Harvard Health Content API

The gut microbiota contains trillions of microbes, including both good and bad bacteria. Good bacteria help digest food and absorb nutrients, regulate appetite, synthesize vitamins, and support the immune system. When the gut microbiota becomes unbalanced because of an increasing number of bad bacteria, problems can arise. Keeping the gut balanced and healthy involves eating more probiotics (foods containing good bacteria) and prebiotics (foods that help existing good bacteria grow).

Bowel preparation (prep) is considered the most unpleasant part of the colonoscopy process, but it’s also crucial. A clean bowel helps the gastroenterologist more easily locate and remove polyps, small growths that can develop into cancer. If the prep is inadequate, the patient will have to repeat the process. Updated guidelines for gastroenterologists, published in 2025, can help them guide their patients to have more successful preps.

Daily nasal irrigation (also called nasal rinses) may reduce symptom severity and the duration of a cold. It can also relieve the congestion caused by sinus infections and allergies. It is unclear whether it can prevent colds. By means of a squeeze bottle, neti pot, or battery-powered system, saline (salt water) is inserted into one nostril and flows out the other. It’s important to always use sterile water, meaning distilled or cooled boiled water. The rinse helps wash away mucus and some inflammatory chemicals, reducing the swelling that’s responsible for congestion.

Total knee and hip replacements are highly successful procedures that can relieve pain and restore mobility for people with severe arthritis. Occasionally, joint replacement fails, and revision surgery is needed. Reasons for revision include infection, implant loosening, dislocation, and fracture. Warning signs of a problem include persistent pain, swelling, or instability. Revision surgeries are more complex, require longer recovery, and carry higher risks than the original surgery. Experienced surgeons who perform these procedures frequently tend to have the most success.

In a 2025 study, skipping breakfast was associated with a 10% increased risk for metabolic syndrome, a disorder defined by having three or more of the following: abdominal obesity, high blood pressure, high blood sugar, high triglycerides, and low HDL cholesterol.

An analysis of 217 trials found that lower-impact aerobic exercise (walking, cycling, and swimming) is most effective for easing knee osteoarthritis pain and improving function. Other exercise types, such as flexibility, mind-body, neuromotor, and strengthening, also offer benefits.

Culinary salts such as Himalayan pink salt, kosher salt, fleur de sel, and flaky sea salt can lend a delightful crunch or flavor to foods. However, they consist largely of sodium chloride, just like table salt, and are no healthier. Consuming too much sodium is tied to increased risks for damage to the heart, kidneys, and brain. Dietitians advise using only a small pinch of a fancy salt, perhaps as a garnish or condiment, to satisfy taste buds without going overboard with the salt shaker.

Dry eye disease is broken down into two types: In aqueous-deficient dry eye, the eyes don’t produce enough tears. In evaporative dry eye (sometimes called meibomian gland dysfunction) there are enough tears, but they’re unstable and evaporate too quickly. Dry eye symptoms include eyes that feel gritty, sandy, stinging, burning, scratchy, tired, or sensitive to light. People with symptoms often forgo seeing a doctor. Artificial tears are an effective starting point for many cases of dry eye.

The term ototoxicity describes inner ear damage from drugs that can cause tinnitus (ringing in the ears), and affect hearing and sometimes balance. Medications more likely to cause ototoxicity include aspirin; the antibiotics azithromycin and clarithromycin; certain chemotherapy drugs; loop diuretics such as furosemide (Lasix); and some biologics. These drugs can damage hearing by injuring hairlike projections in the inner ear. People taking ototoxic drugs should get their hearing tested before, during, and after using the drug.

Women over 60 need less iron than they did before menopause, when they lost iron through menstruation. Many conditions can lead to iron loss and iron-deficiency anemia, when the body can’t make enough red blood cells to properly carry oxygen throughout the body. Signs of iron deficiency include pale skin, fatigue, shortness of breath, weight loss, and chest pain. Tests can reveal iron deficiency and underlying reasons for iron loss. People should not take iron supplements without checking with their doctor. Too much iron can damage organs.