As with many alternative health therapies, the benefits of juicing fruits and vegetables is a source of controversy.
And, as with many therapies, it has its positives and negatives.
Let’s take a look at the pros and cons – and we should note here that most of the cons are associated with sugar-laden fruit juices, rather than vegetable juices.
What is juicing?
Juicing is a process that extracts the liquid content from fresh fruits and vegetables. It usually removes the fibre, pulp and seeds.
Many people fail to achieve adequate levels of vitamins, minerals and other nutrients from their diet alone.
There are many reasons – depletion of nutrients in soil, fast food diets, digestive disorders, medication, illness, ageing, etc
Many people have a hard time being able to eat a sufficient quantity of fresh fruits and vegetables on a daily basis. Indeed, for some folk, the only way they can consume enough of these foods and their nutrients is to drink them or blend them.
Juicing – The Evidence
Does juicing provide all the same vitamins, minerals and phytonutrients as eating whole fruits and veggies?
While there is ample evidence linking the eating of whole fruits and vegetables to a reduction in the the incidence of disease, studies on the drinking of fruit and vegetable juice are more difficult to find.
One study found that when the participants supplemented their diet with mixed fruit and vegetable juices over a 14 week period, nutrient levels improved for vitamin C, vitamin E, beta-carotene, selenium and folate.
A review of 22 studies concluded that consuming juice made from fresh fruits and vegetables (or blended powder concentrate) improved the levels of folate and anti-oxidants, including beta-carotene, Vitamin C and Vitamin E.
One review concluded that the health benefits of fruits and veggies may be due to antioxidants, rather than fibre. While this might suggest that juice, therefore, provides comparable benefits to the whole food, it does not address the role of fibre in the absorption of those antioxidants.
Studies have indicated that juices may reduce the risk of heart disease.
Apple and pomegranate juices have been linked to a reduction in hypertension (high blood pressure) and cholesterol levels.
It has also been found that consuming fruit and vegetable juices, either in liquid form or in blended concentrations, may reduce homocysteine levels and markers of oxidative stress – both of which have been linked to improved heart health.
A relatively large study found that the risk of Alzheimer’s disease was reduced in people who drank fruit and vegetable juices a minimum of three times per week, compared who those who drank juices less than once per week. This reduction in risk of Alzheimer’s may be due to the high levels of polyphenols – antioxidants believed to play a role in protecting brain cells.
These results are promising, but more studies are required to substantiate the links between the effects of consuming juices and various health conditions.
Whole Foods vs. Juice – The Role Of Fiber & Antioxidants
Pro-juicing advocates often make the claim that juicing is more beneficial than eating whole foods, their reason being that fibre can inhibit the absorption of nutrients.
As yet, there is no real scientific evidence to support this claim.
Anti-juicing advocates claim that juicing removes the positive effects of fibre – such as gastrointestinal regulation, the lowering of bad cholesterol levels, blood glucose regulation, and promoting feelings of satiety (fullness). So, when drinking fruit juices (more so than green vegetable juices), you are missing the fibre which will help regulate blood sugar levels – hence the reason many people feel a sugar spike (or energy burst).
The fibre content of fruits limits the rate of absorption of sugar – meaning all the sugar is not delivered to the liver in one hit, because when that happens the liver will likely convert it to fat.
The other problem with fructose is that it suppresses leptin, the hormone that tells you when you are full, so you don’t know when to stop eating.
Important antioxidants that are naturally bound to plant fibres could be lost in the juicing process. These may play an important role in the health benefits associated with whole fruits and vegetables.
Up to 90% of fibre is removed during the juicing process. Some soluble fibre remains, but the majority of insoluble fibre is removed.
High fibre consumption has been associated with lower risks of obesity, type 2 diabetes and heart disease.
Studies have shown that increasing soluble fibre, in particular, may improve blood sugar and cholesterol levels.
