Introduction It's hard to avoid those ads that say drinking milk will make your bones strong. "Got milk?"Does "got strong bones?" really mean that?" People who support milk think that getting more calcium, especially from the three glasses of milk that are recommended every day, will help prevent osteoporosis, which weakens bones. Over 1.5 million fractures happen every year because of osteoporosis. Of these, 300,000 are hip fractures. Some people think that eating a lot of milk and other dairy products may make you more likely to get heart disease or prostate cancer, but it won't really change the number of fractures you get. Which point of view is correct? The last answers haven't come in yet. But here is a summary of what we know about calcium and how it works in the body right now. Where do we get calcium? What is it? Calcium is a mineral that the body needs to do many things, like build and maintain bones and teeth, break down food, help nerves send signals, and keep the heart's rhythm steady. Bones and teeth store 96% of the calcium that people have in their bodies. The last one percent is in the blood and other tissues. There are two ways for the body to get calcium. One way is to eat calcium-rich foods or take calcium supplements. When it comes to good sources, dairy products have the most highly absorbable calcium per serving. Dark leafy greens and dried beans also have some absorbable calcium. Vitamin D is often found in calcium supplements. Taking calcium with vitamin D seems to be better for your bones than taking calcium alone. Find out more about calcium and osteoporosis here. Calcium can also be taken from bones by the body. This happens when the amount of calcium in the blood drops too low, which usually happens after not eating anything with calcium in it for a while. The calcium that is "borrowed" from the bones should be replaced at some point in the future. It doesn't always happen, though. The most important thing is that this payback can't be reached by just eating more calcium. Getting Strong Bones Bone is made of living tissue that is always changing. In a process called remodeling, bones are always breaking down and building back up from birth to old age. The cells that make bone are called osteoblasts. The cells that break down bone are called osteoclasts. Up until about age 30, bone growth is greater than bone loss in healthy people who get enough calcium and exercise. After that, destruction usually happens more than production. What Does Osteoporosis Mean? Osteoporosis, which means "porous bones," is when bones get weaker because they don't build up as much as they break down. As people get older, they often lose bone mass, even if they get the recommended amount of calcium to keep their bones healthy. About 10 million people in the US have osteoporosis, with 8 million women and 2 million men affected. Another 34 million people have low bone mass, which makes them more likely to get osteoporosis. To build a strong foundation for the future, it's important to get enough calcium and build up your bone stores while you're still young (up to age 30). However, it won't stop bone loss later in life. Loss of bone with age is caused by many things, such as genes, not being active enough, and lower levels of hormones in the blood (estrogen in women and testosterone in men). Eighty percent of all cases of osteoporosis are in women who have gone through menopause. This is because estrogen production drops quickly during menopause. Bone loss can happen to both men and women, but men usually wait 5 to 10 years longer than women to get it because their testosterone levels don't drop quickly like women's estrogen levels do. It is thought that half of all women over 50 will break a hip, wrist, or vertebra because they have osteoporosis. What can be done to slow down osteoporosis? Two things are needed to avoid getting osteoporosis: making bones as strong and dense as possible in the first 30 years of life and limiting bone loss as an adult. Several things about your lifestyle can help with the second one: • Doing a lot of exercise every day, preferably exercises that build muscle and bear weight. • Making sure you get enough vitamin D, either through food, sun exposure, or supplements. • Getting enough calcium in your food will lower the amount your body needs to take from your bones. • Getting enough vitamin K, which is found in leafy greens. • Making sure you don't get too much preformed vitamin A. • How to Keep Bones Strong as an Adult • During adulthood and old age, there are a number of complementary strategies that can help stop or slow bone loss. Some of these are: Going for regular walks When you do physical activities that put some stress on your bones, those bones keep their density and may even gain it over time. When cells in the bone feel this stress, they make the bone stronger and denser. Walking, dancing, jogging, weightlifting, stair climbing, racquet sports, and hiking are all examples of "weightbearing" exercises. Working out your heart and lungs is good for you when you swim. Even though water doesn't put stress on the bones, it's not thought of as a good "weight-bearing" exercise for building bone strength. Besides that, exercise only strengthens stressed bones, not all of them. To keep all of your bones healthy, you need a variety of exercises or activities. Getting more exercise also makes muscles stronger and improves coordination. This is probably at least as important as the direct effect on bone mass. When muscles are stronger, people are