Milk is not the food it used to be. It is so highly processed it no longer resembles the milk our ancestors consumed thousands of years ago. Today a cow (a Friesian cow) gives 25 litres per day compared to just the few litres daily that cows produced centuries ago. Modern farming practices have extended the milking period to 305 days per year (1). Pasteurisation was necessary 100 years ago due to poor hygiene, but today it destroys the enzymes that make milk easy to digest, particularly for infants. All milk, including human milk, comes with a rich array of nutrients, including 20 or more enzymes to help digest itself - such as lactase to digest lactose. Homogenisation forces the particles of fat through a series of sieves to mix it with water, just so cream does not settle on top. It then becomes difficult for the body to determine whether it is fat or water. Normally, the two don't go together.
Modern milk has been sold to millions of people around the world based on its supposed benefits in building healthy bones. The research shows that milk has, at best, questionable benefits for preventing osteoporosis and bone fractures and is, in fact, linked with many forms of chronic illness including cancer, cardiovascular disease, multiple sclerosis, diabetes type 1, Parkinson's disease, gut disorders and allergies.
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?
Dr Peter Dingle PhD is an associate professor and researcher who has researched nutritional toxicology for the past 10 or more years. He is not a medical doctor. After completing his honours in environmental toxicology in 1988, he went on to complete his PhD in the same field in 1994. The information he presents is based on the research he and his students carry out at Murdoch University where he is Associate Professor in Health and the Environment.
1. Maruyama et al. 2010
2. Papadimitropoulos et al. 2002
3. Babbar et al. 2006
4. Lanou et al. 2005
5. Feskanich et al. 2003
6. Weinsier and Krumdieck 2000
7. Kanis et al. 2005
8. Roba 2005
9. Allen 1982
10. Atkinson et al. 2008
11. Gallagher et al. 1979
12. Jackson et al. 2001
13. Beresteijn et al. 1990
14. Heaney et al. 1982
15. Alexy et al. 2008
16. Buclin et al. 2001
17. Tucker et al. 1999
18. Allen 1982
19. New 2003
20. Remer 2000
21. Seiquer et al. 2008
22. Black et al. 2002