower levels of intake, alcohol can be protective. At higher levels, it can be detrimental. Alcohol-specific factors also play a role, including ethanol content, drinking frequency, and beverage type (ie, beer, wine, or spirits).

The effects of various aspects of alcohol consumption on chronic disease are elegantly assessed in a review article in the International Journal of Environmental Research and Public Health that includes the gamut of study designs. Below are some highlights.

Ischemic heart disease

The relationship between alcohol consumption and risk of ischemic heart disease is likely J-shaped, with those drinking <30 g/day exhibiting the lowest risk. (The researchers defined a standard drink to contain approximately 12.5 g of alcohol.)

Women appear to benefit most from lower levels of alcohol consumption with respect to ischemic heart disease. Protection appears to be the same across different types of alcohol. However, episodic heavy drinking, defined as 6 or more drinks in 24 hours, could boost the risk of heart attack—particularly in the elderly. Those who survive a heart attack may benefit from moderate alcohol consumption, likely due to lower risks of all-cause and cardiovascular mortality.

In the Physicians’ Health Study, more than 5,000 male doctors with hypertension but without coronary heart disease were evaluated to study the effects of alcohol on heart disease. Investigators found that in this population, those who had 1 to 4 drinks per week had a similar risk for heart attack when compared with those who consumed less than 1 alcoholic drink per week. However, alcohol consumption showed a protective effect in those who consumed between 5 to 7 drinks and in those who had consumed more than 8 drinks per week. 

Results were controlled for covariates such as age, body mass index, exercise levels, and diabetes. Similar results were observed in male physicians for angina pectoris and any CHD.

Stroke

The authors of the International Journal of Environmental Research and Public Health review described a U-shaped association between alcohol intake and risk of stroke. Those drinking <15 g/day exhibited lower total risk of stroke and stroke mortality, whereas moderate drinkers showed little-to-no difference from non-drinkers in terms of stroke. Heavy drinkers (>30 g/day) exhibited increased risk of stroke but not stroke mortality. No significant association between hemorrhagic stroke and drinking appears to exist. 

Among Finnish men, those who drank alcohol more than 2.5 times per week on average had the highest risk of stroke. In other research, men who reported one or more hangovers per year had a 2.5-fold increase in relative risk of stroke.

Hypertension

For men, a non-significant trend was found between an increased risk of hypertension and light-to-moderate drinking. However, heavy drinking (31-40 g/day) significantly increased these risks. For women, a J-shaped correlation between drinking and hypertension was found. Overall, drinking less than 10 g/day of alcohol was protective, whereas drinking more than 20 g/day increased the frequency of hypertension. Research indicated a J-shaped relationship between drinking and all-cause mortality in hypertensive patients, with the nadir at the level of 8 g to 10 g/day.

Sex-based differences in the effects of drinking on hypertension could be due to the fact that at similar amounts of intake, men tend to binge drink more often. 

Liver cancer

Alcohol consumption appears to be the culprit in 32% to 55% of hepatocellular carcinoma (HCC) cases. Drinking more than 3 drinks per day is linked to increased liver cancer risk compared with teetotalling. The authors note that confounding variables may contribute to this association. 

Alcohol could have a deleterious impact on one-carbon metabolism, which could facilitate the development of HCC. High folate intake could mitigate this risk. 

In addition, CYP2E1, a type of cytochrome P-450 enzyme, could be triggered by alcohol and catalyze the formation of reactive oxygen species. 

Colorectal cancer

The amount of alcohol consumed and the risk of colorectal cancer appears to have a J-shaped curve. Light-to-moderate drinking had no effect on colorectal cancer risk, and moderate alcohol intake may even be linked to lower risk of colorectal cancer in men and women. (After a subgroup analysis, the authors state that the protective effects are likely related to red wine.) Heavy drinking was correlated with colorectal cancer risk.

Those with a family history of colorectal cancer who drink ≥30 g/day had higher risk of colorectal cancer vs those who had no family history of the disease. Folate supplementation may decrease the risk of colorectal cancer in those who drink ≥30 g of alcohol per day.

Diabetes

Non-alcoholic bioactive components of alcoholic drinks may enhance glucose and lipid metabolism, insulin sensitivity, and islet function, but excessive drinking could boost the risk of diabetes. 

The authors note that there is a U-shaped correlation between alcohol and diabetes risk, with a nadir at 10 g to 14 g/day. At this lowest level, diabetes risk decreased by 18%. This protective effect extended to 63 g/day. At more than 63 g/day, a linear increase between alcohol intake and diabetes risk occurred. Such protective effects are likely only attributed to wine and beer.

Those with diabetes who engaged in moderate drinking (≤21 drinks/week for men and ≤14 drinks/week for women) had lower risk for cardiovascular accidents, microvascular complications, and all-cause mortality. This phenomenon was particularly prevalent in wine drinkers. Those who drank more heavily (>21 drinks/week in men and >14 drinks/week in women) exhibited higher risk of cardiovascular events and diabetes, as well as all-cause mortality.

Obesity

Lifetime heavy alcohol consumption (>90 g/day for men and >60 g/day for women) is linked to obesity, likely due to the extra calories that alcoholic drinks add to the diet. Abdominal obesity is predominant in men and women in this population, while both abdominal and general obesity were seen specifically in men. Beer was found to make abdominal obesity worse, while spirits were linked to general obesity in men. This suggests that different compounds in the types of alcohol may have separate contributions to obesity.

The majority of the studies analyzed indicated that light-to-moderate drinking protects against obesity. In fact, wine may be most protective, followed by spirits and beer. In men between the ages of 50 and 59 years, drinking frequency was inversely associated with BMI and waist circumference at a given level of alcohol intake and after adjusting for confounding factors.

Last call

While the results of the review were encouraging for those who are light or moderate drinkers, the authors state that even though alcohol may offer some protective effect, there is no reason to start drinking.

“For healthy adult drinkers, no more than one drink for females or two drinks for males every day, especially red wine, is acceptable and relatively safe, and might be protective for the cardiovascular system, but occasional binge drinking should be avoided,” wrote the researchers. 

“On the other hand, for non-drinkers, regular moderated drinking, regardless of beverage types, should not be recommended as a way to attain health, because risks for certain diseases, such as colorectal and breast cancer, [are] already increased [with] light drinking,” they concluded.