A very interesting study was recently published in the British Medical Journal that looked at the ability of a “high protein high calcium” diet to prevent fractures. Well, I say high protein high calcium – what they were actually testing was what happens if you give frail elderly people (the people at greatest risk of fractures) a diet high in dairy – which doesn’t sound either as scientific or as sexy as “high protein high calcium”…
Anyway, this was a randomized trial involving 7,195 nursing home residents spread across 60 nursing homes in Australia. The trial was cluster-randomized, which means that rather than individual nursing home residents being randomized to one diet or the other, entire nursing homes were randomized to follow either a high dairy diet or to continue with their current diet. So 30 nursing homes followed a high dairy diet, and 30 continued doing what they were doing previously.
Since it’s hard to blind people to what they are eating, this was an unblinded study. That should always make us more cautious about a study’s results, because it makes manipulation of the data easier. However, the outcome being analyzed was radiographically confirmed fractures, which is a hard outcome without any subjectiveness – either you’ve broken your hip or you haven’t – so the lack of blinding shouldn’t necessarily be that big a deal.
One thing that’s important to note about the study is that it was largely funded by various dairy farmers’ associations and lobbying groups. It’s been shown many times that studies funded by groups with vested interests usually show more positive results than studied that are independently funded. This lack of independence might in fact be the single biggest weakness with the study – it’s certainly a reason to be sceptical of any positive results. However, it’s rare to see randomized trials in nutrition science – usually all we have is crappy observational studies that can’t say anything about cause and effect, so it’s nice to have a proper randomized trial to look at for once. The fact that this was a randomized trial is likely the reason it ended up being published in the top-tier British Medical Journal instead of one of the many low-quality nutrition journals.
The nursing homes that were randomized to a high dairy diet were required to reformulate their menus so that the residents received more dairy products that were high in protein and calcium (i.e. milk, yogurt, and cheese) in their diets. This was accomplished, for example, by replacing biscuits with yogurt as an afternoon snack. Here we immediately stumble upon a major issue with this study, that in fact plagues most diet studies – whenever you add something to a diet, it generally means that you’re taking something else away from the diet. If we add dairy and remove refined carbs, and we then see a benefit, is it due to the addition of dairy or the removal of refined carbs? It’s impossible to say.
Let’s get to the results.
Average calcium intake among the participants in the intervention group increased from 562 mg to 1142 mg per day, while average daily protein intake increased more modestly, from 0.9 grams per kg of body weight to 1.1 grams. No change in intake was seen in the control group, as you would expect.
The participants were followed for an average of 13 months, and during that time period 5.2% of participants in the control group experienced a fracture, compared with only 3.7% in the intervention group. That might not sound like a very big difference, since the absolute difference in fracture risk was only 1.5%, but if you consider that the participants were only followed for one year, it’s not bad. It represents a 33% reduction in the relative risk of a fracture. The absolute benefit grew bigger and bigger with each additional unit of time, and would likely have continued growing bigger if the study had gone on for longer. The effect size at one year is equivalent to that you would see with a bisphosphonate, which is the type of drug most commonly used to treat people with an increased risk of fractures. Considering that we’re talking about an easy, cheap, safe (and tasty) intervention, that sounds pretty good. Personally, I’d rather eat dairy than take a bisphosphonate.
Let’s assume for a second that the researchers haven’t somehow manipulated their data, and that the reduction is real. Then we have to answer two questions: first, what is responsible for the reduction in risk? And second, how is it having its beneficial effect?
As mentioned, it’s impossible to say whether the benefit is due to adding dairy or removing bad things like biscuits and cakes, which the dairy has now come to replace. And since dairy is itself a collection of lots of different substances, if we assume that it is in fact the addition of dairy that’s having a beneficial effect, it’s still impossible to say whether it’s the increase in calcium that is beneficial, or the increase in protein, or something else entirely. Trials of calcium supplements have generally found much more modest reductions in risk than was found here, so I’m inclined to think that protein is more important for fracture prevention than calcium.
There is one problem with attributing the benefit to protein though, and that is that protein intake only increased modestly, from 0.9 grams per kilogram of body weight to 1.1 grams. However, if 0.9 grams is insufficient for people to maintain their present amount of muscle mass, while 1.1 grams is sufficient, then that small difference in intake could actually result in large downstream consequences.
