With so much information out there on how and what we should or shouldn't be eating, I thought that having a breakdown of the most popular diets would be helpful for those looking to improve their energy, mood, and overall health. Everyone is different and have different dietary needs and beliefs. To summarize, I compare multiple diets and describe the evidence-based benefits for specific groups of people.
Paleolithic Dietary Pattern
The basic parameters to a Paleolithic diet (PD) include foods that do not originate from agricultural practices, such as grains, legumes, dairy products, and processed foods. Food sources are primarily animal meats, fish, eggs, nuts, vegetables, and fruits. The theory behind the PD is that humans did not evolve consuming grains, legumes, or other prohibited foods mentioned, and that these foods will not compliment optimal health (Genori 2020).
Pastore et al. conducted a 2-phase study that had overweight hypercholesterolemia participants consume a heart-healthy diet described by American Heart Association (AHA) for 4 months followed by a Paleolithic diet for 4 months. They found that participants had significantly greater reductions in mean body weight, total cholesterol (TC), triacylglycerols (TG), and low-density lipoprotein (LDL) in the Paleolithic diet phase compared to baseline and the AHA diet (p< .001 for all markers of comparison). Because the researchers indicate that the probability of their findings being false are less than 0.1%, this is a strong primary source (Pastore 2015).
A meta-analysis by de Meneses reviewed the literature regarding PD patterns and concluded that the PD, when compared to other dietary patterns, is associated with a reduction in weight, body mass index (BMI), and waist circumference (WC). After elimination and disocclusion of more than 1200 articles, only 11 randomized control trials were included in their analysis. The evidence presented is stronger than other meta analyses due to the specificity of biomarkers being evaluated, the filters of study disocclusion, statistical tests and significance of p is less than or equal to 0.01 (de Menezes 2019).
Considering these findings, strengths of the PD are strongest for individuals who are overweight and at risk for cardiovascular events due to elevations in TC, TG, and LDL. An important weakness to consider is the potential negative alterations in intestinal microflora due to the absence of resistant starch from whole grains and other important fiber components (Genoni 2020).
Vegan Dietary Pattern
A vegan diet is described as a plant-based diet rich in vegetables, fruits, whole grains, legumes, and avoids all animal meats and other animal products. Most of the studies conducted on vegan populations are small, containing less than 40 participants (Benatar 2018).
The Adventist Health Study-2 (AHS-2) is one of the largest cohorts conducted that followed 504 white men and women of varying ages, socio economic status, vegans, vegetarians, and non-vegetarians. It aimed to determine if and how a vegan or vegetarian diet affected blood pressure (BP). AHS-2 is considered a reputable primary source because of the large population size, length of time that participants adhered to a vegan diet (several years versus weeks in most other studies), and attention to detail concerning blood pressure and other medications (Pettersen 2012).
Benatar et al. conducted a meta-analysis that had a total of 12,619 vegans from several different countries and confirmed from their results that a vegan dietary pattern results in decreased overall energy intake, lower BMI, lower LDL, and lower fasting blood glucose. The study proceeded according to the Meta-Analysis of Observational Studies Epidemiology statement with two reviewers to assess the literature. The reviewers discussed any discrepancies found in the included literature, and assessed the quality of each scale using The Newcastle Ottawa Scale (Benatar 2018).
A vegan diet appears to have remarkable long-term benefits on healthy body weight, cardiovascular health, and glucose control. For most overweight or obese individuals, adhering to a vegan diet for a specified time frame may be a potential diet “prescription” to help reduce high BP, hyperglycemia, and other symptoms of metabolic syndrome. However, the exclusion of animal products may result in deficiencies like vitamin B12, iron, zinc, and omega-3 fatty acids (Bachmeyer 2019, Lederer 2019). Constructing a well-thought-out diet plan for how to avoid these deficiencies would be of benefit for anyone wishing to follow a vegan diet long-term.
Vegetarian Dietary Pattern
A vegetarian diet is plant-based, rich in vegetables, fruits, whole grains, legumes, and nuts. When eggs, fish, or dairy are included, the words “pesca”, “lacto”, and “ovo” are used to describe these types of vegetarian diets. Flesh from animals, such as beef, pork, poultry, or processed meats are excluded from vegetarianism (Rocha 2019).
