Barq’s root beer contains caffeine

Caffeine is a mild stimulant that can promote alertness and wakefulness. According to Wikipedia, it "acts by blocking binding of adenosine to the adenosine A1 receptor, which enhances release of the neurotransmitter acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors." 

On the other hand, some people may feel jittery or experience sleep disruption with the consumption of too much caffeine. I fall into this latter group.

I am trying to reduce my caffeine intake, and so I switched from drinking coke to drinking root beer. But do some brands of root beer contain caffeine? I noticed some brands state they are caffeine-free whereas others do not.

An article on Healthline answers this question quite conclusively. It states: "In general, most brands of root beer sold in North America are caffeine-free. [...] Here are a few popular brands of root beer that don’t contain caffeine:"

• A&W Root Beer
• Diet A&W Root Beer
• Mug Root Beer
• Diet Mug Root Beer
• Dad’s Root Beer
• Diet Dad’s Root Beer
• Barq’s Diet Root Beer

The article goes on to say "[i]n particular, the brand Barq’s is notable for its caffeine content. The regular variety contains around 22 mg in each 12-ounce (355ml) can. However, the diet version contains none."

By comparison an 8-ounce (240 ml) cup of coffee contains 96 mg of caffeine which is roughly 6.5 times the caffeine of a similar volume of Barq's. 

Finally, according to the website Caffeine Informer, Pepsi (38.9 mg per 12 ounces) and Coke (33.9 mg/12 oz) have ~50% more caffeine than Barq's, but 4 times less caffeine than coffee.  

So if you want to stay caffeine-free you will have to avoid Barq’s root beer (Figure 1) and instead choose another brand such as A&W. 

Figure 1. Warning: for those of you who want a caffeine-free experience, Barq's Root Beer contains caffeine.