Interview with Russell Howard

Chatting ageing biology on The Russell Howard Hour

I was lucky enough to have a chat with the amazing Russell Howard for his topical comedy show last week, and the full interview is now online for anyone to watch!

I love spreading the word about ageing biology to new audiences—and, this being a late-night comedy show, it’s quite an unusual interview which takes a rather unexpected turn in the middle! Probably not one to watch with the kids…but I had a lot of fun.

You can read more about this fascinating topic in my book, Ageless: The new science of getting older without getting old.

Spermidine calculations

If you’re wondering about how I got to the, er, numbers I quote in the interview, here’s the calculation!

aClinically relevant quantity of spermidine79.8µmol/day[1]
bMolecular weight of spermidine145.25g/mol[2]
cClinically relevant amount of spermidine in g11.6mg/daya × b
dSpermidine in semen (min)15mg/l[2]
eSpermidine in semen (max)50mg/l[2]
fAverage ejaculation volume3.2ml[3]
gSpermidine per ejaculation (min)0.048mgf × d
hSpermidine per ejaculation (max)0.16mgf × e
Which implies…
iEjaculations/day (max)241a ÷ g
jEjaculations/day (min)94a ÷ h
kAverage volume of semen required536mla ÷ ((i + j) ÷ 2)


  1. Higher spermidine intake is linked to lower mortality: a prospective population-based study (2018)
  2. Spermidine article on Wikipedia
  3. The Semen of Fertile Men: Statistical Analysis of 1300 Men (1975)

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