Enjoyed by everyone from your next door neighbour to Hollywood A-listers, smoothies are undeniably a summer favourite. Actor and entrepreneur Reese Witherspoon recently joined the long list of celebs, including Kourtney KardashianJennifer Aniston and Jessica Alba, to share their swear-by smoothie recipes. However, experts tell us smoothies aren’t always as healthy as you might expect, pointing to tooth decay and high sugar intake as risk factors. We discover the dos and don’ts when making a healthy smoothie.


A smoothie or 100 percent fruit or vegetable juice helps you on your way to five a day, but sticking to the NHS recommended portion size of 150ml per day (roughly 80g of fruit) is important. This is because you can easily consume far more fruit in a smoothie than you would of whole fruit. When you pack in three or four portions, you “end up having a big dose of sugar alongside the healthy components, which can cause more harm than good”, says dietitian Sophie Medlin.

When you eat whole fruit, the sugar is trapped inside the plant cell walls and your body has to break the walls down to access it. This causes the sugar to be released more slowly. When you eat blended fruit, the sugar has already been released from the cell walls and so becomes “free sugars”. The World Health Organisation says we should limit our intake of these, as they can affect teeth and weight. Read more about types of sugar on BBC Food.

Due to the small size of the recommended portion, the NHS says no matter how much fruit or veg you add to your drink or how many smoothies you drink in a day, it will only count as one of your daily five portions of fruit and veg.


“Anything that contains a lot of sugar, such as smoothies, can make us feel very hungry again shortly afterwards”, says Medlin, because “the sugar is absorbed more quickly” than from wholefoods. Adding protein to your smoothie helps slow the digestion of the sugar, so you stay fuller for longer.

Witherspoon suggests adding nut butter and ground flaxseeds to her recipe of spinach, lettuce and fruits, and you can add whole nuts and seeds, such as chia, a tablespoon of (no-added-sugar) yoghurt or oats to any smoothie recipe for a protein boost. Dr Rupy Aujla’s berry banana smoothie includes a milk alternative, nut butter, seeds and oats!

Smoothies contain sugars and acids, which contribute to irreversible enamel erosion and potentially tooth decay. “It is not the amount of sugar or acid you have”, says dental hygienist Anna Middleton, “but the frequency with which you have it that causes dental problems”. She advises using an (environmentally friendly) straw to bypass your teeth. Some flasks have straws attached, or you can buy metal, paper or even pasta straws. Middleton also recommends washing your mouth out with water after drinking a juice or smoothie, but says you should avoid brushing your teeth after eating or drinking anything acidic such as fruit.


Homemade smoothies can be made higher in fibre and lower in free sugars by using whole fruit and water instead of juice. Some ready-made smoothies contain a significant proportion of juice, which “is low in fibre, as the pulp and skin are removed, but fibre helps keep you fuller for longer,” says Medlin. Pay attention to the bottle size too, as it is likely to contain more than the recommended 150ml.

Experts we spoke to make their own smoothies. Medlin drinks one or two a week: “I make mine with mixed frozen berries, frozen kale, cucumber or celery and a tablespoon of Greek yoghurt, topped up with water”, she says. She simply advises you stick to the recommended 80g of fruit, add a protein source and use water rather than fruit juice to thin it down.


Smoothies are sometimes seen “as an elixir”, says dietician Tai Ibitoye. But she urges caution, saying that even if you stick to the NHS guidelines, a healthy choice once a day won’t cancel out an unhealthy diet. The Eat Well guide recommends just over a third of your diet should consist of fruits and vegetables, but of course that must be as part of a balanced diet.