Dear Doc: Me and the guys in my shop drink A LOT of caffeine. I'm not much of a coffee guy, but I do drink two or three energy drinks a day. I drink a lot of water too, and I'm young and in good shape, but sometimes I feel like I'm a little too reliant on these drinks. I sometimes short myself on sleep only because I know I can have an energy drink or two and be fine for most of the day.

Is that a problem? Should I cut back? What are the impacts on my health? Are some forms of caffeine (coffee or tea, for example) better or safer than others? I'd rather focus on this while I'm young and healthy instead of keeping it up for a decade before I realize it's caused a real health problem.

-AO2 Energy

Dear AO2: Full disclosure: Even I relied pretty heavily on caffeine as a young doc, so you're not alone. I'm fairly certain the U.S. military has been using caffeine since around 1776. The key to caffeine use is moderation. Also, nothing beats a normal sleep schedule and good nutrition habits.

To help better answer your questions, I recently spoke to Army 1st Lt. Jessica Wonn, assistant chief of the Education and Research Department in the Nutrition Services Division at Walter Reed National Military Medical Center:

Caffeine is a common stimulant found naturally in the leaves and seeds of many plants and made artificially and added to foods and drinks. Caffeine is found in hundreds of products now - from soda, coffee, and tea (even decaffeinated versions!) to energy drinks, pre-workout supplements and even snack bars and chocolates. Frequently, you hear, "It's okay to have caffeine, but don't have too much."

So how much is too much?

Caffeine is generally safe for use and can even improve tactical or athletic performance. However, it does not replace good sleep and nutrition. In general, the Food and Drug Administration recommends limiting caffeine intake to 400 milligrams of caffeine per day, which is just under two energy drinks or four cups of coffee.

It can be hard to determine how much caffeine is in different items, so the following list may help you to choose wisely:

Food or Beverage - Amount of Caffeine

-Decaf Coffee or Tea (8 oz.) - 2-15 mg

-Soda or Soft Drink (12 oz. can) - 30-40 mg

-Green or Black Tea (8 oz.) - 30-50 mg

-Coffee (8 oz.) - 80-100 mg (Lighter roasts have more caffeine)

-Caffeine Tablets (1 capsule) - 200 mg

-Energy Drinks (8 oz.) - 40-250 mg

-Pre-Workout Supplements (1 scoop) - 100-350 mg

How much caffeine should you consume?

The answer is that it depends. Some individuals are "caffeine responders," while others may not feel the effects. Some people may consume more than the recommended 400 mg without any effects because their bodies break down caffeine faster or may not respond at all, while others feel the effects immediately with a small amount of caffeine.

How do you know if you are a caffeine responder and have too much

Next time you consume caffeinated products, pay attention to side effects that may occur when you have too much. Common symptoms of too much caffeine include jitters, anxiousness, increased heart rate, upset stomach, nausea, difficulty sleeping, headache, and feelings of unhappiness. If these symptoms occur, you should stop consuming caffeine for at least four to six hours to allow your body time to break down what you have consumed. It may also help your sleep patterns if you stop drinking caffeine four to six hours before you intend to go to sleep.

What happens if you consume too much?

Currently, 1,200 mg of caffeine within one to two hours is considered harmful and can lead to serious problems, such as seizures. This is a huge concern when it comes to unlabeled caffeine powders and supplements.

How can you avoid consuming too much?

A simple way is to avoid items that are marketed as concentrated caffeine powders or liquids completely, especially if they do not provide the appropriate serving size and caffeine dosage on the package.

What service members should know:

Some other things to think about when you are considering your caffeine consumption include:

Energy Drinks or Pre-Workout Supplements: These products may utilize an energy blend. Just because the label states it has 250 mg of caffeine, does not mean that the product will not have an increased stimulant effect. If you have never used a product of this nature, use caution, starting with 1/4 to 1/2 of the recommended serving size.

Sodas, Energy Drinks and Specialty Coffees: These items typically contain added sugars that, in large amounts, can lead to weight gain. Choose diet sodas and energy drinks or sugar-free syrups to limit the amount of added sugar and prevent increases in your weight.

Medical Conditions/Medications and Caffeine: Avoid consuming excessive caffeine if you are pregnant or breast feeding. Caffeine may interact with specific medications. Always talk to your doctor or pharmacist to ensure you understand the risks.

Caffeine and Performance: Caffeine can improve physical and mental performance in some instances. Research has even found it improves reaction time, visual vigilance, and overall alertness. A few studies have found that athletes may see performance improvements if they consume 4-6 mg of caffeine per kilogram of body weight 30-120 minutes before exercise. This would be around 1 1/2 cups of coffee for a 150 lb. person, for example.

Caffeine and Sleep: Caffeine can interfere with sleep, specifically falling asleep. If you find that you are having difficulty falling asleep, try to discontinue caffeine use earlier in the day. A common rule of thumb is to not consume caffeine after lunch.

Overall, caffeine does not seem to negatively affect your health and may help keep you alert during an overnight operation or a long day at work when consumed in moderation. However, remember, caffeine use does not replace sleep or energy received from food! So, while it can help keep you awake and alert, you still need to get 6-8 hours of sleep per night and eat enough food to support regular performance. If you have any more questions, make an appointment at your local medical treatment facility's outpatient nutrition clinic to discuss caffeine use and personal recommendations.

AO2, the bottom line is that, no matter what your caffeine consumption may be, there are a variety of factors that may help in determining what an acceptable level of daily caffeine may be for you. Also, keep in mind that it may be completely different for other people in your shop.

Just keep in in mind that any recommendations that Lt. Wonn provided are assuming that you are eating and sleeping regularly. Pay attention to labels, as well as the way your body reacts after you consume products with caffeine in them.

Other than that...take care out there!