Dr. Michael Greger June 13, 2014
For disease prevention and health maintenance, berries of all colors have “emerged as champions.” Research has focused mainly on cancer prevention and treatment. Studies show that the anticancer effects of berries are partially mediated through their abilities to counteract, reduce, and also repair damage resulting from oxidative stress and inflammation. Berries may also have many other positive effects, such as boosting detoxifying enzymes.
One of the more remarkable effects is that of blueberries on natural killer cell counts. Natural killer cells are part of our immune system’s rapid response team against cancer cells, eliminating cancer cells through the activation of cancer cell suicide via death receptors. They’re called natural killers because they don’t require activation by prior exposure. We don’t want to wait until our second tumor before our immune system starts fighting.
We have about two billion of these soldiers circulating in our blood stream at any one time, but we may be able to get a troop surge with blueberries. Researchers had athletes eat about a cup and a half of blueberries a day for six weeks to see if that would reduce the oxidative stress of long-distance running. They indeed saw a blunting of the spike in oxidant stress. But that’s not what sets that study apart.
The number of natural killer cells in the blood typically decreases after prolonged endurance exercise, dropping by half to only about one billion—that is, unless we’ve been eating lots of blueberries. If you click on the video on the next page, you can see a graph comparing natural killer cell numbers with and without blueberries. Those who ate blueberries retained close to the standard two billion cells. This is because six weeks of blueberries had doubled the resting number of natural killer cells up to over four billion. This has never before been demonstrated in humans. There was a study on goji berries, but despite a cup a day for a month, there was no significant change in the number of natural killers.
Another study, though, showed a significant increase in natural killer cell activity thanks to the spice cardamom. (Cardamom and blueberries—I never thought we’d be fighting cancer with blueberry muffins!) When researchers took some lymphoma cells in a petri dish and added cardamom, nothing happened. However, if we add some natural killer cells, about 5% of the cancer cells are wiped out. Add a little more cardamom, and our troops do better still. And then if we add more and more spice, then all of a sudden the natural killer cells are killing cancer like crazy—the same number of natural killer cells, but they’re now able to kill off ten times more cancer cells. While cardamom alone had no effect on cancer cells even at the highest dose, it seemed to enhance our natural killer cells’ killer instincts.
The same thing was found for black pepper: Black pepper alone, nothing, but when combined with natural killer cells, there seemed to be a boosting effect up to around 30 or 40% cancer cell clearance. If cardamom and black pepper are combined, they synergize and their individual effects are doubled. The researchers conclude that “Taken together, these data strongly suggest that black pepper and cardamom have the potential to markedly enhance the anti-cancer activity of natural killer cells.”
Exercise itself can improve immune function in general, but the blueberry finding is so far unique.
It is true that the blueberry study was funded by the North American Blueberry Council and the North Carolina High-bush Blueberry Council. However, just because the study was funded by blueberry councils doesn’t necessarily mean the science is suspect, but we would want to see the study independently verified, especially one so dramatic.