A clue to explain why you should avoid red meat
November 9, 2008
Several years ago, Professor Ajit Varki of the University of California, San Diego
discovered a molecule called Neu5Gc that appears in the tissues of every mammal
except humans (Proceedings of the National Academy of Sciences, September 29, 2003).
Now he has put together the pieces of a puzzle that may explain why humans evolved
with large brains and why, if we want to live into old age, we should probably avoid
eating meat from any other mammals (Science, October 31, 2008).
His theory depends on evolution. Living creatures on earth started as one-celled
organisms, progressed to 2 cells, and eventually to fish and birds. A mutation
occurred in progressing to mammals, who developed the gene to make Neu5Gc. Mammals
progressed to apes and Neanderthals, and as humans evolved, Neu5Gc added a single
oxygen atom to become a different molecule called Neu5Ac. So Neu5Gc is found in all
mammals and their milks except humans. It is not in fish or birds. Interestingly,
the Neu5Ac molecule explains why humans are the only mammal to suffer from malaria.
The malaria parasite cannot enter a cell until it grabs onto the Neu5Ac on the
surface of human cells.
Many epidemiological studies show that people who eat red meat are at increased risk
for heart attacks, strokes, at least 17 different cancers, diabetes, autoimmune
diseases, arthritis and asthma. Scientists have blamed saturated fats or burnt fats,
but this does not explain why red meat is linked to all of these diseases while
poultry, fish or saturated fats from plants are not.
Dr. Varki proposes another theory. When humans ingest the flesh or milk of any
mammal, they absorb Neu5Gc and treat it the same way as an invading germ, so they
make antibodies against it. This turns on their immunity and keeps it active so it
eventually attacks the host itself, the human body. This is called chronic
inflammation, which can lead to heart attacks, strokes, cancers and so forth.
Since humans cannot make Neu5Gc, any amount found in human cells come from the
mammals that they have eaten. Neu5Gc is found in high levels in tumors, with the
highest levels in metastasizing tumors. In our food supply, Dr. Varki found very
high levels of Neu5Gc in beef, pork, lamb and goat, and moderately high amounts in
milk and cheese. Low levels are found in turkey, duck, chicken and eggs; and
negligible amounts occur in plants and seafood.
I stopped eating meat many years ago, and this report makes me even more convinced
that it should be avoided. I eat lots of fruits, vegetables, whole grains, beans
and nuts, as well as fish and shellfish. Eggs, long thought to be a harmful high-
cholesterol food, now appear to be a healthful dietary staple. While poultry
appears to be a healthful food according to Dr. Varki's theory, I still do not eat
it. I do not drink milk and now plan to limit cheese as well.