Abstract
Vegetarian dietary patterns have been reported to be associated with a number of favourable health outcomes in epidemiological studies, including the Adventist Health Study 2 (AHS-2). Such dietary patterns may vary and need further characterisation regarding foods consumed. The aims of the present study were to characterise and compare the food consumption patterns of several vegetarian and non-vegetarian diets. Dietary intake was measured using an FFQ among more than 89000 members of the AHS-2 cohort. Vegetarian dietary patterns were defined a priori, based on the absence of certain animal foods in the diet. Foods were categorised into fifty-eight minor food groups comprising seventeen major food groups. The adjusted mean consumption of each food group for the vegetarian dietary patterns was compared with that for the non-vegetarian dietary pattern. Mean consumption was found to differ significantly across the dietary patterns for all food groups. Increased consumption of many plant foods including fruits, vegetables, avocados, non-fried potatoes, whole grains, legumes, soya foods, nuts and seeds was observed among vegetarians. Conversely, reduced consumption of meats, dairy products, eggs, refined grains, added fats, sweets, snack foods and non-water beverages was observed among vegetarians. Thus, although vegetarian dietary patterns in the AHS-2 have been defined based on the absence of animal foods in the diet, they differ greatly with respect to the consumption of many other food groups. These differences in food consumption patterns may be important in helping to explain the association of vegetarian diets with several important health outcomes.
Generated Summary
This cross-sectional study examined the dietary patterns of vegetarians and non-vegetarians within the Adventist Health Study 2 (AHS-2) cohort, which included over 89,000 participants. The study aimed to characterize and compare the food consumption patterns across different vegetarian diets (vegan, lacto-ovo-vegetarian, pesco-vegetarian, semi-vegetarian) and a non-vegetarian diet. Dietary intake was assessed using a Food Frequency Questionnaire (FFQ), and food groups were categorized into major and minor food groups to analyze consumption differences. The research employed a hypothesis-driven approach, defining vegetarian diets based on the avoidance of animal products. The primary goal was to understand how these dietary patterns vary concerning food consumption, potentially explaining the association between vegetarian diets and health outcomes. Statistical analyses included the calculation of adjusted mean values for food groups, relative mean consumption, and 95% confidence intervals to compare dietary patterns.
Key Findings & Statistics
- The study analyzed data from more than 89,000 members of the AHS-2 cohort.
- Mean values were consistently higher than median values, indicating a right-skewed distribution of consumption.
- P values for all major food groups were less than 0.0001, indicating significant differences in consumption between vegetarian and non-vegetarian diets.
- The FFQ has been validated previously against six 24 h dietary recalls for intake of nutrients, with energy-adjusted de-attenuated validity correlations of 0.60 in whites and 0.52 in blacks across the fifty-one nutrients. For foods and food groups, the average de-attenuated validity correlations were 0.59 in whites and 0.43 in blacks.
- Vegans consumed less than one-third of the quantity of non-water beverages daily consumed by non-vegetarians and less than one-fifth of the amount of sweets.
- The relative mean daily consumption of citrus fruits for vegans was 1.70, lacto-ovo-vegetarians 1.28, pesco-vegetarians 1.35, and semi-vegetarians 1.20, compared to non-vegetarians.
- The consumption of meats, particularly processed meats, was quite low even among non-vegetarians (Table 2).
- The consumption of non-dairy milk (principally rice milk, as soya milk is categorised elsewhere) was highest in the vegan group, lowest in the non-vegetarian group, and intermediate in the other dietary groups.
- The mean consumption of fruits was 330.2 g in the entire sample, with a standard deviation of 292.6 g.
- The mean consumption of vegetables was 327.1 g in the entire sample, with a standard deviation of 230.8 g.
- The mean consumption of avocados was 7.0 g in the entire sample, with a standard deviation of 14.1 g.
- The mean consumption of potatoes was 38.2 g in the entire sample, with a standard deviation of 32.8 g.
- The mean consumption of grains was 296.4 g in the entire sample, with a standard deviation of 179.4 g.
