How much wa­ter do we re­ally need?

Hauraki Herald - - OUT & ABOUT -

Q: Is there any truth to the claim that we need to drink eight glasses of wa­ter a day? Re­gards, Ge­orge

Hi Ge­orge. Hy­dra­tion is such an im­por­tant topic and the im­pact that this can have on how we look, think and feel is far too of­ten un­der­es­ti­mated. De­hy­dra­tion im­pairs phys­i­cal and men­tal per­for­mance, and even slight de­hy­dra­tion can leave us feel­ing fa­tigued.

The idea that ev­ery­one re­quires ex­actly eight glasses of wa­ter a day doesn’t re­ally make sense to me, as we’re all dif­fer­ent so we will have dif­fer­ent needs. Sci­ence cur­rently tells us we re­quire 33 millil­itres of fluid per kilo­gram of body weight, so a per­son weigh­ing 70kg would need around 2.3 litres per day.

How­ever, this is re­ally still just an es­ti­mate, as how much fluid we re­quire will de­pend on the cli­mate and how ac­tive we are. Caf­feinated and al­co­holic bev­er­ages are di­uret­ics and drag wa­ter out of the body so you may need more wa­ter if you con­sume


Email your ques­tions for Dr Libby to ask.dr­libby@fair­fax­me­ Please note, only a se­lec­tion of ques­tions can be an­swered.

these on a reg­u­lar ba­sis.

As a gen­eral guide, most adults will need be­tween two and three litres of fluid a day. Eight glasses of wa­ter would put you at the lower end of this range.How­ever, we also ob­tain some fluid from non-starchy veg­eta­bles, soups and other drinks such as herbal teas.

If you would like to have a num­ber of glasses to aim for each day, eight glasses is prob­a­bly a good start­ing point, but I en­cour­age you to tune in to your body’s thirst sig­nals and be guided by this. Af­ter all, thirst is the body’s way of sig­nalling to you that it re­quires wa­ter.

Q: I’ve been told thatmy to­tal body wa­ter ranges be­tween 56-58 per cent. What should my to­tal body wa­ter be and how do I know if I’m re­tain­ing too

Hi Jen­nifer. Per­cent­age body wa­ter can vary de­pend­ing on a num­ber of fac­tors, such as age, gen­der and level of mus­cle mass. It can be any­where from 45 to 70 per cent of body weight but for adults, it is typ­i­cally be­tween 50 to 60 per cent.

With­out know­ing how your to­tal body wa­ter was mea­sured it’s dif­fi­cult to com­ment on this, but I en­cour­age you to re­flect on


the level of ac­cu­racy that can be ob­tained when mea­sur­ing your body com­po­si­tion out­side a lab­o­ra­tory set­ting. Rather than look­ing to a mea­sure­ment, I can­not en­cour­age you enough to sim­ply bring aware­ness to your body and any signs or symp­toms that may in­di­cate de­hy­dra­tion or fluid re­ten­tion.

A mea­sure­ment of to­tal body wa­ter doesn’t tell us the full pic­ture, as it doesn’t in­di­cate where the fluid ac­tu­ally is in the body (how much is in­side our cells, be­tween and around the cells and in the blood and lymph). Fluid ac­cu­mu­lat­ing out­side the cells is what can lead to feel­ings of fluid re­ten­tion, such as feel­ing ‘‘puffy’’ or feel­ing your clothes dig in as the day pro­gresses. Swollen an­kles can also be a sign of fluid re­ten­tion.

Many women ex­pe­ri­ence fluid re­ten­tion at cer­tain stages of their men­strual cy­cle, due to an im­bal­ance in oe­stro­gen and pro­ges­terone. How­ever, fluid re­ten­tion can also be driven by sub-op­ti­mal liver func­tion, min­eral de­fi­cien­cies or im­bal­ances, and/or poor lym­phatic flow.

Dr Libby is a nu­tri­tional bio­chemist, best-sell­ing au­thor and speaker. The ad­vice con­tained in this col­umn is not in­tended to be a sub­sti­tute for di­rect, per­son­alised ad­vice from a health pro­fes­sional. Join Dr Libby in Christchurch for one week­end to change your life: Novem­ber 25 and 26. More info at dr­


Thirst is the body’s way of sig­nalling to you that it re­quires wa­ter.

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