Calcium for bones?
Findings from long term studies have cast doubt on the value of consuming the large amounts of dairy and calcium currently recommended. In particular, high calcium intake does not actually appear to lower a person's risk for osteoporosis (2). There is evidence that the recommended levels in the West are too high, with countries such as India, Japan and Peru having an average daily calcium intake of around 300 milligrams (mg) per day, less than half that in the Western world, and no increase in the incidence of bone fractures (3). If increased dairy consumption leads to reduced osteoporosis and fracture rates, then multi-country epidemiologic studies would show that countries with the highest dairy consumption - such as Australia, New Zealand, the United States and the UK - would have the lowest osteoporosis and fracture rates, yet this is not the case. Although the consumption of dairy products in the US is among the highest in the world, osteoporosis and fracture rates are simultaneously high (4,5).
Other areas of research also support this finding. A comprehensive literature review found that of 57 evidence-based scientific studies of the effect of dairy foods on bone health, "53% were not significant, 42% were favourable and 5% were unfavourable. Of 21 stronger-evidence studies, 57% were not significant, 29% were favourable and 14% were unfavourable" (6). In other words, despite the huge amount of money the dairy industry invests in research, there are many studies showing that milk has no benefit and that it has potentially negative effects.
In one study, a low intake of calcium (less than one glass of milk daily) was not associated with a significantly increased risk of any fracture, osteoporotic fracture or hip fracture, and no significant relationship was observed by age for low milk intake and hip fracture risk (7). There was also no difference in risk of fracture or osteoporosis between men and women.
In the Harvard Nurses' Study of 77,761 mostly white women aged 34-59 who were followed over a 12 year period, those who drank little or no milk compared to the high milk drinkers (three glasses or more) had no increase in risk of hip or arm fracture (8).
The bottom line is that the studies do not support what we are constantly told by the dairy industry, media, governments and dieticians. So why do we keep getting told this message? If it was so clear cut as to warrant a health message from government authorities, you would expect all the research to support it. Not only is this not the case, but there is also plenty of research to show the complete opposite.
It is simplistic to think that the calcium in our diet goes straight to our bones. The "calcium balance" is where the calcium intake from food is compared to the amount of calcium lost through excretion and unabsorbed mineral in sweat, faeces and urine. The remaining amount, whether positive or negative, is the calcium balance (9).
If a person's calcium balance is positive, there is an excess of calcium in the body, a proportion of which goes directly to increasing bone mineral density (10). If, however, a person's balance is negative, more calcium is lost than is consumed, and therefore calcium from bone mineral must be reabsorbed into the bloodstream to make up the difference (10). This causes a lowering of bone mineral density and therefore is a factor in the onset of osteoporosis and fracture risk in later life (10). The amount of calcium that is absorbed and retained in the body from dairy products is about 30% of the total calcium consumed (9).
A number of factors help explain this discrepancy. First, calcium absorption is inversely related to the amount of calcium consumed in the diet, with low levels of calcium intake resulting in the most efficient absorption rates 11. This phenomenon may be partly responsible for the fact that many non-dairy-consuming societies around the world have few adverse health effects (such as osteoporosis and fracture) even with relatively low calcium intake (12).
Dairy products contain significant levels of protein, fat (in cheese, cream, butter and full cream products), sugar (in flavoured milks and yoghurts), sodium and phosphorous, all of which reduce the bioavailability of the calcium they contain. The presence of proteins has been demonstrated to have a negative influence on calcium absorption. Protein in milk causes an increase in urinary calcium excretion (13). Some dairy products, especially processed cheeses, clearly increase the urinary excretion of calcium as a result of their increased sodium, sulphur-containing amino acid, and phosphorus content (14). Interestingly, high-fat dairy products such as cheese, butter, chocolate and ice cream have also been found to be acid-forming foods (like protein and alcohol) (15,16), and so the question is raised: how effective are dairy products at ensuring bone health and are there other, more effective, dietary alternatives?
What is good for the bone?
While protein has a negative effect on calcium availability, magnesium and potassium, which are found in high concentrations in plants we eat as food, have been recognised as having a largely positive influence (17). These minerals appear to decrease the rate of bone attrition and urinary excretion of calcium from the body when present in moderate quantities. Milk has a poor calcium-to-magnesium ratio and contains low concentrations of potassium, while plant sources have a much higher concentration. Potassium appears to buffer the effects of acidic foods by protecting against calcium loss from the renal acid load of protein (6).
