Our December moods are often not happy. The frantic pulse of holiday preparations is compounded by increasingly early sunsets, miserable weather and, these days, the impact of our financial situation on holiday shopping. The songs of goodwill and cheer that blare over store and mall loudspeakers are a counterpoint to the grumpiness and irritability of the shoppers below.

The solution to getting through this period is to carbo-load for stress: That provides our brains with enough serotonin to get us through holiday preparations feeling calm, tranquil and content.

Carbo-loading is a term usually applied to the diet followed by marathon runners a few days before the race. Because they are racing for 26.2 miles, runners want to "stuff" their muscles with as much stored carbohydrate as possible, as this is the energy their bodies will be using during the race. A typical pre-race week diet  detailed in a recent issue of Runner's World contains about 85% of the calories from low-fat sweet and starchy carbohydrates such as a bagel with jam, baked potatoes, rolls, high- fiber granola bars and orange juice. The extra carbohydrate they eat is converted to glycogen, the stored form of carbohydrate. The theory behind this type of eating is that it will last for the duration of the race.  

Carbo-loading is also a way of ensuring that our brains have enough serotonin to keep us in a state of well-being when we meet the stresses of the pre-holiday weeks. When any carbohydrate is eaten, with the exception of fructose, the carbohydrate in fruit, changes occur in the pattern of amino acids in the blood stream. As a result of these changes, a specific amino acid, tryptophan, gets into the brain and is converted into serotonin. Serotonin has many functions, but the one that concerns us during the coming weeks of overcommitted schedules is its ability to soothe us when we are in stressful situations.

This story, told to me by my neighbor, illustrates the power of a little carbohydrate to replace stress with calm. "There was a line of cars waiting to get into the mall parking lot and my plan—what was I thinking?—to run in and buy a gift for my daughter's music teacher before going to her recital quickly vanished. Not only was I not going to get the gift, I was going to be stuck in line for twenty minutes and then I would be late for the recital. Did I need this stress? Somehow I extracted myself from the line and headed for the nearest Starbucks. Ten minutes, one latte and a chocolate-covered biscotti later, my stress melted away like the chocolate on the biscotti when I dipped it into my drink. Not only did that cookie make me feel better, but, as I was sitting there, I realized I could get the teacher a gift certificate from the coffee shop."

Of course it wasn't the biscotti that accomplished the stress-reduction; it was the serotonin.

Eating small, portion-controlled amounts of carbohydrate on a relatively empty stomach (so digestion occurs quickly) produces the mood-gentling effects of the serotonin within 10-to-15 minutes. Fat-free or very low-fat snacks are best because they are digested quickly and contain fewer calories than other snacks. Several years of laboratory research with volunteers showed that 30-to-35 grams of carbohydrates will start the process that leads to serotonin production. Snacks that travel well include very low-fat granola bars, pretzels, breakfast cereal (packed in sandwich bags) graham crackers, breadsticks, and rice crackers. 

Protein keeps serotonin from being made, so avoid eating protein along with the carb snack. (High-protein diets that limit or avoid carbohydrate may decrease serotonin levels and only add to your stress levels.)

As tempting as it is to snack on a gigantic oatmeal cookie or the fancy chocolate truffles that you had planned to give to your aunt, don't. True, they are carbohydrates and no one will disagree that they probably do taste better than unsweetened cold cereal. But cookies, chocolate, ice cream, French fries, puff pastries and chocolate-covered pretzels (too name just a few of the possibilities) are simply too high in fat. The same can be said for that delicious-looking container of caramel-coated popcorn mixed with chunks of chocolate. Eating that is not the same as plain, air-popped popcorn, which is on the list of acceptable snacks.

It is not necessary to carry high-fiber, whole-grain carbohydrate snacks with you unless you normally go to the mall or to a holiday fair with a plastic container filled with steamed brown rice, bran flakes or balls of cooked quinoa. These healthy carbohydrates should be a part of our diet and may indeed return to our plates in January. But for now, it is necessary to make compromises and one of them is to give convenience a higher priority than fiber.  

When should you snack? The best time is when you are most likely to feel stressed. Is it in the morning when you wake up and confront a foot-long to-do list? Does the stress get worse as the day goes on and you start adding on new obligations and commitments? Are you most agitated when you walk in the house early in the evening and confront everything you normally do, plus all the extra holiday tasks awaiting you after the dishes have been done, dog walked, laundry sorted, and homework monitored?

Eat more than one snack on days the holiday stress is unrelenting. Evenings may be the most stressful, as you are tired by then, yet may have hours of holiday tasks ahead of you. We suggest, in The Serotonin Power Diet, eating a carbohydrate-based dinner with little or no protein. Doing this won't get your holiday chores done any faster but you won't fret about it.

Worried that all these carbs will make you gain weight? Don't. A hidden bonus of making serotonin is that this multifunctional brain chemical also decreases your appetite. Think of that as an early holiday gift.