For more “good bacteria,” you can consume fermented foods and dietary supplements. Photo by Narong Khueankaew

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Q: Is there a recommended daily intake of probiotics?

A: There are two ways to get more good bacteria into your gut: fermented foods and dietary supplements. Fermented foods are the most natural source.

Probiotic supplements, which are typically sold over the counter, are reserved to treat specific ailments as suggested by your doctor and are not recommended for everyday use. Plus, supplements do not have the same FDA oversight as medications do.

So, a big question remains: How many probiotic foods do you need? That’s not easy to answer.

There is no recommended daily intake for probiotics, so there is no way to know exactly which fermented foods or what quantity is best. Therefore, the general guideline is to just add fermented foods to your daily diet when possible.

Why fermented foods? Foods that are fermented go through a process of lacto-fermentation in which natural bacteria feed on the sugar and starch in the food, creating lactic acid.

This process creates an environment that preserves the food and promotes beneficial enzymes, B vitamins and omega-3 fatty acids, as well as various species of good bacteria.

Another way to look at fermentation is that it takes one type of food and transforms it into another kind. For instance, cabbage becomes sauerkraut, cucumbers become pickles, soybeans turn into miso, and milk can be made into yogurt, cheeses, and sour cream.

If there is a potential downside to fermented foods, it is that their taste and smell can be quite strong, which may be unpleasant for some people. The unique flavors and textures of fermented foods are due in part to the different species of bacteria used.

On the upside, there are many types of fermented foods from which to choose, so there is a good chance you can find something you will enjoy.

The most common fermented foods that naturally contain probiotics, or have probiotics added to them, include yogurt, kefir, kombucha, sauerkraut, pickles, miso, tempeh, kimchi, sourdough bread and some cheeses.

Yogurt is considered the go-to player of probiotic foods because it has a flavor and texture that’s generally appealing to Western palates. Look for the words “live and active cultures” on the label.

Yogurt is easy to add to your diet. Besides having it for breakfast or a midday snack, you can substitute yogurt whenever you use mayonnaise in egg salad or potato salad, or in almost any baking recipe. Yogurt also can be the basis for sauces, salad dressings and marinades.

Q: I suspect my back and leg pain are related to spinal stenosis. What causes this and what treatments are available?

A: Spinal stenosis is narrowing of the central spinal canal — the channel inside the vertebrae that contains the spinal cord and nerve roots.

The narrowing may have been there since birth. However, much more often spinal stenosis develops gradually later in life secondary to arthritis, bulging or herniated discs, thickened ligaments or a combination of these.

A narrowed canal in the lumbar spine can cause leg pain, tingling or numbness, along with low back pain. Typically, the discomfort is worse when standing up straight or walking, with some relief by squatting or sitting.

Rarely the cause is infection, a tumor or bleeding — and then the symptoms usually progress rapidly.

When suspected, spinal stenosis and its cause can be confirmed by MRI or CT scan.

Initial treatment options for the most common types of spinal stenosis include:

• Pain medicine, such as acetaminophen
• Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or aspirin
• Muscle relaxants, since muscle spasm may accompany nerve irritation
• Physical therapy for stretching, strengthening and postural training

If there is no improvement, your doctor may recommend corticosteroids, which are powerful anti-inflammatory agents.

Sometimes, doctors prescribe a short course of an oral corticosteroid, such as prednisone. Or, he or she may refer you for a limited number of corticosteroid injections, during which the medication is injected into the space just outside the spinal cord (the epidural space). This reduces swelling and inflammation in or near the compressed nerves.

These injections should be performed by a person experienced in the procedure. The overall success rate varies widely in the published literature.

Some studies (and doctors) are more selective than others in choosing the best candidates for these injections. Also, the specific cause (such as arthritis, disk or ligament calcification) may play a role in the success rate.

Finally, improvement in symptoms may be more dramatic soon after the injection and wane with time.

As with any treatment, there are risks to consider when receiving corticosteroid injections for spinal stenosis. These include:

• Discomfort or numbness during the injection
• Infection
• Bleeding along the path of the needle
• Nerve damage
• Local bone loss (more likely with frequent injections)

Fortunately, serious complications are quite rare.

Surgery is usually the last resort, but it can ease or even eliminate symptoms by relieving pressure on the spinal cord and nerves.

Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, see health.harvard.edu.

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