The good side of bacteria

Probiotics may help maintain a healthy and happy gut — but make sure you choose the right sources.

Published: February, 2021

There are many things in life that can be categorized as coming in both good and bad versions. The same applies to bacteria.

Bad bacteria like salmonella and E. coli can make you sick. Good bacteria like the kind in probiotics play an important role in keeping us healthy.

These good bacteria interact with the intestinal lining to protect the body from harmful invaders. They help the immune system function properly, which means better ability both to fight infections and to dampen chronic inflammation.

Know your bacteria

Some research suggests that certain probiotics help relieve symptoms of gut-related conditions like inflammatory bowel disease and irritable bowel syndrome.

"Many people could probably benefit by increasing their intake of probiotics," says Dr. Allan Walker, a professor of nutrition at Harvard's T.H. Chan School of Public Health. "The problem is the unsubstantiated hype that probiotic supplements have far-reaching health potential, which can keep people from choosing the best sources."

There are hundreds of bacteria classified as probiotics, but most come from two main species: Lactobacillus and Bifidobacterium. Within each of these are various strains.

There are two ways to get probiotics: fermented foods and over-the-counter products. According to Dr. Walker, fermented foods are the better choices primarily because over-the-counter supplements and formulas aren't subject to the necessary oversight. (See "Take care with supplements.")

Take care with supplements

Probiotics are also found in over-the-counter probiotic supplements and formulas. Most use Lactobacillus, Bifidobacterium, or a combination. The bacteria are concentrated and then dried to use as powders or in capsules, tablets, lozenges, and even gums. The issue with these products is that they are sold as dietary supplements and therefore don't require FDA approval. "So you can never be sure that the label claims about health benefits or the type and number of bacteria per serving are accurate," says Dr. Allan Walker, a professor of nutrition at Harvard's T.H. Chan School of Public Health. He advises you to avoid them unless recommended by your doctor.

Eat more fermented foods

Foods contain probiotics after going through lactofermentation, a process in which bacteria feed on the food's sugar and starch to create lactic acid, which helps preserve it.

Another way to think of lactofermentation is that it transforms one type of food into another kind—for instance, cabbage into sauerkraut, cucumbers into pickles, soybeans into miso, and milk into yogurt.

The exact amounts and specific strains of bacteria in fermented foods vary depending on how they are made. Besides probiotics, fermented foods may also contain other valuable nutrients like enzymes, B vitamins, and omega-3 fatty acids.

How much fermented food do you need to eat for optimal gut health? Unfortunately, there is no recommended daily allowance for probiotics, so it's uncertain which fermented foods or what amount is ideal, according to Dr. Walker.

"The general recommendation is simply to add more fermented foods to your diet," he says.

Probiotic Smoothie

Smoothies are a quick and easy way to get probiotics. Here is a recipe that is ideal for a breakfast, snack, or post-workout drink. Combine all the ingredients in a blender or food processor and blend until smooth.

Simple Fruit Smoothie

1 cup plain nonfat yogurt

1/4 cup orange juice

1/2 banana, cut into pieces

1/2 cup fresh or frozen blueberries

1/2 cup ice

Servings: 1

Serving size: 12 ounces

Nutrition: 260 calories, 0.5 g total fat, 0 g saturated fat, 0 mg cholesterol, 110 mg sodium, 42 g total carbohydrate, 3 g fiber, 26 g total sugars (includes 0 g added sugar), 24 g protein

Source: The Harvard Medical School 6-Week Plan for Healthy Eating.

Many choices

There are many fermented foods to choose from. Here are some common ones you can try.

Kefir. The tart yogurt-like drink is often made with dairy milk, but also comes in nondairy alternatives, like coconut water, coconut milk, and rice milk. Kefir also comes in fruit and vegetable flavors.

Kimchi. Kimchi is a spicy, reddish fermented cabbage dish. You can find jars of it at most grocery stores or Asian markets.

Kombucha. This tangy fermented tea drink is found in many grocery and specialty food stores. Some brands have added sugar, so make sure the label lists no more than 5 grams per serving.

Miso. The paste is a staple in Japanese cuisine, especially in soup. It's made from soybeans fermented with brown rice and has a strong, salty flavor.

Pickles. Choose brands brined in water and sea salt instead of vinegar. Vinegar stops good bacteria from growing.

Sauerkraut. Select raw or nonpasteurized sauerkraut, which contains more bacteria strains. You can find them in specialty grocery stores.

Sourdough bread. This kind of bread is baked with fermented flour. Not all store-bought bread labeled "sourdough" uses it, so shop at an artisan bakery or specialty grocery store.

Tempeh. Tempeh is a cake made from fermented soybeans with a firmer texture than tofu. It often comes precooked and ready to eat.

Yogurt. Some brands include a Live & Active Cultures (LAC) seal from the International Dairy Foods Association. This certifies that the product has been fermented. But not all yogurts have this, so look for the words "live and active cultures" on the label. Also, opt for plain, unflavored brands when possible, as they contain less sugar per serving than most flavored and fruit-based yogurts.

Image: © merc67/Getty Images

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