Dear Mark: Dairy Inhibiting Magnesium Absorption, Trampoline Training, and Max Aerobic Heart Rate

Dear Mark Dairy-Magnesium Absorption FinalFor today’s edition of Dear Mark, I’m answering three questions. First, does dairy inhibit magnesium absorption, thus negating the utility of adding blackstrap molasses to milk? There’s a good deal of evidence that points to a probable answer. Next, is mini trampoline training actually good for you, or is it just a silly way to pass the time and look ridiculous (or all of the above)? And finally, how should someone calculate (and train under) their max aerobic heart rate?

Let’s go:

Hi mark, in regards to your recent post and another previous post about blackstrap molasses and some suggestions to how it can be taken, you mention a couple of ways that include dairy.

I have read that the absorbtion of magnesium is affected (decreased) when taken with dairy, I was wondering if there was any truth behind this and if so to what degree?



I’ve heard that too but never saw it substantiated. You spend enough time in alternative health circles and it starts to seem like dairy inhibits the absorption of everything. The calcium content of dairy blocks iron absorption. The dairy protein prevents you from absorbing the polyphenols in blueberries. Dairy supposedly even prevents you from absorbing the calcium it contains, if you listen to the more rabid of the vegans.

So, does dairy inhibit magnesium absorption, as the Weston A Price Foundation has asserted?

Lactose doesn’t block magnesium absorption. A study in live healthy human subjects found that the presence of lactose, even in large amounts, had no effect on magnesium absorption.

Calcium doesn’t block magnesium absorption. The body uses separate pathways to absorb each. The biggest determinant of magnesium bioavailability is your magnesium status. If you’re low, absorption is high. If you’re replete, absorption drops. It’s totally context-dependent.

Casein doesn’t block magnesium absorption. Researchers actually use casein as the control when studying the effects of various proteins on magnesium bioavailability.

I don’t see any route by which dairy would block magnesium absorption. Have at it!

What is your opinion of exercising on a rebounder or mini trampoline? There doesn’t seem to be much research. But webpages and blogs all report glowing benefits. The only research that all sites use is a NASA report about how beneficial rebounding is for returning astronauts. What are your thoughts?

I’ve actually seen a decent amount of research. I’ll go through some of it and then give my thoughts after.

A group of Thai working women performed aerobic dance moves on a hard wooden surface or mini trampoline. Both produced good training effects and improved bone metabolic parameters, but the trampoline produced more leg strength and forced better balance.

A moderate intensity exercise session on a mini trampoline has the ameliorative effect on blood glucose you’d expect.

In patients recovering from a stroke, mini trampoline training improved postural control to a greater degree than balance training. It also led to greater improvements in daily functioning and mobility. Another study in stroke patients found that trampoline training (30 minutes a day, 3 times a week for 6 weeks) led to fewer falls, greater balance, and improved gait.

In elderly women, trampoline training ranks among the best ways to improve balance (and thus reduce falls and catastrophic injuries).

In athletes with ankle instability, training on a mini trampoline improves postural control and reduces sway.

There’s evidence it’s not just good for the elderly and health-compromised. In a group of male gymnasts, training on a mini trampoline for 12 weeks improved sprint speed, standing broad jump, vertical leap, and anaerobic power output.

They’re a little risky, too, particularly the big backyard ones. If you’re going to bounce around on a trampoline, observing the following rules seems to minimize the risk of injury:

  1. Bounce alone. One at a time, please. Most injuries involve collisions with other people.
  2. Don’t jump off of an elevated surface onto the trampoline. Roof to trampoline, bad. Trampoline to roof, awesome (if you can pull it off, but you may need to be a comic book character).
  3. Use a safety net to prevent falls.

Most importantly, trampolines are fun. I have fond childhood memories of bouncing on my buddy’s backyard trampoline. We were reckless, of course, which I wouldn’t recommend. We probably got lucky. But man was it fun.