less likely to fall or do other things that could break their bones. Making exercise a regular habit can help you keep your balance and keep you from falling. How to Get Enough Calcium Even though milk and calcium are controversial, one thing is certain: getting enough calcium is essential for lowering the risk of osteoporosis. Calcium is needed for bone growth and for other functions as well. But the safest or healthiest amount of calcium to eat hasn't been found yet. Estimates from different scientific methods are different, so it's important to look at all the evidence. Studies that look at how much calcium can be forced into bones (called "maximum-calcium-retention studies") suggest a pretty high need. The National Academy of Sciences set the following maximum calcium intake levels to make sure that 95% of people get this much calcium: • 1,000 mg/day for people 19 to 50 years old • 1,200 mg/day for people 50 and older • 1,000 milligrams a day for adult women who are pregnant or breastfeeding But the studies on maximum calcium retention only look at a short time, which means they have some big problems. Longer-term studies are needed to find out how the body changes in response to different calcium intakes over time and to get a better idea of bone strength in general. The outcomes of these types of long-term studies may come as a surprise to some. They don't disagree that calcium is important for strong bones, but they do question whether or not adults should be getting the large amounts that are currently recommended. In particular, these studies show that eating a lot of calcium doesn't seem to lower the risk of getting osteoporosis. One example is the large Harvard studies of male doctors and female nurses. People who drank one glass of milk a week or less were not more likely to break their hip or forearm than people who drank two or more glasses a week. Researchers still couldn't find a link between calcium intake and fracture risk when they put together data from the Harvard studies with data from other large prospective studies. Also, the results of all the randomized trials that tested calcium supplements against a sugar pill showed that they did not protect against hip or other bone fractures. It was also thought that taking calcium supplements without vitamin D might make the risk of breaking your hips even higher. A study from 2014 also found that drinking more milk as a teen was not linked to a lower risk of hip fractures in older adults. More evidence supports the idea that adults in the United States might not need as much calcium as is currently suggested. In places like India, Japan, and Peru, where people get as little as 300 milligrams of calcium a day (less than a third of the U.S. recommendation for adults ages 19 to 50), bone fractures don't happen very often. Obviously, these countries are also different in other ways that are important for bone health, like how active people are and how much sunlight they get. This could be why their fracture rates are so low. It would be best to solve these problems by giving a lot of adults different amounts of calcium at random and then watching to see how many of them break a bone. In fact, a few of these kinds of studies have been done, and as was already said, they have not shown any benefit. There was a small chance that supplementation might help, though, because most of these studies were small or only lasted a short time. In some randomized trials, calcium was combined with vitamin D, which might have made it harder to see what the real effects of calcium are. To show how different groups can come to different conclusions from the same set of data, a British committee similar to the U.S. group that set these calcium requirements decided that 700 milligrams of calcium a day was enough for people aged 19 and up. How to Get Enough Vitamin D Vitamin D is very important for keeping bones healthy. When calcium levels in the blood start to drop, the body does a number of things. It helps vitamin D change into its active form. This form then goes to the intestines to help the body absorb calcium better and to the kidneys to keep calcium from leaving the body through urine. Getting enough vitamin D is just as important for bone health as getting enough calcium. Vitamin D can be found in milk and vitamin supplements. In the summer, your skin can also make it by being out in the sun. But not all sunlight is the same. The winter sun isn't strong enough to make vitamin D above 40 degrees latitude, which is north of San Francisco, Denver, Indianapolis, and Philadelphia. Sunscreens also stop vitamin D from being made, but they are still suggested to lower the risk of skin cancer and damage from the sun. A study that looked at clinical trials of vitamin D for osteoporosis prevention found that getting 700 to 800 IUs of vitamin D every day lowers the risk of hip and other non-vertebral fractures. Taking vitamin D with calcium may make it work even better. A similar study that looked at how vitamin D affects falls found that older people who take vitamin D supplements are more than 20% less likely to fall. Find a multivitamin that gives you between 800 and 1000 IU of vitamin D every day. If the vitamin D in your multivitamin is only 400 IU, you might want to take an extra supplement. A lot of people may need at least 2,000 IU of vitamin D every day to keep their blood levels healthy. This is especially true if they have darker skin, live in northern latitudes during the winter, or don't spend much time in the sun. For most