Boosting Immune Function with Berries

I have a video on preventing infections with kiwifruit, which are technically berries (known originally as Chinese gooseberries before some innovative New Zealand exporters named the fuzzy brown fruit after their fuzzy brown national bird). Any other berries that might help? A randomized, placebo-controlled interventional study entitled “Regular Consumption of Concord Grape Juice Benefits Human Immunity” found that drinking purple grape juice boosted the number of circulating gamma-delta T cells, one of our first lines of immune defense. However, this finding has yet to be followed up with a study to see if this has a meaningful effect on infection rates; but a similar study on cranberry juice did.

Funded, predictably, by Ocean Spray, a 10-week trial found that the gamma delta T cells of those drinking a low-calorie cranberry juice beverage appeared to be proliferating at nearly 5-fold the rate. However, this boost did not translate into fewer colds in the cranberry group compared to placebo. Those who did get a cold on cranberry juice did seem to suffer fewer symptoms, but not enough to make a difference in terms of days missed from work or an impairment of their daily activities. A placebo-controlled cranberry juice study on preschoolers flopped across the board.

Blueberries can have a similar stimulatory effect on natural killer cells, vital members of the immune system’s rapid-response team against virus-infected and cancerous cells, as I previously detailed. Interventional studies found that blueberries can protect against cancer in mice and hamsters but have not yet been tested in cancer patients; but black raspberries have.

Colorectal cancer patients were given the equivalent of more than a pound (0.45+ kg) of fresh berries a day (nearly five cups) for an average of four weeks before and after biopsies of their cancer were taken. There was no control group to verify, but after eating black raspberries, their tumors were infiltrated by nearly twice as many natural killer cells, along with greatly enhanced activity and greater expression of a tumor suppressor gene known as Smad4. In mice this translates into a suppression of cancer progression, but this has yet to be confirmed in people.

Macrophages are another “first responder” type of immune cell whose function tends to decline with age. Derived from the Greek words makros and phagein, meaning “big eater,” macrophages engulf and devour invading pathogens. Sprinkling some freeze-dried açai berries onto human macrophages in a petri dish enables them to munch up to 40 percent more microbes than usual, but as always, we want clinical endpoints. Sea buckthorn berries also appear to boost macrophage activity in vitro, but when put to the test (with an ounce (28 g) a day of frozen puree for three months versus placebo puree) they did not appear to help prevent respiratory, digestive, or urinary tract infections. The sea buckthorn berries did reduce CRP levels, a marker of inflammation, but that’s what randomized controlled trials of fruits and vegetables tend to find in general.

Goji berries are also anti-inflammatory but do appear to have relevant real-world beneficial effects on immune function. Older men and women were randomized to eat four teaspoons (23.70 ml) of powdered goji berries a day for 90 days or an identical-appearing placebo powder. On day 30 everyone received a flu shot. By day 60 the goji group already had significantly better antibody responses such that by day 90 three times more of the goji group achieved seroconversion (a sufficiently protective antibody threshold): 28 percent versus only 9 percent in the placebo group.