Dear Mark,
I must precede my question with a tremendous note of gratitude. I am a fitness trainer and health coach, age 67, and having followed the advice of “Primal Blueprint” and “Primal Endurance”, I’ve gone from 18.3% body fat to 12.3% body fat in 4 months. I feel much better, am stronger and faster, and suffer much less injuries. Before I met you, I was overtraining junky that would yoyo between peaks and painful setbacks. God bless you, Mark, and thanks ever so much.

Here’s my question:
According to various calculations, my heart-rate max should be somewhere between 153 – 161. My HR at rest is about 68 (here in hot Israeli summers). Yet, I jog at 153, run at 180, and at all-out sprints can hit as high as 212. Understandably, I’m confused as how to stay in my aerobic zone. What we be your recommendation.

A million thanks and blessings for your continued success,

Lazer from Israel

Using the Maffetone method outlined in Primal Endurance, you calculate your max aerobic heart rate by subtracting your age from 180. That gives you 113. It means in order to maximize fat burning and minimize sugar burning, you have to keep your heart rate at or under 113 during exercise. It doesn’t sound like much. It probably feels way too easy. But bear with me. It works. This is where the magic happens, where you accumulate easy volume, where the “base” is built, where you begin building more fat-burning mitochondria. It probably feels way too easy, especially for a guy like you with so much experience.

The hard truth: if jogging spikes your heart rate past your aerobic max, you’re not very good at burning fat during exercise. Even if you don’t “mind” pushing that heart rate up. Even if you “feel fine” jogging at 153 bpm. 180 minus age is where you have to be to improve fat burning.

You might be awesome at burning sugar all day at a much higher HR, and even feel quite comfortable for long periods of time (until you burn out), but you will not be improving your fat-burning efficiency if you simply keep doing that. Most endurance athletes find that high-end sugar-burning HR zone and get “comfortable” in it several times a week, but then never really improve race speed (read: efficiency) from that point. It takes patience to stay at the aerobic zone, but over time everyone notices that they are able to handle a higher and higher work load at that rate, which means that you are going faster while still burning mostly fat.

If you’re just interested in immediate objective performance results—fast times, feeling like you “did something” after every training session—keep at it. Just know that you will be undercutting lasting benefits to your fat-burning efficiency, boosts to your fitness, and improvements in your long term health trajectory. You know where I stand on this one.

Thanks for reading, everyone!

TAGS:  dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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32 thoughts on “Dear Mark: Dairy Inhibiting Magnesium Absorption, Trampoline Training, and Max Aerobic Heart Rate”

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  1. I know a ton of folks who do a trampoline based aerobics class at one of those crazy trampoline gyms, including one friend who teaches there. It’s totally anecdotal, of course, but they all say they’ve gotten better benefits from the class and the methodology than they ever got at a typical Jazzercise/Zumba type class.

  2. As far as I understood the Weston Price article, they never asserted that calcium blocks the absorption of magnesium, it’s just the simple fact that the ratio of calcium to magnesium in milk is too high. I think Mark is correct in arguing that nothing in milk is inhibiting magnesium’s absorption, but maybe magnesium should be increased with milk’s consumption anyways!

  3. Wow, great questions (and answers) today! The first one reminded me that I have a jar of blackstrap molasses still sitting in my pantry. Maybe I should open it up and use it! As far as the trampoline, regular or mini, a benefit I see is more energy. Even just using it for a few minutes really gives me a boost. And it’s so much fun!!! And as far as the last question, Lazer you are amazing! Keep up the good work! Happy Monday everyone!

  4. I take a full spectrum digestive enzyme when I eat dairy so the lactose and casein is digested better. Enzymes really help when you eat foods that have anti-nutrients in them like dairy, nuts, and legumes. Even without enzymes though I’ve never heard magnesium being impaired with dairy. Phytic acid impairs magnesium, but this is nuts and legumes not dairy. If you’re at all worried about this just stick to dairy fat like butter and cream or fermented dairy like kefir. However don’t let that negate the fact magnesium is a common mineral people are deficient in. Eat magnesium rich foods like swiss chard, spinach, almonds, coho salmon, halibut, and grassfed beef. Also consider a epsom salt bath a few times each week. Nice way to considerably boost your magnesium levels as well as sulfate levels, which is also important.

