January 2011 Issue
By Sharon Palmer, RD
Today’s Dietitian
Vol. 13 No. 1 P. 20
By enhancing the intestinal flora, these microorganisms may have a macro effect when it comes to keeping people healthy and thriving.
Cold and flu season has arrived, serving as a reminder that eating to enhance the immune system is a hot trend. Sauntering down the supermarket aisle, consumers will surely spot a variety of food products—from cookies to juices—boasting immune health benefits. In fact, food industry insiders consider immune support a new functional food niche. The Nutrition Business Journal reported in February 2010 that immune-support ingredients are enjoying a boost due to issues such as the economic meltdown and the H1N1 pandemic, both of which made people think more about supporting their immune system in times of stress. Numerous other factors contribute to consumers’ increased desire for foods that may improve immune function, according to an October 2010 issue of Nutraceuticals World. Among them are an increasingly polluted world, hard-to-kill microbes, and pandemics lurking in the distance; more stress due to work and family responsibilities and the economy; and a reliance on processed foods that can potentially compromise a person’s immune system and increase his or her risk of illness.
As employees pay more of their healthcare costs, maintaining a strong immune system provides tangible value for many consumers. Mothers are always on the lookout for ways to help their children avoid catching the latest bug. Boomers are determined to live active lifestyles as they age, searching for preventive methods to maintain their health. According to the Natural Marketing Institute’s Health and Wellness Trends Report, consumers believe that maintaining good immune health is the best way to prevent illness. The increased interest in eating for immune health is good since infectious diseases are the world’s leading cause of morbidity.
This new trend is boosting the sales of immune health functional food products, particularly probiotics. According to market researcher Packaged Facts, the global retail market for probiotic and prebiotic foods and beverages was $15 billion in 2008, a 13% increase over 2007, with an estimated market of more than $22 billion by 2013.
But just how much science is there to support probiotics’ role in improving immune health?
Gut’s Role in Immune Function
The immune system, the body’s protective network that fends off the invasion of harmful substances such as bacteria, viruses, and chemicals and guards against the development of cancer, allows humans to flourish in a busy, interactive world. Multiple barriers protect against foreign invaders, including the skin, inflammatory responses, and specific immune responses, such as certain types of immune cells like natural killer cells and macrophages that destroy pathogens.
One key player in immune health is the gut, a part of the body that is constantly exposed to toxins and foreign antigens, such as those from food and microbes. According to nutrition and immune expert Simin Meydani, DVM, PhD, director of the Jean Mayer USDA Human Nutrition Research Center on Aging and the Nutritional Immunology Laboratory at Tufts University, who spoke at a December 4, 2009, Tufts seminar, “The gut is the largest immune organ in the body, accounting for 25% of the immune cells in the body that provide 50% of the body’s immune response. There are more than 400 species of bacteria residing in the gut, and they have symbiotic relationships with your body.” Meydani called the gut flora “the forgotten body organ” because of its vital yet underappreciated health functions.
“There are 100 trillion bacteria in our intestines. The assembly of intestinal bacteria is called the intestinal flora. They form an ecosystem like a flower garden,” reported Haruji Sawada, director of the Yakult Central Institute, at the Yakult International Nutrition and Health Conference on May 17, 2010, in Tokyo (which this writer attended as part of a Yakult-sponsored journalists’ tour). In fact, there are 10 times more intestinal bacteria than there are human cells in the body. Humans develop their intestinal flora after birth, not in the womb. Thus, newborn babies’ gastrointestinal tracts are sterile but quickly become colonized by microorganisms after birth. During babies’ first year of life, the intestinal microbiota begin to develop to resemble that of an adult.
The current knowledge base on intestinal flora is expanding. “It’s pretty clear that the microbes in your body are an important part of the development and function of the immune system. Microbes have evolved mechanisms to communicate with immune cells, and our bodies communicate with microbes,” says Mary Ellen Sanders, PhD, owner of Dairy & Food Culture Technologies, who consults on probiotics for the food and supplement industry. Scientists know that intestinal microbiota may aid in the maturing of immune cells and physically block the passage of pathogenic bacteria and antigenic components of foods.
