MICHAEL MOSLEY

There are plenty of ethical and environmental reasons to go vegan, but is there a catch?

How to stay healthy on a plant-based diet.

One of the major health trends of recent years, particularly in more affluent countries, is the move towards a more plant-based diet. Many people are doing it for ethical reasons, but also because we know that large-scale meat production has a significant impact on climate change. So, is there a downside? I recently had a letter from a BBC Science Focus reader who wants to put her whole family on a plantbased diet but is anxious about doing so, not least because she has a family history of osteoporosis (thinning bones). So how worried should she be?

If you are a vegetarian then you don’t eat meat or fish. But while some vegetarians eat eggs and dairy products (a good source of calcium), others follow a stricter vegan diet and avoid all animal products.

As a vegan, you can still get all the vitamins, minerals and micronutrients you need, including calcium for strong bones, from food, but you might want to consider taking supplements. Remember, though, giving up eating meat entirely won’t necessarily make you healthier, particularly if you replace meat with processed food.

This was graphically demonstrated in a piece of research published in the journal BMC Medicine in 2013. In the study, researchers followed nearly 450,000 people in 10 countries for more than 12

“The highest mortality rates were in those eating large amounts of processed meat”

years. The researchers found, to their surprise, that eating moderate amounts of red meat had no effect on mortality; in fact, it seemed to be protective. The lowest overall mortality rates were in those who were consuming up to 80g a day of meat. The researchers concluded that “a low – but not a zero – consumption of meat might be beneficial for health. This is understandable as meat is an important source of nutrients, such as protein, iron, zinc, several B vitamins as well as vitamin A and essential fatty acids.”

One reason why the vegetarians and vegans in this study weren’t, on average, living longer might have been down to a lack of essential micronutrients such as vitamin B12. B12 deficiency can lead to anaemia, fatigue and memory loss; it has also been linked to depression.

Before meat-eaters rejoice, it is worth pointing out that the highest mortality rates were in those eating large amounts of processed meat, like bacon, sausages and salami.

In another study, researchers from Oxford University recorded B12 levels in the blood of 689 men (226 meat-eaters, 231 vegetarians and 232 vegans). They found that 52 per cent of vegans and 7 per cent of vegetarians were vitamin B12 deficient, but only one omnivore.

So if you want to go vegetarian or vegan, it’s important to ensure you are getting all your micronutrients. There is lots of useful information on the NHS, Vegetarian Society and Vegan Society websites.