[Nutrition Science] Drinking milk every day, why is bone density still low?

[Popular Science Nutrition] I drink milk every day, but why is my bone density still low?

2024-08-07

Author: Fan Zhihong

Researcher at the Department of Nutrition and Health, China Agricultural University, post scientist at Beijing Advanced Center of Food Nutrition and Human Health, PhD in Food Science, and registered dietician.

"Fan Zhihong_Original Nutrition Information" self-media author;Director of the Chinese Society of Food Science and Technology; Vice Chairman of the Food and Culinary Nutrition Branch of the Chinese Nutrition Society; Vice Chairman of the Geriatric Nutrition and Food Branch of the Chinese Society of Gerontology and Geriatrics, etc.

He teaches courses such as food chemistry and food nutrition. His main research direction is foodblood sugarThe impact of food reaction, cooking and processing on the nutritional and health value of food, nutritional environment evaluation, etc. He has edited 6 textbooks, participated in the editing of 12 textbooks, published 133 scientific papers as the first author or corresponding author, published 25 popular science books on food nutrition, and written more than 6,000 popular science articles on food that have been reprinted in newspapers and magazines.

Authorized to reprint on China Clinical Nutrition Network

Recently, several friends who are concerned about nutrition have asked meAbout drinking milkThe questions are all very difficult.

Ms. A asked:Does drinking milk really help to supplement calcium? I drink 1 cup of milk every day, but how come my bone density is still a little low? I am only 29 years old, and I have been working out twice a week for the past two years. My mother doesn't drink milk or work out, and she is in her 50s, but her bone density is actually within the normal range. What's going on?

Ms. B asked:I heard that some nutritionists abroad are vegetarians and don’t drink milk at all, but I haven’t heard that they suffer from osteoporosis or malnutrition?

I thought about it for a long time, sorted the problem into several points, and explained it to you slowly.

First of all, I need to explain that drinking milk every day may not necessarily provide enough calcium.

First of all, how much milk do you drink? Can a glass of milk provide enough calcium?

The calcium content in milk is about 100~120 mg/100 g. 1 box/1 full cup of milk is about 250 g, which contains at least 250 mg of calcium.

However, the daily calcium requirement for adults under 50 is 800 mg, and for those over 50 it is 1000 mg. Drinking half a pound of milk is obviously not enough for the daily requirement.

According to the results of previous dietary nutrition surveys in my country, excluding milk, the average calcium content in three meals a day is about 300 to 400 mg, unless you deliberately eat more high-calcium foods.

Nowadays, many women do not eat much, and the calcium in their diet is only about 300 mg. Add a box of milk containing 250 mg of calcium, and there are only about 550 mg, which does not even reach the reference value of 800 mg, not to mention the target value of 1000 mg for middle-aged and elderly people.

So, drinking a glass of milk is better than not drinking it, but it still cannot completely meet the standard. Of course, milk and yogurt are not just for calcium supplementation. They provide a variety of nutrients and are also convenient to drink. Therefore, just because they cannot guarantee to solve the problem of osteoporosis, it cannot be considered that they are not worth drinking.

Second, what else did you eat besides drinking milk?

Just now I said,In addition to milk, calcium supplied by other foods in the diet is also important.Although the average is 300 to 400 mg, there are huge differences between people.

If you only eat white rice and white flour, with few vegetables, few soy products, few beans and nuts, and no fish or shrimp, then you will not even get 300 mg.
If you increase the intake of tofu/shredded tofu/dried tofu, green leafy vegetables that are not astringent, dried shrimps and small fish, you can increase the calcium intake in your diet. In this case, if you add a glass of milk/yogurt, the calcium intake can easily reach the standard of 800 mg.

Then we say,There are many other factors that affect bone health.

Third, in addition to calcium, other nutrients needed by bonesNutrientsIs it enough?

Calcium is not the only nutrient needed for bone health.

In addition to calcium,protein, potassium, magnesium, zinc,Vitamins D, vitamin K, vitamin C, vitamin A and many other ingredients are related. Moderate intake of two trace elements, boron and fluorine, may also help. In recent years, studies have also found that antioxidants may also help and can reduce bone tissue.Inflammation, which helps prevent osteoporosis.

in addition,Eating staple foods in moderation is also beneficial to bone health.Many people do not eat staple foods in order to lose weight and advocate ketosis, which will increase the rate of bone calcium loss.Long-term calorie and protein deficiency also has an impact.People who are thin are more likely to develop osteoporosis.

Fourth, how is your digestion and absorption ability?

When gastrointestinal health is poor, theMineralsThe absorption and utilization rate will be reduced accordingly. If you often have stomach blockage, bloating, indigestion, and frequentdiarrheaAbdominal distension may mean that the ability to absorb nutrients is reduced. Especially for people who are prone to diarrhea, the utilization rate of calcium will be seriously affected. Not only milk, but also other foods will reduce the utilization rate of calcium.

