Your health on a plant-based diet

Is a plant based diet better or worse for us than a meat-based one? And, indeed, does it need to be an all or nothing thing: do we actually need to choose, or would a shift towards a more plant-based diet for at least some of our meals be a good compromise? Shireen Kassam is a consultant haematologist with the University of Winchester and she has an interest in the management of chronic diseases using plant-rich diets. Shireen spoke to Chris Smith in the studio, starting with what her own diet choices are...

Shireen - I eat a hundred percent plant-based diet. So other people would call that a vegan diet.

Chris - Okay. I just wanted to put that on the table - excuse the pun - because that way people kind of understand where we're coming from. Now in what ways do you believe that eating a plant-based diet is better for a person than a meat-dominated diet?

Shireen - Well the science is clear on this: the greater your shift towards a plant-based diet, minimising animal foods and processed foods, the healthier you are; and that's healthier bodyweight and significantly reduced risk of cardiovascular diseases, type II diabetes, and certain cancers. And more and more it's clear that those same risk factors are leading to dementia in later life, and if we got away from our conventional meat-based diet there would be less incidence of dementia in our society too.

Chris - So is that the case, then, that if one looks at populations such as in parts of Asia where meat-based diets are rare, that you see a correspondingly low rate of dementia, and a correspondingly low rate of things like diabetes, high blood pressure, stroke, and heart attack?

Shireen - Sure, if we look around the world where people are living the longest and the healthiest lives - and these regions in the world are called the Blue Zones - people are eating predominantly plant-based diets, 85-90% plant-based. And when scientific studies have been done looking at difference in the health outcomes for omnivores versus pescatarians, vegetarians, vegans; a stepwise reduction in the amount of animal foods you're eating, the better the health outcomes. So the science is absolutely clear on this.

Chris - But if someone says, well actually I quite like eating meat... and I mean, I'm one of them. You'd have to really twist my arm very hard at my back to dissuade me from occasionally frying up a rasher a bacon; it's just something I really enjoy doing from time to time. Would nevertheless a substitution of some plant-based food stuffs in place of a meat dish still translate into a health benefit? I don't have to go the whole hog... that's probably a bad choice of words isn't it! I don't have to go all the way in order to get some health benefit?

Shireen - No, absolutely. You don't have to be a hundred percent plant-based. But I would like to be clear that you can be perfectly healthy eating a hundred percent plant-based diet. So it comes down to a choice, a choice that we can all make, but any shift towards a plant-based diet is going to be better, as long as it's coming from healthy sources of whole plant foods, fruits, vegetables, whole grains; not the processed plant-based foods that are becoming increasingly available. And if you are going to choose your meat, I really would persuade you not to eat a processed meat like bacon, because it is a Group 1 carcinogen, it causes cancer. So make a better choice.

Chris - Whoops. Okay, well that's that off the menu then. But just coming back to the question of being healthier... because one does hear horror stories where you get people who say, "well, I'm going to turn over a new dietary leaf and I'm going to go down the plant-based diet route, I'm going to eschew meat," and then they wind up in their doctor's surgery with raging anaemia because they're not getting enough iron, and they can also get other micronutrient deficiencies. Is that just poor eating habits because they have embraced the lifestyle without knowing what they're doing, or that is there a high risk that this can happen to anybody?

Shireen - Well I think it can happen to anyone on any diet pattern. And as a haematologist I see plenty of people with iron deficiency, and as you've already pointed out, 94% of the population are not vegan or vegetarian; your risk of anaemia is no greater on a vegan or vegetarian diet. We're doing our current diet pattern very poorly. We're fibre deficient, potassium deficient, folate deficient; and we are eating too much protein from animals and saturated fat. A;l diet patterns need careful planning and we've forgotten how to do that. So if you're shifting a diet pattern, you need to do it with the knowledge and skills to do it properly. As you know, a vegan diet needs supplementation with vitamin B12, because it's not made by humans or animals; but beyond that you need to find your nutrients in the same way as you would on an omnivorous diet.

Chris - And how quickly would one begin to derive benefit? Because if you've been eating a lifetime of meat, is it the fact that if I were to switch to an exclusive plant-based... a) that might upset my system for a while, and b) would it actually be beneficial at a later stage of life to do that?

Shireen - Yeah, it's always beneficial to shift more towards a plant-based diet, but it depends on your starting point. As you pointed out, you can be healthy eating an omnivorous diet if you're doing it with lots of fruits and vegetables and other nutrient-dense foods alongside the meat. So you may not feel anything, but if you did need to improve your health as the majority of the UK population do, you'll find that it's easier to shed a few pounds in the first few weeks because you're eating lower calorie density foods which are more nutrient dense. For example, if you do have prediabetes or type II diabetes, within a few days your blood sugars will come down and you need careful management of that. Within two to four weeks, you'll find that your blood cholesterol level, if it needed to be lower, will come down to a healthier baseline. So yes, within a few days, weeks, months. And of course we're all talking a lot about gut health and the gut microbiome; that only takes a few days of shifting to a healthy plant-based diet to show an increase in the helpful bacteria. But it might be if you're feeling well and healthy, you don't feel any benefits; it's just you're benefiting your long term health, and of course the health of the planet too.