Vitamin D, derived primarily from sunlight, certain oils (including cod liver oil) and fortified foods (including dairy products), is the major nutritional factor affecting calcium absorption (4). Scientific studies have repeatedly shown that inadequate vitamin D levels result in impaired calcium absorption in the body (4,9). The role of vitamin D in milk is also found to significantly lower the risk of fracture (5). Many people in Western populations are now recognised as being deficient in vitamin D. (See "Vitamin D Rethinking Sunshine" - NOVA Magazine Issue 16.8 October 2009 at www.novamagazine.com.au (Articles archive)
The adequacy of non-dairy centred diets to support bone health has been demonstrated by a recent study conducted in Spain among adolescent males. It reported that a Mediterranean-type intervention diet based on fresh fruits and vegetables, olive oil, fish and legumes provided the same amount of dietary calcium as the subject's usual (baseline) diet, although the food sources of that calcium varied significantly.
The intervention diet also resulted in a significant increase in calcium absorption and retention, while significantly reducing the amount of calcium excreted in urine. This may be partially attributed to the lowered potential renal acid load of the diet, particularly from a high intake of fruit and vegetables (19,20). Therefore, the study concludes, the adoption of a Mediterranean-style diet low in dairy can assist in maximising peak bone mass and preventing osteoporosis without milk or other dairy products (21).
Perhaps the most important part of the bone mass equation is a healthy mixture of minerals from unprocessed plant foods and physical activity, particularly weight-bearing exercises (22,6).
In response to learning these facts about milk, many people ask me, "But where can we get our calcium?" No other animal on the planet experiences bone problems at the rate humans do. Most other animals get calcium from their normal, often vegetarian, diet. Our primate cousins, even those such as the gorilla, which are much heavier and stronger than us, get all the calcium they need from unprocessed plant foods and cows get theirs from grass and have an excess of calcium. So where should we be getting our calcium?
African Bantu women take in only 350 mg. of calcium per day. They bear nine children during their lifetime and breast feed them for two years. They never have calcium deficiency, seldom break a bone, rarely lose a tooth... How can they do that on 350 mg. of calcium a day when the (National Dairy Council) recommendation is 1200 mg.? It's very simple. They're on a low-protein diet that doesn't kick the calcium out of the body'.
At the other end of the scale from the Bantus are the native Eskimos.
If osteoporosis were a calcium deficiency disease it would be unheard of among these people. They have the highest dietary calcium intake of any people in the world - more than 2000 mg. a day from fish bones. Their diet is also the very highest in the world in protein - 250 to 400 grams a day. The native Eskimo people have one of the very highest rates of osteoporosis in the world.
In March, 1983, the Journal of Clinical Nutrition reported the results of the largest study of this kind ever undertaken. Researchers in Michigan State and other major universities found that, by the age of 65 in the United States:
- Male vegetarians had an average measurable bone loss of 3%
- Male meat-eaters had an average measurable bone loss of 7%
- Female vegetarians had an average measurable bone loss of 18%
- Female meat-eaters had an average measurable bone loss of 35%
The profitability of the global supplements industry probably plays its part, encouraged by key opinion leaders from the academic and research communities.14 Manufacturers have deep pockets, and there is a tendency for research efforts to follow the money (with accompanying academic prestige), rather than a path defined only by the needs of patients and the public. The research agenda and recommendations can also be influenced by the conflicts of interest that arise when leading academics have shares or management positions in companies making and marketing supplements.
While the study by Chapuy and colleagues has been influential,9 calcium and vitamin D supplements have been marketed well beyond the trial’s target population of older women in residential care with low calcium intake and low vitamin D concentration. By use of guidelines such as those by NOF and the International Osteoporosis Foundation (IOF), marketing now extends to all older people with dietary intakes below the recommended 1200 mg calcium and 800-1000 IU vitamin D daily. By this definition virtually the whole population aged over 50 is at risk.10 11 Most will not benefit from increasing their intakes2 3 10 11 12 13 and will be exposed instead to a higher risk of adverse events such as constipation, cardiovascular events, kidney stones, or admission for acute gastrointestinal symptoms.3 The weight of evidence against such mass medication of older people is now compelling, and it is surely time to reconsider these controversial recommendations.
These data suggest the role for calcium and vitamin D supplements in osteoporosis management is very limited. Neither calcium nor vitamin D supplements should be recommended for fracture prevention in community-dwelling adults, although vitamin D should be considered for prevention of osteomalacia in at-risk individuals.