Osteoporosis and diet
Over three million people in the UK have osteoporosis, a condition where the bones are more porous due to a lack of calcium phosphate. This makes the bones more liable to fracture easily, although there are often no symptoms until a fracture occurs. Anabolic (growth) hormones such as oestrogen and testosterone affect our risk of osteoporosis - as these hormones reduce with age, the amount of bone tissue laid down reduces. Menopausal women can experience a loss of five – 10% bone density each year due to reducing oestrogen levels, and up to 40% of women may suffer with osteoporosis by age 80.
How to prevent bone loss
The most effective way to prevent bone loss is to eat a balanced diet and maximise bone mineral density whilst bone tissue is still forming (before age 35) with weight bearing exercise such as walking, running or exercise classes. Although there are several things that increase the risk of osteoporosis, such as being immobile, increasing age (with reducing hormone levels), very low body weight, and smoking, your diet plays a large role in bone health.
What factors affect bone density?
All of these factors can affect bone density:
- drinking more than two cups of coffee daily
- drinking more than two units of alcohol a day
- drinking fizzy drinks that contain phosphoric acid - this can increase the risk of fractures from 20% to 70%
- excessive protein intake
- excessive salt intake
- lack of essential nutrients in the diet, or inability to absorb them
Let's take a look at each of these factors:
Caffeine has a diuretic effect upon the body – it makes us produce more urine. Whilst this is a natural mechanism, whenever we form urine, essential minerals such as calcium and magnesium may be excreted, reducing the availability of these minerals for various bodily functions. If high amounts are lost in urine production, calcium in particular can be drawn out of the bones to replenish the calcium lost from the bloodstream in the urine. Tea does not appear to have the same effect as coffee, so swapping from coffee to tea, or to a caffeine free drink may be beneficial.
Alcohol intake has been linked with decreased bone density due to its diuretic effects upon urine formation, which increases micronutrient loss. It also affects the intake, absorption and metabolism of other nutrients found in bone tissue, such as zinc. There appears to be no detrimental effect when alcohol intake is low; in fact some studies have shown better bone density in those that drink sparingly (one unit daily) than abstainers.
The phosphorus in fizzy drinks can be detrimental to bone tissue. Calcium phosphate is the main component of bone and levels of calcium and phosphate are closely controlled, with any excess excreted out of the body in urine. If there is too much phosphorus in the bloodstream, excess is passed out in urine, but calcium is excreted with it, potentially leading to a calcium deficiency. Phosphate is added to fizzy drinks (as phosphoric acid), so the best way to reduce your phosphorus intake is to replace fizzy drinks with milk, juice, herbal tea or water.
The amount of salt (sodium chloride) in our diet affects the amount of water we retain in our blood stream – high sodium levels can lead to elevated blood pressure. As blood pressure, fluid and salt levels are closely controlled in the kidneys, high sodium levels can also cause calcium and magnesium losses in the urine, which reduces availability of these minerals for bone formation. One way to offset the effects of excess sodium and reduce calcium loss in urine is to consume plenty of potassium, found in fruits and vegetables, stop adding salt to food or cooking, and limit your intake of processed foods.
We need adequate protein in our diet to make strong bones, but following a long term high protein diet can affect your blood pH, which has to remain within a very small pH (acidity/alkalinity) range of 7.35 to 7.45. Although the body has many buffering systems to maintain a healthy blood pH, in more extreme or chronic circumstances, calcium and magnesium salts may be leached out of the bone to offset the resulting acidity created by excess protein. Considering the detrimental metabolic and inflammatory effects of excess carbohydrate in the diet, a recommended protein intake is approximately 20% of your dietary calorie intake.
Individual nutrients for healthy, strong bones
Calcium is essential for bone formation but recent research shows that there is no substantial evidence of reductions in bone loss or fractures as a result of supplementing with calcium. However, there is a favourable link between calcium in the diet and bone health. Calcium is found in dairy products, dark green leafy and cruciferous vegetables, seeds (especially sesame), beans and tinned sardines.
Vitamin D is needed for calcium and phosphorus absorption and metabolism - it is just as important for strong bones as calcium is. We make most of our vitamin D in the skin in response to sun exposure, even on cloudy days, although wearing sun block will prevent vitamin D production. It is thought that only 15 to 20 minutes sun exposure to the arms and face three to four times weekly is required to make enough vitamin D for the year. However, vitamin D deficiency is increasing, and the Scientific Advisory Committee on Nutrition (SACN) recommend supplementation throughout the year in the UK. Vitamin D is found in oily fish, egg yolks, fortified margarines and cereals in the diet.
Magnesium works in conjunction with calcium and helps vitamin D synthesis. Eat plenty of leafy vegetables, cauliflower, seeds, nuts, pulses and dairy produce to ensure you get enough of this essential mineral.
Newer research shows potential benefits for specialist supplementation with specific types of vitamin E and vitamin K, although professional advice should be sought for this. Many micronutrients are needed for healthy bones including sulphur, iron, zinc, copper, manganese, boron, silicon, vitamin C and B12, so it's clear to see that a very diverse diet with a wide range of foods containing these nutrients is needed for good bone health. There is also evidence illustrating that a healthy microbiome affects bone turnover, so consuming a wide variety and healthy volume of plant foods is crucial for good bone health.
In addition to consuming sufficient amounts of all of these nutrients, it's important to ensure that your body is able to absorb them all - conditions such as coeliac disease or Crohn’s disease can significantly inhibit nutrient absorption. Low gastric acid secretion in the stomach also reduces absorption of several key nutrients such as calcium, iron, zinc and B12, so this is another hidden cause of osteoporosis, and something that merits consideration.
Whilst there are clearly many factors that contribute to osteoporosis and bone loss, most lifestyle factors can be affected by our diet and lifestyle choices, which provides a considerable amount of control over bone health.
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Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. Available at: < https://assets.publishing.service.gov.uk/government/uploads/system/uploads/ attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf>.
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