We've heard them all growing up: carrots improve your eyesight, cracking your knuckles gives you arthritis... Are they old wives' tales? Or actually sound medical advice? We've rounded up the best myths and asked Erik Berger, MD, a Denver-based Internal and Sports Medicine Doctor, to weigh-in to clear up our questions once and for all.

Should you hold in a sneeze?

Theoretically you could cause trauma to your eardrum but you're not going to blow your eyeballs out or anything like that. If you do hold in a sneeze, depending on where you catch it you could cause trauma to the eardrums if you're congested or you have fluid in your ears.

Should you use Q-tips to clean your ears?

It's not typically recommended because most of the time what you end up doing is if you have wax in your ear, you force it up against your eardrum. Ideally, you would use an irrigation system to try to soften the wax and remove it. You can buy an ear wax cleaning kit at the pharmacy.

If you swallow gum does it take seven years to digest?

No. It won't stick to your intestines or anything. You digest it like everything else.

If you crack your knuckles frequently it will give you arthritis when you're older.

I don't think there's really been any evidence to support that. The cracking causes the shifting of gases and that's what you're hearing in the cartilage and the joints. But as far as you doing any kind of trauma to your knuckles, unless you push them in the wrong direction with excessive pressure and do that over a long period of time in theory you could do damage, but that's not typical.

Tryptophan makes you sleepy on Thanksgiving.

Tryptophan is the precursor to melatonin so in theory, yes. But more than likely what is happening is when you eat a big meal you have a shift in your blood flow to your gut and you have a thing that's called alkaline tide from the production of acid in the stomach and that's probably more likely the cause. Tryptophan may contribute to some degree, but it's probably more than one thing. It's probably more from the blood flow shift. It's the big meal and shift in blood flow and the metabolic demands to digest the food, along with tryptophan.

Are natural sugars more healthy than processed sugars?

I really don't know about that one but I would doubt it. Most of them are just simple sugars. There may be other things that they don't refine out that could  theoretically change the glycemic index, but I would say there's probably no real difference. They're both going to be four calories per gram in terms of caloric density. Your insulin response is probably going to be pretty similar. If you're talking about a table sugar like sucrose compared to Sugar In The Raw I think the difference would be pretty negligible.

Do carrots improve your eyesight?

If you are already deficient in beta-carotene and vitamin A then it might. But it won't take someone whose eyesight is poor and who has a pretty well-balanced diet and change their eyesight. It's supportive, but if your eyesight is bad and you need glasses then carrots aren't going to make the difference.

Drinking ice water is bad for digestion.

I don't think it is. The only thing I can think of is if you're drinking cold water it might cause some constriction that in some ways could slow gastric emptying and slow blood supply to the gut. But I don't think there's evidence to support that. If you're drinking ice water would you not get the same absorption of nutrients out of the food than if you drink something at a more moderate temperature? I don't think there's any evidence to support that.

The 5 second rule: If you drop food on the ground and pick it up  before five seconds it’s safe to eat.

Not necessarily. If it's going to get contaminated it can get contaminated as soon as it hits the ground. For safety’s sake, you don't know what has been on the ground. You're probably better off not eating it if you're concerned. If your food comes in contact with something that can contaminate it it's going to do so immediately, but I'm usually not very concerned about it.

Being outside in the cold weather makes you sick in the winter time.

No. Germs make you sick. Being cold does not make you sick. In theory, Eskimos would be the sickest people in the world if that was the case. There's no relationship whatsoever between being cold and getting viruses or colds.

If you can walk on or use a limb it’s not broken.

There is a rule called the Ottawa ankle or the Ottawa knee rule that says if you are able to weight-bear immediately after an injury it’s probably not broken. That is a pretty good indicator but it's not absolute. It is a clinical sign that we use. If someone fell and hurt their ankle and couldn't put weight on it right away we do use that as a clinical indicator that you should probably get X-rays because we're concerned that there is a break. So there is some validity to that. The test is typically for the ankle or the knee. The same rule doesn't necessarily apply to hands or wrists, for example.