As people age, their body functions weaken, which can lower their tolerance for alcohol and drugs.

Although there is tremendous variability among individuals, the aging brain generally becomes more sensitive to the effects of substances in the body, including being more prone to side effects.

I’ve known patients who have reported modest alcohol use throughout their adult lives, and in their 70s or 80s, they find that the glass or two of wine they always drank at dinner now affects their memory or makes them feel hungover in the morning.

As the body ages, its ability to metabolize (break down) and excrete substances declines. The decreased ability to metabolize drugs leads to higher blood levels of a drug for longer durations.

In addition, normal kidney function is essential for getting rid of drugs through the urine. As renal function diminishes with age, the amount of alcohol and drugs that remain in the body can lead to greater and longer-lasting effects.

Reduced liver function also increases levels of drugs and alcohol, as well as their impact on the body and the brain.

In addition, the medications many older people take to manage high blood pressure, heart disease, or other chronic conditions can interact with alcohol and other substances, causing toxic effects.

The average senior consumes a half dozen or more medicines that can augment the effects of intoxicants. Many drugs are also stored in fat tissue, and can remain in the body for a longer duration in overweight or obese adults.

Finally, brain neurotransmitter receptors may become more sensitive with age, which makes it difficult for some people to tolerate the same amounts of substances they could when they were younger.

In light of these kinds of age-related issues, the National Institute on Alcohol Abuse and Alcoholism has recommended reduced daily intake of alcohol for adults 65 or older.

For men, the recommended daily amount of alcohol is one drink — which means 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of hard liquor.

The recommendations for older women are about half those numbers.