Drinking a box of milk, even if it is fully utilized, only provides about 250 mg of calcium, which may not even be enough for the daily intake of 800 mg. Moreover, in the case of poor absorption and utilization, it is even more impossible to reverse bone mineral density. In comparison, drinking yogurt may be more beneficial because yogurt providesDigestive systemThe workload is slightly less than that of milk.

Fifth, how is your bone foundation?

It is hard not to admit that comparison is the thief of envy. Some people are born with large frames, and some have good nutrition and abundant bone minerals since childhood; on the other hand, some people are born with small frames, and some have little bone mineral accumulation in childhood and adolescence, so their bone density is not high when they become adults.

If your foundation is weaker than others, even if you eat and live like others after adulthood, your bone density will not be as good as others. Even if you drink a glass of milk and yogurt every day, you can only maintain it, and it is difficult to catch up with others.

Perhaps many girls think that their "big frame" and "heavy bones" are unfortunate, which makes them look heavier and less petite at the same body fat percentage. But this good foundation may reduce your risk of fractures in the future. After the age of 35, the body's bone density decreases, and its benefits will be reflected.

Sixth, are you losing bone calcium too quickly?

Some situations can cause calcium to run too fast or affect normal bone metabolism.

for exampleFemale menopause, especially in the three years before and after menopause, calcium loss is particularly fast.
for exampleLong-term stress response and inflammatory response, which will increase the level of inflammatory factors in bone tissue and hinder bone renewal.
for exampleMild acidosis. Diabetic ketoacidosis, very high protein diet, and long-termKetogenic DietThis is because in the case of acidosis, the body will use the calcium in the bones to balance the pH of the body fluids in order to save itself.

It’s not that the ketogenic diet can’t be used for short-term treatment, but it is risky to continue it for a long time.Especially those who do not have medical guidance, no nutritionist management, and are casually following the ketogenic diet, as well as other extremely lowcarbohydrateThe diet has serious side effects, one of which is that it affects bone health.

Even if you don't deliberately go ketogenic to lose weight, just dieting regularly can easily damage your bone density.As early as the 1990s, foreign studies have found that Japanese female white-collar workers in their twenties who often diet to lose weight and do not exercise have lower bone density than 50-year-old women who exercised regularly and did not diet when they were young.

For example, smoking, drinking, and taking drugs indiscriminately can affect bone health.

Seventh, did you exercise enough during your growth period? Have you continued to exercise for a long time since then?

As the saying goes, use it or lose it.Exercise is extremely important for promoting bone building.

Space research has found that in a state of weightlessness, human bones will quickly decalcify after they are no longer "pressed" by body weight. Experiments that simulate weightlessness by long-term bed rest have also found that after staying in bed, bone density will decrease significantly. Conversely,Jumping exercises, exercises that resist gravity, and weight-bearing exercises are all beneficial in increasing bone density.

Especially during the growth and development period of children and adolescents, active exercise is particularly important for forming strong bones, which can benefit people throughout their lives.Bone density reaches a plateau after the age of 25, and even decreases after the age of 45. However, insisting on exercise is still of great significance for bone health.With the same dietary nutrition, the bone condition of people who have been exercising since childhood and those who have not been exercising are different.

On the one hand, exercise improves cardiopulmonary function, thereby providing more blood oxygen to bone tissue. On the other hand, exercise can also strengthen muscles, reduce the stress on bones and cartilage, and improve coordination and balance, thereby reducing the risk of falls and joint pain.

Going back to the questions at the beginning, I believe many people have already solved their confusion.

Confusion 1:

My parents never drank milk when they were young. How come they have better bone density than me now that they are in their fifties?

Compared with middle-aged and elderly people, young people today may have the following differences in bone health-related factors:

old generation:There was no concept of sun protection back then, and people could bask in the sun as much as they wanted since they were young. Even when they got old, they would still go out for a walk in the sun every day... This way, their vitamin D levels would be relatively sufficient.
young people:We are busy with sun protection every day, not only using parasols and sun-protective clothing, but also applying sunscreen all over the body. These will affect the skin's ability to receive ultraviolet rays, and the production of vitamin D will be greatly reduced.
old generation:Although I have eaten less meat since I was young, I have eaten a lot of whole grains and I don't go on a diet. I have enough carbohydrates and am rich in potassium and magnesium.Adequate potassium and magnesium can help reduce calcium loss.Green leafy vegetables, soybean oil, rapeseed oil and soy products are good sources of vitamin K, and they eat a lot of them. Vitamin K is a necessary component for bone formation.
young people:They have been picky eaters since childhood, with few vegetables, grains and beans, and do not like to eat green leafy vegetables. They eat more white rice, white flour and meat, and have little vitamin K, potassium and magnesium intake. Many people also often diet to lose weight, causing malnutrition artificially.
old generation:If you don't consume excessive protein for most of your life, don't eat a lot of sweets and snacks, and don't drink sweet drinks like cola, the risk of bone calcium loss is not that great.
young people:Some people eat too much meat, while others often eat sweets and drink beverages, which is not conducive to improving bone density.

