What is a juice diet?

Whether you call it a juice fast, cleanse or detox, these diets claim to promote rapid weight loss. But are they safe and effective? We take a closer look...

Selection of fruits and vegetables with a variety of juices in glasses

Juice diets have become increasingly popular as supposed ‘quick fix’ regimes, promising dramatic weight loss in a relatively short timeframe, as well as sometimes claiming other health benefits such as ‘detoxing’ the liver, clearer skin and improved mood. But can they really improve your health, is the weight loss sustainable, and are there dangers to following such extreme diets?

How does it work?

Whether they're labelled as juice fasts, juice cleanses or juice detoxes, all juice diets are based around consuming a variety of juiced fruits and vegetables. Many juice diets involve abstaining from eating other foods and only drinking juice, while some involve eating particular solid foods as well. The calorie intake is usually very restricted on juice diets.

The most extreme juice diets are usually limited to a short period of time – often between three days and one week. Juice diets which permit some solid foods and more calories are sometimes followed for longer periods of time. 

Juice-only diets are usually vegetarian and can also be vegan, although some plans allow you to add honey or yogurt to the juices.

We asked nutritionist Kerry Torrens for her view...

Are juice diets safe?

There’s little scientific evidence to support juice diets as a sensible approach to better health. Furthermore, if you follow this sort of diet for longer than a couple of days it is unlikely you will meet all your nutritional needs.

That said, fruit and vegetables are an important part of a balanced diet and we should all aim for a minimum of five portions a day. A varied selection of fruit and veg provides vitamins, minerals, antioxidants and fibre. However, juices (unsweetened, 100% juice) only count as one of your five-a-day regardless of how much you drink, this is because juices don’t contain the fibre found in the whole fruit and vegetables.

Which nutrients may be missing from juice diets?

The very action of juicing eliminates certain nutrients — dietary fibre is an obvious one as well as other beneficial nutrients which are found in or just under the skin and in the seeds etc. An example is the white pith of citrus fruits like oranges, which is a useful source of protective flavonoids

The mineral iron, important for supporting energy levels, and fats, including the essential omega-3 variety, are key nutrients which are likely to be missing from a juice-only diet. Fats are essential for hormonal production and regulation, as well as proper brain function. Another important macronutrient which is likely to be lacking is protein. Protein is needed to maintain muscle and to support growth and repair as well as for hormone production.

Woman standing on bathroom scales to read weight

Are juice diets effective for weight loss and is it sustainable?

Most people are likely to lose some weight following a juice diet because it involves cutting out sources of fat and protein and significantly cutting calorie intake. However, the weight loss is unlikely to be sustainable in the longer term as you return to your regular eating habits. You should be aware that the amount of weight you lose will be dependent on your own individual circumstances, including how much weight you have to lose at the outset.

However, there is currently some evidence to suggest that a short-term three-day juice diet may have benefits for gut health and in turn, benefit longer term weight maintenance. This is because the balance of bacteria in the gut is now thought to influence weight.

If you are considering a short-term juice diet, make the juices yourself with fresh, organic produce focusing on vegetables and flavouring with a small amount of fruit. Juice only as much as you need, when you need it to optimise your nutrient intake and add back some of the extracted pulp to ensure the inclusion of fibre and valuable phytonutrients.

What about the sugar in juice?
Juices made mainly or entirely from fruit are likely to be high in sugar. Juicing releases the sugars in fruit – making them ‘free’ sugars, the type we are advised to cut back on – and removes the fibre, meaning that sugar is more quickly absorbed into the blood stream than if you were to eat a whole piece of fruit. The combination of a rapid rise in blood sugar levels and lack of fibre may result in hunger and cravings on a juice-only diet. Some experts have expressed concern that drinking fructose in liquid form may impact the liver, and could potentially fool our brains into thinking we are still hungry, which may also increase appetite and cravings. The British Dental Association has confirmed a link between juice consumption and tooth decay. Read their tips to protect your teeth when drinking juice.

Can juicing help to ‘detox’ the body?

