Myron Yau, HK BioTek Nutritionist
There is a trend being a vegetarian nowadays. It is claimed that vegetarian diet is mutually beneficial to both man kind and the environment. Indeed, vegetarian diet provides a lot of dietary fibers, water- soluble vitamins and wide variety of minerals. All of these nutrients prevent constipation and diseases caused by the deficiency of these nutrients, which are getting more prevalent in the world full of carnivores.
However, have you ever thought about the reasons behind the fact that humans are omnivores? Everything in nature serves a purpose. Different foods are composed of different nutrient content with various proportions. Human beings are designed as omnivores so that we ingest all kinds of foods from a diversity of origins and will not lack certain type of nutrient easily. Fortunately, there are always alternatives for the foods that you don’t eat. Therefore, you have to pay attention to what you eat if you are vegetarian.
First of all, proteins are mainly ingested from animal origins, like meat, poultry, fish and dairy products (but not butter, sour cream and cream cheese). No wonder why vegetarians are commonly protein-malnourished as they exclude all the animal foods. It is lucky to find out that some plant products are also rich in proteins, although the protein contents inside are lower than those in animal products. They are grains, grain products, legumes and vegetables. With adequate intake amount of these foods, protein intake requirement can still be met.
Secondly, vitamin B12 is only present in animal origins, for examples meat, poultry and fish, in which vitamin B12 is derived from microorganisms. Therefore, if you strictly follow a vegetarian diet with absolutely no animal foods, you are very likely to develop a vitamin B12 deficiency in the future as it, unlike other water-soluble vitamins, can be retained and stored in the body for a long period of time in years. Only after all the reserve of this vitamin runs out, will the deficiency diseases appear. The only alternative foods with vitamin B12 are grain products fortified with the vitamin as well as egg yolk and milk or dairy products if one is not a strict vegetarian.
For iron, there are two class of iron in foods, both heme and non-heme. Heme iron is found in animal products, especially meat, fish and poultry while non-heme iron is mainly found in plant sources including tofu, nuts, fruits and vegetables and, to a much lesser extent, dairy products. Heme iron is more readily absorbed by human than non-heme iron. However, since we only need a trace amount of iron a day, we can still get enough iron if we eat a greater amount of plant foods than normal.
Calcium is well known to be beneficial to our teeth and bones. In fact, it is present in a wide variety of foods naturally, ranging from dairy products to deep green vegetables like broccoli and spinach and selected seafoods like salmon and sardine. The absorption rates of both animal and plant calcium are quite similar to each other. Therefore, it shall not be a problem of calcium insufficiency in vegetarians if they do not drink soft drinks too often and eat very salty foods.
Finally, zinc is relatively less famous of its use. Yet it is very important to our immune system. The excellent sources of zinc are red meats and seafoods. Other good sources include poultry, pork and dairy products. For the strict vegetarians, whole grains (especially bran and germs) and vegetables (especially leafy and root) are the relatively good sources of zinc. Actually, plant sources are not only lower zinc in content, but plant zinc is also absorbed to a lesser extent than zinc from meat.
All in all, vegetarian diet is indeed more liable to malnutrition in certain nutrients and is not better than normal diet as long as the latter one is nutritionally well balanced. It is all about wise choices of foods.