your body work, grow and repair itself. The kind of food you eat can
affect the efficiency of these processes. Body function and the food
that sustains it is infinitely complex. Food is in fact one of the
most complicated sets of chemicals imaginable.
to know which nutrients are in which foods can help you to understand
something of this complex relationship between your food and your
composed of many different chemical substances - 'macronutrients'
(major nutritional components that are present in relatively large
amounts, such as protein), 'micronutrients' (major nutritional components
that are present in relatively small amounts, such as vitamins), water,
and roughage (dietary fibre). Many other components can also be present
in food (see Figure 1).
contain colours (natural and synthetic), flavours, pharmacologically
active substances (such as caffeine, steroids, and salicylates, which
chemically affect the body), natural toxicants (naturally occurring
poisons, such as cyanide), additives, and various contaminants (substances resulting from a contaminated environment, such as pesticides). Even
characteristic flavours such as those of oranges and passionfruit
can depend on the presence of a dozen or more chemicals.
nature of food is changed by storage, preservation and, especially,
by cooking. Food chemicals can also interact amongst themselves within
the body. For example, the availability to the body of iron from plant
sources depends on the amount of vitamin C present in the food eaten.
The way in which carbohydrate is absorbed from the bowel depends to
some extent on the presence of dietary fibre, even though the fibre
itself is not absorbed.
form of food
also more than just the chemicals it contains. Its physical characteristics
are important. The size of food particles can affect the extent to
which nutrients are digested and made ready for absorption by the
body. For example, eating an intact apple has nutritional value different
from drinking all the same chemicals in an apple purée. Ground rice
is more rapidly digested than unground rice. Nutrients can be more
easily absorbed from peanut butter (paste) than from peanuts eaten
and alkalinity of food are physical properties often thought to be
important. In fact, they are only important insofar as they might
alter the rate of emptying of the stomach, digestion in the small
bowel and the acidity or alkalinity of the urine. Our bodies can cope
with a wide range in food acidity and alkalinity without much problem.
Acid foods are generally sour while alkaline foods often have a slightly
soapy taste. The use of sodium bicarbonate (baking soda) can make
foods alkaline. It can also cause loss of vitamin C and contribute
to our intake of sodium.