I just did a piece for Channel 4 on their superfoods program (http://www.channel4.com/programmes/superfoods-the-real-story). It was looking into the claim that wheatgrass juice improved blood oxygen content; allegedly this works by increasing the amount of haemoglobin as haem and chlorophyll look so similar. My incredulity contrasted with the health food expert who supplied the wheatgrass enema to the presenter. The expert said there was a lot of scientific evidence that supported her view. There was not time in the program to give the full account for the reasons for my incredulity so I thought it worth expanding a bit here in case anyone is interested.
· Haem is an iron porphyrin and chlorophyll is a magnesium chlorin. Superficially haem and chlorophyll appear similar in chemical structure – one of the ideas that led to Charles Schnabel in the 1930s suggesting wheatgrass could be a superfood. Proponents today suggest it can increase the amount of haemoglobin in the blood. However, in the 1930s the structure of proteins was not known. Not only does chlorophyll contain magnesium rather than iron at its centre, but it has a long organic side chain. Even if you could replace the magnesium with iron, you could not put the iron-chlorin into the haemoglobin structure. It just won’t fit.
· So maybe the chlorophyll provides building blocks to help us make more haem? In this case wheatgrass juice might increase haemoglobin by an indirect mechanism? There are a number of problems with this idea. First there is no evidence that we absorb chlorophyll, whether taken orally or rectally. Even if we did absorb chlorophyll, we cannot convert a chlorin into a haem. The pathways are linked metabolically; plants make haem and chlorophyll from the same organic starting materials. But we have don’t have the enzymes to make this conversion.
· In contrast to chlorophyll, we do absorb haem quite efficiently. But we immediately break it down for its iron content, throwing away the porphyrin cofactor. The result. If you want dietary iron, eat black pudding not wheatgrass juice.
· Still maybe there is an unknown mechanism for the wheatgrass effect? Is there any science that supports the effect of wheatgrass juice increasing blood oxygen content? If there was good human trial data then we could search for a mechanism. After all gut bacteria are increasingly seen as important to health. Maybe feeding our gut chlorophyll has an effect on the body, even if none of that chlorophyll is absorbed? The problem is that there is no good scientific evidence in human studies of any blood oxygen, health benefit or sports performance effects. I looked hard and could find only a very few papers. The first  is full of flaws and, as far as I can see not peer reviewed. However, let’s assume the study was well conducted. The effects observed (0.26% increase in arterial blood oxygen saturation) would have no significant physiological benefit; indeed there was no performance boost reported in this paper.
· If wheatgrass juice really did increase the number of red blood cells it would be a godsend for many patients who have anaemia. Who needs epo or blood transfusions if you can just eat crushed grass? Two papers looked at this effect. The first, a small pilot study , suggested that consuming about 100 mL of wheat grass juice daily could reduce the need for blood transfusions in patients with thalassemia major. However, a later, larger study contradicted this . Neither study was randomised or blinded.
· Lest I be accused of being a complete cynic there is one study published that holds some promise. In a small double blinded, placebo controlled trial in ulcerative colitis (inflammatory bowel disease), wwheatgrass seemed to have some beneficial effects . This study was conducted in 2002 and, as far as I can tell, has not been followed up. But at least it has the benefit of not straining credulity – the chlorophyll is suggesting to act where we know it goes – the gut.
In short wheatgrass juice is no superfood. At least not when it comes to increasing the number of red blood cells. There is no reason for WADA to put it on the sporting banned list or develop chlorophyll anti-doping tests.
 M Handzel, J Sibert, T Harvey, H Deshmukh, C Chambers. Monitoring the Oxygenation of Blood During Exercise After Ingesting Wheatgrass Juice. The Internet Journal of Alternative Medicine (2008) Volume 8 Number 1.
 R.K. Marawaha, D. Bansal, S. Kaur, A. Trehan, Wheat grass juice reduces transfusion requirement in patients with thalassemia major: a pilot study, Indian pediatrics, 41 (2004) 716-720.
 D.R. Choudhary, R. Naithani, I. Panigrahi, R. Kumar, M. Mahapatra, H.P. Pati, R. Saxena, V.P. Choudhry, Effect of wheat grass therapy on transfusion requirement in beta-thalassemia major, Indian journal of pediatrics, 76 (2009) 375-376.