Assuming a non-excessive protein intake (see next section), a carbohydrate intake of 30
grams per day or less is advised during the first weeks of a SKD to allow for adaptations to take
place. After adaptation to the diet, it appears that individuals can tolerate relatively greater
carbohydrate intakes without disrupting ketosis. Although not completely accurate, Ketostix
(tm) can provide a rough measure of how many carbohydrates can be consumed while still
maintaining ketosis. As long as trace ketosis is maintained, carbohydrates can be gradually
added to the diet. See chapter 15 for details on using Ketostix (tm).
An extremely low carbohydrate intake is relatively more important for those individuals
following the CKD, who only have five or six days to establish ketosis. In this case, carbohydrate
intake should be minimized as much as possible (meaning that protein intake must be adequate)
during the first few days of each cycle so that ketosis will occur as quickly as possible.
Individuals on a TKD follow a separate set of rules for daily carbohydrate intake which is
discussed in chapter 11.
Types of carbohydrate consumed on a SKD
Carbohydrates are generally differentiated into complex and simple carbohydrates. This is
a crude measure of the quality of carbohydrates. A more accurate measure of carbohydrate
quality is the Glycemic Index (GI) which is a measure of how much insulin a given carbohydrate
food will cause to be released (see appendix 1 for a partial GI).
The GI of a food is defined relative to white bread, which is arbitrarily given a value of 100.
A food with a GI of 60 will cause glucose levels to rise in the blood 60% as quickly as white bread,
causing the release of 60% as much insulin. Similarly, a food with a GI of 130 will raise blood
glucose 30% more quickly than white bread, causing the body to release 30% more insulin. In
general, starches and complex carbohydrates tend to have lower GI values than simple sugars
like glucose and sucrose.
Since our wish is to minimize insulin release during a standard ketogenic diet, any dietary
carbohydrates which are consumed on a SKD should come from low GI sources. This means that
the majority of carbohydrates consumed will come from vegetable sources, as most starches
have a GI that is too high.
One thing to note is that the GI of carbohydrates is affected by the ingestion of protein,
fats and fiber at the same meal. The ingestion of other nutrients slows digestion of
carbohydrates, lowering the effective GI (less insulin response) than eating that same
carbohydrate by itself.
Timing of carbohydrate consumption on a SKD
Although there is little data on ideal timing of carbohydrates on a SKD, we can create a
few guidelines. While the amount of insulin released from the ingestion of dietary carbohydrates
is related to their quality (GI), it is also related somewhat to the quantity of carbs ingested.
Ingestion of 30 grams of broccoli will cause a greater insulin release than the ingestion of 10
grams of broccoli although the GI is identical.