Chlorella May Help Preserve Immune Function During High Intensity Athletic Training

Sedentary women who start walking briskly on a treadmill for 45 minutes a day for a few months may cut their risk of upper respiratory tract infections in half. How exactly does exercise improve our immune system?

Approximately 95 percent of all infections are initiated at the mucosal surfaces—the moist surfaces, like our eyes, nose, and mouth. These are protected by antibodies like IgA, which provide “an immunological barrier by neutralizing and preventing viral pathogens from penetrating the body through the mucosal surfaces.” The IgA in our saliva, for example, is “the first line of defense against respiratory tract infections such as pneumonia and influenza.” As you can see in my video Preserving Athlete Immunity with Chlorella, moderate aerobic exercise—even just 30 minutes in the gym three times a week—may be all it takes to significantly boost IgA levels and significantly decrease the risk of coming down with flu-like symptoms.

We’ve known for a long time that prolonged heavy exercise, though, may reduce resistance to infectious disease, manifested by an apparent two- to six-fold increase in upper respiratory tract infection symptoms for several weeks following marathon running.

Sport coaches are advised to monitor immune function, since illness could ultimately lead to a decrease in performance. Therefore, it may be necessary to take protective actions to minimize contact with cold viruses, for example. Athletes can’t get away with just washing their hands and wearing a mask, though, because upper respiratory tract infections are often triggered by reactivations of latent viruses already inside our bodies, such as Epstein-Barr virus (EBV). As soon as our immune function dips, the virus becomes reactivated. Researchers found that IgA levels drop the day before EBV comes out of hiding and causes a spike in symptoms. “These results suggest that the appearance of [upper respiratory symptoms] is associated with reactivation of EBV and reduction of [salivary] IgA during training.”

How can we preserve immunity in athletes? In Preserving Immune Function in Athletes with Nutritional Yeast, I discussed the efficacy of using a one-celled fungi—nutritional yeast—to boost the immune systems of athletes. What about a one-celled plant?

Researchers in Japan found that IgA concentrations in breast milk could be increased by giving mothers chlorella, a unicellular, freshwater, green algae sold as powder or compressed into tablets. What about other parts of the body? Thirty tablets of chlorella a day for a month increased IgA secretion in the mouth, too. But does that actually help in a clinically meaningful way? Researchers in Canada tried to see if they could boost the efficacy of flu shots, but a chlorella-derived dietary supplement did not appear to have any effect. They were using some purified extract of chlorella, though, not the real thing.

What about giving it to athletes during training camp? High-intensity physical activity and group living create an environment ripe for infection, and, indeed, the training was so intense IgA levels significantly dropped—but not in those given chlorella each day. So, chlorella intake may attenuate the reduced IgA secretion during athletic training.


There is a caveat to the use of chlorella. See Treating Hepatitis C with Chlorella and Is Chlorella Good for You? to make up your own mind about whether the benefits outweigh the risks.

Interested in some other ways to decrease your risk of upper respiratory tract infections? See:

For the cuddliest way to protect your immune function, see my Are Cats or Dogs More Protective For Children’s Health? video.

What else can exercise do? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Best Foods for Acid Reflux

Gastroesophageal reflux disease (GERD) is one of the most common disorders of the digestive tract. The two most typical symptoms are heartburn and regurgitation of stomach contents into the back of the throat, but GERD is not just burning pain and a sour taste in your mouth. It causes millions of doctor visits and hospitalizations every year in the United States. The most feared complication is cancer. 

You start out with a normal esophagus. If the acid keeps creeping up, your esophagus can get inflamed and result in esophagitis. Esophagitis can transform into Barrett’s esophagus, a precancerous condition which can then turn into adenocarcinoma (a type of cancer). To prevent all that, we need to prevent the acid reflux in the first place.

In the last three decades, the incidence of this cancer in the US has increased six-fold, an increase greater than that of melanoma, breast, or prostate cancer. This is because acid reflux is on the rise. In the United States, we’re up to about 1 in 4 people suffering at least weekly heartburn and/or acid regurgitation, compared to around 5% in Asia. This suggests that dietary factors may play a role.

In general, high fat intake is associated with increased risk, whereas high fiber foods appear to be protective. The reason fat intake may be associated with GERD symptoms and erosive esophagitis is because when we eat fatty foods, the sphincter at the top of the stomach that’s supposed to keep the food down becomes relaxed, so more acid can creep up into the esophagus. In my video Diet & GERD Acid Reflux Heartburn, you can see a study in which researchers fed volunteers a high-fat meal—a McDonald’s sausage and egg McMuffin—compared to a low-fat meal (McDonald’s hot cakes), and there was significantly more acid squirted up in the esophagus after the high-fat meal.

In terms of later stages of disease progression, over the last twenty years 45 studies have been published in the association between diet and Barrett’s esophagus and esophageal cancer. In general, they found that meat and high-fat meals appeared to increase cancer risk. Different meats were associated with cancers in different locations, thoughj. Red meat was more associated with cancer in the esophagus, whereas poultry was more associated with cancer at the top of the stomach. Plant-based sources of protein, such as beans and nuts, were associated with a significantly decreased risk of cancer.

Those eating the most antioxidant-rich foods have half the odds of esophageal cancer, while there is practically no reduction in risk among those who used antioxidant vitamin supplements, such as vitamin C or E pills. The most protective produce may be red-orange vegetables, dark green leafies, berries, apples, and citrus. The benefit may come from more than just eating plants. Eating healthy foods crowds out less healthy foods, so it may be a combination of both.

Based on a study of 3,000 people, the consumption of non-vegetarian foods (including eggs) was an independent predictor of GERD. Egg yolks cause an increase in the hormone cholecystokinin, which may overly relax the sphincter that separates the esophagus from the stomach. The same hormone is increased by meat, which may help explain why plant-based diets appear to be a protective factor for reflux esophagitis.

Researchers found that those eating meat had twice the odds of reflux-induced esophageal inflammation. Therefore, plant-based diets may offer protection, though it’s uncertain whether it’s attributable to the absence of meat in the diet or the increased consumption of healthy foods. Those eating vegetarian consume greater amounts of fruits and vegetables containing innumerable phytochemicals, dietary fiber, and antioxidants. They also restrict their consumption of animal sources of food, which tend to be fattier and can thus relax that sphincter and aggravate reflux.

GERD is common; its burdens are enormous. It relapses frequently and can cause bleeding, strictures, and a deadly cancer. The mainstay of treatment is proton pump inhibitor drugs, which rake in billions of dollars. We spend four billion dollars on Nexium alone, three billion on Prevacid, two billion on Protonix, one billion on Aciphex. These drugs can cause nutrient deficiencies and increase the risk for pneumonia, food poisoning, and bone fractures. Thus, it is important to find correctable risk factors and correct them. Known correctable risk factors have been things like obesity, smoking and alcohol consumption. Until recently, though, there hadn’t been studies on specifically what to eat and what to avoid, but now we have other correctable factors to help prevent this disease.

For more on GERD, see: Diet & Hiatal HerniaCoffee & Mortality, and Club Soda for Stomach Pain & Constipation.

I also have a video about esophageal cancer, detailing the extraordinary reversal of the kinds of precancerous changes that lead to the devastating condition—with nothing but strawberries: Strawberries versus Esophageal Cancer.

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Image Credit: PDPics / Pixabay. Image has been modified.