The 2020 Dietary Guidelines Advisory Committee recommended that adults consume
less than 6% of their total daily calories from added sugar, but most Americans
consume far more. Much of the excess sugar is in the form of sugar-sweetened
beverages (SSBs) such as soft drinks, fruit drinks with added sugar, and 100% fruit
juice. The Framingham Heart Study used a self-report to estimate the dietary intake
of SSBs and evaluated brain health with neuropsychological testing (assessing verbal
memory, processing speed, and other executive functions) and brain imaging (to
assess hippocampal and total brain volume). The study found that high consumption
of SSBs among participants (average age of 54 years) was associated with the
brain pathology markers of early-stage Alzheimer disease: poorer memory, smaller
overall brain volume, and a smaller hippocampus—an area of the brain important
for learning and memory.

Compared to those with no consumption of SSBs, those who drank 1 to 2 SSBs per
day had brain volume changes equivalent to 1.5 additional years of brain aging,
and those who drank more than 2 SSBs per day had the equivalent of 2 years of
brain volume aging. Compared to those with no consumption, those who drank 1
to 2 SSBs per day had Logical Memory Delayed scores equivalent to 5.8 additional
years of brain aging, and those who drank more than 2 SSBs per day had scores
equivalent to 11 additional years of brain aging. The magnitude of these effects was
attenuated when adjustments for physical activity and healthy nutrition were made.
The investigators noted that although their findings are consistent with animal studies,
because their research was an observational study at a single point in time, it
could not be considered conclusive with regard to cause-and-effect. Even so, the results
of the study suggest that minimizing dietary intake of sugar may guard against
the brain atrophy and memory impairment associated with accelerated brain aging
and Alzheimer disease.

This data about SSBs and brain health suggests that it might be a good idea to substitute
artificially sweetened diet soda for SSBs. But a 2012 study found that artificially
sweetened soft drinks were also associated with an increased risk of stroke.
The study found that people who had any recent consumption of diet drinks, regardless
of the amount per day, were about 16% more likely to have a stroke as those
with no consumption of diet drinks. These findings were also attenuated somewhat
when the data were adjusted for hypertension and additional CVD risk factors.

A 2017 follow-up Framingham Heart Study also found that people who drank diet
soda were more likely to develop stroke and dementia compared to those who did
not. In contrast to the previous study on SSBs, the investigators found no correlation
between SSB intake and stroke or dementia. Compared to those who did not
drink diet drinks, they found that people who drank one to six diet drinks a week
had a 1.41 times, but not a statistically significant increase in all-cause dementia.
Those who drank a greater amount, one or more diet soda per day, were 2.47 times
more likely to develop dementia. These findings were attenuated somewhat when
the data were adjusted for additional CVD risk factors, including diabetes and blood
lipid status.

After adjustments for age, sex, education, caloric intake, diet quality, physical activity, and smoking, higher recent and higher cumulative intake of artificially sweetened
soft drinks were associated with an increased risk of ischemic stroke, all-cause
dementia, and Alzheimer disease dementia. When comparing daily consumption
of one or more diet drinks cumulative intake to none per week, the hazard ratios
were 2.96 (the 95% confidence interval was large, 1.26–6.97) for ischemic stroke
and 2.89 (the 95% confidence interval was large, 1.18–7.07) for Alzheimer disease.

Although the researchers adjusted their data for age, smoking, diet, and other factors,
they could not completely control for preexisting conditions like diabetes,
which may have developed over the course of the study and is a known risk factor
for dementia. People with diabetes, as a group, consume more diet soda, so some
of the correlation between diet soda intake and dementia may be due to diabetes, as
well as other vascular risk factors and not related to diet soda consumption.
The study found that diet quality assessed during midlife was not significantly associated
with subsequent risk for dementia. The study authors noted that other
studies, especially those with long follow-up of 15 years or longer, did not find a
significant association between diet, dementia risk, and cognitive decline. Their
conclusion was that whether a healthy diet plays a role in shaping cognitive outcomes
in combination with other healthy behaviors, or in subgroups at increased
risk for dementia, remains unclear.

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.