Dear Doctors: I was surprised when a blood test at my annual checkup found I’m low in B vitamins, especially B12. My doctor gave me a shot, and the fatigue that I had been feeling went away. Why is B12 so important? What kinds of foods do you need to be eating to have enough of it?

Dear Reader: Vitamin B12 is what is known as an essential nutrient. That means two things: First, an essential nutrient is a chemical compound that is crucial to the proper functioning of the body, and thus to good health. The other thing that is important to understand about an essential nutrient is that the body either isn’t able to manufacture it or doesn’t produce it in the quantities needed. As a result, essential nutrients must be acquired through diet.

Although B12 is often referred to as a stand-alone vitamin, it is actually one of a group of eight B vitamins. Known as the B complex, these vitamins work individually and also as a group to maintain health and well-being. They help make nutrients available to the body, are important in maintaining brain function and also in the production of energy. B12 plays a crucial role in the manufacture of red blood cells; keeps nerve fibers throughout the body healthy; helps the body convert protein, carbs and fat into energy; and plays a key role the synthesis of DNA.

A B12 deficiency can cause the general fatigue that you were experiencing. It can also lead to certain types of anemia, malfunction or even structural damage of the nerves, muscle weakness and gastrointestinal issues. Additional symptoms can include tingling or numbness in the feet and hands, problems with vision, changes to balance and mobility, pale or jaundiced skin, a sore or swollen tongue, problems with sleep and changes to memory or cognition.

The body can store B12 in the liver. However, the supply is limited and, thus, must be replenished. Red meat, fish, shellfish, eggs, poultry, milk and other dairy products all contain varying amounts of vitamin B12. Prepared products, including breakfast cereals, nondairy milks, nutritional yeast and meat substitutes are fortified with B12. The nutrient is also available in vitamins, nutritional supplements and, as your own doctor delivered it, as an injection. Vegans and vegetarians, who don’t eat animal products, must make a special effort to get adequate B12 in their diets.

A diet rich in B12 is only half of the equation. The body must also be able to properly digest the foods that contain it. As a result, adults over the age of 50, who begin to produce fewer digestive enzymes, people who have undergone weight loss surgery and those living with certain medical conditions, such as Crohn’s disease, can struggle with absorption. The long-term use of heartburn medications, which reduce production of the stomach acid needed to absorb B12, can also contribute to B12 deficiency. If anyone suspects they may have a B12 deficiency, we encourage them to check in with their doctor.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I know that high-fiber foods keep your gut microbiome healthy. But I just saw on the news that spending a lot of time in nature is also really helpful. Do you know if that is true? One of my goals for 2025 is a better gut microbiome, so as a hiker and gardener, I sure hope so!

Dear Reader: When talking about the health of the gut microbiome, the focus tends to be on diet. You are correct that the care and feeding of the trillions of microbes of the gut microbiome entails a diet rich in a wide variety of fresh vegetables, fruits and leafy greens. Basically, eat the rainbow. Beans, grains and legumes are also important. So are fermented foods such as pickles, sauerkraut, kefir, yogurt and tempeh. High-fiber foods help feed the populations of microbes that make their homes in the large intestine, while fermented foods contribute to their diversity. It is also important to limit ultra-processed foods, keep a lid on added sugars, drink enough water and get adequate sleep and exercise.

Newer research into the health of the gut microbiome suggests another essential piece of the puzzle, and that is the benefits of regularly spending time in the natural world. This appears to work in two ways. One is to expose people to a wide range of beneficial bacteria, which can contribute to the diversity of gut populations. The other is that regularly spending time outdoors helps to lower stress levels and imparts a sense of well-being. Each of these not only help us emotionally and mentally, but they also appear to benefit the populations of microbes in the gut.

In one intriguing study, researchers found that urban preschoolers who took part in a program of outdoor nature-related activities not only showed marked improvements in mood, stress and mental well-being, but their gut microbiomes became healthier as well. Analysis of fecal samples collected at the start and finish of the 10-week study showed greater diversity of microbial populations. There was also an increase in a specific microbe that is associated with improved serotonin production and lower levels of inflammation.

In a different study, researchers compared the gut microbiomes of children who played indoors for four weeks with those who played outdoors only. The result saw similar beneficial changes in gut diversity in the outdoor children, as well as increases in the biomarkers of immune system health.

When you think about it, this all makes sense. Indoors, the primary sources of microbes are other people, pets, dust, water, HVAC emissions and indoor plants. Exposure to cleaning products, which slow microbial growth, also contribute to a decrease in gut diversity. Being outdoors, by contrast, provides exposure to a rich array of microbes from plants, animals, soil and air. They transfer to the body via contact with the skin and through the respiratory and digestive systems.

Emerging research continues to link being outdoors to improved gut diversity, and also to improved immune response. Make being outdoors a regular part of your day, and the tiny residents of your gut microbiome will be grateful.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I just got the new COVID-19 booster, and the nurse said hardly anyone is getting the updated shot this year. I’m not surprised because after years of headlines, COVID-19 is gone from the news. I’m also hearing it’s getting harder to track. Do you know why? Are people still getting sick?

Dear Reader: It was just after the new year in 2020 that COVID-19 first entered the general conversation. A new respiratory illness, similar in many ways to pneumonia, was causing concern. Highly contagious, and with no effective treatments or vaccine, it soon expanded into a global pandemic. In the United States, we have had more than 99 million confirmed cases of COVID-19 to date, and the disease has caused more than 1 million deaths.

Today, thanks to vaccines, growing herd immunity and the emergence of effective drugs and treatments, the COVID-19 emergency has ended. No longer a pandemic, it is now considered to be endemic. That means a disease is embedded in the population, but it occurs at predictable and manageable levels. And, interestingly, as you have heard, this transition is also making COVID-19 data more difficult to track. Thanks to accurate home tests and milder illness, not all cases get reported. Hospitalizations, which do get reported, have also dropped significantly. In an effort to predict and prepare for local surges of illness, many communities are now tracking the ebb and flow of the COVID-19 virus in wastewater.

At this time, the Centers for Disease Control and Prevention reports that viral activity in wastewater for COVID-19, which has been low nationwide, is beginning to surge. The same goes for ER visits and hospitalizations. A handful of states -- including New Mexico, Arizona, Massachusetts and Minnesota -- are now reporting high viral activity in wastewater. A new variant, known as XEC, has recently emerged as the leading cause of disease, accounting for 45% of new cases. The good news is that a nationwide surge in COVID-19 activity has not been detected. This may be due to the summer surge, which left many people with short-term immunity.

The nurse you spoke with is correct about the low rate of vaccination with the updated COVID-19 shot. Information collected by the CDC shows just 20% of adults older than 18 have received the updated COVID-19 vaccine. That number improves to 44% when narrowed down to adults 65 and older. This is unfortunate because, although not nearly as deadly as at the height of the pandemic, COVID-19 can still cause serious illness and lead to hospitalization.

People who become infected also run the risk of developing long COVID. That’s the collection of symptoms that linger for months, and sometimes years, after initial infection. Long COVID affects between 10% and 30% of people who have had COVID-19, including those with mild illness. The cause is still not understood, and there is no targeted treatment. The good news is, being vaccinated not only helps protect against infection and serious illness, it also reduces the risk of long COVID. Anyone who hasn’t gotten the updated COVID-19 vaccine should please consider doing so.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)