Vegan for Life - Jack Norris [20]
• Consuming isolated animal proteins—that is, just the pure protein portion of a food—has a direct and significant effect on calcium losses, but that effect is often lost when subjects are fed whole, high-protein foods. The reason may be that other factors in foods, like phosphorus, counteract the urinary losses.10
• While protein can increase calcium losses, it also enhances calcium absorption from foods. There is evidence that these positive effects on absorption may outweigh or at least compensate for the negative effects of calcium loss.11
• In some studies, higher protein intake is actually associated with better bone health, and protein supplements can help bone fractures heal more quickly. 12,13
The evidence suggests that effects of protein on bone health may be dependent on how much calcium is in your diet. That is, protein is beneficial in people who consume more calcium. In addition to the positive effects of protein on calcium absorption, high-protein diets improve muscle mass, which is associated with better bone health. And protein also boosts levels of compounds that may stimulate bone formation.14
If all of this leaves you feeling confused, you aren’t alone. The complete story about protein and calcium balance is still unfolding. But based on what we know right now, it is far too simplistic to say that vegans have lower calcium needs than omnivores or that restricting protein intake improves bone health. The science of calcium, protein, and bone health is too complex and the research too conflicting to justify those conclusions.
Vegan Diets and Bone Health
Unfortunately, a number of resources for vegans in books and online suggest that calcium requirements are lower for those on plant-based diets, and it is possible that this has not served vegans well. While we don’t have much information about bone health in vegans, the few available studies suggest that some vegans don’t get enough calcium. In the studies that show vegan bone health to be worse than in omnivores, it is due very simply to lower calcium intakes. So far, only one study has looked at actual risk for fracture; it found that vegans had a higher chance of breaking a bone than non-vegans—but when they consumed enough calcium, their risk of fractures was the same as in omnivores. 15
So where does this leave us in terms of calcium requirements? Given all of the inconsistencies in the research and the findings, limited as they are, about bone health in vegans, we recommend that vegans meet the calcium recommendations that have been established for the general population.
Recommendations for daily calcium intake for western populations range from 700 milligrams in the United Kingdom to 1,000 milligrams in the United States. The U.S. recommendation is an AI, which you may remember from Chapter 1 is a “best guess” kind of recommendation. There is evidence to suggest that 700 milligrams may meet the needs of most people, but it also may not be enough for everyone. Calcium needs can vary considerably among individuals, primarily because there is a big genetic variation in absorption rates. Aiming for the U.S. recommendation of 1,000 milligrams for adults can provide good insurance.
Calcium without Milk?
Getting calcium from plants might seem a little strange in a society that is so focused on dairy foods as a source of calcium. But some research suggests that even omnivores get as much as 40 percent of their calcium from plant foods. And really, why should that be surprising? Omnivores eat broccoli, baked beans, hummus, and other plant foods that are good sources of calcium.
While a strong dairy lobby has convinced many consumers that milk and other dairy foods are essential for a healthy diet, the ability to drink milk into adulthood is not the norm throughout the world. Normal development throughout most of the world involves a gradual loss of the enzyme needed to digest milk sugar after children are weaned from breast milk. Indications