This is the main point of this post: Sometimes what your brain craves is not good for your body. We all know that this is true. We’re drawn to any food that has ample quantities of fat, salt, and sugar. Visit any coffee shop in the nation, and you’re likely to see people enjoying a cigarette with their coffee and glazed donut. Why do humans choose to consume chemicals that are so unhealthy? Smoking kills slowly and nicotine is incredibly toxic, caffeine is harmful to the heart muscles and, at high doses, can induce dangerous arrythmias, while the regular consumption of sugar-ladened donuts leads to diabetes and obesity-related disorders.
The reason is simple: Our brains reward us for consuming these foods/chemicals. [For a thorough discussion of this topic, go here: Your Brain on Food: How Chemicals Control Your Thoughts and Feelings.] It’s well known that nicotine, caffeine, and sugar produce euphoria which encourages their continued long-term use. However, science has clearly demonstrated their toxicity for our physical health; Is there any evidence that caffeine, nicotine, and sugar are beneficial to the brain? Yes. Let’s look at the evidence.
Donuts
It’s early morning and you’re having difficulty paying attention to the traffic, to the boss, to whatever you’re trying to accomplish. Why? Your brain is not cooperating because you just woke up that it’s low on one critical ingredient—sugar. You have been fasting since last night’s dinner, and your blood levels of sugar have fallen. Sugar is indispensable. Your brain can’t function without it and will do whatever is necessary to convince you to eat sugar as soon as possible. Why?
Essentially, the presence of sugar in your brain is considered normal, and its absence leads to the craving—and to the initiation of foraging behaviors, such as seeking out a vending machine for cupcakes or a candy bar. There is a reason donut shops and sugar-laden cereals are so popular: You can lay the blame on neurons within the feeding center of your hypothalamus. If your brain did not want those donuts so badly, the shops would not be so densely distributed along your route to work.
Once inside the brain, sugar is also used to produce a very important neurotransmitter chemical called acetylcholine. Acetylcholine allows you to learn and remember, to regulate your attention and mood, and to control how well you can move. Your brain makes acetylcholine from choline. We frequently obtain choline in our diet by eating lecithin, which is present in donuts. Thus, a donut first thing in the morning is going to provide your brain with the sugar and choline it needs to pay attention and learn new things. Your big active brain utilizes the equivalent of 10 donuts worth of sugar every day.
Coffee
While you were dreaming during the few hours prior to waking up, your brain was burning through lots of energy molecules called ATP. All of the cells of your body require ATP to function. When ATP is consumed, the molecule “A” in the ATP falls away and begins to collect as debris. The “A” stands for adenosine. Unfortunately, as the levels of adenosine increases it begins to powerfully turn off your acetylcholine neurons. This is unfortunate because your brain cannot pay attention or learn new things if your acetylcholine neurons are turned off!
What’s the cure? Coffee. The caffeine in your coffee is able to prevent the actions of adenosine and release your acetylcholine neurons from their chemical shackles; your attentiveness improves and you are ready for anything—at least until the caffeine effect wears off. However, typical of just about everything we consume, a little caffeine is good but too much can kill you. Approximately five grams of caffeine—about 25 cups of coffee drank quickly—is a lethal dose for a typical adult. Consuming over 400 mg of caffeine (three espressos) daily increases susceptibility to cardiovascular disease. Chronic caffeine consumption may disturb the autonomic nervous system, leading to elevated blood pressure and heart rates that may predispose some vulnerable individuals to atrial fibrillation.
Human epidemiological studies consistently show that the risk of many age-related neurodegenerative diseases is reduced by chronic, moderate caffeine consumption. Forty years of clinical investigations have confirmed that the incidence of Parkinson’s disease is dose-dependently decreased (up to 85 percent!) as coffee consumption is increased to five cups per day (Tan et al., 2007).
Large epidemiological studies involving over hundreds of thousands of people consistently reported that coffee dose-dependently decreased the risk of brain tumors. The risk of brain gliomas, the most common type of brain tumor, decreased significantly when subjects drank more than three cups of coffee per day (Di Maso, et al., 2021). Coffee consumption was associated with a lower prevalence of small brain infarcts related to ischemic strokes. In addition to improving cognitive function, daily coffee consumption enhances the brain’s endogenous antioxidant systems.
Cigarettes
Humans have a complicated relationship with tobacco. Tobacco was once used to treat persistent headaches, colds, and abscesses or sores on the head. Tobacco enemas were used to treat flatulence, and even more surprising, the smoke was once inhaled deeply to lessen bad coughs. A cigarette made from tobacco will contain about 1 to 2 milligrams of nicotine. Because nicotine is quite volatile and heat labile, only about 20% of it is inhaled into the body. However, because of its exceptional lipid solubility, at least 90% of the inhaled nicotine is absorbed into the body. Sixty milligrams is considered a lethal dose for a human; death takes only a few minutes to occur and results from a loss of control of the nicotinic receptors on the diaphragm muscles.
Nicotine is neuroprotective. Epidemiological studies consistently show an inverse association between smoking and the risk of developing Parkinson’s disease (Yang et al., 2025). Long-term, heavy smokers (who don’t die from lung cancer) have a significantly lower incidence of Parkinson’s disease as compared to non-smokers. This protective effect appears dose-dependent and diminishes after cessation, suggesting that ongoing nicotine exposure may be necessary to maintain the effect. Nicotine is likely the active component responsible for this reduced risk.
So, the next time you see someone enjoying a cigarette with their coffee and donut, congratulate them on working hard to keep their brain healthy.