  5. Some have said that bouncing on the trampoline helps keep the lymphatic system working in good order. I have no idea if that is true. Mark?

    I looked into buying a mini trampoline but could not find one with consistent good reviews. I do not want to deal with another piece of junk in my house. Anyone with a suggestion?

    Lastly, when I was training to be a P.E. teacher, I was told the trampoline was the most dangerous piece of equipment in the gymnastic room. My trampoline teacher had a broken leg to prove it. We took turns being spotters but I always feared that the big guys would come flying off the trampoline in my direction.

    1. Bellicon. Expensive but nicest by far. Easy on joints and quiet. You don’t have to “jump” on it to get benefits i.e. up and down without your feet leaving the trampoline gets the heart rate up some and helps with balance, etc. Run in place, side to side (thinking skiing) – all sorts of things you can do and not break any bones 😉

      1. Thank you, thank you, Sue. I looked up the Bellicon and it looks to be just what I was looking for. Why I didn’t run across it before, I have no idea.

        1. Absolutely. They aren’t as well known as they should be. Hard to get attention in today’s world of constant non-stop information overload. But great quality – doesn’t even compare to those cheapo $50 pieces of junk from the box stores. In this case, I do believe you get what you pay for. Hope if you go that route, you like it as much as I do!

          1. yes I just received my medium size bellicon, it’s worth the price, and with one month free vidéos to train!

  6. Thanks for the info on Magnesium absorption. I’ve been reading up on this subject lately, as I’ve had some symptoms of a deficiency recently, muscle twitching, restless legs and vague angina-like pain. I’m not a milk drinker, but I do include cheeses in my diet, especially on my salads featuring magnesium loaded dark leafy greens. Good to know dairy isn’t blocking my dietary absorption! I’ll still be adding in several Epsom Salts baths a week to up my levels.
    Regarding trampoline workouts, SO. MUCH. FUN! We have a trampoline gym here in town, and for a while I was a regular. I loved it! The fitness classes they have are real butt-kickers, but hilariously entertaining as well. I highly recommend checking it out if you have access to a place like this in your town.

    1. Jessica, Check out magnesium oil. You already know of the trans dermal absorption, so I don’t have to explain that. But, the magnesium oil is a purer form of magnesium.

  7. There’s a trampoline gym not to far from my apartment. A few friends of mine have talked about going for fun, but maybe we can turn it into a great way to get in an extra weekly workout!

  8. Glad you addressed the magnesium issue, Mark. I’ve heard this one floating around the interwebs and didn’t know what to make of it (so much conflicting/unsupported evidence).

  9. If it’s good enough for astronauts, then it’s good enough for me. Time to break out the trampoline: Up, up and awaaayyyyy!

  10. I have heard that jumping on a trampoline helps with the lymphatic system as well. Mark, I would love to hear you weigh in on this…..

    1. Any physical activity promotes movement of lymph through a healthy lymphatic system. (Massage therapist here)

  11. Does anyone have a good fitness tracker recommendation? I don’t need anything complex. I’d mostly use it to measure heart rate and keep it in the fat burning zone like in the example above. I’m thinking of a Fitbit, but I’m open if there are any cheaper/simpler options, too.

    1. I think if you want to track your heart rate to keep in the 180-age zone in primal endurance you should get something like a polar monitor with a chest strap. I have a fitbit, which is great, but the heart rate monitor I’ve found to be unreliable during exercise. When I run I use both my fitbit (for GPS) and a cheaper polar with the chest strap. The fitbit heart rate varies from the chest strap heart rate quite a bit. The polar is more consistent and also has an alarm that will tell you when you exceed your HR target. Just a side note, the alarm is not very loud and precludes me from wearing headphones when I run, which is my biggest complaint. I have the Polar FT7.

