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NUTRITION: From safe to toxic, the scoop on caffeine

Fall is in the air, and a morning dose of coffee or tea is often a must to get us going before the light of day. Many people look forward to that energy jolt from caffeine.

Today more than 80 percent of the world's population consumes caffeine in some form, and it's become the most widely consumed central nervous system stimulant. Caffeine is a legal drug.

Caffeine has been part of the human diet for centuries, primarily through coffee, tea and, more recently, sodas. It's also found in cocoa beans, chocolate and some snack foods. Many craft coffee and tea beverages as well energy drinks contain more caffeine than you may have considered.

Caffeine can have positive and negative effects. There are safe levels of consumption and toxic levels. As we head into the shorter days of the year, educating yourself and your family about the risks and benefits of this legal stimulant can be helpful.

Caffeine has several well-documented positive effects:

• Alertness/wakefulness — This is achieved by blocking adenosine receptors in the brain. Adenosine signals the brain that it's time for the body to slow down and sleep.

• Pain relief — Caffeine reduces inflammation and helps to block the perception of pain in the brain.

• Endurance — Caffeine is believed to influence the way muscles utilize glycogen allowing them to function longer before fatigue sets in.

• Motivation/productivity — Caffeine causes dopamine levels to increase, which produces a positive state of mind.

Caffeine also has negative effects which vary by dose and a person's tolerance and sensitivity level:

• Insomnia — Consuming caffeine too late in the day can interfere with getting to sleep and staying asleep.

• Jitters — In some people, caffeine causes moderate to severe shaking of the hands.

• Addiction — Caffeine is moderately addictive, and some may have trouble consuming in moderation.

• Withdrawal headaches — Habitual caffeine users must consume close to the same amount of the drug each day or a withdrawal headache could result.

• Increased blood pressure — Caffeine metabolism causes stress hormones to be released, which elevates a person's blood pressure for a short period of time.

• Risk of overdose — Doses greater than 400 milligrams per day can elicit mild to severe caffeine overdose symptoms in adults. This can occur with much smaller doses in children or those who are more sensitive to caffeine.

• Anxiety — Caffeine can increase anxiety especially in those diagnosed with anxiety or stress disorders.

• Exacerbates heart conditions — Since caffeine can increases heart rate, it can be dangerous for those with underlying heart conditions. However, it does not cause heart abnormalities. It is good to let your health provider know how much coffee, tea or other caffeinated products you consume if taking heart medications.

Health authorities offer guidelines on consuming caffeine. Some people may be more sensitive or have a lower tolerance. Healthy adults can consume 400 milligrams each day. Teens ages 13-18 should have 100 milligrams or less. Teens have been shown to be the fastest growing population of caffeine users, with some 83 percent regularly consuming caffeinated beverages. Children 12 and younger should have very limited caffeine. A 2014 study in the journal Pediatrics found many American children consume more than we realize, mostly from soda.

The American Psychiatric Association recognizes caffeine intoxication as a clinical syndrome. According to the Diagnostic and Statistical Manual of Mental Disorders, some people can experience caffeine intoxication symptoms, including restlessness, nervousness, excitement, insomnia, flushed face and gastrointestinal complaints after ingesting as little as 100 milligrams per day. At daily levels of 1,000 milligrams, symptoms may include muscle twitching, rapid heartbeats, abnormal electrical activity in the heart and psychomotor agitation.

Caffeine levels are not required on product labels, so it may not be easy to determine how much caffeine is in a product. Caffeine amounts also vary in coffee and tea depending on the type of bean or tea leaf, the brewing method and time and strength of the brew. It's important to watch your serving size since we often consume more than the size listed. The Food and Drug Administration has limited caffeine in soft drinks to not more than 71 milligrams in 12 ounces.

Caffeine is available in pill form and now in a concentrated powder, which if not taken in a proper dose can quickly be toxic. Caffeine pills such as No-Doz are limited to 200 milligrams per capsule.

Bonnie Brost is a licensed and registered dietitian in the Wellness Program at the Essentia Health St. Mary's Heart & Vascular Center in Duluth. Contact her at bonnie.brost@essentiahealth.org.

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