What is the Pescatarian Diet?
The pescatarian diet is considered to be a largely plant-based diet. This means that a majority of calories come from plant foods such as fruits, vegetables, nuts, legumes, and grains. That being said, a pescatarian diet will also include fish and other forms of seafood as a source of calories. While pescatarians avoid consuming poultry and red meat, a pescatarian diet may also include animal products such as eggs or dairy.
How to Follow the Pescatarian Diet
The pescatarian diet can vary widely. An unhealthy version of the diet might include processed foods such as frozen fish sticks and potato chips all day. On the other hand, a healthier version would include a variety of whole foods such as leafy greens, whole grains, and bivalves. For the sake of this review, I’m going to examine a pescatarian diet that consists of mostly whole foods.
Potential Benefits of the Pescatarian Diet
Benefits from Avoiding Poultry and Red Meat
The pescatarian diet provides many health benefits because it prohibits the consumption of unhealthy foods, namely poultry and red meat. So, why should we avoid consumption of these foods? Let’s examine the health benefits we may enjoy from eliminating red meat and poultry from our diet:
1. Reduced Inflammation:
After eating a single meal of animal foods such as a sausage and egg sandwich, an acute inflammatory reaction occurs in our body (1). Inflammation is a natural process that occurs in response to a stress. For example, when we stub our toe, the toe may become red, swollen, and painful, as inflammation increases to help heal the injured area.
However, when we eat three meals of animal foods per day for a long period of time, we can develop chronic inflammation, which damages our body and can prevent our cells from repairing themselves. For that reason, eliminating poultry and red meat will likely decrease the total quantity of animal foods in our diet, which will reduce inflammation in the body.
2. Reduced Risk of Cancer
In 2015, the International Agency for Research on Cancer classified processed meats as a type 1A carcinogen, which means there is a causal relationship between processed meats and cancer. Other substances in this type 1A category include asbestos, alcohol, and tobacco smoke. In addition, red meat was classified as a type 2A carcinogen, which means that red meat “probably causes cancer” (2).
So, how can red meat consumption fuel cancer? While there are a myriad of possible explanations, researchers have pinpointed several potential carcinogens in meat (3).
The role of heme iron
There are two types of iron in the human diet: heme iron which is mostly found in animal foods and non-heme iron which is mostly found in plant foods. Many people believe that we must consume red meat to ensure we are getting enough iron. However, consuming heme iron may do more harm than good. According to a study in the European Journal for Cancer Prevention, “Iron can cause oxidative stress and DNA damage, and heme iron can catalyze… the formation of N-nitroso compounds, which are potent carcinogens” (4).
In fact, these researchers found that heme iron consumption is significantly associated with both esophageal and stomach cancers. Red meat contains roughly 3x more heme iron than most fish. For that reason, a pescatarian diet can reduce our heme iron intake.
Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs)
Both PAHs and HCAs are chemical compounds that are formed when meat is processed and/or cooked at high temperatures, such as pan-frying or grilling. These compounds are known to damage DNA and potentially increase your risk of cancer.
Evidently, whether it be the presence of heme iron, PAHs, HCAs, or the food itself, the science suggests that red meat is carcinogenic to human beings. As a result, many people tend to ditch the red meat and switch to poultry as a “cleaner” or “healthier” option. However, chicken and turkey may be anything but.
3. Weight Loss
From 1992-2000, researchers tracked the diet of 400,000 men and women in ten European countries. After controlling for age, sex, total energy intake, physical activity, and other factors, the researchers concluded that “the strongest relation with annual weight change was observed for poultry” (5). Although many people switch from red meat to chicken or turkey in attempts to lose weight, poultry was most associated with obesity in this large scale study.
4. Reduced Risk of Heart Disease
In addition, both chicken and beef are high in cholesterol and saturated fat. In fact, those following a diet high in red meat have nearly the same level of blood cholesterol as those eating a diet rich in white meat (6). Our consumption of cholesterol and saturated fat both increase our risk of heart disease, which is the leading cause of death in the United States. As a result, avoiding poultry and red meat on the pescatarian diet will likely decrease our long-term risk of heart disease.
Summary: Poultry and red meat consumption is associated with chronic inflammation, cancer, obesity, heart disease, and more. The pescatarian diet eliminates these foods, which reduces our risk of developing these conditions.
Benefits of Whole Plant Foods
When we avoid red meat and poultry, we avoid foods that damage our health. However, even more important are the foods that we do choose to consume on a daily basis. The pescatarian diet is far superior to the standard American diet because it emphasizes the consumption of whole plant foods.
According to the peer-reviewed scientific literature, a diet full of whole, unprocessed plant foods such as fruits, vegetables, whole grains, and legumes can help prevent, treat, and even reverse diseases that plague millions of people across the globe.
