From Brian Parker
The suggestion that drinking heavy water might counter ageing (29 November 2008, p 36) reminds me of the late 1950s when, as a fresh graduate, I joined a team of nuclear physicists at a UK research establishment that I had better not name.
My older colleagues had both formidable intellect and a mischievous sense of humour. One of them was known on at least one occasion to have brewed and drunk a cup of tea using heavy water.
This did him no harm at the time, and he did live to an age substantially greater than that expected by those who considered his daily consumption of beer and cigarettes to be life-shortening.
From John Morton
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It cannot be right, in principle, that “deuterium atoms bound to carbon in amino acids are ‘non-exchangeable’ and so don’t leak into body water”. All the amino acids in proteins are periodically released by the continual breakdown and re-synthesis of proteins.
The amino acids will enter the cellular pool: some will be deaminated, releasing ammonia, and the rest of the molecule (the “carbon skeleton”) will be used to provide energy and will be ultimately converted to carbon dioxide and water. So the deuterium will find its way into the cell water.
But how much? An adult human with a daily dietary protein intake of 70 grams degrades and synthesises about 250 g of protein every day – more than 2 per cent of their total body protein.
When dietary intake is low, the recycling efficiency is about 90 per cent. So if each amino acid molecule carried one deuterium atom, 25 g of amino acids lost per day would produce about 4 g of deuterated water: just 0.01 per cent of your total body water. So the chance of getting up to the toxic 20 to 35 per cent content is minimal, given that the half life for body water is just over a week.
What this calculation does show is that even if you restricted dietary protein intake to encourage recycling, and if you could deuterate all the protein in your body, it would all probably be gone within a year.
Pontypridd, Glamorgan, UK
Dartmouth, Devon, UK
