January is actually the worst time of year to go on a detox or a juice feast, in a northern European climate at least. Generally, I believe juice feasts are a brilliant idea, and a few naturopathic techniques like enemas and liver flushes are always helpful. But, like eating at midnight, pushing your body through an extreme detox regime anytime between November-February is best only done when you feel you really have to. And you're not so likely to get the results you're looking for, as your body doesn't want to let go. Winter is the time for holding on - we are being deprived of light and heat - our bodies need to store. Much better to work with the body and wait until after the March equinox when everything starts to come to life again. If you come out of Christmas wanting a cleanse, now's the time to do the research and stock up on goods and equipment, so you're fully prepared when the Spring energies start to rise.
If you want to feel really good on raw over the winter, give your body what it wants. Lots of healthy fats for insulation and calories, lots of spices to heat you from within, and lots of warmed foods and drinks.
Flaxseeds are good, as flax holds light - flaxseed oils and flaxseed crackers.
Medicinal teas and warm milks to nurture and strengthen the organs.
Warm, spicy soups and sauces, especially ones using root vegetables. Heat them gently using a porringer or double saucepan. Use plenty of garlic, chilli, red onion, and ginger. Technically, food is raw until it reaches 42 deg C, which is relatively warm - not hot, not cold, just warm.