The negative effects of alcohol consumption on bone have long been recognized. Chronic heavy drinking has been identified as a significant risk factor for various diseases, including osteoporosis.

Alcohol and Nutrition

Calcium is important for many functions in the body, where it serves as a key nutrient in the maintenance of bone density. More than 99 percent of the body's calcium is stored in the bones and teeth. The remaining one percent is found in the blood. Blood levels of calcium depend upon how much of this nutrient is consumed in the diet, how well the nutrient is absorbed, and how much of it is excreted. Calcium balance is regulated by many factors, including parathyroid hormone (PTH) and vitamin D.

Alcohol disrupts calcium balance in many ways. To begin with, alcohol exposure increases PTH levels. In cases of chronic alcohol abuse, blood levels of parathyroid hormone can remain elevated, resulting in a strain on the body's calcium reserves. In alcoholics, continuous elevations in parathyroid hormone can precipitate the condition known as secondary hyperparathyroidism, the effects of which further deplete calcium stores.

Alcohol can inhibit the production of enzymes found in the liver and kidney that convert the inactive form of vitamin D to its active form. This interference in vitamin D metabolism results in an impairment of calcium absorption. Vitamin D deficiency can lead to osteomalacia, a bone condition associated with pain, fractures and deformity. Alcohol also increases magnesium excretion, an effect that can further negatively impact bone health.

Alcohol, Hormones, and Other Metabolic Effects

Chronic heavy drinking can result in hormonal deficiencies in both men and women. Alcoholic men tend to produce less testosterone, a hormone known for its positive effect on bone density. Low testosterone levels have been linked to decreased activity of osteoblasts, the cells that stimulate bone formation.

In pre-menopausal women, chronic alcohol exposure can result in irregular menstrual cycles, an occurrence that increases osteoporosis risk. Conversely, in post-menopausal women, alcohol increases the conversion of testosterone into estradiol, a hormone commonly used to prevent bone loss after menopause. For this reason, alcohol consumption may actually have a positive effect on bone density in women after menopause.

Alcoholics have been shown to have high levels of cortisol, a corticosteroid. Excessive levels of cortisol have been linked to decreased bone formation and increased bone resorption. Corticosteroids impair calcium absorption which leads to an increase in PTH secretion, which can result in further bone loss.

Bone loss is evident in a large number of individuals that drink heavily. Alcohol appears to have a direct toxic effect on osteoblasts, suppressing bone formation. On the other hand, osteoclasts (cells responsible for the resorption or breakdown of bone) may be stimulated by alcohol exposure.

Falls and Fractures

Due to the effects of alcohol on balance and gait, alcoholics tend to fall more frequently than the general population. Heavy alcohol consumption has been associated with an increased risk of fracture, including hip fracture. An analysis of alcohol use in an arm of the Framingham study concluded that heavy alcohol consumption increased hip fracture risk in both men and women. As expected, older alcoholics are at substantially greater risk of fractures than younger alcoholics.

Vertebral fractures, which tend to be uncommon in individuals under fifty years of age, are more prevalent in those younger than fifty who abuse alcohol. Additionally, alcohol consumption is linked to other types of fracture, including those of the wrist and ribs.

The Benefits of Abstinence

The most effective treatment for alcohol-induced bone changes is abstinence. Abstinence in alcoholics seems to result in a rapid recovery of osteoblast function. Moreover, studies demonstrate that bone loss may be partially restored when alcohol abuse is discontinued.

Moderation May Be the Key for Postmenopausal Women

While the toxic effects of alcohol abuse are well established, moderate alcohol consumption may actually have a modest favorable effect on bone density in postmenopausal women. This effect may be explained by the fact that after menopause, alcohol enhances the conversion of testosterone into estradiol. Moderate alcohol intake may also be beneficial due to its ability to increase calcitonin, a thyroid hormone that inhibits bone resorption. On the other hand, there is no evidence to suggest that moderate alcohol intake is beneficial to bone density in premenopausal women or in men.