  12. Back in high school, our gym teacher rotated us through all the equipment that made insurers freak out–trampoline, balance beam, uneven parallel bars, rings,…you know, all that stuff our current Olympians use today. Then the whole class took a sharp turn off the mat (record screech sound here) and started a DISCO DANCING group with all the lifts and spins. Up until that point, nobody got hurt, but the disco dancing was sending student after student down to the nurse’s office, and eventually, on to the hospital. The reason? Lifting wrong, spinning too fast, not knowing how to release a partner after spinning her, releasing her too quickly, the list goes on. I never really participated, but enjoyed watching from the sidelines until people started going down. Then, disco dancing became an after-school activity done on wrestling mats–no more regular class-time activity.

  13. I bought a mini-trampoline a few years ago. Cost about $50. It was very, very hard on the knees, and was also very loud (squeaking, creaking). Maybe the more expensive ones are better, but I don’t want to spend the money to find out.

    1. it sounds like you had a spring trampoline. the better ones are the ones with bungees. JumpSport makes a medium range one. The Cadillac of mini trampolines is a Bellicon. I have both and the Bellicon feels great. The kids get the JumpSport.

  14. I am reading this post standing on a 36″ trampoline in my standing workstation at work 🙂

  15. I took my kids & their cousins to a local, indoor trampoline park with my bro & sister-in-law. We decided, “why should the kids have all the fun?” and bought ourselves tickets as well.
    We had a blast! Even being primal 4+ years, I found muscles I didn’t know I had.
    Our tickets were for 60 minutes playtime. I’m not sure I would have lasted much longer! I went to bed in the most blissful state of exhaustion I’ve had in years. Barring the expense, I can’t wait to go back!
    Mark is always talking about exercise as play. play, and this was the epitome of play!

  16. I am curious about the relationship between age and heart rate. Does your system really change tied directly to the calendar? I’m 60 years old and my resting pulse is low. Is my cardiovascular system going to work just like other 60 year olds and not like a 50 or 40 year old, regardless of our conditioning levels?

    I do Orange Theory twice a week, where you can see everyone’s heart rate. I see guys in their 40s and 50s doing the same thing as me, but maybe more stressed but I’m at the upper end of my ranges while they have not hit the zone yet. I have a hard time believing a heavy unfit 52 year old should have a more aggressive target than me.

  17. Thank you Mark!
    Great questions today.
    Funny, over the weekend I was at a party at a friends and they had a trampoline for the kids. I gave it a try and was amazed at how big a work you get from one. Also how much my balance and body control has eroded. I dont remember the trampoline being such a work when we got to use them in school many moons ago.
    I was always against them because of the risk of injury, but now. I see the many benefits they have. And like Mark said.”they are Fun” and bring back many childhood memories.
    I highly recommend give one a try !

  18. The study showing that dairy proteins block the absorption of the phytonutrients in blueberries used fluid milk. I eat my berries (and fruit in general) with cheese, and I wonder if this is a stupid idea, or if cheese has a more moderate effect than fluid milk. It is such a tasty combination; I believe the French pair fruit with cheese.

  19. I was diagnosed with initial osteoporosis in my hip, and have bad knees. I can easily harm them pushing it too hard by walking (moderate) on a treadmill!

    I got a doctor’s note to get a mini-trampoline and was able to get reimbursed through my FSA.

    I wasn’t an exerciser until a year ago Feb, but just started consistent aerobic exercise this Feb. 15 minutes on the Bellicon kicks up my heart rate to vigorous.

  20. Magnesium absorption through the digestive track is not very efficient to begin with. If your gut is all messed up nutrients and minerals aren’t getting where they need to be. Personally I don’t like Magnesium supplements and feel that dietary intake isn’t enough. I use a magnesium oil on my skin. Tingles a little but I have read the science behind trans dermal absorption. Just my $.02.