Plant Protein & Health

By Hillary Siah, Accredited Practising Dietitian

Legumes are often an overlooked source of protein if you don’t follow a vegetarian or vegan diet, as most of us associate protein with a juicy steak, chicken breast or eggs. But that may be about to change as people become aware that legumes such as chickpeas, lentils, beans and peas are also a source of protein.

Not only are legumes higher in protein than most other plant-based foods, they are also an economical and environmentally friendly source of protein. If we all got more of our protein from plant-based sources such as beans and lentils it has been suggested that we would not only help improve the sustainability of the agricultural system but we’d also improve our health(1, 2).

The latest science on plant protein

Current research on the specific effect of plant protein on health and chronic disease risk is limited. However, a recently published study, the largest to date, investigated the link between plant protein intake and risk of early death. The study took data from from cohorts of over 131,000 US adults for 32 years and looked at the relationship between consumption of animal and plant proteins and the risk of early death(3). Whilst this is the first large long-term study to look at the influence of plant protein intake on risk of death, the independent effect of specific dietary sources of plant protein was not assessed. However, adults who consumed more plant protein (>6% of total energy) had a higher intake of fruit, vegetables, legumes, whole grains and nuts compared to those with lower intakes (≤3% total energy).

Previous research has promoted the benefits of a predominately plant-based diet for health and longevity(4, 5). Interestingly, while this study did find that higher plant protein intake was protective against risk of early death, this effect was only observed in individuals with at least one ‘unhealthy’ lifestyle risk factor including smoking, heavy alcohol intake, being physically inactive or being overweight or obese. This may seem limited, but the findings suggest that a higher plant protein intake may be beneficial for the 63% of Australian adults who are currently classified as overweight or obese(6).

The good news is that even a small change in plant protein consumption may have a big impact on health. Increasing plant protein intake by as little as 3% per day was found to reduce the risk of death from all causes by 10%, with similar protective effect observed for risk of death from cardiovascular disease. This association was strongest when sources of plant protein such as legumes were swapped with processed meats.

This research adds to a growing body of evidence that highlights the protective effect that foods high in plant protein can have on health(7). A recent meta-analysis showed that higher intakes of plant protein were associated with lower risk of Type 2 Diabetes(8) and in a study that followed over 29,000 post-menopausal women for 15 years, substituting plant protein for animal protein reduced the risk of death from coronary heart disease(9).

Sources of plant protein such as legumes and whole grains are packed with other health promoting nutrients such as fibre(10) and important vitamins and minerals, as well as being low in saturated fat which may in part contribute the protective effect of foods rich in plant protein.

So, what does this mean for us?

Legumes are a source of protein that should be enjoyed by everyone - vegetarians and meat-eaters alike. Legumes are nutritious, affordable and versatile and should form part of a healthy diet for all Australians, whether you’re bulking for summer or looking forward to a healthy retirement.
Based on the evidence of health benefits, GLNC recommends that all Australians enjoy legumes at least 2-3 times per week. This is simpler than you may think and can be as easy as tossing kidney beans into your spaghetti bolognese, adding chickpeas to your curry or starting the day with baked beans on toast. One great way to increase your plant protein intake is to add legumes to meals that contain grains(11)to amp up the nutritional factor even more.  For a whole host of tasty legume and grain based recipes, visit the GLNC website.

References
1. Saunders AV. Busting the myths about vegetarian and vegan diets. Journal of HEIA. 2014;21(1):2-13.
2. Position of the American Dietetic Association: Vegetarian Diets. Journal of the American Dietetic Association. 2009:1266-82.
3. Minyang Song TF, Frank Hu, Walter Willet, Valter Longo, Andrew Chang, Deward Giovannucci. Association of Animal and Plant Protein Intake With All-Cause and Cause-Sepcific Mortality. JAMA Internal Medicine. 2016.
4. Darmadi-Blackberry I, Wahlqvist ML, Kouris-Blazos A, Steen B, Lukito W, Horie Y, et al. Legumes: the most important dietary predictor of survival in older people of different ethnicities. Asia Pacific journal of clinical nutrition. 2004;13(2):217-20.
5. Kouris-Blazos A, Belsi R. Health benefits of legumes and pulses with a focus on Australian sweet lupins. Asia Pacific journal of clinical nutrition. 2016;25.
6. ABS. Australian Health Survey: First Results. 2011-12.
7. Medina-RemÓn A, Kirwan R, Lamuela-Raventós RM, Estruch R. Dietary Patterns and the Risk of Obesity, Type 2 Diabetes Mellitus, Cardiovascular Diseases, Asthma, and Mental Health Problems. Critical reviews in food science and nutrition. 2016:00-.
8. XW Shang DS, AM Hodge, DR English et al. Dietary protein intake and risk of Type 2 Diabetes: results from the Melbourne Collaborateive Cohort Studies and a meta-analysis of prospective studies. The American Journal of Clinical Nutrition. 2016;104(3).
9. Kelemen LE KL, Jacobs DR Jr, Cerhan JR. Associations of dietary protein with disease and mortality in a prospective study of postmenopausal women. American Journal of of Epidemiology. 2005;2005(161):3.
10. Kate Marsh JB-M. Vegetarian Diets and Diabetes. American Journal of Lifestyle Medicine. 2011;6(2):135-43.
11. Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. The American journal of clinical nutrition. 1994;59(5):1203S-12S.