1. Reduced Risk of Heart Disease
Many of us believe that family history and genetics determine our likelihood to develop heart disease. While our genes are undoubtedly important, our lifestyle choices are far more impactful in determining our health outcomes. Dr. Caldwell Esselstyn of the Cleveland Clinic demonstrated the power of lifestyle intervention in his 2014 study. In his research, 198 patients with advanced cardiovascular disease volunteered to eat a completely plant based diet. Of the 177 patients who stuck with the plant based diet for over three years, 99.4% of them prevented and reversed their heart disease.
On the other hand, of the twenty-one patients who did not comply with the diet, thirteen of them suffered a major cardiac event such as a heart attack or stroke. This landmark study demonstrates that a plant based diet can reverse heart disease — no other diet has ever accomplished this feat (7). While a pescatarian diet may not reverse heart disease, it can still help you protect yourself against heart disease by boosting your consumption of plant foods!
2. Reduced Risk of Diabetes
Insulin resistance is a condition in which our cells have impaired ability to process glucose as a form of energy. Consequently, glucose remains in our bloodstream, which can lead to diabetes. Insulin resistance occurs when we develop a buildup of fat in our muscle cells, also known as intramyocellular fat. This fat prevents insulin from allowing glucose to enter the cell (8).
When we consume foods that are higher in saturated fat such as meat, dairy, eggs, and some oils, we increase our risk of diabetes. On the other hand, when we consume foods that are low in saturated fat such as fruits and vegetables, we decrease our risk of diabetes (9). According to the Canadian Diabetes Association, “intervention studies have shown that plant based diets were just as effective, if not more effective, than other diabetes diets in improving body weight, cardiovascular risk factors, [and] insulin sensitivity” (10).
3. Reduced Risk of Cancer
Fruits and vegetables are full of antioxidants and other health promoting phytochemicals. It is well documented that increased dietary consumption of antioxidants reduces the risk of many cancers (11, 12).
However, can a plant based diet treat or reverse a cancer diagnosis? In 2005, Dr. Dean Ornish answered this question in his study of ninety-three men with early, biopsy proven prostate cancer. Forty-nine of these men were assigned to an untreated control group. The other forty-four exercised daily and ate a whole food, plant based diet. After one year, all participants underwent a protein-specific antigen (PSA) test.
PSA is a protein produced by the prostate and higher levels of PSA in the blood can indicate the presence of prostate cancer. Lo and behold, the blood tests revealed a 4% reduction in PSA for the experimental group and a 6% increase in PSA for the control group. In effect, a plant based diet and lifestyle changes reversed the progression of prostate cancer (13).
Summary: The evidence clearly suggests that a predominantly plant based diet can dramatically improve our ability to combat Western civilization’s most common diseases: heart disease, diabetes, and cancer.
Potential Health Risks of the Pescatarian Diet
While a pescatarian diet can provide significant health benefits due to increased plant food consumption, there are some health concerns associated with eating more seafood.
Unfortunately, our oceans are some of the dirtiest places on Earth. Every year, billions of pounds of trash and pollutants enter the oceans (14). As a result, fish swim around in these polluted waters with their mouths open, ingesting debris and foreign chemicals. Now, what happens when we increase our consumption of fish and other seafood? Let’s take a look at the scientific literature.
1. Impaired Cognitive Function
Mercury is a heavy metal that primarily enters our oceans through the burning of coal, mining of iron, and other human related activities. Mercury is first absorbed by algae, which is then eaten by fish higher up in the food chain. Not only does this present a danger to fish, but mercury is also toxic to human beings, as it causes a variety of problems with our central nervous system.
Researchers in Brazil tested 129 adults for their level of mercury exposure by analyzing their hair samples. After testing each sample, they concluded that mercury exposure was associated with fish consumption. Moreover, the mercury levels were associated with...alterations in performance on tests of fine motor speed and dexterity, and concentration. Some aspects of verbal learning and memory were also disrupted by mercury exposure.”
Most importantly, these scientists concluded that the relationship between mercury exposure and decreased mental performance was dose-dependent. In other words, when these adults consumed more mercury through increased fish consumption, the alterations to their cognitive function increased (15).
These findings in Brazil are consistent with the results of a study conducted on 384 male and female corporate executives in St Petersburg, Florida. After measuring each participant’s mercury blood level and conducting a series of cognitive tests, researchers concluded that the subjects who over-consumed seafood experienced a 4.8% drop in executive functioning (16).
Ironically, these executives reported consuming seafood for the supposed health benefits. A 4.8% decrease in cognitive function may not significantly impact the life of an intelligent corporate executive. That being said, as rates of dementia rise across the globe, we must examine our lifestyle habits as potential factors to cognitive decline, including our consumption of fish.
