Vegetarian Nutrition

VN: Types and Diversity of Vegetarian Diets (2009)

Citation:

Dwyer J. Convergence of plant-rich and plant-only diets. Am J Clin Nutr. 1999 Sep; 70(3 Suppl): 620S-622S.

PubMed ID: 10479241
 
Study Design:
Narrative Review
Class:
R - Click here for explanation of classification scheme.
Quality Rating:
Negative NEGATIVE: See Quality Criteria Checklist below.
Research Purpose:

This is a summary of a six-member panel discussion held at the Third International Congress on Vegetarian Nutrition. The discussants considered the safety, efficacy, advantages and disadvantages of plant-based and plant-only dietary patterns, and whether scientific opinions on these two patterns was converging.

Panelists considered the nutritional adequacy, benefits and health outcomes of plant-only (vegan and fruitarian), plant-based (e.g., macrobiotic, ovolactovegetarian, semi-vegetarian and meatless) and omnivorous dietary patterns.

Inclusion Criteria:

Knowledge and opinions stated by the six panel members: Susan Havala, Timothy Key, Lawrence Kushi, David Nieman, Walter Willett and chair, Johanna Dwyer.

Exclusion Criteria:

Not stated.

Description of Study Protocol:

Review article did not identify the studies the panelists used for drawing their conclusions. 

Panelists were said to have considered the nutritional adequacy, benefits and health outcomes of plant-only (vegan and fruitarian), plant-based (macrobiotic, ovolactovegetarian, semi-vegetarian and meatless) and omnivorous dietary patterns.

Data Collection Summary:

Perspectives on various eating patterns were given by panelists

  • Plant-only diets/vegan
  • Macrobiotic
  • Ovolactovegetarian
  • Omnivorous
  • Audience perspective.
Description of Actual Data Sample:

Not stated.

Summary of Results:

Convergence between essential nutrient profiles due to

  • Increased availability of a variety of plant foods
  • Advent of nutrient-fortified plant foods
  • Use of vitamin and mineral supplements
  • Widespread dissemination of sound information on plant-only, plant-rich and plant-based dietary patterns.

Special attention should be paid to nutrition among vulnerable groups by age or physiologic status if consuming plant-only diets.

 

Research has shown that plant-only and plant-based diets have health benefits, most notably reduction of chronic degenerative diseases.

 

Perspectives on various eating patterns were given by panelists:

 

Plant-only diets/vegan

 

  • Well-planned vegan diets can fulfill nutrient needs if supplements are included
  • Increased importance for vegans to make wise food choices
  • Resources are needed for credible information about vegetarian diets
  • Need to increase efforts to disseminate information via mass media to influence changes in national attitudes and personal food choices based more on scientific considerations
  • A national trend toward plant-based rather than plant-only diets
  • Need for more research with larger numbers of subjects, especially on vegan diets and children, vegetarian and semi-vegetarian diets and health in highly industrialized countries.

Macrobiotic  

 

  • The principle of macrobiotic diets is that foods biologically distant from humans are better and are the basis of the diet
  • Bias in scientific literature: studies with negative findings used the word macrobiotic in the title, whereas if the findings were positive, the word vegetarian was used
  • In the past, rickets and vitamin B12 and other deficiencies existed in children fed macrobiotic diets, but this is no longer the case due to changes in infant feeding practices
  • Macrobiotic diets are associated with decreased blood cholesterol and blood pressure and possible association with lower cancer risk. 

Ovolactovegetarian  

 

  • Adventist Health Study cited among others showing long-term ovolactovegetarians who adhered to their diets for decades weighed less, had lower total serum cholesterol and blood glucose concentrations and had lower blood pressure than did non-vegetarians
  • Increased consumption of fruits, vegetables and dietary fiber seem to be associated with lower rates of coronary artery disease and stroke, even in those who consumed animal foods
  • Evidence cited that ovolactovegetarians have lower prevalence rates of ischemic heart disease, type 2 diabetes, obesity, hypertension, dyslipidemia and some forms of cancer
  • Vegetarian diet is only part of a healthful lifestyle including physical activity
  • Need for those following vegan diets to guard against dietary inadequacies through careful planning
  • Importance of eating whole grains rather than highly processed or refined foods
  • Unsupplemented whole-food diets based on plants are not appropriate because they are devoid of vitamin B12, which is a special problem for pregnant vegans unless supplemented
  • Plant-only diets tend to be low in calcium, vitamin D and iron.

Omnivorous 

 

  • Greek and Japanese plant-based omnivorous eating patterns seem to offer advantages over other patterns
  • Research is needed to decipher what dietary components are responsible for beneficial effects in both vegetarian and omnivorous dietary patterns. 

Audience perspective 

 

  • Concerns about how genetic alterations in the plant-food supply would affect health 
  • An unresolved issue about whether it was better to add phytochemicals to milk or vitamin B12 to soy food 
  • The National Academy of Sciences was a source cited for how much meat semi-vegetarians should eat for optimal health
  • Increased physical activity among vegetarians was encouraged.
Author Conclusion:

The panel concluded that the evidence for a convergence of scientific opinion on the safety and healthfulness of plant-only diets that are appropriately planned to meet all nutritional requirements is considerable as compared with plant-based diets.

 

Dietary guidance systems including the Dietary Guidelines for Americans and the US Department of Agriculture’s Food Guide Pyramid are examples of recommendations that incorporate plant-based and plant-only options. 

 

The author stated that the growing convergence of fact and opinion that plant-only diets are as healthful or more healthful than plant-based diets is a paradigm shift. Two areas were noted as causing this shift: recognition by scientists that essential nutrients can be added to plant-food diets so that essential nutrient profiles are met, and the recognition that diet affects chronic degenerative disease risk and that many chemicals other than nutrients in foods are important to health. 

In addition to health considerations, societal values regarding food taste preferences, ethical, religious and moral considerations are also determinants of the choices made. Dietary diversity shows that there are many healthful ways to eat.

Funding Source:
Government: USDA
Reviewer Comments:

The author and panel chair, Joanna Dwyer, D.Sc., R.D., has impressive credentials and experience from her association with prestigious government, educational institutions and professional organizations.

It was not stated how the six panelists were selected, nor did it state their credentials or qualifications for inclusion on the panel.

Article does not provide definitions of what is included in the diets discussed, nor does it list specific foods.

Under the section on ovolactovegetarian perspectives, eggs where not mentioned, which are part of this diet. The panelist Sujatha Rajaram’s comments were more applicable to the vegan perspective section than the ovolactovegetarian section.

Quality Criteria Checklist: Review Articles
Relevance Questions
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  1. Will the answer if true, have a direct bearing on the health of patients? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  2. Is the outcome or topic something that patients/clients/population groups would care about? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  3. Is the problem addressed in the review one that is relevant to dietetics practice? Yes
  4. Will the information, if true, require a change in practice? Yes
  4. Will the information, if true, require a change in practice? Yes
 
Validity Questions
  1. Was the question for the review clearly focused and appropriate? Yes
  1. Was the question for the review clearly focused and appropriate? Yes
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? No
  2. Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? No
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? No
  3. Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? No
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? No
  4. Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? No
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? No
  5. Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? No
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? No
  6. Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? No
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? No
  7. Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? No
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  8. Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? Yes
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? No
  9. Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? No
  10. Was bias due to the review's funding or sponsorship unlikely? No
  10. Was bias due to the review's funding or sponsorship unlikely? No