Smoothies: Health boost or sugary trap?

NZ Herald

02-08-2025

Smoothies vs juice – which is better?
Smoothies do have an edge here. You could, of course, juice those fruits and vegetables to make them more palatable, but 'when you juice, you're extracting the liquid and getting rid of most or all of the pulp that contains most of the fibre,' says Leeming, whereas, 'when you whizz fruit and veg into a smoothie you keep the fibre'.
Fibre feeds your gut microbiome, producing short-chain fatty acids that our bodies cannot otherwise make and which are vital for the health of both your gut and your brain.
In fact, says Leeming: 'Fibre has many underappreciated benefits. Every additional 5g of fibre you eat each day is related to a 5% lower risk of depression, and every 7g of fibre (that's about half a can of beans) is linked to a 9% lower risk of heart disease, 6% lower risk of Type 2 diabetes and an 8% lower risk of colorectal cancer.'
Most of us eat just 60% of the recommended 30g of fibre per day. So, says Leeming: 'Swapping juice for smoothies can be a great way to get more fibre.'
Why smoothies might not be as healthy as you think
There is, however, a catch, explains Leeming. When you eat a fruit or vegetable in its natural whole state, it adds bulk to your stomach, triggering your stretch receptors and signalling to your brain that you are getting full. When you blend those ingredients into a smoothie, you mess with this system, so you are more likely to eat more than your body actually wants or needs.
Plus, there's your blood sugar to consider says Dr Federica Amati, the head nutritionist at science and nutrition company Zoe and the author of Every Body Should Know This.
'For people who have poor blood sugar control, some smoothies – even if they are pure fruit – are likely to cause a pronounced blood sugar response, and that's another reason why consuming the whole fruit is better. When we make fruit juices, cell walls in the fruit are broken down which releases the sugars inside. This means that the sugar can be more rapidly absorbed into your bloodstream.'
A recent survey conducted in Korea found that the average smoothie served in the country's cafes contained the equivalent of 13 teaspoons of sugar.
If you are buying a bottle (rather than blending your own at home) there may be other things to consider, says Amati. 'Some shop-bought smoothies can be minimally processed, but many products contain emulsifiers, added sugars and sweeteners, and artificial colourings and flavourings. So, as always, it's good to check the label.'
Can smoothies help you lose weight?
The short answer is no.
'Smoothies are often marketed as a quick-fix weight-loss hack, but that's not the case,' says Dr Amati. Smoothie-based diets and so-called detoxes often advise you to replace a meal with a drink. But, warns Amati, this only works if it puts you in a calorie deficit (consuming fewer calories than your body burns).
This pattern, she stresses, is not sustainable in the long term: 'Even if you lose weight, it'll come straight back on when you inevitably give up and start eating more again.
'Also, replacing meals with smoothies can mean people don't eat enough variety of foods and nutrients such as protein.' This, she explains, can be a problem, especially for older adults, as protein helps to keep us healthy in myriad ways, from maintaining your muscles to keeping your immune system strong.
Tips to make your smoothies healthier
Here are some easy ways to get the most nutritional value from your smoothie:
Make your own smoothies
Add in nuts and seeds for fibre
Focus on vegetables over fruits
Add protein powder for extra nutritional value
'If you love smoothies, try to make your own at home,' says Dr Leeming, and try to avoid adding sugars. Instead 'for an extra fibre boost for your gut bacteria, add in nuts and seeds, like chia seeds and peanut butter,' she suggests. Plus: 'Tofu is a great way to bump up both protein and fibre while adding creaminess. Avocados are surprisingly high in fibre considering their healthy fat content, and also make a great add-in.'
Eve Kalinik, a nutritional therapist, agrees: 'I typically recommend that smoothies are more veg than fruit focused, as otherwise they can be rather high in sugar, albeit natural. Add protein powder for extra nutritional value. I really like Hermosa Protein powders for their meticulous sourcing of ingredients.'
Should you ditch bananas from a smoothie?
Ideally, yes. While bananas can make your smoothie creamier, berries are lower in sugar and, last year, a study published in the Royal Society of Chemistry journal Food and Function highlighted another reason to ditch the yellow fruit.
Remember those healthy flavanols? After study participants drank a berry-and-banana smoothie, tests showed they had far lower levels of flavanols in their bodies compared with those who drank a berry-only mix. 'Bananas may be ruled out of the morning smoothie if you want to boost your flavanol intake, but on their own, they are still great fruits and can play an important role in many healthy diets,' writes the lead researcher. If you want to boost your flavanol levels, they conclude, you might consider blending berries with pineapple, oranges, mango or yoghurt instead.
What do the experts say?
Make them at home Don't neglect vegetables Consume slowly
'If you love smoothies, and you make them at home, they can form part of a healthy diet,' says Dr Amati. They are not, however, the quick health fix that many of us take them for.
NHS guidelines state that a 150ml smoothie only counts as one portion of your five-a-day, no matter how many vegetables you squeeze into it. So, even if you have blended all the best ingredients to create a nutritionally balanced smoothie: 'don't neglect including vegetables in other meals during the day,' says Kalinik.
'Often, we don't take time over smoothies as we would do when eating whole foods,' she says. 'I like to encourage more mindful eating, as this can help us to better connect with our satiety cues, develop a better connection with our food and create pockets of recovery (or energy boosts) in the day. So if you are going to have a smoothie, take time to sip slowly and savour.'
Verdict: Are smoothies healthy?
'The important reply is 'compared with what?''' suggests Amati. 'If you are cutting out sugar-sweetened soda by switching to smoothies, then overall – yes, that's healthier. But we shouldn't replace a well-rounded, plant-based meal with a smoothie.'