Our bodies have an in-built detox system which includes the liver, kidneys, lungs, gut and skin. So you do not need to follow a juice diet to kick-start the detox process – your body is working hard to do this for you on an ongoing basis.

Selection of fruit including apples, bananas, oranges and pineapple next to a juicer with freshly squeezed orange juice

Can juicing help to improve skin?

Raw fruit and vegetables are excellent sources of skin supportive nutrients like collagen-supportive vitamin C and skin-friendly beta-carotene (vitamin A). However, some of these beneficial nutrients like vitamins A, E and K need fat for absorption — the lack of fat in a juice diet may, therefore, impact the bio-availability of these vitamins. For healthy, youthful skin you also need to include sources of protein and the omega variety of fats, both of which are typically deficient in a juice only diet.

Other dietary changes that are implicated in a juice diet, such as eliminating refined sugars, processed foods and alcohol, may, however, be helpful for improving skin condition.

Can juicing help to boost your mood?

There are some reports of a general improvement in mood when combined with lifestyle changes. This may be more to do with the other dietary changes implicated, such as cutting back on processed and junk foods, as well as eliminating alcohol, caffeine and refined sugars.

Who should avoid juice diets?

If you have a medical condition, or are on medication, consult your GP or medical practitioner before making any drastic changes to your eating patterns. The high consumption of natural sugars implicit in juicing can cause blood-sugar levels to fluctuate, so those with diabetes or blood sugar management issues should avoid juice diets.

It is advisable to avoid juice diets if you:

  • are pregnant, or breastfeeding
  • are elderly, or under 18
  • are recovering from surgery
  • have kidney or liver conditions
  • have epilepsy
  • have anaemia, or low blood pressure
  • have a history of eating disorders

Please note: if you're considering attempting any form of diet, please consult your GP first to ensure you can do so without risk to health.

Now read...

How to eat a balanced diet
Six things you should consider before starting a diet
All our popular diet guides

This article was published on 9 July 2019 by Kerry Torrens.

A qualified nutritionist (MBANT), Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the The Royal Society of Medicine, Complementary and Natural Healthcare Council (CNHC), British Association for Applied Nutrition and Nutritional Therapy (BANT).

All health content on bbcgoodfood.com is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. If you have any concerns about your general health, you should contact your local health care provider. See our website terms and conditions for more information.

Have you tried a juice diet, or do you have any further questions about them? We'd love to hear from you in the comments below...

Comments, questions and tips

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10th Jul, 2017
This article is really far far too superficial to gain any real insight into the benefits or not of juice fasting. Whilst there is quite a lot of useful advice and links to other important articles, he article itself fails to dig deeper on - and sometimes misses - some important points. For one, the body does have a detox system, but the article does not adress how this detox system is effected when the body isn't expending as many valuable resources in digesting a 'normal' diet. This is seen very effectively in water fasting (there are hundreds of references online) once the body starts relying on ketones for much of its energy and, contrary to what is implied in the article, it seems that the body is very capable of not only surviving but functioning very well when it receives absolutely no calories and nutrients, even for 3 or more weeks. Under these conditions the detox process is accelerated greatly. An important potential problem with juice fasting is that the body might never go into 'ketone mode'. This is a problem because the extra calories it may require will come mainly from the muscles once the energy stores of the liver have been depleted. So a long term juice fast could result in sustantial loss of muscle (your heart muscle included). In 'ketone mode' the body goes into a muscle-sparing phase and you end up losing fat (still a bit of muscle too) as well as other 'none-essential' tissue, which means that even small scars sometimes heal. There appear to be many more benefits too. But why is it that no one really speaks about water fasting? Well (1) it goes against the grain of human nature not to eat (2) people imagine that they will be incredibly hungry (not so after day 3) and most importantly (3) no one makes money from it - there is no special recipe required for water. Thanks for reading.
8th Jul, 2017
"...make the juices yourself with fresh, organic produce..." Why organic??
goodfoodteam's picture
11th Jul, 2017
Thanks for your question. Take a look at our feature on organic food for more information about why we suggest using organic. https://www.bbcgoodfood.com/howto/guide/organic
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