Recently, several middle-aged men have said to me, "I'm so frustrated! How did my medical examination results show that I have osteoporosis? Isn't osteoporosis a problem for older women? How can men in their forties also have osteoporosis? What should I eat to improve it?"
In fact, it's not uncommon for men to have osteoporosis nowadays. The 2012 report from various medical examination institutions in Beijing mentioned the top three reasons for failed examinations: besides being overweight or obese, fatty liver and abnormal blood lipids, the third reason was decreased bone density. Among these individuals with low bone density, it is not uncommon to find women in their thirties and men in their forties, in addition to middle-aged women.
In theory, women experience a rapid decline in estrogen levels after middle age, especially during menopause, which leads to accelerated calcium loss and a higher prevalence of osteoporosis. Men, on the other hand, originally have higher bone density and mass compared to women, and their decline in testosterone levels occurs later. Therefore, men should have a lower risk of osteoporosis compared to women.
However, men often have unhealthier lifestyles compared to women. Smoking and excessive alcohol consumption are both detrimental to the bones. Consuming excessive amounts of meat and protein can increase urinary calcium loss, and a sedentary lifestyle, such as driving everywhere, can promote osteoporosis. In terms of diet, many men don't like to eat vegetables and fruits, especially leafy greens, which is also an important factor that is detrimental to the bones.
When all these harmful factors are combined, premature bone aging is understandable. I usually advise them to not only take calcium supplements and consume calcium-rich dairy and soy products but also pay attention to eating more leafy vegetables.
Can leafy vegetables really help strengthen your bones?
Upon hearing this, many people express their confusion. It is widely known that tofu, dried tofu, tofu skin, and other soy products are rich in calcium, and dairy products like milk and yogurt are also high in calcium. But can leafy greens really help with calcium supplementation? Do they have such great benefits for bones?
In fact, we know very little about the benefits of leafy greens, and there are many misunderstandings. This is truly a pity because, from a global perspective, China is one of the few places where leafy greens are abundant, affordable, and of high quality. Almost all leafy greens are good sources of potassium and magnesium, and some are also rich in calcium. Let's take a look at the data:
Chinese flowering cabbage contains 157mg of calcium, 153mg of potassium, and 27mg of magnesium per 100g. Bok choy contains 90mg of calcium, 178mg of potassium, and 18mg of magnesium per 100g. Spinach contains 73mg of calcium, 220mg of potassium, and 58mg of magnesium per 100g. From these numbers, we can see that daily consumption of leafy greens can provide a significant amount of calcium, potassium, and magnesium. Magnesium is a trace element in bones and teeth and helps improve calcium utilization. Adequate potassium supply can effectively reduce urinary calcium loss.
One might question the quantity of these nutrients in leafy greens with just the data. Let's compare it with two reference data points. Full-fat milk contains 104mg of calcium, 109mg of potassium, and 11mg of magnesium per 100g, while tomatoes contain 10mg of calcium, 163mg of potassium, and 9mg of magnesium per 100g. In other words, the calcium content of some leafy greens can be comparable to milk, and their potassium and magnesium content is even higher. As for tomatoes, cucumbers, eggplants, and other non-leafy greens, although they have higher potassium content, their calcium and magnesium content is much lower compared to leafy greens.
Someone with a little knowledge of nutrition might raise the objection that although leafy greens are rich in potassium, calcium, and magnesium, they also contain a lot of oxalic acid, which hinders calcium absorption. This statement has some truth to it, but it doesn't negate the advantages of leafy greens because, in reality, most common leafy greens have low oxalic acid content. Only a few varieties, such as purslane, spinach, wild amaranth, and amaranth, contain a higher amount of oxalic acid. The oxalic acid content in oilseed rape, bok choy, Chinese cabbage, Chinese mustard, mustard greens, and lettuce, which make up the majority of leafy greens, is very low, and the oxalic acid-to-calcium ratio is also low. Therefore, the calcium they contain can be absorbed and utilized by the human body. In fact, when eating these low oxalic acid vegetables, you can hardly taste any astringency, while spinach is quite astringent due to its oxalic acid content.
Studies using stable isotope tracing have specifically measured the calcium utilization of some vegetables. The results show that the oxalic acid content in Chinese mustard and Chinese flowering cabbage is low, at only about 20mg/100g, and their calcium utilization is also very ideal. If the calcium utilization rate of milk is taken as 1.00 for comparison, the calcium utilization rates of Chinese mustard and Chinese flowering cabbage are 1.08 and 1.10, respectively. In contrast, due to the high oxalic acid content, the calcium utilization rate of spinach is only 0.26. Of course, oxalic acid can be removed, as long as you blanch spinach in water, which can remove more than half of the oxalic acid, while calcium is insoluble in water. This way, the calcium utilization rate of blanched spinach can be effectively improved.
However, the benefits of leafy greens for calcium supplementation go beyond providing potassium, calcium, and magnesium. Leafy greens are rich in vitamin K, which is essential for bone formation. Vitamin D only helps with calcium absorption but does not contribute to bone formation. The final step in bone formation requires a protein called osteocalcin, and vitamin K is necessary in its production. In other words, even if the calcium and vitamin D in the diet are sufficient, without vitamin K, it will not have the desired effect of strengthening bones.
Foods rich in vitamin K include leafy greens, soy products, and soybean oil. Egg yolks, animal liver, and some nuts also contain vitamin K, but they are not the main dietary sources of vitamin K for Chinese people. Therefore, replacing a portion of daily meat consumption with soy products is beneficial for bone health. At the same time, consuming a large amount of leafy greens is also essential for bone health.
Lastly, one should not forget that a lack of beneficial stimulation for bones is an important factor in osteoporosis. The principle that the body follows is "use it or lose it." Sitting in front of the computer or lying on the couch all the time means that the bones are hardly stimulated, making them more prone to osteoporosis. Even if a high-calcium diet is consumed, the effect on bone health is limited. Research abroad has found that weight-bearing exercises, jumping exercises, and resistance exercises are all beneficial for maintaining bone density. Mildly osteoporotic elderly individuals showed improved bone density after engaging in low-intensity exercises such as brisk walking or jogging.
Therefore, while osteoporosis is not yet severe, it is important to adjust one's diet and start exercising to prevent it from worsening.