2. Ingestion of Microplastics
Currently, there are roughly 150 million metric tons of plastic floating in our oceans. About eight million metric tons are added every year (17).
These plastics are most dangerous when they break down over time and become microplastics, which are tiny fragments of plastic less than 5 mm in size. Unsurprisingly, these microplastics then find their way into the flesh of the marine animals. On a pescatarian diet, you are virtually guaranteed to consume microplastics.
For example, an average portion of mussels contains 90 particles of microplastics and an average portion of oysters contains around 50 particles of microplastics. In fact, researchers from Ghent University in Belgium estimate that the average European consumes about 11,000 microplastics every year (18).
Currently, there is no quantity of microplastics that is considered safe to consume in the human diet (19). For that reason, it is difficult to estimate the negative side effects of plastic ingestion.
However, we do know that plastics do a great job of collecting chemicals. Plastic naturally concentrates pollution from the water by factors of up to one million times. In fact, environmental scientists use plastic to measure the concentration of pollutants in the water (20). Researchers from the Environmental Protection Agency state that plastic debris acts as a vector, transferring persistent, bioaccumulative toxic substances (PBTs) from the ocean to the food chain (21).
This graph demonstrates how PBTs can enter the food chain. Microplastics and other chemicals can find their way into small organisms such as phytoplankton. Then, larger concentrations of these chemicals accumulate up the food chain. Apex predators (i.e., human beings) receive the greatest concentration of PBTs. There is significant concern that the mechanical damage inflicted by ingesting pieces of plastic can mutate our DNA. In addition, the chemicals carried by the plastics can lead to cancer cell growth (22).
While more research is required on this topic, the safest decision is to limit or completely avoid consumption of seafood to ensure you do not consume any plastic and potentially hazardous chemicals.
3. Increased Levels of Blood Cholesterol
The human body makes all of the cholesterol we need to survive and thrive on a daily basis. Just like humans, fish, bivalves, and other seafood organisms produce their own cholesterol. For example, three ounces of cod contains 99 mg of cholesterol. 3 oz of salmon contains 52 mg. 3 oz of shrimp contains a whopping 161 mg, which is almost as much as one whole egg.
According to a meta-analysis of randomized control trials in the Journal of Clinical Lipidology, the blood cholesterol levels of people who eat mostly beef does not significantly differ with those who eat mostly fish (23). Because high blood cholesterol is a hallmark of cardiovascular disease, we should aim to limit or completely avoid cholesterol consumption.
Summary: Microplastics, mercury, and other persistent toxins found in fish can increase our risk for neurological disorders, DNA damage, and other unknown side effects. High levels of cholesterol found in fish may also put us at risk for heart disease.
But What About Omega-3s?
Omega-3 fatty acids are considered to be essential fatty acids because our body does not produce them ourselves. Omega-3s form primary structural components of the human brain, skin, cerebral cortex, and retina. The three most important forms of Omega-3 fatty acids are ALA, EPA, and DHA. Whereas EPA and DHA are long-branch fatty acids found mainly in seafood, ALA is a short-chain fatty acid found mainly in plants. In order to support our brain health, our body must convert the short-chain ALA into long-chain DHA.
How Much DHA Do We Need?
Many people believe we must consume fish because they contain essential Omega-3 fatty acids. However, rather than consume mercury, microplastics, toxins, and cholesterol in fish, you can make sure you eat enough ALA from plant sources.
The daily requirement for DHA consumption is about 250-300 mg (23). Scientists estimate that we can convert anywhere from 2-9% of ALA into DHA. The average estimated ALA to DHA conversion is 3.8% (24).
At this average figure, just one small serving of chia seeds provides 200mg of DHA. Hemp seeds, walnuts, and flax seeds are also significant sources of ALA. That being said, for extra peace of mind, you can always opt to take a daily DHA supplement from algae.
Summary: Clearly, you can avoid the health concerns of fish consumption by getting more than enough Omega-3 fatty acids from nutritionally dense, health promoting plant sources.
Overall, the whole food, pescatarian diet represents a dramatic improvement over the standard American diet of meat and processed foods. By cutting out red meat and poultry, pescatarians reduce their chronic inflammation, as well as their intake of cholesterol and saturated fat. Emphasizing the consumption of fruits, vegetables, and whole grains can greatly improve the quality of a pescatarian diet. On the other hand, if red meat and poultry is replaced in equal amounts by seafood, there may still be cause for concern, as seafood often contains heavy metals, dioxins, and plastics.
Ideally, on any pescatarian diet, we should maximize our consumption of whole plant foods and limit our consumption of fish, eggs, and dairy.
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