What is Lactose Intolerance?
Lactose intolerance is a condition that causes certain symptoms when you eat or drink things containing lactose. Lactose is a type of sugar found in dairy and milk products, including milk from mammals. Normally, when you consume lactose, an enzyme in your small intestine called lactase breaks it down into simpler sugars, glucose, and galactose. However, when there isn’t enough lactase, you can develop symptoms of lactose intolerance.
These symptoms can vary in severity from person to person. This condition, also known as lactose malabsorption, represents the most common type of intolerance to disaccharides – a group of sugars that includes lactose. Right after birth, our bodies produce lots of this lactase enzyme, but its levels go down as we grow older, despite continuously consuming lactose.
Interestingly, this decline is more common in some people than in others. For instance, people from South American, Asian, and African backgrounds tend to lose the ability to digest lactose earlier in life, whereas people from Northern Europe, and Northwestern India usually maintain this ability through adulthood.
If you’re lactose intolerant, you may experience belly bloating and pain, diarrhea, nausea, gas, and even loud, gurgling or rumbling noises from your belly (the medical term is ‘borborygmi’). Once people are diagnosed with lactose intolerance, they often start avoiding lactose by noting it on food labels, which can cause them to begin buying special products that have the lactose broken down already, adding to health care costs.
What Causes Lactose Intolerance?
Lactase enzyme deficiency can occur when individuals have lower levels of this enzyme, which is responsible for breaking down lactose (a type of sugar found in milk) into glucose and galactose, which can be easily absorbed by the body. There are four main types of lactase deficiency.
The first is “Primary Lactase Deficiency”, which is the most common type. This type involves a slow decrease in the activity of the lactase enzyme as a person ages. The activity of the enzyme starts to decline from infancy and the symptoms usually start appearing during adolescence or early adulthood. In simple terms, this means that the body gradually becomes less able to digest lactose as it grows older.
The second type is the “Secondary Lactase Deficiency”. This type is caused by illnesses, inflammation, or other conditions that damage the lining of the intestines. Some common causes include stomach or intestinal infections (gastroenteritis), celiac disease, Crohn’s disease, ulcerative colitis, chemotherapy, and antibiotics.
The third type is “Congenital Lactase Deficiency”. In this case, there’s a decrease or total absence of the lactase enzyme activity from birth due to inheritance patterns from both parents. This is a rare type and not much is known about its genetics. This deficiency becomes apparent in the newborn after they consume milk for the first time.
The fourth type is the “Developmental Lactase Deficiency”. This type is seen in babies born prematurely between 28 to 37 weeks of gestation. Their intestines are underdeveloped, resulting in an inability to break down lactose. As the babies mature and their intestines develop, this condition usually improves.
Risk Factors and Frequency for Lactose Intolerance
Lactose intolerance is a common condition that impacts a large part of the global population, including 65% on average. Though rare in children under 5, it typically becomes noticeable in adolescents and young adults. However, the condition’s prevalence widely varies among different ethnic groups. It’s most commonly found in African Americans, Hispanics/Latinos, and Asians, while it’s less common in people of European descent.
- Lactose intolerance affects 65% of people worldwide.
- It’s rare in children under 5 and typically starts appearing in teenagers and young adults.
- Its prevalence is higher in African Americans, Hispanics/Latinos, and Asians.
- People of European descent are least likely to be lactose intolerant.
There are variations in lactose intolerance types. The primary form of lactose intolerance is the most common, affecting up to 70% of people globally. In contrast, the congenital type, present from birth, is extremely rare, with only about 40 cases reported worldwide.
- Primary lactose intolerance is most common.
- The congenital form of lactose intolerance is extremely rare.
In the US, certain ethnic groups like African-Americans, American Indians, Hispanics or Latinos, and Asian-Americans are more likely to have lactose intolerance compared to White Americans. The rates are lowest among North Americans, Australians, and White Northern Europeans, ranging between 2% to 15%. However, the prevalence of lactose intolerance is 50% to 80% in South Americans, 100% in American Indians and some East Asians, 60% to 80% in Ashkenazi Jews and Africans.
- African-Americans, American Indians, Hispanics or Latinos, and Asian-Americans are more likely to be lactose intolerant in the US.
- White Northern Europeans, Australians, and North Americans have the lowest rates of lactose intolerance.
- Lactose intolerance is very common in South Americans, American Indians, East Asians, Ashkenazi Jews, and Africans.
The decrease in lactase, the enzyme that breaks down lactose, happens at different rates among different ethnicities. People of Chinese and Japanese descent lose 80% to 90% of their lactase activity within a few years after weaning. Jews and other Asian groups lose 60% to 70% of lactase activity several years after weaning. For White Northern Europeans and North Americans, it could take between 18 and 20 years for lactase levels to decrease to its lowest. The condition generally starts subtly and progresses over time, with many people first noticing symptoms during their late teenage years or in adulthood.
When it comes to lactose intolerance, men and women are affected equally.
Signs and Symptoms of Lactose Intolerance
Lactose intolerance is a condition that causes uncomfortable symptoms shortly after consuming dairy products, typically within 30 minutes to 2 hours. How severe these symptoms are can depend on how much lactose was consumed, how well the body can break down lactose (lactase function), and how swiftly food passes through the small intestine.
The most common signs and symptoms of lactose intolerance include:
- Diarrhea
- Bloating in the abdomen
- Abdominal pain
- Nausea and vomiting
- Feeling full
- Gas
Less frequently, people with lactose intolerance might experience other symptoms such as headache, muscle pain, joint pain, mouth ulcers, urinary symptoms, and difficulty concentrating.
