Thanks Ben, I hadn't considered this. Actually, I tend to use treacle/molasses and yoghurt in addition to fruits. Great stodgy breakfast if you've struggled to keep weight on like I have. Although, these don't fit the OP's non-sweet vegan question so I've omitted them. "Healthy" is relative but porridge is a great versatile option for many tastes. It's also low FODMAP and (arguably) gluten-free so almost anyone could give it a try.

Thanks, that's research from my university, they do good work. However my comment stands. Your answer is very comprehensive and otherwise good but (as a cancer researcher) I can not endorse it with false claims of cancer risk, the source article you've cited itself calls in to question of it's relevance to dietary intake. Fructose feeds existing cancers. It is well known that cancers are hypoxic and can grow without oxygen or glucose with altered metabolism. This occurs during disease progression and has nothing to do with the risk of getting cancer in the first place.

@Steve It's the complete opposite, the previous question didn't address ethical reasons at all.

However, diets high in fructose/sugar have been linked to risk of diabetes, obesity and more recently Gout along other autoimmune and metabolic disorders.

I don't think your claims about pancreatic cancer are very sound, the original study fed pure fructose or glucose to cancer cells. This is far from the tumour environment and does not compare to high fructose corn syrup, let alone fresh fruits in a balanced diet. The authors were only concerned about fructose for patients with cancers during treatment, not that fructose causes cancer. Media claiming so is scaremongering.

@Turion Yep, dashi is very difficult to avoid in Japanese food. I was hoping an answer would address this.

@Steve すみません、ベジタリアンです is probably sufficient for beginners: thankfully "bejitarian" is an english loanword as it is in many languages. However, in some cultures they do not understand that fish is not vegetarian so perhaps it would be better to be more specific.

I'm more looking for foods (such as miso soup) which often have non-vegetarian ingredients (e.g., daishi / fish stock) to avoid while eating out or visiting a Japanese home rather than cooking strictly vegetarian myself.