people in the U.S., these groups include yourself, so taking 2,000 IU is a good idea and well within the safe range. As always, you should talk to your doctor about taking supplements. He or she may want to order a vitamin D blood test. How to Get Enough Vitamin K Vitamin K is mostly found in leafy green vegetables. It is thought to play at least one important role in keeping calcium levels in check and building bones. Low levels of vitamin K in the blood have been linked to low bone density, and biochemical tests of bone health get better when people take vitamin K supplements. The Nurses' Health Study says that women who get at least 110 micrograms of vitamin K every day are 30% less likely to break their hip than women who don't get that much. If nurses ate a serving of lettuce or another green leafy vegetable every day, their risk of breaking their hip was half as high as if they only ate one serving a week. The Framingham Heart Study also found a link between getting a lot of vitamin K and a lower risk of hip fracture in both men and women, as well as a higher bone mineral density in women. Women should get 90 micrograms of fiber per day and men should get 120 micrograms. One or more servings of broccoli, Brussels sprouts, dark green lettuce, collard greens, or kale should be enough to meet this daily goal. These other things may also help lower the risk of getting osteoporosis: Be careful with coffee and soda. Some evidence suggests that drinking a lot of coffee - four or more cups a day or more - may raise the risk of breaking a bone. However, not all the votes are in yet. Caffeine tends to help the body get rid of calcium through urine. A different study called the Framingham Osteoporosis Study discovered that older women who drink cola every day have less bone mineral density than women who drink it less than once a month. This might be because cola has a lot of phosphorous, which can throw off the balance of calcium and phosphorous in the body and make bones weaker. Don't eat too much protein. Protein is important for building strong bones. But when your body breaks down protein, it releases acids into the bloodstream. To balance these acids, your body pulls calcium from your bones. It's not likely that a high-protein diet will make your bones stronger after a few weeks. But if you do it for a long time, it might weaken your bones. Over the course of 12 years, the Nurses' Health Study found that women who ate more than 95 grams of protein a day were 20% more likely to have broken their wrist than women who ate less than 68 grams of protein a day. But this field of study is still controversial, and different studies have come to different conclusions. Some studies show that eating more protein raises the risk of breaking a bone, while others show that eating a lot of protein raises bone mineral density. It's still not clear what amount of protein protects against osteoporosis the best, and more research is needed. Not too much or too little vitamin A. Vitamin A has been linked to good eyesight for a long time. It has also been shown to control the process of bone calcium borrowing and re-placing. But getting too much preformed vitamin A (also called retinol) can make you more likely to break a bone. Pick a multivitamin supplement that gets most or all of its vitamin A from beta-carotene, which is a form of vitamin A that does not raise the risk of breaking a bone. A lot of companies that make multivitamins have already cut down on the amount of preformed vitamin A they put in their products. Women who have gone through menopause may also want to talk to their doctor about taking a drug that can make bones stronger. Postmenopausal hormones contain estrogen, which can make up for the loss of estrogen after menopause. This can help stop bone loss and may even partially reverse it. Hormone replacement therapy, on the other hand, is no longer the most popular way to prevent osteoporosis because several studies have shown that it raises the risk of breast cancer, stroke, and blood clots. As well as alendronate (Fosamax), risedronate (Actonel), calcitonin (Miacalcin), raloxifene (Evista), and parathyroid hormone (Fortéo), these other drugs have also been approved to prevent or treat osteoporosis. Is milk a good way to get calcium? Most people in the US think of milk right away when they hear the word "calcium." But should it be this way? Milk is not the only food that can give you calcium. Dark leafy greens and some types of legumes are also good sources, and there are important reasons why milk might not be the best choice for everyone. The following are some of these reasons: Intolerance to lactose A lot of people can't handle lactose in some way. They have problems like cramps, bloating, gas, and diarrhea when they eat or drink dairy products. These symptoms can be very bad or very mild. Certain groups are a lot more likely to have trouble with lactose. 