Moderate consumption: consistently lower inflammation markers, even with variable study designs,

Chronic low-grade inflammation (inflammation that fails to resolve or is continuously triggered) can negatively affect tissues and organs over time. It is observed in many chronic non communicable diseases, from obesity to type 2 diabetes mellitus, non-alcoholic fatty liver to cardiovascular disease. While excessive consumption of alcoholic beverages tends to promote the inflammatory process, quite a few studies found lower levels of inflammatory markers with light to moderate consumption of alcoholic beverages. However, is this association “real”?

Acute inflammation is a vital and adaptive response of the body as defense against pathogens and for wound healing. However, if they do not disappear and become chronic, even mild (low-grade) inflammation is part of a vicious cycle that can stress tissues and organs and damage them. Many of today’s common lifestyle diseases are associated with such chronic low-grade inflammation, which can be determined – among other parameters – by elevated hsCRP (high-sensitivity C-reactive protein) levels: a protein that reacts particularly sensitive to inflammatory messenger substances in the body.

Do alcoholic beverages play a role?

Since many lifestyle factors influence the inflammatory process, the influence of alcoholic beverages has also been investigated. While it is assumed that increased inflammation plays a role in the harmful health effects of excessive consumption, either no effects or lower inflammation markers were found with low to moderate consumption of alcoholic beverages.

But how robust and how consistent are these findings considering the fact that research about the influence of moderate alcohol consumption is influenced by many factors? This starts with the selection of the comparison group (abstainers, ex-drinkers and/or occasional consumers), includes the drinking guidelines, which vary greatly from region to region, and extends to other influencing factors (covariates) that should be taken into account in the respective studies – but are not always considered. These include also sociodemographic characteristics, physical and mental health, and other lifestyle factors such as smoking, diet, and physical activity.

To answer this question, an Australian-British research team used the data of  3,100 British individuals who were born in a specific week in 1970. Their consumption data at age 36 and 42 and a measurement of hsCRP at age 46 were available. New statistical methods and modelling (*) were used to calculate all the possible combinations of influencing factors, drinking patterns, time periods and recommendations for moderate consumption. For example, low-to-moderate consumption data (**) and consumption above various international drinking guidelines were compared to an abstinent reference.

Would they arrive at consistent conclusions in their analysis? If yes, this would mean that there would be a more robust evidence for an association between light to moderate consumption of alcoholic beverages and lower inflammatory markers (here: hsCRP). Although this would not yet prove a causal relationship, it would support a more robust relationship than the observational studies to date allow.

Moderate consumption: consistently lower inflammation levels

This extensive evaluation of the data led to several insights:

• The best comparison group is not lifelong abstainers and/or ex-users, because there are too few of them. It is better to use the occasional users (here: less than once a week) for comparison.
• No matter which drinking guidelines were used (Spanish, English, American, or Dutch): Light to moderate consumers always had lower hsCRP levels than occasional consumers.
• No matter what kind and how many influencing factors (covariates) were taken into consideration: Light to moderate consumption of alcoholic beverages was always associated with lower hsCRP levels than in occasional consumers.
• Regardless of whether the consumption data were averaged or calculated individually, or whether only the maximum consumption was included in the calculations, lower hsCRP values were always observed in light to moderate consumers than in occasional consumers.
• In contrast, the associations were no longer obvious for consumption above moderate amounts.

The differences to the group of occasional consumers were not very large, but in most cases significant. Thus, the favorable association between light to moderate drinking levels and lower inflammatory markers in middle-aged individuals may be considered “robust.”

(*) (so-called multiverse and effect-vibration analyses)

(**) Definitions:

Low to moderate consumption (drinking guidelines)

• • Netherlands: < 70 g aöcphpl/week
  • UK: < 112 g alcohol/week
  • USA: women < 98, men < 196 g alcohol/week
  • Spain (former guidelines): women < 170, men < 280 g alcohol/week