- The mean consumption of legumes was 62.0 g in the entire sample, with a standard deviation of 63.0 g.
- The mean consumption of soya foods and meat analogues was 125.2 g in the entire sample, with a standard deviation of 166.0 g.
- The mean consumption of nuts and seeds was 23.6 g in the entire sample, with a standard deviation of 25.7 g.
- The mean consumption of meat was 27.9 g in the entire sample, with a standard deviation of 41.0 g.
- The mean consumption of dairy products was 146.3 g in the entire sample, with a standard deviation of 209.6 g.
- The mean consumption of eggs was 9.6 g in the entire sample, with a standard deviation of 15.9 g.
- The mean consumption of added fats was 41.3 g in the entire sample, with a standard deviation of 30.1 g.
- The mean consumption of sweets was 39.4 g in the entire sample, with a standard deviation of 53.6 g.
- The mean consumption of snack foods was 3.6 g in the entire sample, with a standard deviation of 5.9 g.
- The mean consumption of beverages was 419.7 g in the entire sample, with a standard deviation of 473.2 g.
- The mean consumption of drinking-water was 1122.9 g in the entire sample, with a standard deviation of 594.6 g.
Other Important Findings
- Vegetarian dietary patterns were defined based on the absence of animal foods in the diet but differ greatly with respect to the consumption of many other food groups.
- Increased consumption of plant foods (fruits, vegetables, avocados, non-fried potatoes, whole grains, legumes, soya foods, nuts, and seeds) was observed among vegetarians.
- Reduced consumption of meats, dairy products, eggs, refined grains, added fats, sweets, snack foods, and non-water beverages was observed among vegetarians.
- Vegans consumed the lowest amounts of eggs and dairy products, and non-vegetarians the highest amounts, with the other vegetarian groups consuming intermediate amounts.
- Vegetarians consumed lower amounts of added fats, sweets, snack foods, and non-water beverages.
- Vegetarians consumed lower amounts of fried potatoes.
- Vegetarians consumed more whole grains and mixed grains.
- Semi-vegetarians consumed less processed red meat, unprocessed red meat, processed poultry, unprocessed poultry, fatty fish, and other fish.
- Pesco-vegetarians consumed more fatty fish and other fish.
- Vegetarians consumed more tree nuts and seeds when compared with non-vegetarians, with vegans consuming notably increased amounts.
- Consumption of coconut milk was highest among pesco-vegetarians, followed by vegans and non-vegetarians, and lowest among lacto-ovo-vegetarians and semi-vegetarians.
Limitations Noted in the Document
- The study relied on self-reported dietary intake data collected through an FFQ, which may be subject to recall bias and potential inaccuracies in portion size estimation.
- The cross-sectional nature of the study limits the ability to establish causal relationships between dietary patterns and health outcomes.
- The study population consisted of Seventh-day Adventists, which may limit the generalizability of the findings to other populations.
- The study’s focus on a hypothesis-driven approach, based on animal food avoidance, may not fully capture the complexity of vegetarian dietary patterns and their potential impact on health.
Conclusion
The study underscores the diverse nature of vegetarian diets and their varied consumption of food groups. The findings demonstrate that vegetarian dietary patterns are associated with reduced consumption of animal products and increased consumption of plant-based foods. The observed differences in food consumption patterns among vegetarian and non-vegetarian diets may explain the association of vegetarian diets with favorable health outcomes. The increased consumption of plant foods, including legumes, soya foods, nuts and seeds, grains, potatoes, avocados, fruits, and vegetables, is a notable aspect of vegetarian diets. The study’s findings emphasize that vegetarian diets are not uniform but vary significantly in food choices. These differences may influence the health effects of these diets. The study provides insights into the dietary decision-making of vegetarians and may inform dietary recommendations. Increased consumption of many plant foods would be expected to result in higher intakes of a variety of phytochemicals, many of which are hypothesised to confer health benefits. Future dietary guidelines might use this information to formulate recommendations.