24 October 2010

Why protein from animal-source should be reduced?

The requirement of daily intake of protein has been a subject of great debate with many unresolved questions. After reading Esselstyn's book "Prevent and Reverse Heart Disease", I learn certain bio-chemical process in our body that answer the question.

The internal surface of our blood vessels are lined with thin-layer of endothelium cells which  (one of its function) is responsible for vasodilation. It does that by making Nitric Oxide (NO) through Nitric Oxide Synthases (NOS3). To make NO, NOS3 require L-arginine which is a L-from alpha-amino-acid. Though Arginine is non-essential amino acid (that means our body can manufacture it), the biosynthetic pathway does not produce enough hence require supplementation through diet (either through animal-sources or plant-sources).

However there are other chemicals that compete/interfere with L-Arginine on the production of NO, for example Asymmetric dimethylarginine (ADMA) and MMA. ADMA is naturally found in blood-plasma as a metabolic by-product of protein methylation process. This is why too much protein is not good. As a general guideline, human breast-milk which is optimized for newborn baby unusually high protein requirement, contain only 5% calories from protein (compared to 20% in cow's milk). The Okinawan Diet, which have the world highest number of Centenarian and most healthy people, only have 10% calories from protein on their diet.

In healthy person (that is total cholesterol level less 150mg/dL and LDL cholesterol less than 80mg/dL), presence of ADMA and MMA are not a big issue since our body will also have Dimethylargininase (DDAH) enzyme which function is to degrades those methylarginines (ADMA and MMA). Unfortunately, DDAH itself is sensitive to oxidative stress, such as oxidized LDL-cholestrol. Hence the attenuation of DDAH level cause the elevation in ADMA, blocking the NO synthesis which lead to vasoconstriction. This is why when we try to fulfill our protein requirement, we should try to get it from plant (which have less fat) rather than animal (where even a lean meat, that is defined by USDA as 90% lean and 10% fat, actually calculated to be about 50% calories from fat). The actual correlation between high fat content and rise of LDL level is very complex, read more in the "Regulation of cholesterol synthesis" section of Wikipedia article.

Nitric Oxide aside, two more things to consider. First of all, animal-sourced protein have a high level of methionine amino-acid. One need to be careful here, methionine amino-acid is part of essential amino-acid that our body need, however high level of it can lead to increase of homocysteine level which is an artery-toxic substance that strongly linked to coronary heart disease and aging. Second is that meat protein have higher sulfur content that will increase uric-acid which will lead to medical condition such as kidney stones and gout.

In conclusion, the general dietary literature that recommend very high protein diet is false. One only need 10% of their calories from protein. Sourcing protein from animal-product unfortunately will bring in more unwanted stuff, hence the safer option to meet your protein requirement is through plant-based food. But remember, we still need protein. It helps with satiety (i.e. make us feel full) and preserving our muscle tissue.

If you have any comment on potential pitfall on my arguments, do drop me a comment.

11 October 2010

Plant-based diet

In the current modern society where a large array of different kind of foods are available at an instant, there are many reasons why some choose to be "vegetarian". However, most of them can fall within one or more of these broad categories:
  1. Animal welfare
  2. Environment
  3. Religion
  4. Health
As the title of this post is plant-based diet, I am only pursuing the question on the benefits of vegetarian diet practice. This is not a veganism, where one seek to exclude even the use of animals in clothing or any other purpose.
Those who know me knows that I love my thick cut of juicy steak from Morton's of Chicago. However, as I scientist I am always open minded with different opinions. Okay, let us see those 4 categories one by one.

Animal Welfare
I frankly find that PETA moral/ethical arguments are not sufficiently convincing. See Steven Davis rebuttal on typical vegans argument of "The Least Harm Principle" or this free article.

If you are concern about the modern cattle/poultry/fishing industry, you could opt for animal products that come from free-range poultry, organic/natural pasture-fed cattle, and dolphin friendly fishing.

One of the primary argument in this category is the methane emission by cattle. As you know methane is one of the powerful greenhouse-gas that contribute to global warming. The research on this is indisputable, such as this paper. Just like the great horse-manure crisis of 1894, I don't believe the solution of this problem is solved by being a vegan. We invent technology to solve problem. What is needed here is a proper economic incentive for that. For an immediate short-term action, we can cut our meat consumption and/or buy food products from farmers/industry that practice sustainable food system.

Wikipedia have a nice article summarizing the relation of Vegetarianism with various religions. Some vegetarian diet on certain religion I find it weird (and arbitrary), such as no garlic. I can't see any logic behind that at all. Anyway, since my believe is in Christianity, here are some relevant verses on this discussion.
  • Genesis 1:29
  • Genesis 9:3
  • Daniel 1:8-16
  • Acts 11:5-10
  • Romans 14:20-21
So, the way I see it is that during the point of creation, God mandated a vegans diet on Gen 1:29. After the flood, which presumably destroy most crops since Noah only took the animals on the ark, God allows animal to be part of the diet. And Leviticus will further refine what food considered clean (kosher) and unclean. Interesting to note the in Daniel 1:8-16, dispel the common preconception that plant-based diet will make you weak.

When we move on to the new-testament area, God even lift up the prohibition of non-kosher food on Acts 11. However Romans 14 put a caution that our choice/belief on dietary issue should not become a stumbling block for other brothers.

Hence there is no arguments against eating meat in the Bible (most of Jesus disciples are fisherman and remember the miracle of five loaves and two fish; and more importantly the lamb on the passover meal). But it poses a question why did the original diet plan from God is plant-based diet? And Daniel example shows the possibility of healthy plant-based diet.

Now I come to the core part of this article. My initial interest in this subject is due to health concern. Unfortunately the plethora of informations out there suggesting all difference kinds of diet approaches made us only more confused. We always get ads saying things like milk and cheese are rich in calcium that help you having stronger bone. Meat are mostly protein, and protein are important for your health. Hence my belief has always been a healthy balanced diet of everything (not that I have been eat a balanced one, in fact I love meat more than my vegy).

Let me digress a little bit. On my last year oh high-school I was shocked with the news that my friend who teach at UK Petra died of a heart attack. I know him to be a slim person and led a typical healthy lifestyle (i.e. cycle to work). How could this be? Many people suggested, maybe its gene. And from there on I have encountered 2 more friends in NUS that suddenly died of heart-attack while exercising. This all doesn't seems to make sense. Then I come across a blog post of my good friend Rhandeev, which detailed how his athlete father got a heart-attack and how he discover a plant-based diet that reverse the medical condition.

I know my friend Rhandeev as someone who wouldn't just buy into someone idea if it is not backed up with a solid scientific grounding. Hence I ask him for some resources for me to investigate further. Here are some links he gave me (first 3 are videos, and the rest are books):

I am astonished by what I learned from the first 3 videos. So, now I am planning to read those 3 books, and will let you know. I want to find out how they address Vit D, Vit B12, and Omega-3 fatty acid (especially the EPA and DHA) on plant-based diet. Also why no milk, egg, fish and avocado on their suggested diet?
Although now I am not completely buy the full-scale vegan-diet (see Flexitarianism), I have made certain changes on the diet. No more soft-drinks (or any high sugar content stuff), reduce eating fried stuff, no pre-processed snacks, mix brown-rice and white-rice at home. Let see whether the books give enough convincing arguments for me to give up on animal proteins :-)
And of course, I will also balance my reading by taking into account the opposite camp arguments.