Would eating heavy atoms lengthen our lives? (Life enhacing)

A sip a day of heavy water could reduce damage to ageing tissue that is caused by oxygen free radicals (Image: John Sann/Stone/Getty)

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In a back room of New Scientist's offices in London, I sit down at a table with the Russian biochemist Mikhail Shchepinov. In front of us are two teaspoons and a brown glass bottle. Shchepinov opens the bottle, pours out a teaspoon of clear liquid and drinks it down. He smiles. It's my turn.

I put a spoonful of the liquid in my mouth and swallow. It tastes slightly sweet, which is a surprise. I was expecting it to be exactly like water since that, in fact, is what it is - heavy water to be precise, chemical formula D₂O. The D stands for deuterium, an isotope of hydrogen with an atomic mass of 2 instead of 1. Deuterium is what puts the heavy in heavy water. An ice cube made out of it would sink in normal water.

My sip of heavy water is the culmination of a long journey trying to get to the bottom of a remarkable claim that Shchepinov first made around 18 months ago. He believes he has discovered an elixir of youth, a way to drink (or more likely eat) your way to a longer life. You may think that makes Shchepinov sound like a snake-oil salesman. I thought so too, but the more I found out about his idea, the more it began to make sense.

The story began two years ago, while Shchepinov was working at a biotechology company in Oxford, UK, and using his spare time to read up on the latest ideas about what causes us to age.

The most widely accepted idea is the free-radical theory. This holds that our slide into decrepitude is the result of irreversible damage to the biomolecules that make up our bodies. The main agents of this destruction are oxygen free radicals, aggressive chemical compounds that are an unavoidable by-product of metabolism.

The reason oxygen radicals are so dangerous is that they have a voracious appetite for electrons, which they rip out of anything they can lay their hands on - water, proteins, fats, DNA - leaving a trail of destruction in their wake. This damage gradually builds up over a lifetime and eventually leads the body's basic biochemical processes to fail.

One of the worst types of damage is something called protein carbonylation, in which an oxygen radical attacks vulnerable carbon-hydrogen bonds in a protein (see diagram). This has been linked to many of the worst diseases of old age, including Parkinson's, Alzheimer's, cancer, chronic renal failure and diabetes (The EMBO Journal, vol 24, p 1311). Other important targets of free-radical attack are DNA and the fatty acids in cell membranes.

The human body produces legions of antioxidants, including vitamins and enzymes, that quench free radicals before they can do any harm. But over a lifetime these defence systems eventually fall victim to oxidative attack too, leading to an inevitable decline.

Many anti-ageing medications are based on supplementing the body's own defences with antioxidant compounds such as vitamin C and beta-carotene, though there is scant evidence that this does any good (New Scientist, 5 August 2006, p 40).

Shchepinov realised there was another way to defeat free radicals. While he was familiarising himself with research on ageing, his day job involved a well-established - if slightly obscure - bit of chemistry called the isotope effect. On Christmas day 2006, it dawned on him that putting the two together could lead to a new way of postponing the ravages of time.

The basic concept of the isotope effect is that the presence of heavy isotopes in a molecule can slow down its chemical reactions. This is because heavy isotopes form stronger covalent bonds than their lighter counterparts; for example, a carbon-deuterium bond is stronger than a carbon-hydrogen bond. While the effect applies to all heavy isotopes, including carbon-13, nitrogen-15 and oxygen-18 (see chart), it is most marked with deuterium as it is proportionally so much heavier than hydrogen. Deuterated bonds can be up to 80 times stronger than those containing hydrogen.

All of this is conventional chemistry: the isotope effect was discovered back in the 1930s and its mechanism explained in the 1940s. The effect has a long pedigree as a research tool in basic chemistry for probing the mechanisms of complex reactions.

Shchepinov, however, is the first researcher to link the effect with ageing. It dawned on him that if ageing is caused by free radicals trashing covalent bonds, and if those same bonds can be strengthened using the isotope effect, why not use it to make vulnerable biomolecules more resistant to attack? All you would have to do is judiciously place deuterium or carbon-13 in the bonds that are most vulnerable to attack, and chemistry should take care of the rest.

In early 2007 Shchepinov wrote up his idea and submitted it to a journal called Rejuvenation Research. Unbeknown to him, the journal's editor is controversial gerontologist Aubrey de Grey of the Methuselah Foundation in Lorton, Virginia, who is well known for supporting ideas other gerontologists consider outlandish. De Grey sent the paper out for review and eventually accepted it (Rejuvenation Research, vol 10, p 47).