The debate was on 'effects of Earth's magnetic field on brain depending on sleeping positions'.

According to the Indians, Earth's magnetic field affects the human brain based on sleep direction and position. They said if you place your head to the north and stay that way for 5 to 6 hours, the magnetic pull will cause pressure on your brain. And that Blood has 12-16g iron which will pool at foot end, causing deficiency in oxygen to brain! This, they say, is ancient 'science' which was supported by a recent research paper (1).  The blood supply to the brain should be constant in a given amount of time. Too much blood or too little blood can damage the brain in their own respective ways. 

But  Western physicists rubbished this and said... We have the greatest respect for the religious and cultural beliefs of others, but we are obliged to say that there is a considerable amount of rubbish associated with what we  call "men and magnetism".
To start with, the human body is transparent to magnetism (just as well, or you would explode in an electric train). Secondly, the iron in the blood is in an organically-bound form which doesn't produce any personal field or localised magnetic disturbance whatsoever: this is why you can carry a credit card without wiping it, amongst many other things.

The Earth's magnetic dipole is several hundred miles under the ground. And it is very weak to effect the human brain although the magnetic field extends outer into space.

Strong magnetic fields can affect the brain. For example this article from MIT shows how. However, the magnetic fields used in these studies are much, much stronger than Earth's magnetic field. There is no reason for such an effect to occur with Earth's magnetic field.  For there to be a preferred direction of orientation, that would require a preferred direction of structure in the brain---which there is no evidence is the case. If the brain, somehow (magically), was able to 'know' which direction magnetic fields pointed, then presumably we would have evolved the ability to utilize it like birds. This is not the case*. Sleep studies are often done in (f)MRI machines with fields thousands of times stronger.

*There have been some reports of evidence for magnetoception in humans, but these claims are consistently  not reproducible.

The intense fields used by medical scanners, which are around 100,000 times stronger than the Earth’s magnetic field, can trigger nausea, dizziness and a metallic taste in the mouth, but these effects are temporary.

 International guidelines for public exposure to magnetic fields set an upper limit of 40 millitesla – several times stronger than the Earth’s magnetic field whose magnitude at the Earth's surface ranges from 25 to 65 microteslas.

Another aspect to consider here  is blood is not magnetic in a conventional sense eventhough it contains iron. In other words, it is not ferromagnetic which is what most people understand as magnetism. If blood 's ferromagnetic, then people would bleed to death or explode in MRI scanners which produce much strong magnetic forces. So although deoxygenated haemoglobin is paramagnetic and very slightly attracted to a magnet, and also both oxygenated haemoglobin and plasma are diamagnetic or in other words, slightly repelled by a magnet. Firstly, any influence in the polarity of ions within red blood cells would be lost because blood flows in a pressurised and turbulent way. Secondly, blood is warm, so for any paramagnetic effect to occur it would need to overcome the forces of brownian motion. All of which are extremely unlikely. 

The most popular argument is:

The human blood contains iron and since iron is affected by magnets, the Earth's magnetic field also affects the human body.

But  scientists argue that ...

The statement is not true and even the part where there is a chance of possibility, our blood doesn't interact with a magnet in the way we think it does. The iron in our blood is not present as loose iron particles but is part of a metalloprotein called haemoglobin. It is a complex molecule that is responsible for carrying oxygen to all parts of the body by reacting with oxygen to form oxyhaemoglobin. And then releasing the oxygen at the target location to form deoxyhaemoglobin. Haemoglobin also reacts with carbon dioxide to form carbaminohaemoglobin and also with carbon monoxide to form carboxyhaemoglobin which is a stable compound and bad for the body. 

The iron in the blood and the human body in general is very miniscule. But even then is it enough for any magnetic field to have any influence on the body?

Safety matches have in their heads tiny amounts of ferric oxide as impurites. The match heads are not attracted towards a magnet but on a sensitive water bath it is slightly attracted towards the magnet. However when we burn them, the ferric oxide in the match head reacts to form carbon dioxide and iron. And then the burnt match sticks are attracted towards the magnet due to the presence of iron as a separate element in the burnt match head.  This gives us a clue that iron atoms don't always have the same magnetic properties but depends on the molecule it is a part of.

Do you think the human blood will react to a magnet?

In reality the blood is very slightly repelled by a magnet. Yes!

This happens because blood is a diamagnetic substance. Now magnetism is actually a Quantum Mechanical effect. Very simply put the magnetism of any substance is determined by the number of unpaired electrons in it. Now deoxygenated blood has four unpaired electrons making it paramagnetic. A paramagnetic substance is weakly attracted towards a magnet. But the oxygenated blood containing oxyhaemoglobin has no unpaired electrons in it. Which makes it a diamagnetic substance. Diamagnetic substances are repelled by a magnet.

