The
question is simple: do we avoid all sugary drinks, including fruit juices? The
best I can come up with is to withhold judgment and don’t get excited about it
for now. Let’s take a look at what the concerns of the researchers were and
then my concerns.
Researchers’
Concerns
The first is that the
NutriNet-Santé study was not a randomized sample. That means that only those
people who were interested in participating for whatever reason did so. The
sample was predominantly women at 78.7% of the cohort with a mean age of 42
years. The researchers accounted for age and gender in the statistical analyses,
but that doesn’t account for the lack of randomization.
Researchers also stated that
the rate of cancer was much lower: 620 of the 100,000 people in the study compared
with 972 per 100,000 people in all of France. They adjusted the numbers to
reflect the age and gender distribution in France, but I used the numbers
actually given in the study. They also said the diagnosis of cancer was
self-reported. I can’t believe anyone would say they have cancer if they don’t,
but it would have been better if it were verified.
Related to that, some cancers
were limited, thus affecting the statistics. If you don’t have enough of any
type of cancer, it’s difficult and scientifically shaky to calculate a
relationship.
Younger subjects consumed
higher amounts of sugary drinks than older subjects. There were other factors
as well, but these also were taken care of statistically. Further, they
acknowledge what I alluded to: when people self-report, they can over- and
under-estimate their intake. They also chose only the subjects that had at
least two diet records completed in the first two years; the potential was 10
if all records were completed by all subjects. That seems low to me—there’s too
much missing data.
Finally, this was an
observational study and thus cause and effect can’t be attributed to the
results. But it does raise questions.
My Questions
I
think they could have gone a long way to answering the question about sugar
intake if they had compared the fruit intake with the juice intake: take the
fruit intake, calculate the sugar content, then match it with juice intake with
the same sugar content. What was the rate of cancer in each group? Doing the
direct comparison could go a long way to suggest whether it’s the sugar alone
or if the effects were ameliorated with the fiber and phytonutrients of whole
fruit with the same amount of sugar. That’s an obvious question; this is an
ongoing study so maybe they’ll do that in the future.
I
also think that running a comparison of total carbohydrate intake could also
give us insight. If someone had a high carbohydrate intake, especially if it
were high in refined carbohydrates, that might be meaningful as well.
The Bottom
Line
The
question I was left with was this: how could less than a half-cup per day of
any type of added sugary drink that contained fewer than 50 sugar calories
cause an increase in cancer? It just doesn’t make any kind of sense when you
consider the total mean average calorie intake of the subjects was 1,850
calories. If the total sugar intake from solid foods of the individuals was
high, or it was highly refined carbohydrates, that could make a difference.
That analysis wasn’t done.
At this point, I wouldn’t stop drinking a glass of fruit juice or adding some juice to a smoothie. Don’t go out of your way to drink more fruit juice, but don’t avoid it either; certainly you should choose fruit juice from whole fruit over soda with sugar. If you have an artificial sweetener you like, use that instead of sugar. As for other drinks that contain sugar, they’re highly refined carbohydrates so you should be keeping those under control anyway. While this was an interesting and controversial report, nutrition is still about balance. Keep that in mind as you choose what you eat and drink every day.
What are you prepared to do today?
Dr. Chet
Reference: BMJ 2019; 366 doi:
https://doi.org/10.1136/bmj.l2408.
