68 BBC SCIENCE FOCUS MAGAZINE COLLECTION
DIETSt John’s Wor t is
a good natural
antidepressantThe nectar from the
Manuka tree in New
Zealand can be
made into honeyL- c a r ni t ine is t houg h t
to help repair muscle
damage post exerciseI
IS FOR
IRON
Iron deficiency is the most common
nutritional deficiency in the world, but
i n t he U K it’s ra re because f lou r, cerea ls
and some other foods are fortified with
iron. A 2012 study found that adult
women may be mildly iron deficient
even if they are not medically anaemic,
and taking iron supplements reduced
how tired they felt. The effect was
very small, however, and too much
iron is certainly harmful. Accidental
overdoses of iron supplements are
a leading cause of child poisoning
deaths in the US, so keep your tablets
locked safely away.RATING
M
IS FOR
MANUKA HONEY
Honey is a broad spectrum antibiotic,
but we still don’t fully understand
how it kills bacteria. Manuka honey
is made from the nectar of the New
Zealand Manuka tree and has the
strongest antibacterial effect. But lab
studies have so far failed to translate
t h is i nto sig n if ica nt benef it s i n hu ma n
patients. Manuka honey dressings
might shorten healing times slightly
for moderate burns, but the evidence
for other wounds is quite weak.RATING
K
IS FOR
KRILL OIL
Red krill oil comes from the shrimp-
like crustaceans that whales eat. It
contains eicosapentaenoic acid and
docosahexaenoic acid, commonly
known as omega-3 fatty acids – well
known for reducing the risk of heart
disease. It’s claimed that krill oil is
more effective than fish oil, but the
evidence is much less conclusive. It may
be that the slightly different chemical
composition of the omega-3 in krill
oil means it’s more easily absorbed.
But, even if that’s true, it would only
mean you need a smaller dose to
achieve the same effect.RATING
L
IS FOR
L-CARNITINE
Carnitine is an amino acid used by
virtually all your cells in the release
of energy. It’s produced in the body,
so normally there’s no need to take
it as a supplement. There is some
evidence that taking L-carnitine (which
is the biologically active form) can
improve sperm function and it may also
help repair muscle damage following
exercise. Research doesn’t support
other claims that it boosts athletic
performance or increases muscle mass.RATING
J
IS FOR
ST JOHN’S WORT
Large-scale reviews of studies involving
St John’s Wort have concluded that it
is more ef fec t ive at t reat i ng depression
than standard antidepressants. The
resu lt s of i nd iv idua l t r ia ls va r y w ild ly,
though, in part because the amount of
t he act ive i ng red ient i n St Joh n’s Wor t
tablets can differ from the amount
claimed on the bottle by a factor of
two or more.RATING