Dear Doctors: Why is there so much different advice about walking? I just read that doing 15 minutes a day can help you live longer. I've also heard that a few minutes after a meal is important, long walks help your brain and just a few short walks a day are good as long as you walk really fast.

Dear Reader: You've asked a great and reasonable question. With so many studies looking into the health benefits of walking, it's no surprise that the variety of findings might lead to confusion. The truth is -- and we're not trying to be cute here -- they are all correct. Walking is a great form of exercise. It's free, doesn't require special equipment and can be done virtually anywhere at any time. What these walking studies show is that the practice yields some type of health benefit when done at any pace, for any duration at any frequency.

Our bodies were built for walking. The biomechanics of how our muscles, bones and connective tissues move contribute more than just locomotion. With each step, the compression and release of the skeletal muscle helps move lymph throughout the body. The gentle shifts of weight that take place with each step keep connective tissues supple and lubricated. The simple act of maintaining good posture engages the core muscles. Add in how walking supports the heart and lungs, can lift mood and has been found to have a protective effect on cognition and it’s easy to see why it is often referred to as the perfect exercise.

When it comes to the different advice that has emerged from decades of research into walking, it isn’t actually contradictory. Each study simply highlights a different piece of what is a much larger puzzle. A walk after eating engages the large muscles of the legs, which leads to improved post-meal blood sugar control. Walking just a few times a day at a swift pace helps heart health and circulation. Studies have found that even a few minutes of walking several times a day leads to improved health. And now, a new study has linked the practice of walking 15 minutes or more each day to improved longevity.

The study, conducted by researchers in Australia, looked at health data from more than 33,500 adults in their 60s. Those who walked for 10 to 15 continuous minutes each day lowered their risk of heart disease and early death. As with all observational studies, the results can only suggest a link between walking and improved longevity; they can’t prove the connection. Still, with so many studies pointing to the health benefits of walking, the conclusions become hard to ignore.

When it comes to your own life, choose the type of walking that best fits your circumstances. Maybe it’s a post-meal stroll, a short brisk walk, a long weekend hike or a rotating mix of all three. The kind of exercise you genuinely enjoy is the one you’ll keep doing -- and that’s the one that will make the biggest difference.

(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: Does taking calcium help keep your bones strong or not? I am going through perimenopause now, and osteoporosis is on my mind. A friend says that just a calcium supplement isn't enough, you need to think about vitamin K. I haven't even heard of that. Can you please explain?

Dear Reader: Perimenopause refers to the physical changes that take place as a woman nears the end of her reproductive years. A shift in hormone production by the ovaries triggers these changes. Most notably, estrogen begins to fluctuate and gradually decline. As blood levels of estrogen and other reproductive hormones rise and fall, a range of symptoms occur. These include irregular periods, hot flashes, sleep disruption and mood changes. Because estrogen helps maintain bone density, perimenopause can also set the stage for osteoporosis. This is when the cycle of bone remodeling falls out of balance. Bone tissue is broken down more rapidly than it can be rebuilt. This results in porous, brittle and fragile bones that can be easily injured.

That brings us to the concept of supplemental calcium. The idea is that, because dietary calcium provides the raw material for bone remodeling, adding the mineral to the diet should help offset the bone loss. But as with many of our bodily processes, the reality is more complex. Calcium does not act alone. Its efficacy in bone remodeling is tied to vitamin D, zinc, magnesium, phosphate and vitamin K -- more specifically, vitamin K2.

Vitamin D boosts the absorption of calcium and phosphate from the intestine. It keeps blood levels of these minerals within the range needed to build bone. Zinc, magnesium and vitamin D each play a role in promoting bone formation. They support the balance between bone growth and resorption. Phosphorus contributes to bone mineralization. Vitamin K2 makes sure that calcium in the blood gets to the matrix of the bone, not the soft tissues of the circulatory system. It does this by activating a protein that binds calcium to the bone matrix.

As one reader wrote to us on this topic, "... taking calcium alone without zinc, magnesium and vitamin K2 is like trying to make a cake when the only ingredient you put in the bowl is flour." That means thinking about multiple dimensions when eating for skeletal health. It is possible to get each of these important building blocks in dietary supplements. However, we always urge patients to seek out real food sources.

You can find vitamin K2 in animal-based and fermented foods, including cheese, butter, egg yolks and liver. The traditional Japanese dish known as natto, made from fermented soybeans, is also a rich source of vitamin K2. Vitamin K2 is also produced in the gut microbiome. Good sources of zinc and phosphorus include red meat, poultry, seafood and shellfish, eggs and milk. You'll find vitamin D in fatty fish like salmon, eggs, liver and dairy products. And for magnesium, look to the plant-based world with leafy greens, avocados, bananas, nuts, seeds and legumes. Bottom line: Strong bones aren’t built by calcium alone.

(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.)

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Dear Doctors: My question is about the holidays, and it's two parts. The to-do list just seems to get longer each year, and I'm already feeling stressed-out. Also, I just turned 44 and I don't recover from the eating and drinking like I used to. Do you have any realistic ideas other than “just say no”?

Dear Reader: The holidays can be too much of a good thing for many of us. Health surveys find that in the weeks between Thanksgiving and the start of the new year, people sleep less, eat and drink much more, and as the season plays out, feel increasingly bad about all of it. Add in the increasing pressure to put together the perfect holiday -- think of it as the Instagram effect -- and a time of year when we seek warmth and community can feel more like an endurance test.

Rather than completely opting out of the holidays, try a gentle edit. Choose a few moments that bring genuine pleasure -- maybe a twilight walk, trying a new cookie recipe or watching a Hallmark movie with your phone turned off. Schedule these in, one or two per week, just as you would any social obligation. Small pauses can be an antidote to the relentless pace of the season and restore your sense of enjoyment. They can also give you a second wind to face your holiday obligations and the breathing room to enjoy them.

Eating and drinking are a big part of this time of year, and it's important to have a plan. Last week, we looked at food strategies. Now let’s focus on drinking. In a season of open bars and “just one more” rounds, be strategic. Create a template for how you will navigate the alcohol at any gathering. The buzzy enjoyment of a cocktail or glass of wine comes with a physical price. It disrupts sleep, your immune system takes a hit, your liver works overtime and blood sugar takes big swings. This can leave you feeling tired and irritable and, as research has shown, even more vulnerable to junk food cravings the next day.

Set a drinking limit before each event, including the option to not drink at all. When you do plan to indulge, have something in your stomach first. Start with at least a snack before the event. Then double down by making the protein and high-fiber foods your first stop. They will help stabilize blood sugar, keep you feeling full and slow the effects of alcohol. You can also start with something nonalcoholic to quench thirst. When you do switch to adult beverages, track not just how many, but also portion size. If you’re having more than one drink, you can alternate with something nonalcoholic.

Pacing yourself with food, drink and your commitments is practicing preventive medicine in real time. You're setting the stage for better sleep, steadier mood and the energy to enjoy the things you love about this season.

(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.)