We hear about nutrition trends and fad diets everyday. Some come and go, some are around for a while. Do any of them work???
The Paleo diet is one that's been around for a while. Some people are completely convinced, some increasingly skeptical. Do the research and decide for yourself what you think. Or read my current event paper and see what I found after doing some research!
The “Paleo Diet”
is a popular nutrition trend commonly discussed in the media. Self proclaimed
world leader and founder of the paleo diet movement, Loren Cordain, PhD. (2015),
advertises that adopting the paleo diet may help you reduce your risk for
chronic disease, lose weight, have more energy, and slow or reverse your
autoimmune disease among other advantageous health and lifestyle benefits. The
paleo diet is a nutrition plan based on that of our hunter-gatherer ancestors
around 10,000 B.C. The diet is rich in lean meats, poultry, fish, fruits,
vegetables, nuts, seeds, and eggs (Mullin, 2010). Because the Homo sapiens from which the diet is
based had not developed agriculture, the diet excludes grains, legumes, and
dairy (Frassetto, Schloetter, Mietus-Synder, Morris, & Sebastian,
2009). Despite Cordain’s (2015)
desirable claims, scientific research supporting the benefits of a Paleolithic
diet is conflicting.
Frassetto,
Schloetter, Mietus-Synder, and Sebastian (2009) conducted a study investigating
the health benefits of a Paleolithic (paleo) diet. The outpatient,
metabolically controlled study conducted at the University of San Francisco
School of Medicine included six males and three females aged 26-50 years, whose
BMI placed them in a slightly overweight, but not obese category (Frassetto et
al., 2009). Participants were fed three paleo
meals and three paleo snacks for a period of ten days. Meals were prepared and portioned by the
clinical research center kitchen staff to ensure control. For three days prior
to the diet, participants were instructed to eat their usual western diet. This
was followed by seven “ramp up” diet days, which consisted of an increasingly
high fiber and high potassium diet. Biochemical measurements such as glucose
tolerance, insulin sensitivity, blood pressure (BP), lipid profiles, vascular
reactivity, and electrolyte excretion rates were performed during the western
diet phase to achieve baseline results (Frassetto et al., 2009). Baseline
results were compared with those taken during and after consumption of the
paleo diet plan.
Results showed
that switching to the paleo diet lowered BP, reduced fasting plasma insulin
levels, improved insulin sensitivity, reduced total cholesterol, reduced LDL
levels, and reduced triglyceride levels, among other positive, potentially
health improving results (Frassetto et al., 2009). While these results should
strongly endorse the paleo diet, limitations of the study give pause to the
actual meaning of the results. The study was limited because of the small sample
size, but was justified by the authors because, “…[the authors] had an estimate
of the effect-size and variability from [their] first subject for both changes
in BP and in lipid profiles, and both suggested that 10 subjects would be a
reasonable sample size” (Frassetto et al., 2009). Despite this questionable
justification, even the broad age range of participants restricts the meaning
of the results. Additional limitations delineated by the authors in the
discussion include the heterogeneity of the test subjects and the lack of a
control group. Finally, the study never reveals the western diet of the
participants. The introduction of the article comments on the highly refined,
processed food intake of the western diet, but never reveals a description of
the actual diet of participants before starting the study. This is a major
limitation that could significantly alter the meaning of the results. A
participant that previously ate a diet of fast food and prepackaged items would
likely show far greater metabolic improvements after switching to the paleo diet
than would a participant who ate a diet rich in whole grains and legumes,
vegetables, fruits, and lean meats. For the purpose of this study, both of
these diets could be considered western, but are nothing alike: posing a
noteworthy limitation. Assuming the results are valid even considering the
aforementioned limitations, Frassetto et al., 2009 is restricted to short term
outcomes.
Additional factors
must be considered before claiming long term health benefits of a paleo diet. Regardless
of short term metabolic improvements, inflammation can increase the risk for
chronic illness (Nilsson, Winkvist, Johansson, Lindahl, Hallmans, Lenner, &
Van Guelpen, 2013). Increased inflammatory factors brought on by a low
carbohydrate, high protein diet, not considered by Frassetto et al., 2009 could
negate the potential health benefits and lead to chronic illnesses such as
cancer. A study conducted in northern Sweden through the Vasterbotten
Intervention Programme researched the correlation of a low carbohydrate, high protein
diet and incidence of cancer (Nilsson et al., 2013). The population based
prospective cohort study included 62, 582 men and women. Low carbohydrate, high
protein (LCHP) scores were established and measured in relation to incidence of
various types of cancer. The LCHP score was determined for participants using
Food Frequency Questionnaires and telephoned 24-hour recall follow ups to
ensure accuracy. Follow up ranged from one day to 17.8 years, with an average
of 9.7 years (Nilsson et al., 2013). Results showed no overall relationship
between LCHP scores and cancer diagnoses and the study did not find that a low
carbohydrate, high protein diet reduced the risk of cancer (Nilsson et al.,
2013).
Scientific
research has not yet proved the grand claims made by the proponents of the
paleo diet. Both of the previously mentioned studies have limitations that
threaten the validity of the results. While Nilsson, Winkvist, Johansson,
Lindahl, Hallmans, Lenner, & Van Guelpen (2013) had a much larger sample
size, the study did not exclude participants based on family history of cancer,
possibly skewing results. More research must be done on the subject before
valid conclusions can be drawn.
Before conducting
any additional human research, a bench study should be performed to allow for
adequate control and careful metabolic regulation. Ideally, such a study would
include multiple groups consuming different variations of western and paleo diets.
This could be followed by a sequential design study on human subjects using
biochemical assays similar to those used by Frassetto et al., 2009 and with a
specific paleo menu and control groups. A sequential study would exploit the
best aspects of each study, combining longitudinal and cross sectional designs
to study carefully chosen experimental and control groups for an extended
period of time. Only after studies such as these have been properly
executed will a valid answer exist as to the benefits or risks of consuming a
paleo diet.
