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NHANES: Marijuana May Have Beneficial Effects for Glucose Control

The National Health and Nutrition Survey found a positive association between use of marijuana and reduced insulin resistance….

Marijuana, one of the most commonly used illicit drugs in the US, has been linked to a lower BMI and decreased prevalence of obesity and type 2 diabetes among its users. A recent study published in the American Journal of Medicine has found that marijuana use was associated with better glucose control and less insulin resistance.

4657 participants out of the National Health and Nutrition Examination Survey (NHANES) from 2005-2010 were studied to find a possible association between marijuana use and glucose control through fasting blood levels of glucose, insulin and determination of insulin resistance. During the survey time range, 11,335 adults aged 20 to 59 years, answered a survey on illicit drug use. From this group, 4,657 participants provided a 9hr overnight fasting blood sample. Each blood sample was analyzed for insulin, glucose, homeostatic model assessment insulin resistance (HOMA-IR) score, HDL, Hemoglobin A1c, and Triglycerides. The HOMA-IR measure of insulin resistance was calculated as fasting serum insulin (μU/mL) × fasting plasma glucose (mg/dL)/405.

Lead researcher Murray Mittleman, MD, DrPH reported, "Previous epidemiologic studies have found lower prevalence rates of obesity and diabetes mellitus in marijuana users compared to people who have never used marijuana, suggesting a relationship between cannabinoids and peripheral metabolic processes, but ours is the first study to investigate the relationship between marijuana use and fasting insulin, glucose, and insulin resistance."

Marijuana use among participants was assessed by a computer based questionnaire. Of the 4657 participants, 2,103 had never smoked or ingested marijuana; 1,975 participants had used marijuana before but not within the last 30 days; and 579 current users who had use marijuana at least once within 30 days of the survey.

The study found that those participants who were considered current users of marijuana (use within 30 days) had an average of 16% lower fasting insulin level compared to those who have never used the drug. Current use was also associated with a 17% lower insulin resistance score determined by HOMA-IR in comparison to those who reported never using marijuana. The average HDL level was 1.63mg/dL higher in current users of the drug than those who had never used. The study also found a smaller waist circumference in current users of the drug than those who never used.

In regards to possible confounding, co-author Elizabeth Penner, MD, MPH stated, "It is possible that the inverse association in fasting insulin levels and insulin resistance seen among current marijuana users could be in part due to changes in usage patterns among those with a diagnosis of diabetes (i.e., those with diabetes may have been told to cease smoking). However, after we excluded those subjects with a diagnosis of diabetes mellitus, the associations between marijuana use and insulin levels, HOMA-IR, waist circumference, and HDL-C were similar and remained statistically significant."

The study did not find the beneficial effects on insulin and insulin resistance in participants who had used the marijuana in the past compared to current use. The authors concluded, "These associations were attenuated among those who reported using marijuana at least once, but not in the past 30 days, suggesting that the impact of marijuana use on insulin and insulin resistance exists during periods of recent use."

This study is not a proponent of illicit drug use; however, a better understanding of the relationship between cannabinoids and metabolic processes may help physicians in the future decide when to use the herbal or synthetic form of this drug when other treatment options have failed.

The Impact of Marijuana Use on Glucose, Insulin, and Insulin Resistance among US Adults. The American Journal of Medicine, 2013; DOI:10.1016/j.amjmed.2013.03.002