How Does Alcohol Impact Blood Sugar?

Our metabolism is a wonderfully complex network of feedback, checks, and balances. This system can accommodate a few occasional disturbances, but an overload can significantly impact our metabolic health. Learning about how certain stressors impact our metabolism can help us intelligibly anticipate our blood sugar response. In order to understand the relationship between alcohol and blood sugar, we must first understand how the liver plays a role in glucose regulation.

What does the liver have to do with blood sugar? 

The liver has seven primary functions, one of which is the creation of new glucose molecules (gluconeogenesis). By combining lactate, alanine, and glycerol, our livers can generate glucose and release it into the bloodstream to help us maintain stable blood sugar levels throughout the day.  This process allows the body to automatically give our blood sugar a boost without us having to consume food constantly.

Another function of the liver is storage. When we have excess glucose in circulation, the liver has the ability to grab that glucose out of circulation and pull it into the liver (or muscle) to be stored as glycogen for us to use later. In this way, our liver (and skeletal muscles) can be used as a “reserve tank” of glucose. This reserve tank is great for a quick source of glucose to power short bursts of energy or allow us to function for a period of time without eating. However, there is a limit to the amount of glycogen our body can store. The average male (154 lbs) can store between 1600 and 2400 kcals of glycogen-based energy in the muscle and liver combined. That translates to about 10-15 kcals per pound of body weight. To give perspective, that amount of fuel will be significantly depleted after only about 90 min of high-intensity exercise. Overall, the liver plays a role in releasing new glucose molecules into the bloodstream as well as pulling existing excess glucose out of circulation for storage.

What happens to our blood sugar after an alcoholic drink? 

The impact of alcohol on blood sugar can be deceiving. Beers, cocktails, ciders, and many other alcoholic drinks contain carbohydrates. These carbohydrates will initially cause blood sugar levels to rise. However, alcohol has a trick up its sleeve. Alcohol decreases the liver’s ability to make new glucose via the previously described process, gluconeogenesis. This can lead to lower glucose concentrations in the blood. Since the liver’s ability to make new glucose is compromised, alcohol compensates by breaking down the glucose we have previously made and stored in the liver and muscles. This swap means that healthy individuals on a standard diet should be able to adequately compensate for the impaired ability to make new glucose. However, this compensation only applies to light alcohol consumption, and certain populations (described below) should be cautious.

What is special about individuals who are fasting, on a ketogenic diet, or participate in high levels of physical activity?

These three groupings of people all have one thing in common. They are more likely to have depleted glycogen stores than individuals who eat a standard diet. By virtue of abstaining from carbohydrate intake for extended periods of time, individuals practicing these diets have depleted their glycogen stores. Individuals who partake in high-intensity exercise use their stored glycogen to power their athletic performance and, thus, have little reserves left in their muscles and liver. 

Thus, those who are fasting, in ketosis, or highly active will react in a different way to alcohol.  After having a drink, the body will not have a way to compensate for the liver’s inability to make new glucose because all of its natural stores are empty.  The result will be for alcohol to have a more significant impact on the blood sugar levels of these individuals. For someone with depleted glycogen stores, post-alcohol glucose levels will drop, in some cases they will drop significantly enough to fall into a hypoglycemic state. This can lead to serious health concerns if drinking persists. For these reasons, individuals who are fasting, on a ketogenic diet, or have just completed a high-intensity workout (and have not had the chance to eat) should be very cautious with their alcohol intake.

Do things change with heavy alcohol use?

Occasional evenings of higher alcohol consumption can set back the progress we have made toward our metabolic health goals. Binge drinking (five drinks within two hours for men or four drinks within two hours for women) increases the body’s inflammatory processes and can negatively impact a wide range of bodily functions including our metabolism.  When drinking is concentrated to a short time period, the increased inflammation blocks the signals sent from the brain to the parts of the body that regulate metabolic control.  This damage can persist even after the alcohol has been metabolized. Some studies show that the insulin resistance incurred from heavy drinking can last for two days after alcohol consumption.  In the long run, when drinking rises to the level of binge drinking even once a month, it significantly increases the risk of type 2 diabetes.

What about chronic alcohol consumption?

Chronic and heavy alcohol use can cause permanent damage to the liver and its cells that produce insulin (pancreatic beta cells). This damage can lead to blood sugar levels that abnormally fluctuate. For this reason, individuals with a history of heavy alcohol use are at a higher risk of developing insulin resistance, type 2 diabetes, and other metabolic conditions.

Putting it all together

The overall impact of alcohol on our blood sugar regulation depends on multiple factors, chief among them being the volume and regularity of alcohol consumed. Most healthy individuals on a standard diet will be able to accommodate the impact of an occasional drink. Regular or higher volume drinkers may be hindering their metabolic health goals by virtue of limiting the liver’s ability to make new glucose molecules and/or damaging its ability to produce insulin. Individuals who are fasting, in ketosis, or have just participated in high-intensity exercise should be aware that drinking can have a more severe impact on their blood sugar levels.

For anyone seeking to improve their relationship with alcohol, or maybe just take a break for a bit, our metabolic systems are resilient. In most cases, when we significantly reduce alcohol consumption our body adjusts, and our blood sugar regulation improves.  Swapping an alcoholic beverage for a functional beverage designed to lower blood sugar (like GOOD IDEA) can be a great place to start for individuals seeking to improve metabolic health.

Author: Dr. Colleen Gulick