Is it healthier to go plant-based? How do processed foods affect this?

The question of whether a vegan or vegetarian diet is healthier seems to repeatedly come up, especially when processed foods are thrown into the mix.

Recently, Martin Freeman revealed gave up on 38 years of vegetarianism and began eating meat again. "I like meat-replacement things, but my reservation about them is they can be very, very processed, and I'm trying to eat less processed food," he said on the Dish podcast. He went on to talk about his love of pork pies and scotch eggs, which, ironically, can be included in the category of processed foods.

But, are plant-based alternatives really worse off than their meaty counterparts, and how does the health of the two diets generally compare? We consult Rohini Bajekal, nutritionist and a board-certified lifestyle medicine professional at Plant Based Health Professionals (plant-based herself) and Dr. Lawrence Cunningham, a retired GP and medical contributing expert at UK Care Guide (who eats meat in moderation).

Can the 'health' of a vegan or vegetarian vary?

"Yes," says Dr Cunningham. "The health benefits of a vegan or vegetarian diet heavily depend on the choices within the diet itself.

"In my experience, removing animal products does not automatically translate to a healthier lifestyle. It must still be balanced and nutritionally adequate.

"For instance, relying heavily on processed vegan foods, which can be high in additives, rather than whole foods like vegetables, fruits, grains, and legumes, can certainly lessen the health benefits typically associated with plant-based nutrition."

But, aware there has been a lot on ultra-processed foods (UPFs) recently in the media, Bajekal flags, "Some of this attention is being used to create a negative narrative around vegan diets, suggesting that products frequently consumed by vegans fall into this UPF category.

"For example, plant milks and plant-based meat alternatives are often deemed to be highly processed and hence considered by some to be unhealthy. This is then being used as an excuse to continue promoting the consumption of meat, milk and eggs as they are 'natural and 'unprocessed'. All ultra-processed foods are not created equal and each product should be assessed on their own merit."

Is it healthier to go plant-based than to eat meat?

"A plant-based diet can be healthier, as I have observed lower rates of heart disease, high blood pressure, and diabetes in patients who typically follow these diets," says Dr Cunningham.

"However, the key is the nutritional quality and diversity of the diet. Meat-eaters who consume lean, unprocessed meats with plenty of fruits and vegetables might also maintain good health."

Bajekal also points to various benefits – she says it reduces the risk of coronary heart disease by 25%, certain cancers by around 15% and type 2 diabetes by at least 50%, as well as improving our energy levels.

"A diet centred around healthy plant foods, whilst minimising or avoiding ultra-processed food and meat is a key recommendation for cancer prevention. People consuming vegan and vegetarian diets have consistently lower rates of cancer than meat eaters," Bajekal explains.

"This is because a fibre-rich diet consisting of fruit, vegetables, whole grains, beans, nuts and seeds and herbs and spices, maximises the consumption of anti-cancer compounds found in food leading to a healthier gut microbiome, lower levels of inflammation and cellular stress and a healthier body weight, all important for preventing cancer."

In a similar vein to Dr Cunningham, she adds, "Although no one food defines a healthy or unhealthy diet, the one food to leave off the plate is processed meat, since it is known to be a direct cause of cancer." However, Bajekal further emphasises that replacing red meat and chicken with chickpeas or any whole plant foods or healthy sources of protein like beans and nuts is "going to significantly reduce the risk of common chronic diseases and lower the risk of dying".

What is the effect of plant-based processed foods?

"Processed foods, whether vegan or not," says Dr Cunningham, "often have unhealthy levels of fats, sugars, and salts, and lack important nutrients. "Examples of plant-based processed foods could include vegan sausages, burgers, and ready meals. These often contain preservatives, colourants, and excess salt.

"In the cases I’ve had, patients consuming large amounts of processed foods typically exhibit poorer health outcomes compared to those eating fresh, whole foods. In my experience, this holds true across both plant-based and meat-based diets."

But while Bajekal acknowledges processed plant-based foods can warp the health of a vegan or vegetarian, she reminds us that not all processed foods are created equal. "Tofu is a lightly processed food that will certainly improve health when it is used to replace red meat and processed meats of any kind!" she explains.

"The term 'processed food' has a largely negative connotation. However, some gently processed foods can contribute to a healthy dietary pattern. They play an important role in many people’s diets whether it’s due to time, cost, cooking ability, medical issues or any unique nutritional needs – for example, when feeding children or older adults who have higher protein needs."

Some examples she gives of lightly processed foods include fortified plant milk, canned beans, frozen vegetables and berries, dried fruits, whole grain pastas, wholemeal bread and tofu. "Fortified plant-based (vitamin D, B2 (riboflavin), B12 and calcium) drinks typically contain calcium at similar levels to cow’s milk (120mg/100ml). It is therefore important to consider the role of food in the overall diet, rather than solely on the level of processing," the nutritionist explains.

Bajekal suggests basing meals around nutritious plant foods, but says it's okay to allow for some processed foods to help make it easier for us to meet nutritional needs. "For example, frozen fruit and veg have a similar nutritional value to their fresh counterparts and frozen blueberries have been shown to be even higher in antioxidants."

One category she says to avoid where possible are the UFPs, 'food-like substances' that offer almost no nutritive benefits. "These include fizzy sugar-sweetened beverages, instant noodles, crisps and packaged biscuits which can also sometimes include unhealthy trans fats."

Processed meats have been compared to smoking, so is there an equivalent for processed plant-based foods? "While processed meats may have been linked to higher cancer risk, particularly bowel, plant-based processed foods are not necessarily completely immune from such risks. They can still contribute to health issues such as obesity, heart disease, and diabetes if consumed in excess," says Dr Cunningham.

But, from what we've learnt, this may depend on the type of processed food, and how much is consumed.

Balance really is key

Bajekal acknowledges that while the 'everything in moderation' stance may sometimes be used to justify unhealthy behaviours (like smoking, drinking or bacon), she adds, "However, not all processed foods are bad and it is what you eat the majority of the time that makes a difference, not what you do as a one off or once in a while.

"For example, that slice of birthday cake is not going to break your health any more than that one-off green smoothie will make your health!"

She adds that it's the overall dietary pattern and your general wellbeing that matters. "Stressing about your diet, macronutrient composition or individual meals is counterproductive and exacerbates disordered eating. It is important to nurture a positive relationship with food and your body as being stressed raises cortisol (stress hormone). Fixating on food and viewing foods as categorically 'good' or 'bad' has been shown to negatively impact mental health."

And as a reminder, says Dr Cunningham, "A healthy plant-based diet should be rich in fruits, vegetables, whole grains, and protein sources like legumes and nuts. It's also essential to include B12 supplements [or have fortified foods] as this vitamin is predominantly available from animal sources."

• Read more: The five worst ultra-processed foods you need to avoid (Yahoo Life UK, 6-min read)

• Read more: Are vegan and vegetarian diets safe during pregnancy? (Yahoo Life UK, 6-min read)