Without a doubt, blueberries are one of my favorite fruits. I love their flavor and the way that they are so easy to eat, to freeze and to use when they’re frozen.
Their health benefits don’t hurt matters either.
After all, blueberries are sometimes called a superfood and they are certainly a good source of phytochemicals.
Many of us find that the best way to have blueberries is in a smoothie, particularly a protein smoothie or maybe even in a smoothie bowl or as blueberry milk.
But, some researchers are calling this practice into question, due to a possible interaction between blueberries and milk. This was examined in a research study (Testa et al., 2009).
The Study Itself
This research study involved 11 human participants. These were split into two groups. The first group (the control) consumed 200 g of blueberries along with 200 ml of water. The second group (the experimental group) consumed the same amount of blueberries and 200 ml of whole milk.
For two days before the study, the participants followed a low-antioxidant diet. This was to ensure that any antioxidant impact was evident. The researchers collected blood samples from the participants before the study began as well as 1, 2 and 5 hours after consumption of the blueberries and milk/water.
These samples were then used to test a range of outcomes, including: concentrations of ferulic and caffeic acid, reducing and chain-breaking potential as well as antioxidant capacity of the plasma. All of these areas are indications of the antioxidant role of blueberries.
The authors noted that the blueberries acted to increase all of these areas.
However, when milk was consumed at the same time as blueberries, the levels of the two acids were reduced and there was a lower level of absorption of caffeic acid. Most significantly, consumption of blueberries and milk prevented the blueberries from raising the antioxidant capacity.
The author also did some in vitro (literally: in glass, i.e. in a test tube) research, which looked at the impacts of milk on blueberry extracts. The outcomes of this part of the study agreed with the impacts that blueberries and milk had on the blood of participants – showing that the milk dramatically decreased the antioxidant activity of the berries.
Strengths and Limitations
A key strength of the study was that it was experimental in nature. Experimental studies provide researchers with the chance to examine cause and effect. In this case, the design of the study allowed the researchers to clearly see the difference between consuming blueberries and water (the control) and consuming blueberries and milk.
Additionally, the design focused on the researchers testing outcomes in the blood of participants. This offered insight into the impacts that the blueberries were having in the body. The inclusion of an in vitro component to this study also made it strong, as this helped to confirm the observed results.
However, the study did also have one key limitation, which was the sample size. In total, the study involved just 11 participants. That’s an extremely small sample size for any study, especially for one that split participants into two groups.
In general, a small sample size makes the results of a study less reliable.The site Good, Bad, and Bogus offers a useful explanation of why small sample size is such an issue.
This means that the study is a good early look into the field but more research is needed to see whether this effect is actually occurring and how significant it is. Likewise, additional research is needed to see whether the same effect is present with other types of milk, as this study just considered the impacts of whole milk.
It is also worth noting that this study also just considered blueberries.
Berries in general offer significant antioxidant benefits and this is one reason why they are so popular. Many of the mechanisms that this study examined for blueberries would also apply for other berries. As such, future research needs to look at whether milk decreases the antioxidant impacts of all berries.
The Implications of Blueberries and Milk
The human body consists of a wide range of interconnected systems. These systems interact with each other as well as with the food that we eat. Because of this, there can often be unexpected outcomes, such as the proposed interaction between blueberries and milk.
In their study, the authors clearly showed that when people consumed blueberries and milk together, there was no increase in antioxidant activity. Now, the limitations in research do suggest that more research needs to be done.
However, even with just the results of this one study, there is a strong indication that consuming blueberries and milk may be counterproductive. This means that things like blueberry milk or blueberry smoothies might not be as healthy as most people assume.
The authors only tested the impacts of consuming blueberries and milk at the same time, so it’s likely that you could safely consume them at different points during the day if you wanted antioxidant benefits from the blueberries.
Realistically, this outcome shouldn’t be a reason to stop having blueberry milk or blueberries in smoothies (like this Blueberry Yogurt Smoothie from Jessica Garvin).
Instead, it’s an indication that we make sure that, at least some of the time, we have berries without milk. Maybe that would be in a fruit salad, a plateful of berries or even a glass of tart cherry juice.
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