It's the holidays, that ambiguous time of indulgence that used to be confined to Thanksgiving but which now encompasses the chunk of the year between Halloween and Valentine's Day — and, oh, why not, let's just throw in St. Patrick's Day.

Focusing just on Christmas, though, here are five pervasive health misconceptions you might encounter during your time of merriment:

Dehydration is just a summer thing

Dehydration isn't just for summer anymore. Cold weather can actually increase your risk of becoming dehydrated because you don't have signals such as heat and sweat to remind you to drink water.

The holidays up the risk even more, because common drinks such as alcohol and coffee (or anything with significant amounts of caffeine) are diuretics, substances that make you urinate more and lose fluids and electrolytes. The most common early warnings of dehydration are headaches and nausea, otherwise attributed to little Johnny playing with his new Zhu Zhu hamsters.

Water is the best cure; space your wine with some of the clear stuff. And don't forget that some soda pops such as Mountain Dew have as much caffeine as a half cup of coffee.

Sugar makes kids crazy

No one can believe it, but sugar doesn't seem to cause hyperactivity in children. The kids are likely just hyped up from all the excitement of Christmas.

More than a dozen large, double-blind, randomized controlled studies dating back to 1980 have found no relationship between cookies, cakes, candy and Billy racing around the table whirling his socks around his head. That said, a large study published in the European Journal of Clinical Nutrition in April 2009 found that kids at age 4.5 on a junk-food diet were more likely to be hyperactive by age 7.

This could be the result of a long-term nutritional imbalance, lousy parenting, or both.

You'll gain about 5 pounds

A common figure tossed around this time of year is that Americans on average gain 5 pounds during the holidays. Fortunately this isn't close to the real figure.

Independent studies published in the New England Journal of Medicine, Nutrition Review and Nutrition Journal found the gain between Thanksgiving and New Year's to be modest, between 0.8 and 1 pound. The gain was indeed higher among obese subjects, though, some of whom did pack on 5 pounds.

Nevertheless, a pound gained in just a little over a month can add up to serious heft in a year or two if such habits last year round.

Alcohol burns off in cooking

Alcohol has many ways of sneaking up on you during the holidays. For starters, you might be tired from holiday chaos with one family visit piled on top of another. Alcohol hits you harder when you're tired. Also, alcohol doesn't completely burn off when cooked in those festive dishes you might encounter, counter to what is said colloquially.

Alcohol evaporates at around 175° F, so slow cooking and simmering won't burn off anything. Baking for an hour will still leave 25 percent of the booze. Flaming it for that dramatic walk to the table can still leave most of alcohol behind. So consider your rum-accented glaze as fully spiked.

When fixing yourself or a friend a drink, it's easy to be too generous. Short, wide glasses typical in formal settings are easier to over-pour compared to tall glasses. Legitimate studies have been conducted on this, such as one published in 2005 in the British Medical Journal finding that even experienced bartenders routinely overestimated a shot of booze by over 20 percent in such a glass. So between fatigue, rum cake and what you thought was just two mixed drinks, you could find yourself further down the road to tipsy than expected.

A plate-full is a typical serving

So, as Uncle Joe manages to lift his massive backside out of the lounge chair to go back for seconds, and while you contemplate the depth of the crater he left in the vinyl cushion, you also might wonder whether what he had on his first plate was really just a single serving of myriad holiday delights.

A serving size isn't simply what fits on your plate. With holiday foods, in particular, it is easy to overestimate serving size. A serving size of canned cranberry sauce, for example, is just a slice. A serving of cheese is just four or so cubes. A serving of mashed potatoes or stuffing is about the size of a small ice-cream scoop.

At this rate, a heaping first plate could contain a dozen servings of stuff before you even get to dessert. (Pie is too deadly and delicious to warrant any official serving size.) While it is true that weight gain over the holidays is not as high as reported in the popular press, be careful not to push your luck.