In a randomized control trial (RCT) done on 74 patients with type II diabetes, Kahleova and researchers showed a vegetarian diet when compared to a standard diabetic diet had more positive health outcomes. Duration of the study was a total of 24 weeks with 12 weeks of diet alone and 12 weeks of an exercise protocol. The experimental vegetarian group (n=37) had a bigger reduction in weight (-6.2kg), reduction in visceral adipose tissue, increased insulin sensitivity, and increased antioxidants (Kahleova 2012).
Craddock et al. found in their systematic review of n=2,040 of observational and intervention trials, that a vegetarian diet was correlated with lower inflammation markers C-reactive protein (CRP) and fibrinogen in both types of studies. They used Newcastle Ottawa Scale by 2 researchers and a 3rd whenever a discrepancy arose. Gradings of Recommendations, Assessments, Development, and Evaluation (GRADE) method was used to assess quality of evidence (Craddock 2019).
A vegetarian diet can help a person increase their total fiber, antioxidant, and phytonutrient intake while reducing intake of potential carcinogens from processed meats, saturated fats, and AGEs. However, there is still potential that a vegetarian diet may not meet the nutritional needs of individuals, especially adolescents (Segovia-Siapco 2019).
DASH Dietary Pattern
The Dietary Approach to Stop Hypertension is a diet protocol designed to help individuals reduce blood pressure by eating a variety of vegetables, fruits, nuts, legumes, lean animal meat and fish, low-fat dairy, and limiting sodium, saturated fats, processed meats, and alcohol.
The EPIC-NL (European Prospective Investigation into Cancer and Nutrition) cohort provided Beisbroek and researchers with a large population size of 40,011 participants to investigate adherence to dietary guidelines and incidences of all-cause mortality. They concluded that higher rates of dietary adherence to the DASH diet, which was measured by DASH score, was inversely correlated with all-cause mortality (Beisbroek 2017).
Soltani et al. conducted a meta-analysis surveying DASH diet studies to identify the shape of the dose-response relationship of adherence to the DASH diet and risk of all-cause and specific-cause mortality risk. Results indicated that every 5-points increase in DASH adherence was associated with a -5% reduction in all-cause mortality. They used The Newcastle Ottawa scale to assess the quality of included studies and four DASH diet scoring methods for most cohorts that were then converted into a conventional DASH score for results and discussion.
The DASH recommendations are appropriate for most humans in all age groups, sex, health status, and ethnicities. It encompasses all food groups, encourages higher fiber intake, and can be affordable for those of lower income. Some individuals with chronic kidney disease may have a risk of hyperkalemia as a result of following a DASH diet protocol, but further studies are warranted (Tyson 2016).
Low Carbohydrate Dietary Pattern
In the 2015-2020 Dietary Guidelines for Americans, nutrition recommendations for a standard diet is that carbohydrate (CHO) should generally make up approximately 45-55% of total energy intake (TEI) and the remaining calories from protein and fat calories distribute almost evenly (Manore 2005). A low CHO diet needs to be defined as to what percentage CHO calories are as well as how many total grams of CHO is consumed daily.
Petrisko et al. conducted a randomized trial of seventeen obese individuals to examine how altering macronutrients composition would affect body weight and composition. Diets compared were low fat (LF), very low CHO with animal protein (VLCA), and very low CHO plant and mushroom based (VLCPM). They concluded that in the low CHO diets participants consumed less than provided calories possibly because of increased satiety, reduced fasting insulin and fasting glucose, and lower TG and TC levels. It appeared that the LF had a preservation of lean muscle mass, but the researchers hypothesize that this might be muscle glycogen and low CHO diets deplete glycogen (Petrisko 2020).
Gjuladin-Hellon et al. reviewed the available research of various low CHO diets’ influence on lipid profiles according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Statement. The CHO restricted diets (CRD) were compared to low-fat diets (LFDs). The CRDs were defined as medium CHO restricted diet (MCRD) <45% CHO TEI, low carbohydrate diet (LCD) <26% CHO TEI, and very low carbohydrate diet (VLCD) <10% CHO TEI. LFDs were defined as total TEI from fat <35% of calories. From the included 8 RCTS, researchers concluded that VLCD were superior to LFD by raising HDL and lowering TG (Gjuladin-Hellon 2019).
