Celebs and gym junkies have been at it for years - but is it worth it? And what's the deal with all this hemp and wheatgrass? Still a bit confused about blending and blitzing? Then here's our expert guide :: Are smoothies meant to be a meal replacement, or can you have them alongside meals?

"Either - it depends what you're trying to achieve and what you put in them," says Becki Douglas, chief nutritionist at Champneys (champneys.com). "They can make a great snack between meals, deterring you from the less healthy lure of the biscuit tin. Alternatively you could create a nutritionally-balanced green smoothie by adding protein and essential fats, like some natural yoghurt and flaxseed oil, and that could be a great breakfast."

:: It seems everybody's adding 'superfood' and protein powders to their smoothies these days - what's that about?

"There are lots of powders on the market - it can be a bit of a minefield," agrees Primrose Matheson, founder of Primrose's Kitchen (primroseskitchen.com). "Generally, green powders like barley grass, spirulina, wheatgrass and chlorella are about nutrient support and detoxification. These can be added to smoothies, although on their own, the last three can be rather challenging on the palette! It helps to add more fruit to smoothies that you use green powders in, or add baobab, acai or lucuma powder, which are vitamin-rich dried fruit powders.

"Protein powders are popular with athletes; the main ones are whey, hemp, pea and soya. Protein's important for sustaining our nervous system, building muscle and maintaining blood sugar balance, so it's great to add a teaspoon of any of these.”

:: Why is everybody obsessed with 'green juice'?

"A green juice is the industry name for a juice made without using any fruit - it is purely vegetable based and tends to be more 'savoury'," explains West. "These are normally favoured by people trying to cut down their sugar intake, or tackling health conditions. The calorie content tends to be lower, because vegetables have less calories than fruit. Other juices normally have a fruit base, something like apple. This gives it a sweeter taste."

:: Can you add anything to a juice or smoothie?

"You can juice almost any fruits and vegetables," says Plant-based nutritionist Carol West (obsidianwellness.com; juiceprogrammes.com), "but there are some that need a bit of preparation. Oranges, grapefruit and limes we always suggest you peel first; oils in the skin can sometimes cause reactions as they're quite strong and hard to digest.

"The harder the fruit or vegetable the more juice you'll get from it, as it's at its peak of ripeness. Things you cannot juice are things you wouldn't normally get any liquid from, like mushroom or aubergine. You can juice chilli and garlic, but be aware these tend to intensify when juiced, so only put a small amount in to start with. Ginger's a great addition to give it a little bit of a kick without the intense heat of chilli."

READY, STEADY, BLITZ!

Here are three recipes to get you started.

:: Kale, Banana And Kiwi Smoothie (courtesy of Primrose's Kitchen) 1 ripe banana 2 kiwis, peeled and sliced in half 1 cup kale, washed and tightly packed 1/4 cup almond milk 1tsp honey (can add 1tsp of PK Cleanse powder too if you like!) 1/2 cup ice :: Basic Recipe For 'Creamy' Smoothie (courtesy of Champneys) 1 cup milk of choice (cows'/goats'/soya/almond/coconut etc) Handful of mixed berries 1/2 banana 1tbsp ground nuts/seeds 1tbsp of silken tofu, or 1/2 an avocado, or 1 tbsp natural live yoghurt Add any other fruit of choice (mango, kiwi, pineapple etc) :: Basic Recipe For Juice Based Veg Smoothie (courtesy of Champneys) Handful of Dark green leafy vegetables such as spinach, kale or broccoli 1/2 stick of celery 1 cup Apple juice/water (50/5O) Fresh/frozen fruit such as mango, berries or pineapple Green powder (spirulina/wheatgrass - optional) 1tbsp ground nuts/seeds, or 1tbsp flaxseed oil Make 2016 - New Year – New You!

Juicing may be the new black for 2016, but with over 25 years of organic fruit and veg growing experience, farmer-owned vegbox scheme Riverford is no stranger to the benefits of getting your 5-a-day.

Riverford’s farmers select their fruit and veg for flavour, therefore always bringing you the freshest produce right to your door.

We’ve created some wonderfully tasty juicing recipes to accompany our produce and with our free home delivery service what could be better? See riverford.co.uk/shop/fruit-veg/juicing for details.

(You will need a juicer to make these): Green juice Full of green goodness. It tastes fresh - add an apple if you prefer it a little sweeter.

150g curly kale ½ cucumber ½ head of broccoli (stalk & florets) squeeze of lemon juice, to taste Juice the kale, cucumber and broccoli, then squeeze in a little lemon juice to taste.

parsnip, pear & apple juice Sounds weird, but parsnips are sweet, so they work well in this juice.

2 medium-large parsnips 2 pears 1 apple carrot, apple & ginger Our favourite juice, by a carrot top length!

3 large carrots (350-400g), scrubbed very clean 1 apple, whole, stalk removed 10g piece fresh ginger, unpeeled