Evidence-Based Nutritional Counseling in the Primary Care Setting

March 15, 2018

By Oscar E. Dimant

Peer Reviewed

Nutritional counseling is an integral part of helping patients live healthier lives, as research demonstrates the ability of proper nutrition to prevent disease and even treat and reverse chronic disease. This article provides an overview of evidence-based nutrition and clinical tips for counseling adult patients in a primary care setting.

It is useful to discuss nutrition in terms of specific foods and food groups, rather than macronutrients. For example, carbohydrates in the form of whole grains are extraordinarily healthful, but they are harmful when highly processed, so the term “carbohydrate” can be misleading.

Meats: Red meats are mammalian muscle meats, such as beef, pork, lamb, veal, and goat. Processed meats are those that have undergone a preservation process including salting, curing, smoking, or the addition of preservatives; examples include hot dogs, ham, pepperoni, deli meats, bacon, and sausage. In 2015 the World Health Organization classified processed meat as a Group 1 Carcinogen (the strongest level of evidence available), finding that processed meat causes colorectal cancer in a dose-response relationship. They classified unprocessed red meat as probably carcinogenic to humans (Group 2A level of evidence), since it is linked to colorectal, pancreatic, and prostate cancer, but without demonstration of causality. The mechanisms are still under investigation, but we know that processing and even just cooking red meat can produce carcinogens, and heme iron in the gastrointestinal tract mediates formation of carcinogenic chemicals and lipid oxidation products. 1,13

Poultry, fish, eggs, and dairy: There is mixed evidence on their healthfulness, but vegetarian diets without these foods have consistently demonstrated health benefits, including improved glycemic control, lipid profile, and weight loss, as well as a decreased risk of ischemic heart disease and cancer; 2,3 similar effects have held up in randomized clinical trials. 2,4

Grains: Whole grains such as oats, whole wheat, brown rice, and barley support healthy weight, cardiovascular health, and improved glycemic control and insulin homeostasis in healthy controls and patients with type 2 diabetes, while refined grains contribute to the risk of chronic disease. 5,6,7 Three servings of whole grains a day has also been demonstrated to decrease the risk of colorectal cancer by 17% and total cancer mortality by 15%. 14,15

Legumes: Beans, lentils, and peas are valuable sources of fiber and protein. Legumes have been shown to be the most important food group predictor of survival among older adults of different ethnicities, with a 7-8% reduction in mortality hazard for every 20-gram increase in legume intake. 17

Fruits and vegetables: These have been shown to support health in myriad ways and decrease the risk of many chronic diseases, including hypertension, coronary artery disease, and stroke, and are associated with a reduced risk of cancer and all-cause mortality.2,3,9,18

Nuts and seeds: These are valuable sources of protein and unsaturated fat, and have been shown to protect cardiovascular health and improve insulin homeostasis.2 Certain nuts and seeds, including flaxseed, walnuts, chia seeds, and hemp seeds are also excellent sources of omega-3 fatty acids. Nuts have demonstrated mortality benefits in a dose-response relationship, lowering all-cause mortality and mortality related to cancer, diabetes, cardiovascular, respiratory, and neurodegenerative diseases. Interestingly, although peanuts have been shown to decrease mortality, peanut butter does not demonstrate this effect. This may be due to the addition of trans-fats to many commercial peanut butter preparations. 16

Sugar: Added sugars contribute to the risk of chronic disease and should be limited or avoided. However, sugars found in whole produce are not of concern. Fruits are associated with a decreased risk of developing type 2 diabetes and a lower risk of death and major vascular complications in diabetic patients. It is important to emphasize that these benefits apply to whole fruits, while fruit juice actually carries increased health risks. 19,20

It is difficult to overeat with a whole-foods, plant-based diet because fiber, protein, and unsaturated fat work together to increase satiety. Fiber (found only in plants) decreases the calorie density of foods and fosters healthy gut bacterial patterns, both of which promote a healthy body weight.21,22 This aspect of dietary change can help motivate patients: rather than counting calories and restricting food, patients can eat until they are satisfied.2 Research demonstrates that vegan/vegetarian diets are often acceptable to and sustainable for patients, , and the internet is full of recipes (https://www.forksoverknives.com/recipes/, http://allrecipes.com/recipes/1988/everyday-cooking/vegetarian, www.vegweb.com) that can help patients cook with familiar tastes and try new styles.

