When people talk about the benefits of plant-based diets for athletes, the focus is often on recovery. Of course, recovery is extremely important; this is the time when the body is adapting, repairing, and growing. But what about the proven benefits during performance?
The key to this is good blood circulation.
But before we explore the mechanisms behind this, and how to improve yours, let’s take a look at why good circulation is so important to athletes.
What is circulation?
Your circulation is everything that makes your blood, well… circulate. Thanks to the non-stop work of your heart, blood is pumped around your body through your arteries and capillaries, then back to your heart again through your veins.
During this process, your blood picks up oxygen in your lungs, and nutrients from your gut, which it then transports throughout your body. At the same time, it conveniently picks up and takes away waste products. For example, it transports carbon dioxide back to the lungs, where it’s expelled as we breathe.
How can circulation affect performance?
Good circulation is vital to your health. Clearly, getting oxygen to – and removing waste products from – vital organs like your brain, liver, kidneys, and the heart itself, is critical for our survival. But for athletes, improved circulation is especially important because it can have a direct effect on performance (1), (2).
That’s because oxygen-rich blood can be delivered more easily to the muscles when they need it most – during exercise – it can help the muscles use ATP (adenosine triphosphate – the energy currency of our cells) more efficiently.
A healthy circulatory system can also reduce blood pressure during exercise, which can decrease the workload of the heart. These effects can in turn help to improve exercise efficiency, delay the onset of fatigue, and increase your exercise capacity.
How do plant-based diets affect circulation?
Let’s start by looking at the blood itself. If you think of your blood as liquid within a plumbing network, then you can imagine that thinner, more fluid liquid will flow through the piping system much more quickly and efficiently than thicker, viscous liquid would. And plant-based diets have been shown to significantly improve the fluidity of the blood (a measure known as ‘blood rheology’) within just six weeks of adopting plant-based diet (3).
The reasons behind this are complex but are mostly due to the typically increased antioxidant intake and lower saturated fat intake of plant-based diets (4). However the biological mechanisms work, the result is blood that can flow through your capillaries more efficiently and transport and deliver oxygen to your muscles more easily during exercise (5).
Continuing with the plumbing analogy, another effective way of improving the flow of liquid is to enhance the piping system itself. Within the body, this can be achieved by improving vascular function. This refers to the control of blood flow, which is usually regulated by a balance between vasoconstriction (narrowing of blood vessels) and vasodilation (relaxation and widening of blood vessels).
During exercise, vasodilator signals fire up in the active muscle tissue, which helps to widen the blood vessels in the muscle, to increase blood flow and oxygen supply. Dietary nitrates and nitrites, rich in many plant foods, can help to improve this vascular function. How? Within the body, they get turned into nitric oxide, which signals to the smooth muscle surrounding blood vessels to relax, therefore increasing blood flow (6).
How to optimise these effects
Good news if you’re on a plant-based diet – the likelihood is that you’ll already have higher intakes of antioxidant-rich plant foods and nitrate-rich vegetables (7). You’ll also probably have a lower intake of saturated fat because the main dietary sources are meat, dairy, and eggs. But remember that exotic oils like coconut and palm oils are also high in saturated fat, so it’s a good idea to try and limit these.
You could look to boost your antioxidant intake even further – brightly coloured foods tend to be excellent sources. Think orange, purple, red, and dark green vegetables, a variety of different fruits, berries, herbs, spices, legumes, and wholegrains.
The foods highest in nitrates include celery, cress, chervil, lettuce, beetroot, spinach, and rocket (8). Fennel, leek, parsley, celeriac, and Chinese cabbage are also great sources. Interestingly, as well as the long-term performance benefits of regular nitrate intake, boosting intake shortly before exercise has a more immediate performance-enhancing effect too (9).
A registered plant-based sports nutritionist, TJ Waterfall works with elite vegan athletes including Premier League footballers, Premiership rugby players, ultra-distance triathletes and Team GB Olympians. TJ's book, The Plant-Based Power Plan, is designed to provide you with all the evidence-based tips, advice and strategies he uses with elite sportspeople to help you thrive.
(1) Al-Dashti, Yousef & Holt, Roberta & Stebbins, Charles & Keen, Carl & Hackman, Robert. (2018). Dietary Flavanols: A Review of Select Effects on Vascular Function, Blood Pressure, and Exercise Performance. Journal of the American College of Nutrition. 37. 1-15.
(2) Poole, D., Behnke, B., & Musch, T. (2020). The role of vascular function on exercise capacity in health and disease. The Journal of Physiology, The Journal of physiology, 24 January 2020.
(3) Naghedi-Baghdar, H., Nazari, S., Taghipour, A., Nematy, M., Shokri, S., Mehri, M., . . . Javan, R. (2018). Effect of diet on blood viscosity in healthy humans: A systematic review. Electronic Physician, 10(3), 6563-6570.
(4) Ernst E, Franz A. Blood fluidity score during vegetarian and hypocaloric diets - a pilot study. Complementary Therapies in Medicine. 1995; 3(2): 70-1. doi: 10.1016/S0965-2299(95)80002-6.
(5) Smith, M., Lucas, A., Hamlin, R., & Devor, S. (2015). Associations among hemorheological factors and maximal oxygen consumption. Is there a role for blood viscosity in explaining athletic performance? Clinical Hemorheology and Microcirculation, 60(4), 347-362.
(6) Jonvik, Kristin & Nyakayiru, Jean & van Dijk, Jan-Willem & Wardenaar, Floris & Loon, Luc & Verdijk, Lex. (2016). Habitual Dietary Nitrate Intake in Highly Trained Athletes. International Journal of Sport Nutrition and Exercise Metabolism. 27. 1-25. 10.1123/ijsnem.2016-0239.
(7) Parker, H., & Vadiveloo, M. (2019). Diet quality of vegetarian diets compared with nonvegetarian diets: A systematic review. Nutrition Reviews, 77(3), 144-160.
(8) Norman G Hord, Yaoping Tang, Nathan S Bryan, Food sources of nitrates and nitrites: the physiologic context for potential health benefits, The American Journal of Clinical Nutrition, Volume 90, Issue 1, July 2009, Pages 1–10
(9) Raúl Domínguez, Eduardo Cuenca, José Luis Maté-Muñoz, Pablo García-Fernández, Noemí Serra-Paya, María Carmen Lozano Estevan, . . . Manuel Vicente Garnacho-Castaño. (2017). Effects of Beetroot Juice Supplementation on Cardiorespiratory Endurance in Athletes. A Systematic Review. Nutrients, 9(1), 43.