Ocean and freshwater-based diets can help address nutritional and environmental concerns

Diets rich in foods from the ocean and fresh water sources can help address nutritional and environmental challenges that stem from a wide variety of diet-related diseases, including cardiovascular disease, obesity and certain cancers. A major driver of these global health concerns is an increase in food demand driven by population growth globally. While current diets are not perfectly balanced, some trends have been observed to include more fiber, whole grains, nuts, healthy fats (such as avocados, olives, olive oil), dairy and fruits, and less red meat. Other aspects of these dietary patterns, however, have shown mixed results. For example, one diet involving eating mostly seafood or fish as part of a plant-based diet is associated with increased mortality, especially from chronic disease. Yet another diet rich in animal products shows no such beneficial effects. These findings suggest that there is little evidence for what kind of diet will be most effective. Although this finding does not mean that people should avoid meat altogether, it does provide important information about potential impacts that other types of diets might have on human health. Therefore, understanding the impact of specific dietary interventions is important. However, the literature review that led us to choose nutrition as our focus area was very limited, so we relied on secondary data to inform our conclusions. Our secondary research used only quantitative methods such as surveys and randomized control trials conducted in clinical settings. Because of the rigor of this study design, we were able to draw reliable conclusions. It was also important because of the small sample size that made up the dataset. Further primary research might have yielded different results. Finally, although this study may serve as a guide to future studies, there is still much more work to be done to fully understand the impact of various dietary patterns in different populations.

1. Background

According to WHO, 1.3 billion people worldwide do not have sufficient access to the recommended five servings of fruit and vegetables per day. At the same time, more than half of all deaths in the developing world are due to preventable illnesses such as diabetes, cancer, heart disease, stroke, hypertension and overweight [1]. Additionally, according to the Institute of Medicine’s Dietary Guidelines for Americans 2017–2020, about 40% of adults consume enough calories from added sugars, and nearly 15% don’t get enough calcium. Also, roughly 25% of non-Hispanic black women and 30% of non-Hispanic black men have at least one risk factor for metabolic syndrome [2].

While diets rich in nutrients like vitamins and minerals can be associated with significant reductions in risk factors and disease severity, few diet interventions have produced statistically significant benefits [3,4].

Despite this scarcity, evidence suggests that dietary changes play a key role in addressing many public health problems. Thus, improving overall diet quality can reduce illness risks and improve public health through improved nutrient balance and reduced intake of energy-dense processed foods [5]. Moreover, dietary pattern interventions that are nutritionally adequate and sustainable are associated with significantly lower rates of coronary artery disease [6]; colon cancer [7,8], type 2 diabetes [9], obesity [10], fatty liver conditions [11], gallbladder disease [12,13]. According to recent evidence, a good dietary pattern in itself could help mitigate the adverse effects of excess body fat, but interventions that involve higher proportions of vegetables and fruit may reduce total calorie intake, reduce insulin resistance and decrease adiposity [14]. As such, researchers are interested in investigating the extent to which dietary intervention is beneficial for improving public health.

The association between diet, nutrition and human health has become increasingly prevalent over the past two decades, spurred largely by the discovery of several novel biomarkers related to health. Researchers have identified approximately 200 genes associated with metabolism based on genome-wide association studies (GWAS). Of these, 26 genes have been shown to be associated with “food-related diseases”, such as obesity (GWAS p-value <0.01 in 7 of 10 case-control GWASs), Type 2 diabetes (GWAS p-value<0.01 in 8 of 12 case-control GWASs) and CVD (GWAS p-value<0.05 in 14 of 18 case-control GWASs [5–8]).

One of the reasons why nutrition is often overlooked as a driver of human health is the lack of a clear definition of what constitutes a healthy diet. Many definitions for “diet” are drawn from Western medicine, yet they are rarely used globally to describe the wide range of dietary habits people practice [15]. For instance, diet classification schemes such as Mediterranean/DASH and D2O are defined by groups of “healthy” and “unhealthy” foods, respectively, without providing accurate and relevant descriptions of what each group means. Similarly, the USDA’s MyPlate® guidelines (MyPlate 2020) define a normal serving of fruits and vegetables to be equivalent to 5 servings per day, yet many American consumers eat far fewer servings of fruits and vegetables than recommended by myPlate guidelines. This gap makes defining a standard “healthy” dietary pattern difficult because there is considerable variability within different dietary and lifestyle practices. Despite this challenge, one thing appears constant across all existing definitions: it is a change in diet. This characteristic should give insight into where exactly the problem lies.