In a balanced, plant-based diet, patients can expect to meet almost all of their nutritional requirements. Vitamin B12 is an exception: since it is made by bacteria and consumed through some animal products, vegans and vegetarians should use a supplement. Additionally, attention should be paid to calcium, vitamin D, iodine, and omega 3 fatty acids. A more in-depth discussion to help allay fears and plan a healthful diet can be found in the article Position of the Academy of Nutrition and Dietetics: Vegetarian Diets.23

When discussing nutrition, first assess the patient’s current dietary habits (for example, with a 24-hour dietary recall) and state of knowledge, provide education, ask the patient what changes they want to start, and support the goals and speed of change that the patient chooses. Food plays many roles in people’s lives and choosing what to eat is an emotional and social choice at least as much as it is a logical one. Plant-Based Diets: A Physician’s Guide provides a helpful guide for initiating and maintaining a dialogue with patients. 12

Multiple sources of support are available, including counseling with a registered dietitian, community cooking classes, online guides (eg https://share.kaiserpermanente.org/wp-content/uploads/2015/10/The-Plant-Based-Diet-booklet.pdf ), and even a free 21-day plant-based kickstart service ( http://www.pcrm.org/health/diets/kickstart/kickstart-programs) that emails patients tips and recipes (available in English, Spanish, and Chinese). Patients concerned about cost may benefit from becoming familiar with the variety of stores in their neighborhood, batch cooking and eating more at home, buying frozen fruits and vegetables, using local farmers’ markets, and buying in bulk, especially legumes, whole grains, and root vegetables. A good review of how to eat plant-based on a budget can be found at http://nutritionstudies.org/plant-based-on-a-budget/. Patients in New York City who receive SNAP benefits have access to HealthBucks, which provides $2 to spend on produce for every $5 spent at farmers markets using SNAP/EBT. Patients outside of New York can inquire about what programs may be available and clinicians can inquire as to how we can help create programs.

Finally, it is important to remember and remind patients that lasting change often happens slowly, and the foundation of sustainable health behavior change is the clinician-patient relationship and the willingness to continue talking about and making attempts toward change.


Oscar E. Dimant is a 3rd year medical student at NYU School of Medicine

Reviewed by Michelle McMacken, MD, Medicine, NYU Langone Health

Image courtesy of Wikimedia


1. Domingo JL, Nadal M. Carcinogenicity of consumption of red meat and processed meat: a review of scientific news since the IARC decision. Food Chem Toxicol. 2017;105:256-261. doi:10.1016/j.fct.2017.04.028 https://www.ncbi.nlm.nih.gov/pubmed/28450127

2. McMacken M, Shah S. A plant-based diet for the prevention and treatment of type 2 diabetes. J Geriatr Cardiol. 2017;14(5):342–354. doi:10.11909/j.issn.1671-5411.2017.05.009 https://www.ncbi.nlm.nih.gov/pubmed/28630614

3. Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr. 2017;57(17):3640-3649. doi:10.1080/10408398.2016.1138447

4. Barnard ND, Katcher HI, Jenkins DJ, Cohen J, Turner-McGrievy G. Vegetarian and vegan diets in type 2 diabetes management. Nutr Rev. 2009;67(5):255-263. doi:10.1111/j.1753-4887.2009.00198.x

5. Ye EQ, Chacko SA, Chou EL, Kugizaki M, Liu S. Greater whole-grain intake is associated with lower risk of type 2 diabetes, cardiovascular disease, and weight gain. J Nutr. 2012;142(7):1304-1313. doi:10.3945/jn.111.155325  https://www.ncbi.nlm.nih.gov/pubmed/22649266

