Dehydration 脫水

Hong Kong Hiking Web: 戶外大夫專欄 Outdoor Doctor Forum: Dehydration 脫水
   By TT on Tuesday, March 27, 2001 - 7:54 pm:  Edit

I saw a statement from a website. It said that

What is your opinion, Outdoor Doctor?

   By K.K. on Tuesday, March 27, 2001 - 10:20 pm:  Edit

I am not sure about whether pure water is the best drink for dehydration, but sugar solution is definitely not better than pure water, and surelt not concentrated suger solution.

The digestion of suger (broken down into glucose molecules) consummes water, that is, will taken up some of the water molecules you have drunk.

Beside, learnt from the physics lessons, we know that water will move from a less concebtrated solution to a more concentrated, that is, draw water from the stomach blood vessel to the suger solution in the stomach in our case.

However, a rapid in-take of large quantity of pure water might cause the sudden dropping of the blood glucose level.

I normally take pure water with a very small amount of glucose added under those situations, and also a small amount of salt added if it was caused by heavy sweating under very hot condition.

Please correct me if I am wrong.

   By Outdoor Doctor (Doctor) on Tuesday, March 27, 2001 - 11:20 pm:  Edit

That statement is wrong.
Water absorption through the gut is not slowed down by the presence of glucose in the drink.

KK, human body is not so simple. I know that you are talking about osmotic pressure. It is right that water will move from a less concentrated solution to a more concentrated one. However, our guts have a lot of mechanisms to draw water, minerals and glucose into the blood vessel (Many of these mechanisms are independent of
each other). The absoption of water would not be slowed down by the increased glucose concentration in the drink. Also, you will not get low blood glucose even if you take a rapid intake of a large amount of water during hiking. Our body has many auto-regulation function.

Concerning dehydration, the main thing that we need to take is simply water. Some minerals (especially sodium) in the water is good , but not essential (unless you lost a lot of minerals through toileting and sweating + no food intake at all). Glucose just give you more energy.

   By Outdoor Doctor (Doctor) on Wednesday, March 28, 2001 - 10:13 am:  Edit

For certain disease (e.g. cholera 霍亂), glucose would help to increase the absorption of water.

The cholera bacteria destroys the inner surface of the gut, making the gut unable to absorb water and other minerals properly. Instead the gut lost a lot of water and minerals leading to severe diarrhoea. In that situation, it is found that the addition of glucose into the water could help to promote water and sodium absorption through the gut. Why? Because there exists a special mechanism of water absorption which is not affected by the cholera bacteria. Glucose is used to carry water and sodium into the bloodstream of the gut by this mechanism.

Practically speaking: If you were unlucky to get a severe diarrhoea (which may be a case of cholera) in the wild nature and you could not find a doctor yet, you can try the following formula to avoid further dehydration:

1L clean water + 5 teaspoon sugar + 1 teaspoon salt + 2 oranges/ grapefruit.

   By 小L on Wednesday, April 11, 2001 - 12:59 am:  Edit

thank u doctor, it's a very good suggestion to prepare a anti-diarrhoea drink. for hikers reference: this ratio is mimic the concentration human body fluid 5% glucose and 0.9% sodium chloride

   By .. on Tuesday, October 09, 2001 - 1:44 pm:  Edit

對一般人來說, 行山喝的水, 有少少 鹽, 係唔係好D ?

   By SL on Sunday, October 14, 2001 - 9:13 pm:  Edit



   By Siu 忠 on Monday, October 15, 2001 - 10:01 am:  Edit


   By Outdoor Doctor (Doctor) on Thursday, March 21, 2002 - 9:47 am:  Edit

Drinking plain water is good enough for a simple day hiking in Hong Kong.

But for some serious trekkers who walk for a very long distance strenuously, a balanced diet with adequate amount of electrolytes (including sodium) is important. Sodium chloride (salt,鹽) is available in many food. Adding salt into water might be a good idea if you didn't eat anything (containg salt) at all for a long while.

   By djball on Thursday, July 10, 2003 - 10:43 pm:  Edit

我本身吾系成日行山, 有一次同朋友行夜山, 我能心理上未 ready, 行山之前只系食左兩件蛋糕飲左 d 紙包檸檬茶, 當時系 3 月, 氣溫系 15 度左右, 但系我就背負 around 40L backpack, 行左一小時左右, 一直都有汗流, 但之後就覺得越來越 tired, 又吾知重有幾多先行完, 心理同生理上都有 pressure, 行左約 1.5 hrs, 我終於都要停下休息, 當時我冇流汗 (可能天氣涼,濕度低), 腳軟, 口乾, 冇體力, 我放低左個 backpack, 坐左響地下, 飲寶礦力, 食麵包, 但系越食越個口乾, 食都 d 麵包張住個口腔, 飲寶礦力都冇用, 系食完幾個包過左 5-10 mins 先覺得有番 d 體力, 請問我當時系脫水定體力透支?? (當日我9am 起床工作, 晚上8pm 先行山)

   By Outdoor Doctor (Doctor) on Saturday, July 19, 2003 - 2:24 am:  Edit

Thirsty (口乾) is a sign meaning that you are deprived of water in your body. It is advisable that one should drink more water before hiking (especially when he is carrying a heavy backpack). Dehyration does not necessarily happen in daytime.

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