One study compared the difference in cholesterol levels from eating whole apples, compared to drinking clear apple juice. It was found that the juice increased LDL (bad) cholesterol levels by 6.9%, compared to the actual whole apple. It was concluded that the fibre in the whole apples contributed to this result.
An observational study found an increased risk of type 2 diabetes in subjects who drank fruit juices. This compared to reduced risk in people who ate whole fruits.
Another study compared the effects on nutrient levels of juicing versus blending of grapefruits. The results found that blending, which retains more fibre and pulp, exhibited higher levels of beneficial plant compounds.
Despite the lack of fibre, people suffering from constipation often find that a daily serving of green juice helps to keep them regular, without the need for laxatives.
Smoothies are often a better option than juice, as they retain more of the whole food, including pulp and fibre.
It is also worth noting that some folk are sensitive to fibre – in some people it can cause intestinal distress, even in relatively small amounts. In this case, many individuals find they can more easily digest vegetables and fruits when they are in the form of juice.
Juicing & Digestion
One of the key reasons that fresh juice is referred to as a “live food” is because it contains active enzymes (as do raw whole foods).
Enzymes are composed of vitamins and minerals. Their job is to speed up chemical reactions. Without enzymes, there would be no life in our cells.
Enzymes are in greater concentration in raw foods, including fresh juice, because they are extremely sensitive to heat and are destroyed during cooking and pasteurization.
There are two major types of enzymes: synthetases and hydrolases. The synthetases help build body structures by making or synthesizing larger molecules. The synthetases are also referred to as metabolic enzymes. The hydrolases or digestive enzymes work to break down large molecules into smaller more readily digestible ones by adding water to the larger molecule. This process is known as hydrolysis.
Digestion is the body process that utilizes the greatest level of energy. That is why one of the key energy-enhancing benefits of fresh juice is its highly digestible form.
When we eat, our body works very hard at separating out the juice from the fiber in our food. (Remember, it is the juice that nourishes our cells.)
The juice extractor does this for the body, but that is not the only benefit to digestion with fresh juice. Fresh juice and other live foods contain digestive enzymes that help break down the foods in the digestive tract, thereby sparing the body’s valuable digestive enzymes.
This sparing action is referred to as the law of adaptive secretion of digestive enzymes. That means if some of the food is digested by the enzymes contained in the food, the body will secrete fewer of its own enzymes. This allows vital energy in the body to be shifted from digestion to other body functions, such as repair and rejuvenation.
Fresh juices require very little energy to digest, taking as few as 5 minutes to begin to be absorbed. In contrast, a large meal of meat and potatoes may sit in the stomach for several hours. If a meal is composed entirely from cooked (low-enzyme) foods, most of the body’s energy is directed at digestion. Hence, the reason many people experience a slump in energy after eating.
Juicing, Sugar & Weight Loss
While juicing green vegetables (as a supplement to a healthy diet) may assist with weight loss, caution should be taken with fruit juices. Over-consumption can easily lead to an increase in weight.
Juicing fruits can significantly increase your free sugar intake. When fruit and vegetables are juiced, the sugar is released as free sugar, which is very much the same as added sugar in processed foods.
There is also the potential danger of dental decay from too much juice, as the acid strips tooth enamel. Children who drink too much fruit juice often experience tooth decay.
Obviously, fruits contain significantly more sugar and calories than vegetables.
An excess of fructose (naturally occurring sugar in fruit) has been associated with high blood sugar levels, weight gain and an increased risk of type 2 diabetes.
Some people are unable to digest the sugars in fruit and vegetables, known as FODMAPs, which hit the gut faster if reduced to a liquid.
This can cause Irritable Bowel Syndrome (IBS) type symptoms including stomach pain, bloating and diarrhea, and excessive gas.
Since juicing has become more popular, some doctors and gastroenterologists are reporting increased cases of patients presenting with IBS-like symptoms which are, in fact, just their body’s reaction to these increased sugars hitting the gut too quickly.
