Is a vegan diet healthy?                    Worksheet

Dr Karl: G'day, Dr Karl here.

Way back in 1925, Donald Watson was just 14 years old and living with his family on a farm in Great Britain. One day, he saw a pig being slaughtered.

The pig was terrified and screaming.

This moved Donald so much that he stopped eating meat, and then eventually avoided dairy as well. A few decades later, in 1944 he invented the word "vegan" -- by joining together the first and last syllables of the word "vegetarian".

People sometimes wonder if you can be truly healthy on a diet that excludes both meat and dairy. The answer is definitely yes -- but you have to understand your food much more deeply than the person living on meat-and-three-veg.

There are many reasons for changing to a plant-based diet. Some include concerns about animal suffering and cruelty, or about health, while other reasons relate to the environment.

From a health point-of-view, plant-based diets have been linked to lower risks of obesity and many chronic diseases, such as type II diabetes, heart disease, inflammation and cancer. And the evidence does link colorectal cancer with red and processed meats.

But these benefits don't come without risk.

Clare Collins, Professor in Nutrition and Dietetics at the University of Newcastle, says there are four essential nutrients that have to be especially considered if you choose to go vegan. They are vitamin B12, iron, calcium and iodine. If you're not eating meat or dairy products, you'll struggle to get a decent supply of them.

Let's start with vitamin B-12. It's essential for making DNA, fatty acids, red blood cells and some neurotransmitters in the brain.

A deficiency of B12 can cause a fast heart rate, palpitations, bleeding gums, bowel or bladder changes, tiredness, weakness, and light-headedness -- which doesn't make for a healthy lifestyle.

Vitamin B12 is easily found in animal foods such as meat, milk and dairy products.

vegans really need to consume foods with vitamin B12 specifically added, like fortified non-dairy milks.SoBut vegans can get only traces of vitamin B12 in some algae and plants that have been exposed to bacteria contaminated by soil or insects, and in some mushrooms or fermented soybeans.

The second micronutrient, calcium, is essential for good bone health - as well as for proper function of the heart, muscles and nerves.

Calcium is abundant in milk and milk-based foods. Vegans can get calcium from tofu, some non-dairy milks with added calcium, as well as nuts, legumes, seeds and some breakfast cereals.

But both vegans and vegetarians usually need a higher calcium intake than meat eaters. That's because vegetarians and vegans usually eat more plant foods containing chemicals that reduce the absorption of calcium into your body.

These chemicals include oxalic acid (found in spinach and beans) and phytic acid (found in soy, grains, nuts and some raw beans).

Surprisingly, vegans can also be deficient in iodine - which is essential for making thyroid hormones, and the developing central nervous system.

Vegans don't eat the usual sources of iodine - seafood, dairy products and eggs -- but they do eat seaweed, and foods that have added iodine such as salt, some breads, and some non-dairy milks.

So why would vegans be prone to iodine deficiency? Well swallowing iodine is only half the battle -- like with calcium, some other foods can reduce your absorption of iodine. If you love your Brassicas - things like cabbage, broccoli, and Brussels sprouts -- you're also getting a dose of chemicals in these vegetables that can interfere with the production of the thyroid hormones.

in your red blood cells, which carry oxygen around your body.haemoglobinAnd finally, we come to iron. Most people know that iron can be a problem on a vegetarian or vegan diet. Iron is essential to make the

It is easy to get enough iron if you eat wholegrain cereals, meats, chicken and fish. And there is iron in some plants -- but your body can't absorb this type of iron as well as it absorbs iron from meat.

at the same time -- tea contains chemicals that can reduce your absorption of plant iron even more!cuppa' iron) by eating vegetables and fruit that are rich in vitamin C. Just don't have a haemYou can boost your absorption of plant iron (or 'non-

I did say vegans need to understand food much more deeply than meat-eaters!

And if you've been a vegan for long time, the list of nutrients you need to keep an eye on gets longer. You also need to watch your vitamin D, omega-3 fats and protein intake.

Finally, vegans have to take even more care with their diet plans if they are pregnant or breastfeeding, or bringing up the children as vegans. In this case, it's very worthwhile to get the advice of a professional dietician.

So it does take a bit of effort to get all your nutrients from a vegan diet. But take a look around - it's not like eating meat and animal products is a sure-fire guarantee of healthy eating!