Ask Dr. Bob: The Truth About B12 Injections, Soreness and Age, Coconut Oil’s Benefits

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 Alix Minde / Getty Images

Myth, Busted
I pop my knuckles a lot, which my friends say is terrible for my joints. Should I stop?

It can make people around you cringe, but cracking your knuckles may not be bad for you after all. This spring, Canadian researchers used MRI video to see exactly what happens when you pop your knuckles. It turns out that pulling the joints apart draws gas into the space. The gas expands and mixes with the synovial fluid, which lubricates your joints, until it builds up so much that it pops, creating the "crack" sound. (All this happens in milliseconds.) Rather than being harmful, the study authors suspect, the ability to pop your knuckles may actually be related to joint health. Tell that to the next friend who gives you a hard time.

Boost Recovery
The older I get, the sorer I feel after a workout? Why?

As we age, our bodies become less efficient at repairing and rebuilding muscles, so it takes a little longer to bounce back from workouts. But there are three things you can do to make it easier to recover, no matter your age. First, if you exercise every day, be sure to dial back the intensity for at least two days after each hard workout. Treat those days as active recovery, which will ensure that your body has time to repair before you go hard again. Second, always eat or drink something with protein immediately after exercise — my go-to is a Greek yogurt smoothie with chia seeds — to immediately help your muscles repair. Finally, hit the foam roller for 10 minutes after every workout. Research shows it may help reduce soreness the next day, and it prevents injuries down the line.


Health Hoax
I've seen a lot of ads lately for vitamin B12 injections to help you feel more energetic and healthy. Do these treatments really work?

Not unless you have a legitimate B12 deficiency. Celebrities tout the "energy boosting" virtues of injections of the nutrient, which helps keep nerve and blood cells healthy — and treatments are often marketed as a way to boost metabolism to help shed weight. But most of us absorb all the B12 we need through eating a decent diet; pump in any more through a drip or injection, and your body will simply eliminate the water-soluble vitamin in your urine. If you do feel a small boost after a treatment, it's likely that it's a placebo effect. Whether that's worth the $50 or more that the treatments cost is up to you.

The Right Fat
I've heard coconut oil has tons of health benefits and have been stirring it into my oatmeal each morning. What's your take?

As recently as five years ago, coconut oil had a bad health rap because it was often combined with partially hydrogenated vegetable oil, which is loaded with toxic trans fats. Now it's easy to find jars of pure oil — labeled "virgin" —that contain the medium-chain triglycerides, or MCTs, that research has shown help raise your good HDL cholesterol, improve your blood sugar, and control your appetite. But note: Coconut oil is 100 percent fat — even if it is the good kind. Each tablespoon has 117 calories, nearly 14 grams of fat, and almost no vitamins or minerals. Adding a teaspoon to oatmeal or a smoothie, or using it as a substitute for processed vegetable oils in baking, are smart, heart-healthy moves. Just be sure your serving stays small.

The Doc is online Email your questions for Dr. Bob Arnot to dr.bob@mensjournal.com.