Letters from the SCD support group:
Date: Sat, 14 Nov 1998 08:49:23 -0600
Subject: Iodine Starch Test
You can test for starch in foods using iodine. For more information,
see the following web site:
read the following info, taken from that web site.
Often when I thought I had eliminated every possible source from my
diet, the dreaded symptoms would return and I would be desperate again.
There seemed to be no answer to identifying starch in some food, except
to eat it and suffer. And then my friendly local chemist reminded me of
the easy test for starch: simply drop iodine onto the suspect food. If
it contains starch, the colour of the iodine will darken from orange to
shades ranging from inky blue to black. Needless to say, I tested all
sorts of food immediately. Flour, bread, cakes, potatoes and rice go a
very dark blue-black colour - almost like carbon. Raw sliced vegetables
show signs of starch by going greyish around the edges - where the cell
wall has been damaged by cutting, I suppose - but it's not enough to
cause problems. On meat, cheese, butter, eggs and animal products, the
iodine colour remains unchanged (it may tend to go a little darker as it
dries). The same is true of most fruits - except bananans, which in
varying degrees, depending on how ripe they are, turn dark when tested,
proving they're full of starch.
Unfortunately, I sometimes still discover new sources of starch in
foods. This is where the iodine starch test is a great help. If the
starch content in the food is significant enough to cause IBS problems,
it will show up. There are other methods of testing for starch, but the
iodine test seems to be very reliable as far as the digestion of starch
is concerned, and it's easy and quick.
Buy a small bottle of iodine (which costs in the U.K. about 40 to 50
pence) from your local chemist and an eyedropper. Drop a small amount of
iodine onto the suspect food, then wait a few minutes to see if the
iodine changes from its normal orange colour into shades ranging from
reddish-brown to dark inky-blue or even black. Some foods take longer
than others to show the starch content. On nutmeg, for instance, it
takes about 30 minutes before the iodine drop turns almost black.
It's surprising to discover that some foods which most people believe
to be basically protein - such as certian varieties of nuts - contain
high quantities of starch. Ground almonds had never caused me problems,
so I wasn't surprised when the iodine test showed they contained no
starch, but walnuts are a different matter - I discovered that the skin
contains starch, while the meat of the nut does not. Cashew nuts are
very rich in starch as are chestnuts and sunflower seeds. Peanuts also
contain starch. Sadly, some of the foods we think of as 'health foods'
have high starch content.
Even some cheeses, such as Brie and Camembert sometimes have starch in
their outer white crust, although of course, the main cheese part is
protein and fat. This is not always the case and may perhaps be because
potato flour or other starch has been used in the final processing. It's
always wise to test before eating. If you're unsure about any food, the
iodine test will help you to identify quickly and easily whether it's
safe for you to eat.
Recently I have made one further discovery: ordinary sugar, i.e. table
sugar, caster sugar, brown sugar or raw sugar all of which is processed
from cane sugar or sugar beet, can cause problems if I eat too much.
This trouble is compounded if the sugar has been cooked too long or at
too high a temperature - the scientific term is 'caramelisation'.
Caramelisation produces digestive resistant starch or RS.
Sugar can be cooked at low temperatures (as in meringues) or dissolved
in cold solutions, as in cold puddings such as ice cream. It's safer
eaten in this way, but you can also subsitute fruit sugar in almost
exactly the same way for most cooking or sweetening. The previous
chapter in the book 'IBS Starch-Free Diet' explains why.