There is mounting evidence that a low carbohydrate diet has many benefits regarding improving glucose and lipid metabolism. These studies indicate that long-term weight loss with any calorie restricted diet will result in the same amount of weight lost. However, avoiding carbohydrates for most people will help improve insulin sensitivity and can also promote beta hydroxybutyrate, which is has neurological benefits (Petrisko 2020). Low CHO is certainly not an option for people with type I diabetes.
Low Fat Dietary Pattern (The Starch Solution)
Depending on the source, a low-fat diet is less than 30% of total calories consumed from fat. One theory behind the benefit of a low-fat diet is that a person can still consume a similar volume of food, but reduced calories since 1 gram of fat is more than twice as many calories as a gram of protein or carbohydrate.
Thomson and researchers conducted a study that compared weight loss and other markers between low-fat and low-CHO diets. They found that breast cancer survivors on both diet for 24 weeks had significant weight and fat loss regardless of macronutrient composition (Thomson 2010). These findings are beneficial when considering a vegetarian or vegan diet approach since many plant-protein sources are higher in carbohydrate than omnivorous animal-based proteins.
Mediterranean Dietary Patten
The Mediterranean diet (MD) embraces a variety of fibrous vegetables, fruits, legumes, whole grains, nuts and seeds, olive oil, seafood and shellfish, dairy products, and moderate intake of red wine and other animal proteins. MD is limited in intake from red and processed meat, other processed foods, and refined grains (Cano-Ibáñez 2020).
In a primary cardiovascular prevention trial done on 6646 healthy, Spanish participants with metabolic syndrome, researchers assessed the effects and nutrient density of a calorie-restricted MD. They assessed 10 nutrients, used a food-frequency questionnaire, and compared total intakes of nutrients to the recommended dietary intakes. Common deficiencies were vitamins A, D, E, B9, calcium, magnesium, and dietary fiber. 17% of participants had deficiencies of 4 or more out of 10 nutrients. Adherence to the MD was significantly associated with higher nutrient density (Cano-Ibáñez 2020).
Sanchez wt al. Performed review of observational and intervention studies to assess the impact of a MD on nutrition-related non-communicable diseases. In their research, they included the Women’s Health Initiative, EPIC PANACEA, PREDIMED, and the SUN study. They found that adherence to the MD was associated with less incidence of NCD. NCD listed in their review included cardiovascular disease, diabetes, cancer, cognitive decline, and depression (Sánchez-Sánchez 2020).
MD diet and Mediterranean way of living has consistently been observed as a sustainable, health-promoting lifestyle approach. The research shown here, and the thousands of non-mentioned studies, support the MD as a healthy dietary pattern. A potential weakness could be the inclusion of dairy products, which is a major allergen, and remains controversial as to if and how it contributes to good health (Prasad 2020).
Mediterranean Diet and Paleolithic Diet
As mentioned previously, adherence to a MD has been correlated with less incidence of CVD. It has also been seen to positively impact the gut microbiome in comparison to other diets by increasing microbial diversity, mitigating the harmful effects of atherogenic metabolites from animal proteins (Park 2019), and decreasing metabolic endotoxins (Bailey 2018). The PD does not contain any dairy or wheat and can be used as a nutritional prescription for those who would benefit from an elimination diet (Wahls 2018).
A few differences between the MD and PD to consider are 1: While both diets embrace the concept of consuming primarily vegetables, fruits, nuts, and lean proteins, the MD contains more resistant starch from whole grains that the PD does not. 2: The PD is low in carbohydrates and may improve insulin resistance in a short time frame compared to the MD. 3: The MD is likely more sustainable and easier to adhere to socially compared to PD.
In conclusion, a MD can be modified for those who would like to eliminate wheat and gluten as well as dairy and still obtain resistant starches from other whole grains, proteins from legumes, and limit intake from processed foods. Because the PD is restrictive, it appears prescribing a MD would be easier to adhere to for most people.
References
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