What does science say about the juicing versus smoothies? That’s a big question so let’s break it down. Which is healthier – juicing versus smoothies? Let’s define healthy as the ability to maintain a steady blood glucose level without inducing or promoting hypoglycemia. Hypoglycemia is dangerous because our body needs glucose in our blood at a steady state to maintain the function of organs. The brain, for example, uses ONLY glucose for energy so hypoglycemia has profound effects on brain function.
In 1997, Haber et al published a paper in The Lancet entitled, “Depletion and Disruption of Dietary Fibre Effects on Satiety, Plasma-Glucose and Serum-Insulin“. The researched measured subjects’ blood glucose levels before and after ingestion of whole fruit, fruit juice and fruit smoothies. The results showed that:
- Eating Whole Apples: The body was able to maintain a fairly constant level of blood glucose when the subject ingested whole apples. This means low risk for hypoglycemia in non-diabetic patients.
- Drinking Apple Juice: The body was not able to maintain a blood glucose level when subjects ingested apple juice. The researchers noted that drinking apple juice was associated with postprandial (which means after eating/ingesting) blood glucose level that was considered hypoglycemic. This is called “rebound hypoglycemia”. Even if you drink the juice quickly, the rebound hypoglycemia is still there.
- Drinking Apple Smoothie: The body was also able to maintain a fairly constant blood glucose level in smoothies (which is basically just pureed fruit) if the smoothie was ingested over 20 minutes. If the smoothie was consumed too fast, then the overload of glucose would causes a similar rebound hypoglycemia seen in subjects who drank the fruit juices.
The research here suggests that fiber has a role in regulating blood glucose in our bodies. When the fiber is disrupted (as in smoothies) or removed (as in juices) this means that our bodies (mainly our pancreas) will handle the glucose load differently than it would if we just ate whole apples. In general, it’s better to eat whole apples as this is associated with the most steady postprandial blood glucose levels. Okay, what about other fruits? While postprandial levels dipped to hypoglycemic levels with apples, this was NOT the case for berries. One study actually showed that added blended berries to smoothie actually improved blood glucose control.
So…in general, this is NOT to say fruit juicing is inherently unhealthy. This just means that if we look at it from the perspective of blood glucose levels and risk of hypoglycemia – juicing may not be the best option. But if you had to drink fruit juicing, make sure there is no added sugar!
So in terms of our questions of JUICING vs. SMOOTHIES, here’s my verdict:
- Apple smoothies are not as good as whole apples
- Apple fruit juices are associated with rebound hypoglycemia
- Add berries to smoothies because it may improve blood sugar control