Understanding the dairy and bone relationship

Dairy can be a mixed nutritional bag, and there have been different views about its benefit for bone. But an Australian study on people in their 80s concluded that it improved bone density and reduced falls.

The study was done over two years with residents from 60 aged care facilities across Melbourne and regional Victoria. Just under 70% were women.

Dairy can be a source of both calcium and protein. The recommended calcium intake for post-menopausal women is 1300mg per day. The recommended protein intake to preserve or increase muscle is 1-1.5 g per kilogram of body weight.

In these facilities daily calcium and protein intakes fell short of those recommendations. Vitamin D levels were adequate because residents were given supplements.

The plan was to randomly select half of the facilities and over the two years boost dairy intake in those and not in the other half to compare the prevalence of fractures and falls between the two groups.

When residents moved out of a facility or died, new people were recruited in their place. The study started with 3980 participants, and over time another 3215 were added — 7195 in total.

The dairy in question was milk, yoghurt and cheese. While butter and cream also come under this umbrella, they’re mainly fat without much calcium or protein. Commercial ice cream contains milk, but it also includes sugar, emulsifiers, thickeners, colouring and flavouring, none of which do bone any favours.

The extra diary was slotted into residents’ diets by, for example, the provision of dairy-based desserts or substituting cheese and crackers as a snack in place of cake or biscuits. So no one was loading up on additional calories.

This took the dairy residents’ daily intakes to around 1100 mg calcium and 1.1 g of protein per kilogram of body weight. While 1100 isn’t quite 1300, it’s close, and vastly more than most women have.

Over the two years the dairy group maintained their weight, while the control group lost an average of 1.4 kgs, comprising both muscle and fat. That’s important: we don’t want to be losing weight, especially muscle weight, in our 80s.

There was also a positive effect on fractures and falls.

The dairy group had 33% fewer fractures of any type, 46% fewer hip fractures, and 11% fewer falls, all of which showed up within the first five months.

Bone is constantly remodeling itself — building up and breaking down. The problem after menopause is that with less available estrogen, breaking down can outstrip building up.

The extra calcium and protein appear to have helped slow the bone loss that would have otherwise occurred.

As well as providing mineral content for bones, calcium helps muscles contract and relax. Since bones only grow when muscles contract and tug on them, we need good muscle function for healthy bone.

Protein is also vital for the growth, repair and maintenance of muscle.

A lot of previous studies — on calcium, at least — have failed to show similar results to this one though. Probably because they relied on supplements rather than whole food.

Whole foods are better absorbed, but they also contain a range of nutrients aside from calcium.

The research on milk alone isn’t overly positive, but yoghurt and cheese (and fermented dairy generally) seem to be beneficial because of their good bacteria. Evidence is mounting that gut bacteria have a major role to play in improving bone formation and reducing bone loss.

At least one study has suggested that probiotics might speed up the healing of fractures in older people.

At the risk of making this too long, if dairy — especially fermented forms — has a positive effect on bone, why do countries with a high dairy intake have a high incidence of osteoporosis? Scandinavian countries, for example.

To find an answer we’d have to recognise that many factors affect bone health, not just food.

Norway has the dubious distinction of leading the world in fractures and there is speculation that this might be explained in part by body build. Norwegian women are relatively tall and lean, and anatomically more at risk of a fracture if they fall.

In addition, a comparative study of the bones of Spanish and Norwegian women showed that the bone content of the Norwegians was weaker, perhaps a reflection of ethnic differences in bone. Vitamin D levels don’t seem to be the issue, despite the lack of winter sun.

Finally, it’d be useful if there were similar studies to the Victorian one on women younger than their 80s to see whether these findings can be generalized beyond aged care residents.

For now there aren’t, but we can tentatively conclude that since calcium, protein and probiotics in the form of whole foods appear to support bone health, yoghurt and cheese deserve place in our diets.

P.S. What does 1300mg of calcium look like?

Sifting through nutrition tables on the internet suggests that estimates of calcium content in foods can vary wildly. But here’s a (very) rough guide. Check food labels too. As always, choose the best quality you can.

• A 200g tub of yoghurt provides 250-300mg calcium (but avoid the sugary, fruit-flavoured type)
• A slice of cheese (whatever size a ‘slice’ is, but some say it’s 30 g) provides somewhere around 200-300mg (e.g. Edam or Gouda 260 mg, Emmental 330 mg)
• Half a cup of tinned salmon with bones (say 100 g or the size of a small John West can) delivers at least another 200 mg, though I’ve seen higher estimates.
• Half a standard-sized can of sardines provides 150-200mg.
• Almonds are the nuts with most calcium, and 15 provide 40-50g.
• A teaspoon of tahini contains around 20 mg.
• A glass of milk (200 g) contains about 240 mg. There are also ‘mylks’, some of which have added calcium, so read the labels.
• Tofu made using calcium sulphate is another source. Check the label.
• Leafy greens and legumes contain calcium but how much we absorb is another thing. Include them in your diet but don’t rely on them as your key sources of calcium.
• Sometimes calcium is added to foods that don’t naturally contain it — breads and cereals, for example.

I won’t list protein contents of foods as well. You can chase those up. Some of the foods listed above will contribute to your daily protein intake, along with others such as meat, eggs, fish and legumes.

As a rule of thumb, look to include protein and calcium at each meal and consider the value of adding fermented food to your diet.

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