Last week I watched the History Channel’s second installment of Evolution – this time on the evolution of guts. Pharyngula has a write up of the episode. One item that especially interested me was the bit about how cows and other ruminants evolved to eat grass. I’ve been involved over the years in several debates about whether humans can gain any benefit from drinking wheatgrass, as is sold at Jamba Juice and other health food outlets. As I wrote in Wheatgrass madness over three years ago, I don’t think we can, primarily because we can’t digest grass. The presenters of this program appeared to agree with me.
The first point the presenter made was that grass is a low-quality food – something that seems inconsistent with the claims of wheatgrass proponents that somehow wheatgrass is “superfood”. Its low quality is probably one reason cows have to eat so much of it – watch them and that’s all they do all day. It seems unlikely one small 2oz shot would make much difference, even if we could absorb its nutrients.
The second point was that only ruminants can digest grass, and I see no reason wheatgrass should be an exception. I’ve had several wheatgrass proponents respond that the juicing process breaks down the cell walls to make the nutrients available to humans, but the History Channel program made it clear there’s more to it than that. To demonstrate this they showed a surgically fistulated cow – a cow with a surgically implanted hole in its side that allows researchers to get their hands right into its gut. It sounds a little disgusting (and looks even more so - see the picture on the right), but apparently the cow is fine (although to be honest, no one actually asked the cow what it thought). In the TV program they showed you the inside of the cow’s gut through the fistula, and someone actually put a hand in to withdraw some of the partially fermented grass. (Ew!) Anyway, the conclusion was that the gut of the cow, in addition to containing unique bacteria that are necessary to break down the cellulose to smaller molecules, also acts as a fermentation vat for the grass-digestion process. This lengthy fermentation process produces cellulase enzymes that break down the cellulose. And according to The New Scientist, this fermentation process is necessarily slow to prolong contact with the microbes so they have enough time to do their job. So not only does it seem unlikely that humans can get any benefit from wheatgrass, even cows don’t get an immediate benefit – it takes days fermenting. Claims of an “instant high” or that its nutrients are “assimilated into the blood in about 20 minutes”, are clearly false.
Ruminants swallow the grass they graze almost without chewing and it passes down the oesophagus to the rumen and reticulum. Here liquid is added and the muscular walls churn the food. These chambers provide the main fermentation vat of the ruminant stomach. Here bacteria and single-celled animals start to act on the cellulose plant cell walls. These organisms break down the cellulose to smaller molecules that are absorbed to provide the cow or sheep with energy. In the process, the gases methane and carbon dioxide are produced. These cause the “burps” you may hear cows and sheep making.
Not only do the micro-organisms break down the cellulose but they also produce the vitamins E, B and K for use by the animal. Their digested bodies provide the ruminant with the majority of its protein requirements.
Not only do I see no reason to modify my original wheatgrass post, this Evolution program seemed to confirm what I originally thought, namely that wheatgrass is useless as food for humans.
Wheatgrass Myths v. Facts
From the above, I think we can say that most of the favorable claims for wheatgrass are myths at best. Some facts about wheatgrass:
- Wheatgrass is a low quality food that does not contain anything even remotely close to "all of the vitamins and most of the minerals we need". (See Jamba Juice's wheatgrass nutrition data: 7% daily values (%DV) of Vitamin C; 10% iron; zero percent of everything else. Zero! Sheesh - eat an orange.)
- Wheatgrass does not contain enzymes that aid human digestion. Any enzymes that wheatgrass contains are enzymes that help wheatgrass metabolize its food; wheatgrass enzymes do not help you digest wheatgrass or anything else. (They may both be called "enzymes", but they are different molecules.)
- Special microbes and enzymes are necessary in the gut to break down the cellulose in grass. Humans do not have these enzymes, and so humans can't digest grass, whether it is juiced first or not.
- The digestion process, even in ruminants, is necessarily slow. This means that (a) human digestion would not be slow enough to digest wheatgrass (even if human guts had the necessary microbes, which they don't), and (b) if it was that slow (and had the microbes), wheatgrass would still not be absorbed into the body "within 20 minutes" as is claimed.
- Likewise, claims of a "high" after drinking wheatgrass are due either to the power of suggestion or some physiological reaction due to the body not being able to digest what it was just fed.
- Because it cannot be digested, wheatgrass cannot possibly be an energizer, build your blood (whatever that means), cleanse your body, or do any of the other magical things claimed for it.
So there you have it. On the plus side, aren't you impressed I didn't use any version of "Holy Cow" in the headline?
You charge how much for 2 oz!?