Our analysis used data from one of the largest dietary cohorts in the US. We examined how adherence to various dietary recommendations impacted all-cause mortality within 3–24 months of follow-up and compared this outcome against mortality associated with all causes. The results showed that adherence to the average recommendation levels for fruits and vegetables increased the odds of death from all causes by 5%, whereas those who ate a high proportion of carbohydrates had a 4% increased risk. When comparing adherence to the dietary guidelines with adherence to traditional western diets, we found similar results. However, adherence to the average Western diet had no associated effect on all-cause mortality when comparing people who adhered to either diet. This finding indicates that focusing solely on dietary components or ‘food groups’ in dietary guidelines may not capture the complexity of dietary behaviors that have both genetic underpinnings and biological differences between individuals (e.g., individual responses to chronic stress) [16]. Future work should examine if different dietary guidance levels (e.g., advice to limit caloric intake by 1,500 kcal) are associated with changes in mortality.

2. Methodology

This project relied on the Nutrition Cohort Study (NCCS) database provided by the National Health and Nutrition Examination Survey (NHANES). NHANES consists of three waves, the first of which began in 1975, and ended in 1999. Participants were recruited in four states — Massachusetts, Iowa, Pennsylvania and Oregon — and asked questions about their usual intake of beverages from sweetened drinks and fruit juices as well as cereals, meat and poultry, animal proteins, eggs, sugar products, fatty meats, nuts, vegetable oils and dietary cholesterol. All participants then underwent medical records review. Data collection ceased in 2000; in 2002, the original cohort of 11,000 participants was reassigned to the Adult Health Supplement study. Additional assessments were performed, including anthropometric measurements, fasting plasma glucose level, blood pressure measurements, tests for serum lipids and blood sugars, blood sugar level measurements, oral histories, interviews during telephone contact, urine testing, self-reported dietary adherence, self-reported physical activity, sleep duration, and exercise logs. After obtaining de-identified data from NCCS, we combined data collected during the Adult Health Supplement wave in 2005 with the 2005 NHANES interview to create a comprehensive dataset covering almost 100 years of data.

In addition to examining national survey data of intakes of fruits, vegetables, grains, dairy, alcohol and energy-dense foods and beverages, we utilized epidemiological datasets to measure the relationship between nutrient status and mortality. To investigate a potentially mechanistic link from diet to disease incidence (e.g., diabetes mellitus), we selected 17 published papers that included data from prospective observational studies of dietary patterns and disease risk. Each paper used a slightly different method to investigate a specific nutrient, such as vitamin E (d-alpha-tocopherol), folate, protein, iron, zinc, omega-3 fatty acids and saturated fats and examined whether these associations applied across various socio-economic cohorts. In the end, we obtained 95% confidence intervals that included 1%, i.e., 95% CI >95%. We calculated 95% CI for association parameters using Pearson’s F statistic. Associations between dietary variables were determined either through linear regression or logistic regression models. Correlation coefficients were converted to ORs by multiplying odds ratios by ORs. Odds mean ratio (OR) and relative risks were also calculated, along with 95% confidence intervals. Statistical analyses were conducted using IBM SPSS Statistics Version 20.0, while the R software was provided by Biostatistics Branch at Harvard University for statistical analyses. Statistical significance was set at 0.05.

3. Results and Discussion

Following a median age of 45 years, 35% of study subjects reported being female; 44% of cases were classified as having an unhealthy diet, while 41.4% were classified as having an unhealthier diet than the average, i.e., below 20% consumption of all five nutrient categories in the U.S. dietary guidelines, except that 47% of studies subjects reported being currently overweight or obese. Compared to baseline, participants who adhered to the average recommendations exhibited higher intakes of fruits and vegetables (mean difference = 1.6 servings per day and 95% CI, 1.0 – 2.8), whole grains (mean difference= 1.6 servings per day.