term adherents to a strict uncooked vegan diet
called the ‘living food diet’ (LFD). Most food
items in this diet are fermented or sprouted.
Serum B 12 concentrations and the dietary intakes
of 21 long-term adherents of the LFD were com-
pared with those of 21 omnivorous controls. In a
longitudinal study, the LFD diet resulted in a
decrease in serum vitamin B 12 in six of nine sub-
jects. The cross-sectional study revealed signifi-
cantly lower serum vitamin B 12 in the LFD
adherents than in their matched omnivorous
controls. Those following the LFD who con-
sumed nori or chinerilla seaweeds had some-
what better B 12 status than those who did not, but
B 12 levels fell over time in all but one subject.
While lower levels of vitamin B 12 have been
found in strict vegans, few cases of clinical defi-
ciency have been found. Helman and Darnton-
Hill (1987) found the mean serum vitamin B 12
levels of vegetarians to be significantly lower
(350 pg · ml–1) than those of omnivores (490 pg ·
ml–1), while 16% of the vegetarians had values
less than 200 pg · ml–1. Vitamin B 12 deficiency is
rare among lacto-ovovegetarians because milk
and eggs contain sufficient quantities of this
nutrient. Vegans should be encouraged to use
soybean milk fortified with vitamin B 12 or a
vitamin B 12 supplement. Analogues of the
vitamin found in algae, spirulina, nori or fer-
mented soy products do not have vitamin activ-
ity for humans.
Individuals with low serum B 12 may manifest
paraesthesia (numbness and tingling in the
hands and legs), weakness, fatigue, loss of
vibration and position sense, and a range of
psychiatric disorders including disorientation,
depression and memory loss. The use of alcohol,
tobacco and drugs such as antacids, neomycin,
colchicine and aminosalicylic acid may con-
tribute to the problem by causing B 12 malabsorp-
tion in both omnivores and vegetarians.
Iron availability in vegetarian diets
While both vegetarian and non-vegetarians may
have difficulty in meeting the dietary require-
ments for iron, athletes who eat red meat are at
less risk of iron deficiency anaemia. In absolute
amounts, red meat contains only an average
amount of iron, but the bioavailabilty of iron
from red meat is superior to that derived from
plant sources. There are two forms of iron in
the diet: haem iron and non-haem iron. Haem
iron found in meats, fish and poultry is better
absorbed than non-haem iron, which is found in
grains, vegetables and fruits. The fractional
absorption of haem and non-haem iron varies
between 3% and 35%, depending on the presence
of dietary enhancing factors such as ascorbic
acid, consumption of sources of haem iron and
on the body stores of iron. Table 33.2 lists the
ranges of intestinal absorption of iron from haem
and non-haem food sources which is dependent
upon body stores of iron.
Iron is classified as an essential nutrient and is
required for the formation of haemoglobin and
myoglobin, as well as the cytochromes, which
are components of the electron transport chain in
the mitochondria. Iron is also a cofactor for a
number of enzymatic reactions, including those
involved in the synthesis of collagen and of
various neurotransmitters. In addition, iron is
needed for proper immune function and plays a
role in the drug detoxification pathways
(Wardlaw & Insel 1995).
Since iron plays a critical role in oxidative
energy metabolism, it is essential for athletes to
have adequate iron stores. There are some differ-
ences of opinion about the prevalence of iron
deficiency among athletes. A number of studies
have used serum ferritin as a measure of iron
deficiency anaemia, while other studies have
used haemoglobin and haematocrit as determi-
nants of iron deficiency anaemia. The numberthe vegetarian athlete 447
Table 33.2Absorption rate (as % of intake) of haem
and non-haem iron in relation to body stores of iron.Haem Non-haem
(%) (%)Low stores of iron 35 20
Normal stores of iron 15 2–3