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What are the health benefits of eating plant-based?
Before answering this question, I want to address two points. First, keep in mind that there isn’t one way to eat a plant-based diet; the nutrient profile of someone eating mostly unprocessed fruits, vegetables, whole grains, and legumes will look very different compared to someone eating cereal, pasta, takeout, and vegan Ben and Jerry’s. Second, despite eating very distinct diets, vegetarians and vegans are often grouped in the same category in nutrition research, making it more challenging to draw conclusions.
Nonetheless, a growing body of literature shows that compared to omnivores, vegans and vegetarians have less obesity and lower rates of both cardiovascular disease and type 2 diabetes (1). The health benefits of eating plant-based may be even greater among vegans who have been found to have the lowest rates of obesity (2), hypertension (3), and cancer (1) compared to any other dietary group.
Can you really get enough protein from plants?
Yes, 100%.
The adult Recommended Dietary Allowance for protein is 0.8 g/kg/day* based on the results of nitrogen balance studies (4). Protein needs may be slightly higher (by ~10%) among those following a plant-based diet given that plant protein is slightly less absorbed. As such, I err on the side of caution and recommend vegans aim for an intake of 1 g of protein per kg per day, which is around 60-65 g for females and around 75-80 g for males.
Plant-based sources of protein:
*Protein and amino acid requirements should be based on “ideal” not actual body weight if your weight falls into the body mass index categories of “overweight” or “obese”. An ideal body weight is your weight at a body mass index of 24.9 kg/msq. You can calculate your ideal weight using the following formula: height2 (in meters) x 24.9.
Are plant-proteins complete?
Complete proteins are those that contain all essential amino acids (the building blocks of protein) in the amount similar to human protein. Technically, the only “complete” plant protein is soy, although essential amino acids exist in all plant-foods (albeit in lower concentrations than soy). The amino acid that is the most challenging to meet on a plant-based diet is lysine and as such, is referred to as the “limiting amino acid”. Vegan sources of lysine to include daily include beans, lentils, soy, seitan, quinoa, and pumpkin seeds. Also, keep in mind that you can track lysine intake (and all essential amino acids) in Cronometer.
Should I stay away from soy?
Interest in the health benefits of soy peaked after it was noted that Asian populations have significantly lower cancer rates compared to the US. Yet, when researchers began studying the effects of phytoestrogens from soy on mice and rats, they observed an increased growth of estrogen-receptor positive cancer cells (5). However, it was later discovered that rodents are not able to metabolise soy in the way that humans do, which results in blood concentrations of soy 20x to 150x the concentration found in humans (6). Furthermore, human research has found that early intake of soy actually reduces breast cancer risk by 25-60% (7) and soy intake following breast-cancer has been shown to significantly reduce breast cancer recurrence and mortality (8).
Another area of concern is that of fertility and breast growth in men. This fear has not been supported by research with a meta analysis and systematic review failing to show an effect of soy protein or isoflavones on testosterone or other-related sex hormones (9). In addition, there is no quality evidence to suggest that that the consumption of soy leads to an increase in the growth of breast tissue in men or women.
At the end of the day, it’s worthwhile to remember that we are talking about a bean that has been consumed in Asian populations since the 11th century BC. There does not appear to be any reason to avoid this protein unless you have an allergy to soy. And for anyone following a plant-based diet, I encourage the consumption of whole-food, unprocessed soy (like tofu, tempeh, soy beans, or edamame) at least once per day, given that it is a rich source of iron, zinc, calcium, ALA, and other essential nutrients.
Stay tuned for part 2 of my series on plant-based diets where I will discuss the trending topic of antinutrients, the use of oil, and how to raise a child on a plant-based diet.
References:
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016 Dec;116(12):1970-1980. Abstract available from: http://jandonline.org/article/S2212-2672(16)31192-3/pdf
- Stahler C. How often do Americans eat vegetarian meals? And how many adults in the US are vegetarian? The Vegetarian Resource Group website. http://www. vrg.org/nutshell/Polls/2016_adults_veg. Accessed Mar 14, 2018.
- Appleby PN, Davey GK, Key TJ. Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC Oxford. Public Health Nutr. 2002;5(5):645-654. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/12372158
- Institute of Medicine. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington D.C.: The National Academies Press; 2006. Protein and Amino Acids; p 144-155.
- Getz L. Soyfoods & Cancer. Today’s Dietitian. 2013 Apr;15(4):30. Article available from: http://www.todaysdietitian.com/newarchives/040113p30.shtml
- Setchell KD, Brown NM, Zhao X, Lindley SL, Heubi JE, King EC, et al. Soy isoflavone phase II metabolism differs between rodents and humans: implications for the effect on breast cancer risk. Am J Clin Nutr. 2011 Nov;94(5):1284-94. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/21955647
- Messina M. Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature. Nutrients. 2016 Nov 24;8(12). pii: E754. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/27886135.
- Chi F., Wu R., Zeng Y.C., Xing R., Liu Y., Xu Z.G. Post-diagnosis soy food intake and breast cancer survival: A meta-analysis of cohort studies. Asian Pac. J. Cancer Prev. 2013;14:2407–2412. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/23725149
- Hamilton-Reeves JM, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina MJ. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertil Steril. 2010 Aug;94(3):997-1007. Abstract available from: https://www.ncbi.nlm.nih.gov/pubmed/19524224