90 percent of Asians, 70 percent of blacks and Native Americans, and 50 percent of Hispanics can't handle lactose, but only about 15 percent of people from Northern Europe can. If you can't handle lactose but still want to eat dairy products, you could take a pill with enzymes that break down milk sugar along with the dairy product, or you could drink milk that has the lactase enzyme added to it. High Level of Saturated Fat There are a lot of saturated fats in dairy products, and eating a lot of saturated fats can make you more likely to get heart disease. It's true that most dairy products now come in fat-reduced or nonfat versions, but someone will still eat the saturated fat that is taken out of dairy products, usually in the form of premium ice cream, butter, or baked goods. The strange thing is that the same people who buy these higher-fat foods also buy the low-fat dairy foods, so it's not clear that they're really trying to cut back on saturated fat. Read the article Fats and Cholesterol: Out with the Bad, In with the Good from Nutrition Source to learn more about fats in food. Possible Rise in the Risk of Ovarian Cancer Researchers have looked into how high levels of galactose, a sugar that is made when lactose in milk is broken down, might hurt the ovaries and cause ovarian cancer. Some studies have found links like these, but not all of them have. Eating a lot of lactose may be bad for you.... A recent analysis of 12 prospective cohort studies that included more than 500,000 women found that women who ate a lot of lactose - about 3 cups of milk a day - had a slightly higher risk of ovarian cancer than women who ate the least amount of lactose. The study did not find a link between eating a lot of milk or dairy products and getting ovarian cancer. Some researchers think that the way modern industrial milk is made has changed the hormones that are in milk in ways that could make ovarian and other hormonerelated cancers more likely. We need to do more research. Probably a higher chance of getting prostate cancer A diet high in calcium has been linked to a likely increased risk of getting prostate cancer. It was found that men who drank two or more glasses of milk a day were almost twice as likely as men who didn't drink milk at all to get advanced prostate cancer. The link seems to be with calcium itself, not dairy products in general. A more recent look at the Harvard study participants found that men who ate the most calcium (at least 2,000 milligrams a day) had almost twice the risk of dying from prostate cancer as men who ate the least calcium (less than 500 milligrams a day). It's clear that we can't be sure that drinking a lot of milk or calcium is safe, even though more research is needed. Last but not least, suggestions for getting enough calcium and keeping your bones healthy To lower the risk of osteoporosis, you need to eat enough calcium throughout your life. For the strongest and densest bones, it's also important to get enough calcium and vitamin D and do regular weight-bearing exercises. Once you hit 30 years old, these things can help slow bone loss, but they can't stop it completely. A lot of people find it easy to get calcium from milk and other dairy products. Plus, they have extra vitamins D and A and are a good source of protein. But at this point, it's not clear what the best amount of calcium is or where the best calcium should come from. As we already said, the National Academy of Sciences says that people 19 to 50 years old should get 1,000 milligrams of calcium every day, and people 50 and older should get 1,200 milligrams every day. To get 1,200 milligrams of calcium every day, most people would need to drink two to three glasses of milk or take calcium supplements on top of eating a healthy diet. These suggestions, on the other hand, come from very short-term studies and are probably more than what people need. There isn't strong evidence yet that drinking more than one serving of milk a day, along with a healthy diet that gives you about 300 milligrams of calcium a day from foods other than dairy, will lower your risk of breaking a bone. Concerns about the risk of ovarian and prostate cancer have not been fully resolved, so it may be best to avoid eating a lot of dairy products. But if you eat dairy products and calcium in moderation, they may help your health in other ways too, like lowering your risk of high blood pressure and colon cancer. The benefits for blood pressure seem pretty small, but the benefits for colon cancer seem a bit bigger. Most of the benefits for colon cancer come from drinking just one or two glasses of milk a day, on top of what we get from other foods. There doesn't seem to be any more risk when you get above this. There are other options for people who can't digest dairy products or don't like them, or who just don't want to eat a lot of them. Dark green leafy vegetables, like kale and collard greens, and dried beans and legumes are also good sources of calcium. Spinach and chard also have calcium, but they also have oxalic acid, which mixes with the calcium to make calcium oxalate. This is a chemical salt that makes the calcium less available to the body. Now there are many foods on the market that have extra calcium in them, like orange juice and soy milk. Taking calcium supplements is another option. If you choose to do this, it's best to pick one that also has vitamin D. Studies show that calcium-only supplements may not keep you from breaking bones, and may even make them more likely to happen. There is also growing evidence that taking supplements that only contain calcium may possibly raise the risk of heart attacks. This is another reason to stay away from these supplements. There are concerns about the possible risks of prostate cancer in men who take calcium supplements. If men do take a calcium supplement, it seems smart to limit their daily intake to 500 milligrams of calcium. Antacids have calcium in them, but not vitamin D. That's why you might want to take a separate vitamin D supplement if you choose antacids as a calcium source. Talk to a health care provider about your choices. (Find out more about vitamin D and health.)