6. Marventano S, Vetrani C, Vitale M, Godos G, Riccardi G, Grosso G. Whole grain intake and glycaemic control in healthy subjects: a systematic review and meta-analysis of randomized controlled trials. Nutrients. 2017;9(7). pii:E769. doi:10.3390/nu9070769

7. Venn BJ, Mann JI. Cereal grains, legumes and diabetes. Eur J Clin Nutr. 2004;58(11):1443-1461. doi:10.1038/sj.ejcn.1601995

8. Ros E, Hu FB. Consumption of plant seeds and cardiovascular health: epidemiologic and clinical trial evidence. Circulation. 2013;128(5): 553-565. doi:10.1161/CIRCULATIONAHA.112.001119

9. Boeing H, Bechthold A, Bub A, et al. Critical review: vegetables and fruit in the prevention of chronic diseases. Eur J Nutr. 2012;51(6):637–663. doi:10.1007/s00394-012-0380-y

10. Barnard ND, Gloede L, Cohen J, et al. A low-fat vegan diet elicits greater macronutrient changes, but is comparable in adherence and acceptability, compared with a more conventional diabetes diet among individuals with type 2 diabetes. J Am Diet Assoc.  2009;109(2): 263-272. doi:10.1016/j.jada.2008.10.049

11. Barnard ND, Scialli AR, Turner-McGrievy G, Lanou AJ. Acceptability of a low-fat vegan diet compares favorably to a step II diet in a randomized, controlled trial. J Cardiopulm Rehabil. 2004;24(4):229-235.

12. Hever J. Plant-based diets: a physician’s guide. Perm J. 2016;20(3):93–101. doi:10.7812/TPP/15-082 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991921/

13. Bouvard V, Loomis D, Guyton KZ, et al. Carcinogenicity of consumption of red meat and processed meat. Lancet Oncol. 2015;16(16):1599-1600. doi:10.1016/S1470-2045(15)00444-1

14. World Cancer Research Fund International/American Institute for Cancer Research. Continuous update project report: diet, nutrition, physical activity and colorectal cancer. wcrf.org/colorectal-cancer-2017. Published 2017. Accessed August 24, 2017. https://www.wcrf.org/int/research-we-fund/continuous-update-project-cup

15. Aune D, Keum N, Giovannucci E, et al. Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies. BMJ. 2016;353:i2716. doi:10.1136/bmj.i2716

16. van den Brandt PA, Schouten LJ. Relationship of tree nut, peanut and peanut butter intake with total and cause-specific mortality: a cohort study and meta-analysis. Int J Epidemiol. 2015;44(3):1038-1049. doi:10.1093/ije/dyv039  https://www.ncbi.nlm.nih.gov/pubmed/26066329

17. Darmadi-Blackberry I, Wahlgvist ML, Kouris-Blazos A, et al. Legumes: the most important dietary predictor of survival in older people of different ethnicities. Asia Pac J Clin Nutr. 2004;13(2):217-220.

18. Aune D, Giovannucci E, Boffetta P, et al. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol. 2017;46(3):1029-1056. doi:10.1093/ije/dyw319

19. Du H, Li L, Bennett D, et al. Fresh fruit consumption in relation to incident diabetes and diabetic vascular complications: A 7-y prospective study of 0.5 million Chinese adults. PLoS Med. 2017;14(4):e1002279. doi:10.1371/journal.pmed.1002279 http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002279

20. Muraki I, Imamura F, Manson JE, et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ. 2013;347:f5001. doi:10.1136/bmj.f5001

21. Kim MS, Hwang SS, Park EJ, Bae JW. Strict vegetarian diet improves the risk factors associated with metabolic diseases by modulating gut microbiota and reducing intestinal inflammation. Environ Microbiol Rep. 2013;5(5):765-775. doi:10.1111/1758-2229.12079

22. Glick-Bauer M, Yeh MC. The health advantage of a vegan diet: exploring the gut microbiota connection. Nutrients. 2014;6(11):4822-4838. doi:10.3390/nu6114822

23. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016;116(12):1970-1980. doi:10.1016/j.jand.2016.09.025 https://www.ncbi.nlm.nih.gov/pubmed/27886704