Diet and Bone Health

As if we needed another reason to eat more fruits and vegetables. Well, here is one anyway. Fruits and vegetables can strengthen bones. Whoa...you say. Calcium and vitamin D are what we need to prevent osteoporosis. Yes, we certainly need those nutrients but bone health has more determinants than just calcium and vitamin D intake.

Joe Schwarcz | 20 Mar 2017 General Science

As if we needed another reason to eat more fruits and vegetables. Well, here is one anyway. Fruits and vegetables can strengthen bones. Whoa...you say. Calcium and vitamin D are what we need to prevent osteoporosis. Yes, we certainly need those nutrients but bone health has more determinants than just calcium and vitamin D intake. It is the overall content of the diet that matters. Hip fractures, for example, are higher in milk consuming countries. That may come as a surprise given that dairy products are an excellent source of calcium. So how is it that Asians, with a lower calcium intake, are less prone to osteoporosis. Because it is the overall content of the diet that matters, not just the amount of calcium or vitamin D it contains. The acid-base balance of the diet seems to be an important feature. But this is not quite what people may think. You think acid, and you think of vinegar or orange juice or soda pop. Think base, and baking soda probably pops into your mind. However what matters is not the acidity or alkalinity of the food or beverages we may put in our mouth, but what happens to their components after ingestion and metabolism. Foods with a lot of protein are acid forming because proteins contain sulphur and the sulphur eventually is converted in the body to sulphuric acid. Eggs, fish, meat and poultry are therefore acidic foods. Breads and cereals are also metabolized to acids, but surprisingly, citrus foods are not acid producing. That’s because citric acid is broken down in the body to non-acidic substances. Most fruits and vegetables yield an alkaline residue in the body, although corn and lentils are acid forming.

So what does all of this have to do with bone strength? A proper acid-base balance is critical to health and it is well established that the body requires that the fluid surrounding cells be maintained at a pH between 7.35 and 7.45. pH of course is just a measure of acidity. The lower the number the more acidic the solution. Now, if a food with an acid residue is consumed, the body will take steps to ensure that extracellular fluid pH doesn’t drop below 7.35. The extra acid may be excreted by the kidneys, exhaling carbon dioxide also raises pH, or bones may release alkaline calcium salts to neutralize the excess acid. Bone is dynamic, some is always being formed by osteoblasts, and some broken down by osteoclasts. Unfortunately increased acidity enhances the activity of osteoclasts, increasing the risk of osteoporosis. Now, if the diet does not lead to an acid residue, there is no need for the bones to release calcium. So an increase in fruits and vegetables, with their alkaline residue, is great for bone structure. And there is still more. Studies have shown that carotenoids such as beta carotene, lycopene, lutein and zeaxanthin, as found in many fruits and vegetables can increase bone density, although the mechanism of this is not clear. Seniors who have a tough time increasing their fruit and vegetable intake may have another option. A study at Tufts University showed that taking bicarbonate supplements can have a favourable effect on bone structure by neutralizing dietary acidic residues. The problem is that in the study subjects were given about six grams of bicarbonate a day, a hefty dose. It is easier to bone up by eating more fruits and veggies.