Buddhists and Hindus have been advocating vegetarianism for centuries.
These days, a growing number of adherents do so for reasons unrelated to these two faiths.
They include people who choose to become vegetarian for ethical or environmental reasons, or some who do so because they think it will benefit their health.
The term 'vegetarian' has in fact become a broad category for different subsets of the practice. It includes those who eat honey, eggs and milk; and vegans, at the other end of the spectrum, who are strictly vegetarian and do not eat any animal products.
Then there are vegetarians who eat only one type of vegetable or fruit, or only those of the same colour, at each meal.
Even within veganism, there are different beliefs, such as fruitarians who eat only fruit, nuts and seeds but no leaves and stems.
With the bad press that fatty meat and processed foods have received, and with chronic diseases on the rise, the vegetarian diet has become a draw for the health-conscious.
Plant food diets tend to be lower in saturated fat and cholesterol.
They also have higher levels of dietary fibre, magnesium and potassium, vitamins C and E, folate, carotenoids, flavonoids and other phytochemicals, said Madam Koay Saw Lan, who heads the dietetics and nutrition services at Singapore General Hospital.
Various research findings link these ingredients to a lowered risk for chronic diseases, she added.
For example, a 2004 publication in the Archives Of Internal Medicine by a team of researchers in the United States found that every 10g increase of dietary fibre a day reduced heart diseases by 14 per cent and coronary deaths by 27 per cent.
While the fruit and vegetables in a vegetarian diet do prevent heart disease, it is more important for the diet to be balanced, said cardiology consultant Jack Tan from the National Heart Centre.
This means eating enough of various nutrients. Diet aside, exercise and a healthy body weight are equally important, he added.
Madam Koay said that vegetarians are also less likely to be saddled with conditions like obesity and constipation. The United Kingdom-based World Cancer Research Fund reported in 2007 that fruit and vegetables can protect against various types of cancer like that of the mouth, stomach and lung. It recommends at least five portions of these foods a day.
However, as in all good things, there are always caveats. Dietitians caution that going vegetarian may not always be a good thing, nor is it suitable for everyone.
Problems with some diets
For instance, vegetarians who include milk and egg products in their diet will usually have adequate nutrients but those on a vegan diet may run into problems, said Eliza Resurreccion, a dietitian at The Nutrition Place.
Vegans may lack nutrients like calcium, iron, vitamin B12, omega-3 fatty acids and certain amino acids unless their diets take these into account.
A lack of calcium in the long run, for example, may lead to lower bone mass and osteoporosis, said orthopaedic doctor Khong Kok Sun from Mount Elizabeth Hospital.
In particular, he noted that elderly vegetarians do tend to become osteoporotic.
Dr Khong attributes this not just to the lack of calcium in their diet but, more importantly, to the presence of the compound phytate in many plant-based foods such as grains and legumes.
He explained that phytate binds to calcium and renders it unabsorbable by the body. So vegetarians who take calcium tablets should do so in the morning or at night when their stomachs are relatively empty.
Children, pregnant or lactating women and the elderly should take extra care of their diets.
For example, pregnant or lactating vegans should get more protein from whole grains and legumes, and calcium from tofu or soya products, said
Dr Choo Wan Ling, a consultant gynaecologist at Pacific Healthcare Specialist Centre. These women should eat more plant-based items high in iron, zinc and vitamin B12, or take supplements.
A vegetarian diet has much bulk and the mother's overall calorie intake may be insufficient because she may often feel full. So she should snack on dried fruit like raisins and prunes to bump up the calorie count, said Dr Choo. Otherwise, a vegan diet is generally not a problem for mothers, she said.