This is supported by the fact that the dairy group maintained its lean mass over the course of the study, while the control group lost on average 300 grams of lean mass. Again, this might not sound like a lot, but if the control group is losing 300 grams more lean mass per year than the intervention group, then there is quickly going to be a very big and noticeable difference in strength between the groups. More muscle mass means greater strength and thereby a greater ability to avoid falling, and also more dampening tissue on top of the bone if a fall does happen.
The dairy group both suffered fewer falls than the control group (suggesting an effect on muscle mass and thereby strength), and when they fell, they had fewer fractures (suggesting an effect on bone strength). The dairy group did in fact appear to have better bone density overall than the control group at the end of the study, when measurements were taken from a subset of study participants. This could perhaps be explained by the increase in calcium intake, or the increase in protein intake (protein is a central component of bone), or something else entirely. Dairy is a pretty good source of vitamin A, to take one example.
That all assumes the benefit seen in this study is real. Is it though?
The fact that this was an industry funded study makes me very sceptical. Even if everything seems kosher on the surface in a short study report in a medical journal, there are so many little easily hidden manipulations that can happen along the way as a trial progresses, which can sway the trial in favour of showing benefit. One thing that I find particularly concerning is that much of the data in the trial report is presented in text form only, without accompanying tables. That makes it much harder to analyze the data. It makes me wonder if the authors are trying to hide something. So, from my perspective, this study is encouraging, but hardly constitutes conclusive proof. For that, you would need a truly independent trial that confirms the findings of this study. In the meantime, have some cheese.
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18 thoughts on “Can a “high protein high calcium” diet prevent fractures?”
I read the study to find out what they had done about vitamin D, not enough vit D means low absorption of calcium from the gut, the body then takes it from bone to maintain blood calcium within very narrow and vital boundaries. The residents were all apparently vitamin D replete, so that wasn’t a confounder. The level of fat in the dairy products used didn’t seem to be specified, I would go for the full fat versions every time, given that the fat contains the vitamins needed to utilise the nutrients in the rest of the product.
The thing that stood out for me in the study is that the nursing home residents were malnourished – ie according to the study they were getting less than recommended amounts of both protein and calcium. Quote – “However, these people often have calcium intakes below 700 mg daily, an amount unlikely to offset obligatory loss of calcium.4 They also often have protein intakes below 1 g/kg body weight/day, predisposing to loss of lean muscle mass.5 ” If that was the case for these two nutrients are there others also lacking? The study showed that if you improve nutrition in malnourished older people you improve health – what a surprise!……and how is it we allow those in institutions to be malnourished?
Good question. The food served in these institutions is often very low in nutritional value. This is made worse by the fact that elderly people often have lower appetite and eat less, so it’s extra important that everything they do eat is nutrient dense. Dairy has a high nutrient density, so is likely to be beneficial. As you suggest, they could likely have gotten good results with other interventions that also increased nutrient density in the diet.
Was the ‘quality’ of care in each of the homes taken into account? Maybe those who had less falls were because they had the best care as opposed to any change in diet?
All the best
Since there were 60 nursing homes in the study and they were randomly assigned to one or other intervention, that should neutralize that type of confounding variable.
Thank you again Dr Rushworth. Interesting as always.
So, doesn’t it seem like any diet that reduces (refined) carbs lead one or another way to better health?
Be it, high fat, high protein, high fiber…
Well, refined carbs are one of the least healthy things you can choose to eat so… pretty much.
Probably the important difference between the two groups was the increased vitamin K2 in the dairy intervention group.
“The participants were followed for an average of 13 months, ”
That sounds odd for nursing homes. A study I saw said the median stay in a nursing home was 5 months, and the mean was 7 months. And in my limited experience as an occasional visitor, the biggest factor in breaks is whether they are still attempting to walk by themselves (a minority).
I suspect the term “Nursing Home” needs some clarification.
“7,195 nursing home residents spread across 60 nursing homes in Australia. ”
UK homes are typically half that average size. It sounds like they are talking about something closer to sheltered accommodation.
Great post. I have learned so much from Dr. Kendrick and Dr. Rushworth and have gone on to do some reading of research articles on my own, which has led me to make some changes. I hope some others might find my experience helpful and maybe give them some ideas.
I’ve recently begun paying more attention to my diet. I’ve increased dairy and meat along with seeds and nuts. Sugar is somewhat less and I’ve reduced wheat products about 20%.
Dairy for the K2, including butter and sour cream
Seeds and nuts for the magnesium and potassium and fiber
Apricots with lunch and dinner for various nutrients, especially fiber
Blueberries for vitamin C
Meat for the protein, B vitamins, and zinc
10 oz V-8 vegetable juice with lunch and dinner for potassium and vitamin A
I look for pasture-raised dairy and free range chickens to up the K2.
