‘Pie hole’, colloquial for one’s mouth, is believed to have evolved in the USA in the 1980s from the British expression ‘cake hole’ (coined in the mid 20th century). Pie hole refers to a mouth, as in: Shut your pie hole or, in this case: Put less in your pie hole.

Wednesday, March 20, 2013

Ice Cream and Potato Chips are Vegetarian Too (part II)

Now that we’ve covered the fundamentals of vegetarian diets and discussed the small print behind those news articles making snap claims about vegetarians being healthier, we can jump over the fence and explore why the grass isn’t always greener in the grass-only pasture.

Research into vegetarian diets has not shown adverse health effects; but a recent meta-analysis (combination and analysis of independent studies) presented the danger of monotonous and restrictive vegetarian diets. Results showed restrictive vegetarian and vegan diets often lead to nutrient deficiencies that are damaging to overall health.

Before we untangle the web of nutrients herbivorous human pie holes often miss out on, we need to decipher the concept of ‘bioavailability’. As simply put as possible, bioavailablity is the extent to which vitamins and minerals in food are absorbed and used for normal function in the body. If a vitamin or mineral in a certain food is highly bioavailable, it means the body can easily extract and use it. The opposite is true for low or poor bioavailability foods. Spinach, for example, has a similar iron content per 100g to lean beef, but the iron in spinach is much less bioavailable. Think of your car, just because the marketing department says it can get 45 miles per gallon, doesn’t mean you’ll achieve this theoretical maximum in reality.

So let’s get into the meaty heart of this topic. Since vegetarian diets restrict animal products, it makes sense that vitamins and minerals abundant in these foods are consumed less. Protein, iron, calcium, zinc and vitamin B12 are the common ones.

Protein is not stored in the body. Muscles are constantly turning over and rebuilding, therefore eating protein daily is vital. Protein is needed for muscle, bone and skin maintenance. The best sources are dairy, eggs and meat. Non-animal products like beans, legumes, nuts, seeds and tofu also contain protein. Eating a wide variety of these foods ensures protein requirements are met.

Iron is essential for carrying oxygen around body. The best sources are listed in Table 1. Iron from meat products (called haem iron) is highly bioavailable. Plant sources of iron (called non-haem iron) on the other hand, have poor bioavailability. All is not lost for non-haem iron because cooking these plant sources can increase bioavailability. For example, the human body can absorb about 6% of iron from raw broccoli compared with 30% in cooked broccoli. If iron was like Las Vegas: eating raw broccoli is blackjack, cooked broccoli is bingo, and red meat is the ATM.

Table 1: Iron Foods. Adapted from QLD Gov Iron Resource 2011

The mineral calcium is critical for maintaining strong bones and teeth, as well as assisting in muscle contractions. The best sources are milk, cheese, yoghurt and canned fish with soft bones like sardines or salmon. Other sources include dark green leafy vegetables, almonds, beans and fortified cereals: however, similar to iron, calcium from animal products is much more bioavailable than calcium from plant products.

Zinc plays an important role in the immune system, cell division and wound healing. High protein foods also contain high amounts of zinc, with meat and fish being the best sources. Lower amounts are found in legumes and whole grains. Plant sources of zinc from fruits and vegetables are not good sources because zinc in plant proteins has poor bioavailability.

Vitamin B12 is needed for red blood cell production and maintenance of the central nervous system. Animal products: eggs, beef, poultry, shellfish and milk are the best sources of B12. Non-animal sources of B12 are not reliable as they vary in amounts and are poorly absorbed by the body. Eating fortified food products for supplementation are recommended eg: fortified breakfast cereals.

What’s the bottom line? Restrictive diets take careful planning and execution. Here is some food for thought:
  • Vegetarian diets that include some animal products (pesco, lacto or lacto-ovo) and a wide variety of foods  are more likely nutritionally sound compared with very restrictive vegetarian or vegan diets
  • Restrictive vegetarian and vegan diets that are well planned and monitored, can deliver adequate nutrition
  • Recent research shows plant-based diets that include small amounts of red meat offer significant health improvements compared with a diet high in processed meats like bacon and sausage (but hey, that’s another article)
  • Evidence linking vegetarian diets to cancer prevention is limited
  • Diets described by national guidelines that are high in fruit and vegetables, and low in refined sugar, saturated fat, processed meats and salt, help reduce risks of chronic disease like type two diabetes and heart disease.
Hopefully these articles have shed some light on the small print behind claims that herbivory is supreme to omnivory. Vegetarianism may sustain a cow, but they have four stomach compartments to digest and break down food that is chewed and re-chewed in their pie hole all day. And if you are reading this, your pie hole can't do that because you are not a cow.


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