Sawada explained that intestinal bacteria are separated into good (beneficial), opportunistic, and bad categories. Beneficial bacteria, such as Bifidobacteria or Lactobacilli, help maintain health by resisting bad bacteria and harmful substances and aiding digestion and nutrient absorption. Opportunistic bacteria such as Enterobacteria take advantage of certain conditions to cause disease. And bad bacteria such as Staphylococcus and Clostridium cause disease because they produce toxins or are carcinogens.
“Factors influencing the intestinal flora include an unbalanced diet, stress, fatigue, aging, antibiotic therapy, and bacteria-contaminated food,” said Sawada. “These conditions increase the levels of harmful bacteria in the intestines.”
Science on Probiotics and Immune Health
Looking to probiotics to support immune health is nothing new; the idea has existed for more than 100 years. Probiotics’ main benefit is that they help restore balance in the intestinal microbiota. “Probiotics are live microorganisms that beneficially affect the host by improving the intestinal flora,” said Sawada.
Scientific evidence is now emerging to further support probiotics’ role in immune health. “There are mechanistic studies that show when you consume a probiotic, it can interact with different immune cells and lead to potentially positive changes,” says Sanders. Tetsuji Hori, Yakult USA science manager, reports that while there are other mechanisms involved in probiotics’ immune benefits, natural killer cell, a lymphocyte that functions in the rejection of tumor cells and cells infected by viruses, is of particular interest. He reports that research indicates the probiotic Lactobacillus casei Shirota (LcS) augments natural killer cell activity.
“A growing number of studies show that probiotics can help healthy subjects stay healthy,” says Sanders. “For example, studies have shown that children in day care centers don’t get sick as often when they consume probiotics. If you combine the mechanistic studies with the studies showing fewer respiratory and GI [gastrointestinal] infections, it suggests that the immune effects are meaningful.”
Sanders reports that there are several examples of probiotics with scientific evidence supporting immune health benefits, including Lactobacillus casei DN-114 001 (DanActive), Lactobacillus reuteri ATCC 55730 (BioGaia Probiotic drops), Lactobacillus rhamnosus GG (Culturelle), and LcS (Yakult). The following are several examples of studies that show the immune benefits of probiotics among healthy subjects:
• In a randomized, double-blind Swedish study published in Environmental Health in November 2005, 262 TetraPak employees (day workers and three-shift workers who were healthy at the start of the study) received either a daily dose of L reuteri or placebo for 80 days. In the placebo group, 26.4% reported sick leave during the study compared with 10.6% in the L reuteri group. Among the shift workers, 33% in the placebo group reported being sick during the study period compared with none in the L reuteri group.
• Reported in Clinical Nutrition in August 2005, a randomized, double-blind, placebo-controlled intervention study was performed to investigate the effects of the consumption of Lactobacillus gasseri PA 16/8, Bifidobacterium longum SP 07/3, and Bifidobacterium bifidum MF 20/5 on the severity of symptoms and the incidence and duration of the common cold. Over at least three months during two winter/spring periods, 479 healthy adults were supplemented daily with vitamins and minerals with or without the probiotic bacteria. A significantly higher enhancement of cytotoxic plus T suppressor cells and a higher enhancement of T helper cells as well as significantly increased fecal Lactobacilli and Bifidobacteria were observed in the probiotic group. The intake of probiotic bacteria shortened common cold episodes by almost two days and reduced the severity of symptoms.
• Researchers studied the effects of Bifidobacterium lactis (BB-12) and L reuteri in a double-blind, placebo-controlled, randomized trial at 14 child care centers in Israel, with the results reported in Pediatrics in January 2005. Healthy term infants aged 4 to 10 months were randomly assigned to receive formula with one of the two probiotics or no probotics for 12 weeks. The L reuteri group, compared with BB-12 or controls, experienced a significant decrease in the number of days with fever, clinic visits, child care absences, and antibiotic prescriptions. Infants in the L reuteri or B lactis group had fewer and shorter episodes of diarrhea, with no effect seen on respiratory illnesses. These effects were more prominent with L reuteri, which also improved additional morbidity parameters.
• In a double-blinded, placebo-controlled study published in Clinical & Experimental Allergy in August 2008, scientists explored the relationship between LcS and seasonal allergic rhinitis, considering that changes in the gut microbiota have been implicated in the development of allergic disorders. A daily milk drink with or without live LcS was provided to one of two groups of 10 seasonal allergy rhinitis patients over a period of five months, after which time the researchers documented changes in immune status. Changes in the antigen-induced production of cytokines were observed in patients treated with probiotics, indicating modulation of the immune responses in allergic rhinitis.
While the research is building in support of immune-protection benefits in general populations, professionals might also consider the implications of probiotics in treating special conditions or groups of people. For example, Koji Nomoto, PhD, chief researcher of the Yakult Central Institute, presented data at the Yakult International Nutrition and Health Conference on the effects of the preoperative oral administration of synbiotics (prebiotics and probiotics) in patients with biliary cancer who were undergoing high-risk hepatobiliary resection. The study, published in the Annals of Surgery in November 2006, found that the preoperative oral administration of synbiotics enhanced immune responses, attenuated systemic postoperative inflammatory responses, and improved intestinal microbial environment. Such benefits may reduce postoperative infectious complications after hepatobiliary resection for biliary tract cancer.
“The emerging science on probiotics and immune health is exciting. Probiotic research also stands to gain tremendously as results from human microbiome projects become available. This global research seeks to characterize the microbes associated with humans and their role in health and disease,” says Sanders.
Recommendations
Just because science suggests that probiotics may support immune health doesn’t mean every product on the market offers the same advantages. “It’s important to remember that probiotic benefits are strain specific, dose specific, and maybe even matrix specific. For example, probiotics in capsules may have different effects than probiotics in yogurt. Also remember that not all products in the marketplace called ‘probiotic’ have solid science backing them,” stresses Sanders.
Indeed, there are scores of probiotic products available, and they’ve moved beyond fermented dairy products such as yogurt and kefir; today, dietary supplements and products such as frozen yogurt, cereal, juice, and cookies claim to contain probiotics. To complicate matters, consumers are easily confused by probiotics. This complex concept involves good and bad bacteria as well as a slew of complicated scientific terms about the immune system. And whether a particular probiotic product contains adequate amounts of efficacious probiotic strains is another matter.
“My strongest recommendation is to use probiotics with good-quality evidence behind them. But it can be hard to see benefits with immune health in consumers who are generally healthy anyway. Since there is a good history of safety with probiotics from genera such as Lactobacillus and Bifidobacterium, I don’t see anything wrong with people trying products out to see if they work for them,” advises Sanders. “If consumers choose probiotics in foods, they may see a reduction in being sick with GI or upper respiratory illnesses, and they can also benefit from the nutrients in the product, such as calcium and protein in yogurt. When it comes to specific applications in certain illnesses, such as immune-suppressed individuals, the science is emerging, so stay tuned. Be familiar with the research and look at the quality of the studies.”
— Sharon Palmer, RD, is a contributing editor at Today’s Dietitian and a freelance food and nutrition writer based in southern California.
Give Good Advice on Probiotics
• Not all probiotics are created equal. Different strains of even the same species can be different and may not produce the same effects. A probiotic is defined by its genus (eg, Lactobacillus), species (eg, rhamnosus), and strain designation (often a combination of letters or numbers).
• Trademarked names, often used by manufacturers for marketing purposes, are essentially an alias for the probiotic strain.
• Whether probiotics are found in foods or supplements, the content of the probiotic is generally more important than the way in which it is consumed.
• Probiotics sold as dietary supplements or food ingredients cannot legally claim to cure, treat, or prevent disease, but claims that relate the product to health are allowable.
• Ensure that sound science backs probiotics using the term “clinically proven” on their label and ensure that the products contain the specific strain(s) of bacteria at the same levels as those used in published research. The studies should be performed in humans and published in reputable peer-reviewed journals.
• Just because a product says “probiotic” doesn’t mean it is a probiotic. Some products do not have clinically validated strains or levels.
• People should discuss their use of probiotics with a physician, and warnings of side effects or symptoms should be reviewed.
• Consumers should look for the right quantity of probiotics, which are measured in colony-forming units (CFUs), the measure of live microbes in a probiotic. The CFU amount should be the same as that shown to be effective in clinical studies. Different probiotics have been shown to be effective at different levels; thus, it’s impossible to provide one count for all probiotics.
• People should pick a product from a trusted manufacturer, who is more likely to ensure that the probiotic product has the same strain(s) and is as potent through the end of shelf life as what was used in clinical studies.
• The product label should reveal the following: strain, CFUs, expiration date, suggested serving size, health benefits, proper storage conditions, and corporate contact information.
— Author adapted information from The International Scientific Association for Probiotics and Prebiotics (www.isapp.net)
