Giraffe
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They measured urinary sodium excretion. I wonder if this accurately reflects the sodium intake at all. A lot of sodium is lost in sweat. Most hypothyroid folk does not sweat a lot, and their cortisol and lipid levels are high. Also hypothyroid people lose more sodium in their urine, so they need to ingest more in order to maintain a certain level. -- To blame increased urinary cortisol, insulin resistane etc. on a 'high sodium diet' is short-sighted (or criminal).High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome - Baudrand - 2013 - Clinical Endocrinology - Wiley Online Library
"High sodium diet was associated with increased urinary cortisol and its metabolites. Also, HS diet was associated with HT, insulin resistance, dyslipidaemia and hypoadiponectinaemia, even when adjusting by confounding variables"
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Below a few figures to get an impression of the magnitude:
The study linked by @Barry Obummer considered an estimated salt intake of maximum 9 grams (= 3,510 mg sodium) as adequate. Everything above is called 'high sodium intake'.
Perspiration - Wikipedia
The solute loss can be as much as 350 mmol/day (or 90 mmol/day acclimatised) of sodium under the most extreme conditions. During average intensity exercise, sweat losses can average up to 2 litres of water/hour. In a cool climate and in the absence of exercise, sodium loss can be very low (less than 5 mmols/day). Sodium concentration in sweat is 30-65 mmol/l, depending on the degree of acclimatisation.
Expressed in milligrams of sodium this is:
- 8,050 mg/day (extreme conditions) or 2,070 mg/day (acclimatised)
- 115 mg/day (very low loss in cold climate, absence of exercise)
- 690 - 1490 mg/l (sweat).
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Ray Peat said:A person should take in 2 quarts more fluids than they lose per day in urine. That two quarts would be an average evaporation if your thyroid is good. But many people evaporate less than a quart a day [...]
Ray Peat said:[...] in the average level of activity and the average relative humidity, a person will evaporate a liter per thousand of calories burned so if you only have a missing liter of fluid a day, you know you are only burning 1000 calories.
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Renal sodium and water handling in hypothyroid patients: the role of renal insufficiency.
Hypothyroidism has been associated with abnormalities in renal sodium and water handling. There is a defect in maximal free water clearance during water loading and an impaired ability to conserve sodium during dietary salt restriction. These effects are not corrected by the administration of corticosteroids or mineralocorticoids, but they do improve after thyroid hormone replacement.
The fractional excretion of sodium was twice as high in the hypothyroid patients than in the normal subjects, but it was similar to that in the CRF patients.
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I found it mentioned quite often that dietary recalls of sodium intake and urinary excretion do not correlate well.
Difference between 24-h diet recall and urine excretion for assessing population sodium and potassium intake in adults aged 18–39 y
You could also put it this way: In men with normal BMI you grossly underestimate sodium intake when you base your estimate on 24-hour urinary sodium excretion. The difference between dietary intake and 'adjusted urinary excretion' of sodium was ~ 1,150mg in normal-weight men, but only ~110 mg in women. Go figure!We found the difference between sodium and potassium estimates to be greater in men than in women and in those with a normal BMI compared with overweight or obese participants.
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Water: swelling, tension, pain, fatigue, aging
Ray Pat said:When extra water consumption is combined with a low salt diet--as physicians have so often recommended--a healthy person can adapt easily, but for a hypothyroid person it can have disastrous effects.