An alternative or supplement to juicing that is superior in my opinion is using the Vitamix machine to break up the fiber and include that in your consumption.
Juicing throws away all fiber. Which means that any sugar that's in the product you're juicing is not buffered by the fiber.
Since cancer is a pancreatic disease and the pancreas is also responsible for producing insulin and managing blood sugar I don't recommend stressing it with regular carrot and apple juice.
One of the main reasons to juice is to get enzymes. Since enzymes are very fragile after they have been extracted from the food according Gerson Therapy all juices should be fresh and consumed immediately after removal from the machine. Most people are unable to comply with this rule.
Green juices are fine as they are not going to produce an insulin response.
In the Gerson clinic, salads and baked potatoes are given three time a day. Apples, bananas, grapes and a host of other fruits are encouraged throughout the day. Juices thirteen times a day alternating vegetable and fruit (liver and carrot two times a day when the liver was readily available) these were fresh made and consumed in 8 ounce portions, Insulin response was not a problem due to the adjacent consumption of foods.
What I regularly hear from patients is there putting together a 32 ounce container of juice and taking with them. By the time they finish it many of the enzymes have diminished in their effectiveness.