old generation:Running and jumping outdoors since childhood, doing a lot of physical activities when young, the bone foundation is relatively good. As an adult, you are also more willing to walk and work, which is conducive to maintaining a good bone density.
young people:Most people have been sedentary since childhood and adolescence, with little time for physical exercise. Some people prefer leisure to leisure and lack physical activity. The bone density during the growth and adolescence period is poor, and the risk of osteoporosis in the future is greater.

In short, if you have not paid attention to bone health for many years, even if you start to increase exercise and improve nutrition in the last two or three years, it will not be able to completely make up for the impact of your lifestyle since childhood. As mentioned earlier, bone health issues are very complicated, and drinking a glass of milk alone cannot solve all problems.

Of course, not all young people have weak bones since childhood, and not all parents have healthy bones. Regardless of age, if the original foundation is not good enough and you don’t pay attention now, the future will be even more worrying.

Confusion 2:

Some people are vegans and don't drink milk, so why don't they all have osteoporosis?

A vegetarian diet does not mean insufficient calcium intake. If there is a good nutritional balance, a vegetarian diet can also provide enough calcium.

For example, tofu and dried tofu, non-astringent green leafy vegetables (such as rapeseed, Chinese cabbage, kale, celery, cabbage, etc.) are rich in calcium. Sesame paste, sesame seeds, melon seeds, flax seeds, etc. also contain a lot of calcium.

Potassium, magnesium, vitamin C, vitamin A, vitamin K and other nutrients can be obtained from plant foods. Vitamin D mainly depends on sun exposure. Although there is a small amount of vitamin D in fish, meat, eggs and milk, as long as there is enough outdoor activities, it will not have much impact if you do not eat them.

The sulfur-containing amino acids in bean protein are relatively low, lower than those in meat, eggs and milk, which in a sense helps reduce calcium loss because too much sulfur promotes urinary calcium excretion.

The nutritional value of various plant milks cannot compare with that of cow's milk.Soy milk can be comparable to cow's milk in terms of protein, but its calcium content is very low unless enough calcium is added. In developed countries, you can buy a variety of milk substitutes fortified with calcium and vitamin D, but the situation in my country is not satisfactory.

Of course, if vegans eat more green leafy vegetables, nuts, oil seeds, and soy products, the bone-healthy ingredients they get may make up for the loss of not drinking dairy.

only,It is best for vegetarians to have sufficient nutritional awareness and combine nutritional supplements with fortified foods.Because there are healthy vegetarian diets and unhealthy vegetarian diets. Not all vegans can obtain all the nutrients mentioned above.

in conclusion:

1. Drinking a glass of milk/yogurt is very helpful for dietary calcium supplementation.There is no such thing as "the more milk you drink, the more calcium you lack."

2. The calcium content of just one glass of milk is not enough to reach the daily recommended amount.Need to be combined with other foods.

3.Bone health requires the combined action of multiple nutrients.Drinking a glass of milk alone cannot be the only measure to solve the problem of preventing osteoporosis.

4. Although people in the past did not have the conditions to drink milk,But they are exposed to more sunlight, have more physical activities, and consume more vegetables and grains.These are all factors that are beneficial to bone health, and bones tend to be in good condition.

5.Now many peopleLack of exercise, excessive sun protection, unreasonable eating habits since childhood, poor bone foundation,May increase the risk of osteoporosis in the future.

6.Plant milk cannot replace the nutritional value and calcium supplement value of milk.

7. If you have ever thought aboutVegan Lifestyle, you should pay attention to eating more green leafy vegetables, nuts, oil seeds and soy products, and supplement calcium, vitamin D and related nutrients when necessary.

A few more pieces of advice:

1. Even if you are young, don't be too pretentious.Starvation weight loss and extremely low-carb diets are extremely unfriendly to bones, so don’t do them often!

2.Improve digestion and absorption, avoid gastrointestinal diseases,It is very important for musculoskeletal health!

3.Don't forget to measure your bone density during your physical examination.Don’t assume that your bone density is normal just because you are young and can drink a glass of milk every day!

4.If you have reached menopause, you need to pay more attention to bone-building nutrients in your diet and monitor your bone density every one or two years.If it has reached a dangerous state, treatment must be sought!

Cover image source:WeChat public platform public image library

Editorial Department of China Clinical Nutrition Network

news

[Popular Science Nutrition] I drink milk every day, but why is my bone density still low?

Introduction

my contact information