Excess sugars are also the favourite diet of the intestinal fungus known as candida – if you suffer from this complaint, you would be well advised to avoid fruit juices.
Additionally, excess intake of sugars can hinder absorption of minerals such as magnesium.
Fruit juice can be much higher in calories, when compared to eating the whole fruit.
A cup of pineapple pieces has about 83 calories. A cup of pineapple juice has 120 calories.
A cup of whole pomegranate contains 12 grams of sugar. A cup of pomegranate juice has 37 grams of sugar.
A 236 ml glass of orange juice may contain up to 4 oranges – imagine that quantity of sugar hitting your intestines in one hit.
Liquids tend to be less filling than foods with fibre, so there is a tendency to eat more, rather than less.
Drinking juice in lieu of all foods is not healthy for long-term nutrition. Juices should be a supplement to your daily meals, not a replacement for them.
For people with digestive disorders – such as constipation, hemorrhoids, dyspepsia – I often recommend a one day juice fast. This should comprise mostly green juices, nut milks, plenty of water. It is not intended to be a calorie reduction fast, but more of a rest for your digestive system. Digesting solid foods can be hard work for the organs of the body, especially if you have a tendency to over-eat processed foods. An occasional break can do wonders for an over-taxed gut.
Side Effects of Juicing
Consuming a diet of 100% fruit juice has been linked to increased risk of metabolic syndrome, liver damage and obesity.
For people with kidney problems, a high consumption of juices rich in oxalate has been associated with kidney failure.
If you take prescription medications, you should be aware of potential interactions.
For example, large amounts of vitamin K found in green leafy vegetables (such as kale and spinach) can interfere with anti-coagulant drugs.
As mentioned previously, the high sugar content in some juices can 1. cause pain and discomfort in the stomach, intestines and bowel; 2. aggravate certain conditions such as candida; 3. interfere with the absorption of some minerals; 4. contribute to tooth decay.
What to Juice
Some vitamins are more easily absorbed as juice, such as vitamin C and the B group vitamins. Others, like vitamins A, E, K are best taken through the full digestion process.
And some vegetables, such as tomatoes, actually provide more nutritional value when cooked.
So, the best bets for maximum juicing nutrition: Leafy greens (spinach, collard greens, swiss chard, kale, mustard greens), parsley, broccoli, beets, asparagus, cucumbers, red bell peppers, ginger, garlic.
And these fruits – kiwi, papaya, grapefruit, strawberries, oranges, lemons.
To sweeten up your veggie juice, throw in low-sugar items such as lemon, lime or green apple instead of fruits that are higher on the glycemic scale.
I often include avocado in juices to add essential fatty acids to the diet.
Nutrient Loss in Fresh Juices & Smoothies
The nutrients in freshly juiced or blended fruits and vegetables deteriorate quickly.
Cooking is not the only way fruits and vegetables can lose their nutritional value: Oxygen exposure can be just as detrimental. A slice of cantaloupe left uncovered in the refrigerator will lose 35 percent of its vitamin C content in 24 hours. Freshly sliced cucumbers, if left standing, will lose between 41 and 49 percent of their vitamin C content within the first three hours.
From this information we can conclude that it is best to drink fresh juice as soon as it is prepared. If this is not possible, juice should be stored in a thermos or in an air tight container in the refrigerator. It is best consumed within 12-24 hours.
Fresh Juice vs Canned & Bottle Juice
Fresh is always best. Many bottled and canned juices have very little to offer nutritionally, their only advantage is convenience.
Fresh juice not only contains greater nutritional values than its canned, bottled, or frozen counterparts, but it also contains enzymes and other “living” ingredients.
In contrast, canned, bottled, and packaged juices have been pasteurized, which significantly lengthens their shelf-life, but contributes to the loss of identifiable vitamins and minerals (as well as the loss of other factors not yet fully understood).