I eat my fat-soluble vitamins with my meals, which always have some fat content.
I avoid nutrient-empty fat and carbs.
I enjoy an alcoholic beverage with meals a couple of times a week–5 oz lunch and dinner each.
I use 1/2 packet of saccharine with one heaping teaspoon of sugar in coffee and oatmeal.
I snack on dark chocolate and coconut granola some.
I supplement 150 mcg K2, 100 mg B1, 4,000 units D3, and an over-50 men’s multivitamin daily.
I’ll take a cup of decaf green tea over the course of a day, mostly for rinsing my mouth after meals.
My non-dietary supplements get me around 20 mg zinc daily, averaged over a week.
I get sun exposure weather permitting, even this late in the fall.
It is great that you are looking after your health.
If you can, I would actually avoid using saccharin, the safety studies done were inconclusive and there are only observational studies done on humans.
With regards to a multivitamin preparation, most – if not all of them contain iron, which actually prevents the absorption of other nutrients and vitamins, so effectively you are not getting the benefit you are intending. In addition, they usually use very cheap ingredients that are not bioavailable for your body to use properly, and the concentrations of ingredients are mostly too low to have an effect.
I would check, which vitamins and/or minerals you would most benefit from and supplement these individually, rather than taking a ‘one fits all’ approach, which might cost you quite a bit of money, but unfortunately will not have the desired health outcomes.
If I look back decades and compare the diet recommended by the medical/political nexus versus the diet recommended by my Dear Old Mum, I have to say that DOM wins at a canter.
She believed in a mixed diet, meaning meat, fish (she had a Jeevesian admiration for fish), eggs, dairy, fruit, veg, and nuts. For what she wouldn’t have called carbohydrates she preferred oats and potatoes, and cautioned against pasta. (Slips down too easily, and in huge amounts: beware!)
I’ll grant that the m/p nexus was sounder on smoking than DOM but on food they’ve been stupid, ignorant and, I dare say, corrupt.
My own explanation for the merits of a mixed diet is that it covers you for (i) what the medics know, (ii) for what they don’t know, and (iii) for what they do know but are wrong about.
Your view may differ but I find that compelling.
Thank you for your studies!!
A few points that could have an impact: In what form was the dairy product served? Milk? Yogurt
(meaning fermented), fresh cheese or old? Organic or not? Etc. as far as I understand all these could
give different results. Dairy is does not simply mean one thing. O r was it what is know as “fortified”
Milk, yogurt, and cheese. That’s all they say.
My father-in-law had poor bone density. He went through a protocol of doing box jumps to activate shock/gravity to his bones. Did this every day – his scores went through the roof.
I have lost the reference, but about 15 years ago I read a report from China in which postmenopausal women were randomized to 200ml dairy milk or soy milk. They said that even “lactose intolerant” could tolerate this without much trouble. They reported a significant increase in measured bone density in those drinking dairy milk as opposed to the soy product.
In regard to the fat soluble vitamins like A and K2, these would be removed if the milk was “defatted”. In the current climate in the Western world, I suspect this would be the case. Certainly here in Canada, nutritional regulations pertaining to hospitals and care homes specify low fat, especially animal fats.
One thing increasing milk products, even defatted ones, is increase sodium intake, especially if cheese is included. This is another thing that is severely limited in hospitals and care homes. There are two ways increasing sodium might be beneficial: first in increasing food palatability and hence intake (decreasing weight loss) and second, improving Na/K balance in those on diuretic antihypertensives. Either of the latter could improve metabolic health generally and decrease bone loss.
The hospital food given to my husband after an emergency bipass operation was truly disgusting.
Were all the fractures the results of falls? It’s just possible that the changed diet improved the residents’ balance rather than bone density.
Almost all the fractures were due to falls. The participants in the dairy group both had fewer falls and fewer fractures when they fell.
I always enjoy your articles, thank you.
I eat a lower glycemic index diet, high in protein and fat both meat and full-fat dairy with plenty of nuts, berries, salad, and vegetables. I have no trouble maintaining my weight and versus my tennis teammates who eat a SAD [Standard American Diet], I am healthier and thinner.
I have also started taking the vitamins linked below–do you think their research is of good quality? I have my 80-year-old parents taking them and my mother said she thought it improved her sleep which has been a major issue for her. They eat well and are very active compared to average 80-year-olds. Are they over-kill if you are otherwise healthy and eating right? I take the regular ones, not the super high dose ones.