基於不同原因，包括保持皮膚健康﹑信仰限制，甚至保護環境，現在越來越多人選擇做一個素食者。素食者聲稱素食對人類和自然環境都有好處。確實，素食有它的好處，例如高纖維﹑豐富水溶性維他命和礦物質。這些營養素可以預防便秘和其他常見於多肉少菜都市人的某種營養素缺乏症。

不過，你又有否想過為何人類天生是雜食性動物，而不是草食性動物？大自然的一切都有原因和目的。其實，不同食物所含有的營養素及各種營養素的份量都不盡一致。人類被設計成雜食者，可以食盡不同來源的食物，從而避免因為偏食而導致某營養素的缺乏。幸而，即使你是素食者，世界上仍然有很多食物可以代替。因此，所有素食者都應該要額外留神。

一般來說，有五種營養素是素食者會經常缺乏的，包括蛋白質﹑維他命Ｂ１２﹑鐵﹑鈣和鋅。

其次，維他命Ｂ１２只會於動物來源的食物出現，例如肉類﹑家禽類和魚類；而維他命Ｂ１２則只會由微生物製造。因此，如果你是一個嚴格的素食者而完全不食動物類食物，維他命缺乏症的症狀會很容易出現於長期素食者身上。不同於其他水溶性維他命，維他命Ｂ１２可以被保留和貯存於身體內一段數以年計的長時間。直至所有貯存用盡，這些維他命缺乏症的症狀才會出現。可作為代替品的食物包括一些添加了維他命Ｂ１２的穀類食物。如果你不是一個嚴格素食者的話，蛋黃和奶制品也是好的選擇。

　　 食物中的鐵有兩種，動物性和植物性鐵質。動物性鐵質可於肉類﹑魚類和家禽中找到；植物性鐵質可於豆腐﹑果仁﹑水果和蔬菜，而牛奶的植物性鐵質含量會少很多。動物性鐵質較植物性鐵質易吸引。不過，人類一日只需要很少鐵質。只要我們食植物類食物比平常多，仍然可以吸收到足夠的鐵質。

　　每個人都知道鈣質是對我們的牙齒和骨骼有益。事實上，鈣質出現於很多不同的天然食物，由奶制品到深綠色蔬菜（例如，西蘭花和菠菜）和部分海鮮（例如，三文魚和沙丁魚）都有。人體對動物和植物類鈣質的吸收率都差不多。因此，鈣質不足應該對素食者不是一個問題，只要他們不是經常飲用有氣飲料和食得太鹹。

最後，鋅算是一種較容易受忽視的營養素，但它卻對我們的免疫系統有著不可或缺的重要性。它十分好的來源包括紅肉和海鮮。其他好的來源包括家禽﹑豬肉和牛奶制品。對嚴格素食者來說，全麥制製品（包括麥糠和胚芽）和蔬菜（綠葉和根部）都是相對好的來源。不過，植物的鋅不但含量比動物中的鋅含量低，而且植物類鋅的吸收率會比動物類的為低。

　　其實，素食的確會比正常飲食更容易導致營養不良；而且素食其實不一定比均衡飲食健康。這些全部都是取決於你的決定明智與否。

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.



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