Testing for Lactose Intolerance
If your doctor suspects you might be lactose intolerant, they will use a combination of methods to identify the problem. These methods usually include asking detailed questions about your past health, diet, and any family history of lactose intolerance, conducting a physical exam, and performing certain medical tests.
During your physical exam, your doctor will check for swelling, tenderness, and pain in your stomach area. These are some of the common signs of lactose intolerance.
As for medical tests, there are several types they can use to identify lactose intolerance:
- Hydrogen breath test: This test involves you consuming something containing lactose and then measuring the hydrogen levels in your breath. If these levels rise by more than 20 parts per million compared to your regular levels, it may suggest you can’t properly digest lactose.
- Stool acidity test: Lactose that doesn’t get properly absorbed in your body gets broken down in the colon into a substance called lactic acid. This lactic acid will make your stool (feces) more acidic than usual, and this test measures that acidity.
- Dietary elimination: To see whether lactose is causing your symptoms, your doctor might suggest you cut out food and drinks that contain lactose from your diet. If your symptoms go away, and then return when you start consuming lactose again, it’s a clear sign of lactose intolerance.
- Milk tolerance test: In this test, you drink a large amount of milk (500 mL), and then the doctor checks your blood sugar levels. An increase of less than 9 mg/dL may indicate that you have problems digesting lactose.
- Lactose tolerance test: Similar to the above, this test involves you consuming a load of lactose, and the doctor checking your blood sugar levels at different times. If these levels don’t increase by 20g, it could mean you’re lactose intolerant. But it’s worth noting that this test might give false results in people with diabetes or overgrowth of bacteria in the small bowel, and in people with abnormal movement of food and fluid through their gut.
Other tests like small bowel biopsy (which involves taking a small tissue sample from your small intestine) and genotyping (which examines your genes) can be used in some instances, but these are more invasive or not widely available.
Treatment Options for Lactose Intolerance
Lactose intolerance is managed by changing one’s diet, taking lactase supplements, and treating any underlying issues if the lactose intolerance is a secondary condition.
Changes to one’s diet usually involves consuming products that contain lactase, such as certain types of milk and calcium supplements. It’s also important to avoid foods that contain lactose to alleviate the symptoms. Some lactose-containing foods that should be avoided include:
* Soft and processed cheese
* Buttermilk
* Cream
* Milk
* Ice cream
* Sour cream
* Whey, an ingredient found in some foods
* Pancakes and waffles
* Mashed potatoes
* Butter
* Margarine
* Custard and pudding
Yogurt can contain different levels of lactose, depending on the type. Some people who are lactose intolerant might not be able to tolerate certain yogurts. However, Greek yogurt usually contains the least amount of lactose. Another option is plant-based milk, but these can have issues with taste and nutrition balance. Some people also find that probiotics, such as the DDS-1 strain of Lactobacillus acidophilus, can help improve symptoms. In addition to these alternatives, calcium and vitamin D supplements should be taken. If lactose intolerance is the result of another health condition (i.e., it’s secondary lactase deficiency), it’s important to get treatment for that underlying condition.
Another possible treatment for lactose intolerance is the use of lactase pills or drops. These supplements contain the lactase enzyme, which helps break down the lactose found in milk and milk-related products. They can be quite helpful for those dealing with lactose intolerance.
What else can Lactose Intolerance be?
When a doctor is trying to diagnose lactose intolerance, there are several other conditions that they might consider which can cause similar symptoms, including:
- Irritable bowel syndrome
- Celiac disease (an autoimmune disorder affecting the small intestine)
- Tropical sprue (a disease affecting absorption in the gut)
- Cystic fibrosis (a genetic disorder affecting the lungs and digestive system)
- Inflammatory bowel disease
- Diverticular disease (where small pouches develop in the colon wall)
- Intestinal tumors or polyps
- Excessive use of laxatives
- Viral stomach flu
- Bacterial infection
- Giardiasis (an infection in your small intestine caused by a microscopic parasite)
- Gastrinoma (a tumor in the pancreas or duodenum)
What to expect with Lactose Intolerance
Lactose intolerance, the inability to digest lactose found in dairy products, typically has a good outcome. Most people find significant relief from the symptoms simply by adjusting their diet and reducing their lactose intake. However, it’s important to note that lactose intolerance could potentially lead to osteopenia, a condition where bone density is lower than normal.
Interestingly, there’s a connection between Vitamin D deficiency and a specific gene variant related to lactose intolerance, specifically among white individuals. This is called the LCT-13910C>T gene variant. Hence, it is essential to maintain a balanced diet and monitor any concerning symptoms.
Possible Complications When Diagnosed with Lactose Intolerance
Here are some common complications:
- Thinning of the bones (Osteopenia)
- Extreme thinning of the bones causing them to become fragile (Osteoporosis)
- Lack of proper nutrients in the body (Malnutrition)
- Losing weight
- Bone softening disease, typically in children (Rickets)
- Lack of normal growth or development (Growth failure)
Preventing Lactose Intolerance
If you or a family member can’t tolerate lactose, it’s key to know that eating foods with lactose won’t cause lasting harm to your digestive system. This is different from celiac disease, which can cause permanent damage. If someone with lactose intolerance ensures they’re getting enough proteins, calories, calcium, and vitamin D, there’s no risk of long-term complications.
It’s impossible to prevent forms of lactose intolerance that are primary or inborn. But other types of lactose intolerance that come from issues with the digestive system can be prevented. If these issues are found and treated early to maintain the health of the digestive system, lactose intolerance can be avoided. Also, staying clear of foods with lactose can help limit the severity of the condition.
