We often take our bones for granted— they’re just a part of us—keeping us standing, walking, running, sitting a lot, maybe skiing or biking. We don’t think about them much until something goes wrong—one breaks or bends or somehow interferes with what we want to do. As we age, we’re less able to be complacent about our bones. Maybe we’re more worried about slipping on a throw rug and breaking a hip, or maybe we’ve been diagnosed with osteoporosis or have noticed a decrease in height.

While following a vegan diet can promote bone health, it does not guarantee healthy bones. We’ve received notes like this one from a VRG member:

This article was written to explain what osteoporosis is, what causes it, and what vegans can do at every age to reduce their risk of developing osteoporosis.

Osteoporosis is a disease that affects more than 25 million Americans. In 2001, the estimated national direct expenditure for osteoporosis and fractures related to this condition was $17 billion, and this cost is rising. Osteoporosis simply means porous bones. It is a condition in which the bones become less dense and fragile, and they can break easily. It affects women more than men, although men are also affected as they get older. If osteoporosis leads to a bone fracture, it can seriously affect function and even lead to death.

To understand osteoporosis, we’ll need to look more closely at bones. Although bones seem very simple, they are actually fairly complicated. The scaffolding for bone is made from a protein called collagen. As bones form, calcium and phosphorus combine to make hydroxyapatite, a mineral-rich substance that crystallizes on the collagen scaffold, making a strong, rigid material. Bone minerals do not remain in the bone forever. Even after bones are formed, they are constantly changing. When another part of the body needs calcium, it is taken from the bone to meet the need. When more calcium is available, it is used to rebuild the bone.

Early in life, more bone is being built than is being broken down. After about age 30, though, more bone is being broken down than is being built, resulting in a net loss of bone. Although bone loss is inevitable with aging, if you have larger, stronger bones at the start, the normal loss of bone mass will not be as severe. Also, anything that can be done to slow the rate of loss helps to spare bones.

Women are at much greater risk for osteoporosis than men because women start out with less bone and lose bone mass more quickly, particularly in the years immediately after menopause. Women between the ages of 20 and 29 have about 76 percent the bone matter of men; by their 70s, this decreases to about 60 percent.¹ Thus, when women age and start losing bone mass, they develop very fragile bones. Genetics also appears to play a role in that osteoporosis runs in families.

Factors like gender and genes can’t be changed. Others are within our control, though, and can have a marked effect on risk of osteoporosis. These include dietary factors, such as calcium, vitamin D, protein, sodium, caffeine, phosphorus, fluoride, vitamin A, and vitamin K, as well as weight-bearing activity.

Calcium, the main mineral in bones, plays an important role in bone health. Children whose diets are low in calcium may develop osteoporosis as adults and have a greater risk of breaking bones.^2-4 Some studies,^5-7 although not all,⁸ have shown that older adults with a high calcium intake have stronger bones and a lower fracture risk. There is a limited number of studies of vegans, most of which find low bone density as well as low calcium intakes.^9-10 One study¹¹ where vegans had calcium intakes close to recommended levels found that calcium was well-absorbed from a vegan diet. Sources of well-absorbed calcium include calcium-fortified soymilk and juice, calcium-set tofu, soybeans and soynuts, bok choy, broccoli, collards, Chinese cabbage, kale, mustard greens, and okra.¹² Grains, beans (other than soybeans), fruits, and vegetables other than those listed can contribute to calcium intake but cannot replace the key foods mentioned above.

Nevertheless, it’s not enough to have a high-calcium diet. Adequate vitamin D is needed for calcium to be absorbed. Vitamin D is necessary throughout life to help build strong bones in childhood and adolescence and to maintain bones throughout adulthood.^8,13,14 Our skin produces Vitamin D with sun exposure, but many factors, including season, time of day, age, sunscreen use, and pollution, can interfere with this production. Therefore, dietary sources of vitamin D are important for most people. Since there are only very small amounts of naturally-occurring vitamin D in plant foods, vegans—both children and adults—should rely on foods fortified with vitamin D, including fortified non-dairy milks, juices, and breakfast cereals. Vitamin D supplements are another option.

Some popular publications suggest that vegans don’t have to be concerned about bone health because the lower animal protein content of vegan diets will minimize calcium losses. In reality, vegans do need adequate calcium and vitamin D, and they should also be sure that they are getting adequate, but not excessive, protein. Vegan diets generally contain adequate amounts of protein unless they are very low in calories or do not contain a variety of whole plant foods.

Protein’s effect on bones remains uncertain. Some studies show that diets that are high in protein, especially animal protein, do cause increased losses of calcium in the urine (seen at 0.45 grams of protein per pound of body weight and at 0.95 grams of protein per pound)¹⁵ and may even increase fracture risk.^16,17 The effects of protein may be especially important in those with low calcium intakes.¹⁸ Other studies suggest that a higher protein intake (as much as 0.95 grams per pound of body weight) is needed to promote calcium absorption,¹⁹ reduce the risk of fracture,²⁰ and increase bone density.^21,22

Additional research is needed, but at this time it seems that both an adequate intake of calcium and protein (near the RDA of 0.8 grams of protein per kilogram or 0.36 grams of protein per pound) can optimize bone health.

In addition, phosphorus, fluoride, vitamin A, and vitamin K are important for bone health. Phosphorus, like calcium, is a major part of bone. Phosphorus is found in many foods and is abundant in vegan diets. Fluoride promotes the accumulation of calcium and phosphate in bone. It comes primarily from fluoridated water. Vitamin A is needed for bone growth, although excessive amounts of retinol (the form of vitamin A found in many animal foods) can increase fracture risk.²³ Beta-carotene, the vitamin A precursor found in plant foods, does not appear to increase the risk of fracture. Vitamin K, a vitamin that comes from green vegetables and other plant foods, is needed to make a protein that strengthens bones.

Many substances that support bone health have been mentioned. Caffeine and sodium have the opposite effect—excesses of these can be harmful to bones. Large amounts of caffeine increase calcium losses in urine. This is especially problematic for those with low calcium intakes.^24-25 Excess sodium can also increase urinary calcium and compromise bone health.^26-27

Any exercise that makes bones support weight—walking, running, dancing, weight-training, or roller-blading—can stimulate an increase in bone size and strength. For elementary school children, even 30 minutes of this type of exercise a couple of times a week can contribute to an increase in bone strength, which should lead to a reduced risk of osteoporosis later in life.²⁸ It won’t hurt teens^29,30 or adults,³¹ either. Besides helping strengthen bones, exercise can also improve balance and flexibility, both important factors in preventing and recuperating from falls.

In conclusion, vegans of all ages can promote bone health by: