A MICROSCOPIC VIEW OF THIS CHAPTER
• Food intolerance is different than a food allergy.
• Lactose intolerance is the inability to digest lactose.
• Probiotics can assist in lactose digestion.
• Lactobacilli contain lactase, which helps break down lactose.
• Bifidobacteria ferment lactose, which helps with its digestion.
What is lactose? Lactose is a sugar found in milk and dairy products. In a healthy digestive tract, lactose is broken down into two simpler forms of sugar called glucose and galactose by the enzyme lactase.
Canadian milk consumption has fallen substantially over the past two decades—from about 430 glasses per person in 1980 to 370 glasses in 1999.
Glucose and galactose can then be easily absorbed into the blood and used as energy around the body.
Lactose Intolerance versus Milk Intolerance
It is common to confuse lactose intolerance with cow’s milk intolerance because the symptoms are often the same. However, the two are not related. Being intolerant to cow’s milk is an allergic reaction to proteins in the milk and involves the immune system. Lactose intolerance is a problem with digesting a sugar and thus involves the digestive system.
The majority of the world’s population cannot digest lactose. It is estimated that about two-thirds of the world’s adult population suffers from lactose maldigestion, also called lactose intolerance. Symptoms include loose stools, abdominal pain, bloating, flatulence and nausea. Typically these symptoms will begin about 30 minutes to two hours after eating or drinking foods containing lactose. The severity of the symptoms will vary depending on the amount of lactose a person can tolerate, a person’s age, digestive rate and ethnicity.
Estimated Prevalence of Lactose Intolerance
Native Americans 90%-100% Asians 90%-100% Afro-Americans 80%-90% Mediterranean descendents 80%-90% Jewish descendents 80%-90% Northern Europeans 40%-55%
Many humans are unable to properly digest lactose. It is a normal condition in adult mammals and thus cannot be regarded as a disorder. Despite not being classified as a disorder, people who cannot properly digest lactose find this illness causes them a lot of discomfort and requires that they alter their lifestyle and diet. Individuals with lactose intolerance tend to eliminate dairy products from their diet. Dairy products are good sources of dietary calcium and other nutrients. As this illness is not seen as a disorder, these people do not receive proper counseling on how to ensure their diet is rebalanced to ensure they still get sufficient amounts of calcium and other key nutrients. Lactose intolerance is a major health problem. It can result in dietary deficiencies in nutrients, such as calcium, and this can lead to degenerative diseases including osteoporosis.
Two major types of lactose maldigestion can occur. At birth, the enzyme β-galactosidase, more commonly known as lactase, is present in high quantities. Yet, as we become children and adolescents, the concentration of lactase in our digestive system decreases and we are less able to digest lactose.
Non-Dairy Dietary Sources of Calcium
Dairy is not the only source of calcium, despite misleading representations on North American Food Guides. Millions of Asians who use the Chinese food guide, called The Pagoda, are told about dairy equivalents. Appendix 12-1 has a more complete list of calcium food sources. These include:
broccoli
bok choy
kale
sardines
salmon
almonds
sesame seeds
The second type of lactose maldigestion is caused by a loss of mucus on the lining of the small intestine. This happens in cases of diarrhea or bowel resection. A loss in intestinal mucosa is a problem for lactose digestion. Lactase is produced by the cells that line the small intestine. The loss of intestinal mucosa is an unhealthy event for these cells. Less lactase is produced, in turn, reducing the ability of the body to properly digest lactose. As such, it is no surprise that lactose maldigestion is frequently experienced by adults who suffer from acute or chronic enteritis or bowel resection.
Certain probiotic species are capable of helping with lactose digestion. Lactobacilli species can help digest lactose. Lactobacilli can produce the enzyme lactase. Bifidobacteria use fermentation to break down lactose. As such, those suffering from lactose intolerance may benefit from consuming a variety of probiotic species.
LACTOBACILLI FOR LACTOSE INTOLERANCE
One of the first beneficial effects of probiotics ever demonstrated was their ability to ease lactose intolerance. Perhaps it started with the observation that lactose-intolerant individuals can handle the lactose in yogurt better than that found in milk. This is likely because yogurt is also a source of lactase, the enzyme that aids in the breakdown of lactose in the digestive system. When the bacteria (Lactobacilli) in the yogurt are broken open by the bile salts in the small intestine, they release high levels of lactase in the gastrointestinal tract. Lactase acts on the lactose and aids in its proper digestion. When there is no undigested lactose in the intestinal track, there is no discomfort, and other lactose intolerant symptoms.
Lactose-intolerant adults tolerate yogurt better than milk.
Clinical trials have tried to identify which probiotic species offer the best reduction in lactose intolerance symptoms. One of the most common bacteria species found in yogurt is Lactobacillus acidophilus. L. acidophilus is a lactase-containing bacteria. However, L. acidophilus has a higher resistance to bile and thus it may not break down as well as other bacteria. This may explain why preliminiary clinical trials in which L. acidophilus was given in supplement form do not show significant improvements in lactose intolerance symptoms.
The study was conducted just before 2000. Subjects took the strain Lactobacillus acidophilus BG2FO4 twice daily for seven days in a randomized, controlled human trial. The results were not statistically significant and failed to produce convincing evidence that this species eliminated lactose intolerance in these subjects.
A study using milk containing L. acidophilus and L. bulgaricus confirmed that L. acidophilus is not the best choice for lactose-intolerant people. They both have similar abilities to produce lactase, but L. bulgaricus is superior for those with lactose intolerance. It has a cell structure that allows its lactase to more easily enter the intestines. In fact, L. bulgaricus was found in the study to effectively assist with lactose digestion in those who suffered from lactose intolerance.
It is likely that other probiotic supplements can help improve lactose intolerance symptoms. VSL#3 is a blend of probiotics produced by Seaford Pharmaceuticals in Ontario, Canada. It has been used in a number of clinical trials. Some studies noted in other chapters of this book have found this supplement has positive results on health; however, VSL#3 does not appear to assist in lactose intolerance. In a clinical study, VSL#3 was given to 10 volunteers for one or four days. Two weeks later, a lactose challenge was carried out by the volunteers. No statistically significant changes were observed, but there was a trend toward improvement. To date, the research does not suggest that this combination of probiotics is effective in treating lactose intolerance.
Current research is working to discover probiotic strains, which are rapidly destroyed by bile in the small intestine. These strains can be carriers of lactase into the body to help with lactose digestion. These probiotics will help with lactose digestion and potentially will alleviate lactose intolerance more efficiently. For now, having a healthy Lactobacilli population in the small intestine and consuming yogurt over other dairy products are strategies that can be used by people who suffer from lactose intolerance.
Some experts suggest that it is not the Lactobacilli that are so important, but Bifidobacteria that improve lactose intolerance symptoms.
BIFIDOBACTERIA FOR LACTOSE INTOLERANCE
Lactose intolerance can be reduced by lactase released into the small intestine when Lactobacilli are broken down by bile salts. Probiotics may also play a helpful role in lactose intolerance in the large intestine. When researchers compared the differences in lactose intolerance symptoms in volunteers, they found that their symptoms were caused by differences in the colon’s ability to break down lactose. In other words, it may not be the lactase from probiotics in the small intestine that aids symptoms of lactose intolerance, but the fermentation of lactose by probiotics in the colon. As such, changing the probiotic colonies in the colon may help lactose digestion. The probiotics best suited to do this are Bifidobacteria, the most prominent probiotics in the colon.
Bifidobacterium longum has been investigated as a potential probiotic treatment for lactose intolerance. It appears to have a positive effect. In a study, 11 lactose-intolerant volunteers were given a capsule (B. longum) and yogurt (B. animalis, L. bulgaricus and S. thermophilus ) respectively for 14 days. The subjects were given a food containing lactose to see how these probiotics helped them digest it. The researchers found that taking the high dosages of Bifidobacteria was helpful. The probiotics made it through the stomach and small intestine and were living in the colon. The Bifidobacteria in the yogurt and supplement caused an increase in the number of Bifidobacteria living in the colon of the 11 volunteers. Bifidobacteria are effective fermentors of lactose and other carbohydrates. The volunteers noted improvements in their ability to handle lactose-containing foods. Bifidobacteria appear to play an important role in alleviating lactose intolerance symptoms.
SUMMARY
Clinical research on probiotics and lactose intolerance suggests that an increased number of probiotics in the intestinal tract might contribute to the reduction of lactose intolerance symptoms. It is thought that the release of lactase by broken Lactobacilli in the small intestine and fermentation of lactose by Bifidobacteria in the colon help reduce the symptoms of lactose intolerance. The use of both families of probiotics may be helpful for people with lactose intolerance. Probiotic strains behave differently, and there is some evidence that suggests certain strains, concentrations and preparations are likely effective against lactose intolerance. Which strain or concentration is best is yet to be discovered.