 As the majority of the blood in our body is in an oxygenated state that means it has more of oxyhaemoglobin which is diamagnetic. Also water makes up half of our blood which again is a diamagnetic substance. Hence overall blood of any animal is diamagnetic.

So  it can be concluded that the iron in our blood is not in a ferromagnetic state which is strongly attracted towards a magnetic field. Rather it is weakly repelled. The iron in our blood is in no way or form to be dangerously affected by even the the strongest magnetic fields. If that would have been the case people taking an MRI( Magnetic Resonance Imaging) scan would have died. So in no way can the weak magnetic field of the Earth affect our body. You can be confident about it. Evolution and science has taken care of that!

Sleeping positions don't affect you in any way and if anybody says they do by creating a link between your iron-containing blood and the Earth's magnetic field,  just remember that it is pseudo-science based on ignorance.

                                                              **************************

Then I contacted one of the physicists and asked him why he cannot consider the research paper published by Indians on this topic (whose reference has been given below). 

This is his (he clearly told me not to add his name here for fear of backlash) reply: "We find it  difficult to reproduce the results published in papers from Asia most of the time. Most Asian researchers show a bit of favouritism  for things said  in their cultures and religion and while doing research they try to authenticate it using manipulated data and biased reasoning. They don't publish their results in high class journals and find dubious journals favourable for their work. The peer-reviewers there too are prejudiced and recommend these papers. I can give an example of research with regard to an ancient treatment called Acupuncture. The papers published in China and other Eastern countries say it works. But when these were tested in the West, we failed to get the same results. Papers published in Asia are not reliable, at least in some cases.

The paper you mentioned is flawed because the sample size is small, the researchers used unreliable books as citations, they tried to make 'connections' between effects of strong magnetic fields with earth's low field, to name a few. I didn't go into full details and if I do that I can find more. The authors themselves say more work is needed to come to any conclusions. This shows they themselves don't have confidence in their work. If I were the reviewer of this paper, I would have asked the publisher to reject it". 

And I was shocked!

Are we really biased? And if we are, is it reflecting in our research work and debates on science?

It is true that a single paper doesn't authenticate any thing.  A single study by just a group of researchers need not be accurate. Personal experiences don’t count for the purposes of scientific research. Self-reports are notoriously unreliable. A single person’s testimony is not useful for scientific knowledge, which requires reproducibility. Only when several studies by people in well established research institutes and universities confirm the reports, then they will become facts of science.

Scientific claims gain credibility by accumulating evidence from multiple experiments, and a single study cannot provide conclusive evidence for or against a claim. Equally, a single replication cannot make a definitive statement about the original finding. However, the new evidence provided by a replication can increase or decrease confidence in the reproducibility of the original finding. Most scientists appreciate the fact that a single published paper is a step in the process, not the end of it. Post-publication peer review is more important.

Therefore, you cannot use a single published paper in debates with regard to science to support your argument.

What else can be prohibited from using in debates in matters of science? Most of the time people use these things which should not be done...

Presenting religious and cultural stories while dealing with science. Sorry to say that science doesn't accept them. 

Using anecdotal evidence which is not evidence at all. What you experience is your personal thing. You could be lying, delusional or being an example of wishful thinking. Just because you want something to be real doesn't make it real. Your beliefs and opinions don't count in science.

Trying to make some connections when there are none.

Using natural things like Sun, Earth, flowers and other beautiful things etc.  to say they are miracles. They are real things alright but they are not miracles according to science.

Using threats like 'you will go to hell if you don't believe or accept this'. Scientists don't believe in such things.

Wasting a scientist's precious time with unnecessary arguments using biased and lopsided logic. Don't use fallacies or apologetic dialectics. These will not have any effect on scientists.

Trying to argue without understanding the scientific method and methodology and science properly.

Using books and blogs as references. Using papers published in dubious journals to authenticate your arguments. Using news paper reports which are not reliable. Using celebrity and political statements is a complete no-no.

Using pseudo-science.

Using 'ancient wisdom'.

Using speculations based on incomplete research. 

Yes, I came across people using these things while discussing and debating things scientific several times. Need I say the moment people use these things, they lose the debate in the special field called science.

Here you have to follow the rules set by only true science. If that sounds authoritative we cannot help it. Sorry. 

When a magnet meets blood ....

Citations:

1. http://medind.nic.in/ibl/t09/i3/iblt09i3p162.pdf