Is dairy good for your bones?

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It appears that there are still conflicting opinions about the health benefits of cow’s milk. This is made worse by many “health” advisors who tell the public that cow’s milk is only good for calves and the evil cause of every unexplained ailment under the sun! 

Milk makes a valuable contribution to a healthy diet, as it contains all the macronutrients (protein, carbohydrates and fat). Milk protein has a high biological value because it contains all the essential amino acids needed by the body. The carbohydrate and lactose, supplies energy and helps your body to absorb calcium. Milk is considered by many national and international opinion-leaders in the bone field as  the best source of calcium because of its high calcium content, the absence of factors that may influence absorption (like phytates and oxalates in bran and green, leafy vegetables) and the presence of lactose which aids the absorption of calcium. 

Milk also contains significant amounts of minerals and trace-elements like calcium, phosphate, magnesium, and selenium and vitamins A, D and B (riboflavin and niacin). 

Milk and bone health
The two key nutrients for bone health are calcium and Vitamin D. Milk and other dairy foods are the most easily available sources of calcium in the diet. Dairy foods also have the advantage of being a good source of protein and other micronutrients. The importance of nutrition to bone health has been shown in research studies in human subjects of every age. Intervention trials (the gold standard in supplying scientific evidence), in children and adolescents, have shown that supplementation with either calcium, dairy calcium-enriched foods, liquid milk, or calcium-enriched milk powder enhances the rate of bone mineral acquisition, compared with un-supplemented (placebo) control groups. In general, these trials increased the usual calcium intake of the supplemented children from about 600-800mg/day to around 1 000-1 300mg/day. Some retrospective studies suggested that adults who consumed milk regularly during childhood had a higher bone mass than those who did not.

Does the protein in milk cause calcium loss? 
In one study, elderly men and women with lower total and animal protein intakes had greater rates of hip and spine bone loss than those consuming higher amounts of protein. There's also evidence that increasing protein intake has a positive effect on bone mineral density in elderly men and women receiving calcium and Vitamin D supplements. Randomised clinical trials in elderly people with hip fractures have shown the beneficial effects of giving protein supplements on the clinical outcomes following surgery to repair the fracture. Protein supplementation resulted in fewer deaths, shorter hospital stays and a greater likelihood of returning to independent living.                                                                                                                           

Despite this evidence, there has been speculation that a higher dietary intake of protein could have negative effects on calcium metabolism and could possibly induce bone loss. This relates to the hypothesis that the "acid-base balance" of the diet is a potential risk factor for osteoporosis and if a diet contains predominantly acidic foods (which include key protein sources) and not enough alkali-rich basic foods (fruits and vegetables), the alkaline salts of the skeleton may be drawn on to buffer this effect and in the long term, lead to bone loss.

The majority of scientific evidence supports the beneficial effects of protein intake on bone health. Although protein is needed for healthy bones, it's recommended that it be limited to 75 grams a day.

What if I'm lactose intolerant? 
Lactose intolerance needs to be diagnosed by a doctor with certain tests, as the abdominal symptoms can be confused with other digestive disorders, like irritable bowel syndrome. Lactose intolerance is a potential risk factor for osteoporosis because patients tend to avoid dairy products. Being lactose intolerant doesn't necessarily preclude all dairy products from the diet, and some people can tolerate small quantities of milk without symptoms. Fermented milk products like yoghurt can be well tolerated because the live cultures actually produce the enzyme lactase which helps to break down lactose to the more digestible sugars, glucose and galactose.

Dairy is good for you in more ways than one: helping to preserve bone mass and strength in the young and elderly, speeds up healing in those who have had a fracture, and helps prevent further fractures.


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