I gotta pee

As a child, most of us were told at some point to “hold it in”, “cross our legs”, “tie a knot in it” or “just wait”. From my own experience this was usually said through gritted parental teeth as I was dragged through some store or shopping area without adequate toilet facilities.

It is also a frequent problem at schools with supervisors reluctant to let charges out of their sight, or children too embarrassed to admit their need in front of the class.

Even as adults, many people will reduce the need for frequent urination by drinking less or waiting for extended periods of time to reduce disruptions at work or to avoid unpleasant toilet facilities (if you have visited public toilets in Greece or China, you know just how long you’d wait to avoid them).

But can repeated delays lead to long term urinary problems?

The bladder is a balloon-like organ which expands to hold fluids. Once it contains a certain amount (for adults around 200 ml of liquid) the urge to urinate becomes apparent. However, unless people have incontinence problems, most people can wait up to 5 hours before urinating. So long as you continue to drink, the longer you wait, the more liquid is put into the bladder. This means that the bladder keeps expanding. Indeed this is part of toilet training for children – their bladders expand over time.

If you do this too often, or wait too long, the bladder may become oversized and weak, leading to dribbling or incontinence. For children who are forced to hold on, often employing characteristic behaviours such as holding genitalia, squatting or pressing their legs together, tension in the pelvic floor muscles may make it harder to squeeze all the urine out of the bladder and thus some may be retained – leading to more frequent urges to urinate.

Infections of the kidneys and urinary tract may also be affected, with one study showing significantly higher levels of urinary tract infections in women who voided three or less times per day compared to those who urinated 4 or more times. However, this may be due more to reduced fluid intake than urine retention.

It seems that there needs to be a balance between toilet training children by teaching them to delay urination for a while, and asking them to hold on “too long”. Also city designers should perhaps increase access to clean, public toilets.

BTW on a more cultural note, I have noticed a significant lack of public amenities in New York City and a general American tendency to avoid the word “toilet” – instead people here use euphemisms such as “restroom”, “bathroom” or the strange “comfort station”.

Anyway, I must go, I feel an urgent bathroom visit calling…

References

Nielsen AF, Walter S (1994) Epidemiology of infrequent voiding and associated symptoms. Scand J Urol Nephrol Suppl. 157:49-53.

Nygaard I, Linder M (1997) Thirst at work–an occupational hazard? Int Urogynecol J Pelvic Floor Dysfunct. 8(6):340-3

Smith, D.B (2004) Female Pelvic Floor Health: A Developmental Review, Journal of wound, ostomy, and continence nursing 31(3):130–137

Do brown eyes see better than blue?

Recent research shows that blue-eyed men prefer blue-eyed women. Thus it appears that, at least to some observers, eye colour is important.

But why do humans have different eye colours?

It mostly comes down to the amount and location of melanin (yes, the same substance which controls skin colour) in the human eye. Pale eyes such as blue, grey or green eyes contain little melanin, dark brown eyes more. Which eye colour you get is primarily determined from genetic variation based on the eye colour of your parents.

But does your eye colour influence how you see?

It turns out that it does. The darker the eyes, the more light is absorbed as light waves pass through the eye, and the less light is available to reflect within the eye. Light reflection (scatter) within the eye can cause susceptibility to glare (eg. sun or headlights) and to poor contrast discernment. Thus it seems that people with darker eyes may have better vision in high-glare situations – perhaps this makes them better night drivers, for example.

Eye colour may also affect your colour vision. Here it seems that lighter eyes may provide some advantages.

So it seems to me that blue-eyed people should really go for dark-eyed partners – this way one can pick the paint colours, and the other can drive home at night.

References

Coppens JE, Franssen L, van den Berg TJ (2006) Wavelength dependence of intraocular straylight Exp. Eye Res. 82(4):688-92

Coren S, Porac C (1978) Iris pigmentation and visual-geometric illusions Perception 7(4):473-7.

Dain SJ, Cassimaty VT, Psarakis DT (2004) Differences in FM100-Hue test performance related to iris colour may be due to pupil size as well as presumed amounts of macular pigmentation Clin. Exp. Optom. 87(4-5):322-5.

IJspeert JK, de Waard PW, van den Berg TJ, de Jong PT (1990) The intraocular straylight function in 129 healthy volunteers; dependence on angle, age and pigmentation Vision Res. 30(5):699-707.

Does the Aussie “pie and sauce” protect against sunburn?

The classic Australian meat pie advertisement shows tough men in shorts eating a pie with tomato sauce (similar to ketchup) in the blazing sun.

But could this quintessential Down Under delicacy help to protect Aussie skins from the harmful effects of UV radiation?

Sunlight can cause the formation of free radicals in the skin cells. Free radicals are atoms which exist with an unstable number of electrons in an electron shell. Ultraviolet (UV) radiation can “force” electrons from atoms such as oxygen and create free radicals. Since the electron state of a free radical is so unstable, they are likely to react with anything they touch in the cell – be it a protein or DNA strand. This can lead to temporary damage (such as sunburn) or permanent damage including cataracts – and even to cancers such as melanomas.

Tomatoes contain caretenoids such as lycopene. These are the chemicals which give tomatoes their rich colour. Lycopene is perhaps the most powerful of the anti-oxidants found in any fruit or vegetable.

Anti-oxidants react with oxygen (and other) free radicals to neutralise them before they can harm biological processes. To some extent, the more anti-oxidant molecules in a cell, the more likely a free radical is to hit one of those before hitting a vital part.

Putting caretenoids – especially lycopene – onto the skin has been shown to help prevent and even partially reverse the damage done by exposure to UV light. But it’s not just an external form of sun block – leaving the sauce your pie provides benefits too.

A diet rich in tomatoes has been shown to reduce sunburn and the effects of UV exposure. In fact concentrated cooked tomato (such as tomato paste or sauce) is an even better source of such anti-oxidants than are fresh tomatoes. Forty grams (4 tablespoons) of tomato paste eaten daily has been shown to significantly reduce visible sunburn after only a few weeks.

While not a substitute for sunblock or sun-safe practices, eating a diet rich in tomatoes could thus provide some level of continuous protection. Indeed, it is likely that increasing tomato consumption in your diet may help protect not only against sunburn, but the visible signs of aging, cataracts and skin cancer.

Perhaps in the “sunburnt country” of Australia, it is no coincidence that tomato sauce became the condiment of choice.

References

Aust O, Stahl W, Sies H, Tronnier H, Heinrich U (2005) Supplementation with tomato-based products increases lycopene, phytofluene, and phytoene levels in human serum and protects against UV-light-induced erythema.
Int. J. Vitam. Nutr. Res. 75(1):54-60.

Fazekas Z, Gao D, Saladi RN, Lu Y, Lebwohl M, Wei H (2003) Protective effects of lycopene against ultraviolet B-induced photodamage Nutr. Cancer 47(2):181-7.

Stahl W, Heinrich U, Aust O, Tronnier H, Sies H (2006) Lycopene-rich products and dietary photoprotection. Photochem Photobiol Sci. 5(2):238-42.

Stahl W, Heinrich U, Wiseman S, Eichler O, Sies H, Tronnier H (2001) Dietary tomato paste protects against ultraviolet light-induced erythema in humans. J. Nutr. 131(5):1449-51.