The good news is there are things you can do to help alleviate those symptoms. Firstly, you should see your doctor before going on the diet to get the thumbs up. Then, if you're experiencing such symptoms and they're not the result of something else (like the actual flu), start by drinking plenty of fluid, while avoiding activities that can dehydrate you such as an intense workout. Dr Evelyn Lewin also suggest increasing your salt intake by adding half a teaspoon to two teaspoons of salt into your food. if you're able to persist through these symptoms, you’ll quickly transition through this stage and come out the other side bursting with energy.
The first modern study of fasting as a treatment for epilepsy was in France in 1911. Twenty epilepsy patients of all ages were "detoxified" by consuming a low-calorie vegetarian diet, combined with periods of fasting and purging. Two benefited enormously, but most failed to maintain compliance with the imposed restrictions. The diet improved the patients' mental capabilities, in contrast to their medication, potassium bromide, which dulled the mind.