Thursday, 5 June 2014

Juices, smoothies or plain old fruit and veggies?


I was sitting in the waiting room of my doctor's office today, watching rubbish daytime television (lucky me!) which included a stream of infomercials for juicers, blenders and shakes in packets. Many diet sites and nutrition books talk about juices  and smoothies, and everywhere you look lately someone is carrying a glass jar with something green in it (what is it with jars?) Movies like "Fat sick and nearly dead" promote juicing for weight loss and many magazines promote juice "cleanses". Boost juice and other juice franchises are booming and fancy appliances are for sale in every shopping centre. You may feel that if you're not making juices or smoothies then you must be doing it wrong. So what's the lowdown on juices and smoothies and are there any health benefits over and above just eating fruit and vegetables? Let's have a look. 

What's the difference between juices and smoothies?
To make a juice you need a juice extractor (or "juicer") which removes the liquid from fruit and vegetables leaving the pulp and fibre behind. A smoothie, however, is made in a blender or food processor and uses the whole fruit including the fibre. This difference in preparation has a big impact on the health effects of these drinks. 

Let's start with juices
Proponents of juicing can be an extreme lot, with websites using words like "miracle cure", "cleansing healing" and many other health claims that make me distinctly uneasy. There are significant health benefits found from eating more fruit and vegetables but no reputable science to suggest that there is any health benefit specific to juicing. In fact there are some reasons why juicing should be  approached with caution. 

When using a juicer, the juice and most of the vitamins and nutrients of the fruit and vegetables are extracted, and the pulp and fibre are left behind.  So does this matter? In fact it does.  Dietary fibre is vitally important for the normal functioning of the bowel and only around 2/3 of Australians and half of Americans meet the recommended 30g of dietary fibre a day. Meeting that 30g a day can decrease the risk of heart disease, diabetes and bowel cancer. Juicing your vegetables will lower your fibre intake and make this situation worse. 

Fibre not only provides benefit to your bowel, but within fruit it also binds the fructose (natural sugars) of the fruit so they are released more slowly. Remove the fibre and the juices can play havoc with your blood sugar level even if you are healthy, and dramatically so if you have diabetes.

Fibre also makes up a significant volume of the fruit - remove this and it will take a lot of fruit and vegetables to make a glass of juice. You may need to juice 5 or 6 oranges to make a glass of juice. Apart from being expensive, this also means the calories add up and even the natural sugars of fruit that are healthy in regular doses can end up being a problem in that big a dose. Have you ever tried to eat 6 oranges in a row? Probably not because you would get too full. Yet we would not think twice about drinking a glass of orange juice with our meal. That is just not healthy.

By definition juices do not contain protein or fibre, both of which are important to satiate hunger and make you feel full. This means that juices can leave you quite hungry afterwards so can lead to added unnecessary calories. 

"Juice cleanses" are heavily promoted and should be avoided. The lack of protein, fibre and fluctuating sugars involved in a juice only diet can leave people fatigued, weak, and with rapid weight loss (which is usually muscle rather than fat.) This kind of rapid weight loss can have significant effects on the long term metabolism and make future attempts to lose weight harder (see this post). For people with diabetes or impaired glucose tolerance the risks are magnified and the blood sugar effects of juicing can be dangerous.

Some of the health claims made by juicing proponents are quite preposterous. Just looking at a couple of websites recently I found some claims that do not make sense.  One site said that juices were excellent for "cleansing  and detoxification" which is completely unjustified. Your body does not need to be "detoxified" - your liver and kidneys do that for you all the time without any intervention from you. And as for cleansing, considering it is the fibre in fruit and vegetables that "sweep" your bowel clean and keep it functioning efficiently, cutting out all the fibre by juicing is likely to not cleanse but in fact have the opposite effect!  And apart from all the crazy claims of miracle cures of every disease known to man, one site even said juicing meant "nutrients were available in much larger quantities than if you eat them whole" - I am not sure how the juice extractor is going to actually make MORE vitamins? That's some scientifically magical appliance that I really need to see to believe!

So what about smoothies then?
As smoothies are made in  a blender, the whole fruit or vegetable including all the fibre  and pulp is retained.  This resolves a lot of the problems with juices losing the pulp (and the fibre and nutrients contained in that pulp). It also means the volume of the fruit/vegetable is maintained so you use less of the whole product and it fills you up.


Smoothies use blenders rather than juice extractors (cheaper to buy and easier to clean) and are therefore a bit more versatile.  If you use your smoothie as a base to add some protein (such as Greek yoghurt, egg or nut butters) and some low GI carbohydrates (oats, quinoa, low GI fruit) you can have a balanced home made meal replacement if you wish. Some people add protein powders, which is probably quite unnecessary but is an option.  Some recipes have 4-5 pieces of fruit on board - just be careful if you start adding those commercial supplements, plus fruit, yoghurt, honey etc you can end up with a high calorie option. Be very careful of commercially made smoothies as some have up to 30g sugar (that's 6 teaspoons full).

So what's the bottom line?
Eating fruit and vegetables is very good for you - in fact is an essential part of a healthy diet. There is no scientific evidence that blending them and keeping the fibre has any nutritional or health benefit over eating them whole. Juicing them without the fibre can have significant health impacts (especially if you have bowel problems or diabetes).

1. If you are meeting your daily requirements of 2 serves of fruit and 5+ serves of vegetables and are happy with what you are doing, there is no health reason for you to start making smoothies. You're already doing it right! 

2. If you are struggling to get all your serves of fruit and veg in a day and need another way, or if you are bored and you think a blended smoothie might be a nice change for you, then go right ahead. There are some great smoothie recipes online, but here's some basic principles. Treat it like a proper balanced meal, not just a drink with extra calories. Add dairy or alternatives, natural  lean protein, low GI carbohydrates and keep the ingredients simple with one or two serves of vegetable or fruit. Remember the calories add up. It can make a great breakfast on the run and is certainly far superior to eating a processed breakfast bar, a fatty take away or skipping breakfast altogether. I believe there is no need to add a processed protein powder to your meal unless it has been recommended by a doctor or dietitian - there is very little evidence they are of benefit to most people with a healthy balanced diet. 

3. I wouldn't recommend anybody take part in a "juice fast" or a "juice cleanse" at all. If you are going to drink juices, then stick to mainly vegetable juices, have them occasionally, and keep fruit juice as a drink for special occasions only. Treat all extracted juices with caution and monitor regularly if you have diabetes. 


For me, I think I'll just stick with eating my fruit and vegetables and drinking my water :)

Lyndal @ Lean Green and Healthy






Related posts you may wish to read:
Stop dieting now. Please!
What to eat for a healthier you
The beauty of breakfast 
When it comes to diets, one-size-doesn't-fit-all