Probiotics and African American health
Probiotics are everywhere, from yogurt aisles to supplement shelves. They may help digestion, and researchers are finding that the bacteria living in our gut may influence the risk of colon cancer, a disease that hits African Americans harder than any other group. But the science behind probiotic pills is still catching up to the marketing, so it helps to know what they can and cannot do (see this review of probiotics and cancer prevention).
What are probiotics?
Probiotics are live microorganisms, often called “good” bacteria, that provide health benefits when consumed in adequate amounts. They are found in fermented foods like yogurt, kefir, sauerkraut, and kimchi, and in supplements.
Good bacteria help keep harmful bacteria in check and can reduce inflammation in the gut. What you eat matters even more than what you swallow in a capsule: fiber, beans, whole grains, fruits, and vegetables feed the good bacteria you already have, while diets high in processed foods and sugar push the balance the wrong way.
Probiotics, lactose intolerance, and IBS
Lactose intolerance (trouble digesting the sugar in milk) is common in African Americans, and here probiotics have real evidence: the live cultures in yogurt and kefir help break down lactose, so many people who cannot drink milk can enjoy yogurt without symptoms.
Irritable bowel syndrome (IBS) causes abdominal pain, bloating, and changes in bowel habits. Some people with IBS feel better on probiotics, but results vary by strain, and the American College of Gastroenterology does not recommend them for overall IBS symptoms because the evidence is inconsistent. If you try one, give it about four weeks and stop if it does not help.
Your immune system
Most of the immune system lives along the gut. Healthy gut bacteria help maintain the gut lining, which keeps harmful germs out of the bloodstream, and they help regulate inflammation. Probiotics have the best evidence for preventing diarrhea caused by antibiotics; broader claims about “boosting immunity” are not well proven.
Can probiotics lower your risk of colon cancer?
A 2018 study comparing African American and White patients having screening colonoscopies found big differences in their gut bacteria. African Americans had more inflammatory bacteria, such as Fusobacterium nucleatum, and fewer protective bacteria, such as Bifidobacterium and Akkermansia, along with less bacterial diversity overall. These differences may help explain why colon cancer is more common and more deadly in African Americans.
Whether probiotic supplements can change that risk has not been proven. The strongest evidence points to fiber: good bacteria turn fiber into short-chain fatty acids such as butyrate, which protect the cells lining the colon. I wrote an article on colon cancer and the benefits of screening; click the picture below to read more.
The precision medicine connection
Precision medicine asks what is driving your risk. For the gut, the answer is part genes and part environment, and the environment part is something you can change.
1. Our gut bacteria reflect our diet more than our race
In a famous “diet swap” study, 20 African Americans and 20 rural South Africans traded diets for just two weeks (Nature Communications, 2015). At the start, almost half of the Americans had colon polyps; none of the Africans did. On a high-fiber, low-fat traditional African diet, the African Americans’ gut bacteria made more butyrate, and their colon inflammation and cancer-risk markers dropped. The Africans eating an American diet saw the opposite. The differences in our gut bacteria are not fixed; two weeks of eating differently changed them.
2. Lactose intolerance is in our genes
Most adults of African ancestry lose the gene activity that digests lactose after childhood. Yet in a national survey, only about 1 in 4 African Americans believed they were lactose intolerant, even though about half had felt discomfort after eating dairy. That gap matters because many of us cut out dairy and miss its calcium and vitamin D. Yogurt and kefir with live cultures are a practical way to get those nutrients with fewer symptoms.
3. Screening still comes first
No probiotic replaces a colonoscopy or stool test. Colon cancer screening now starts at age 45 for average-risk adults, and Black Americans have the highest colon cancer death rates. Ask your doctor which screening test is right for you.
4. Know who should be careful
Probiotic supplements are not reviewed by the FDA for safety or effectiveness, and strains differ widely. People with weakened immune systems, including those on chemotherapy, organ transplant recipients, and people with central IV lines, have developed serious infections from probiotics and should check with their doctor first.
These are the kinds of differences covered in Better Black Health, written for patients and families, and Precision Medicine for African Americans (Springer Nature), written for clinicians.
Always consult your doctor
Much of the research on probiotics and cancer is early or observational, and gut bacteria vary from person to person. The safest bet is to eat a high-fiber diet with fermented foods, get screened, and talk with your doctor before starting a supplement. Check out my podcast interview with gut health specialist Dr. Janese Laster below.
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