Vegan for Life (7 page)

It wouldn’t be right to ignore the four-hundred-pound gorilla in the room, so let’s ask the obvious question: Since vitamin B
₁₂
is not found in plant foods and vegans must take supplements, doesn’t that make a vegan diet unnatural?

Many vegans have bent over backwards to convince themselves and others that humans evolved as vegans and that supplemental vitamin B
₁₂
is only needed because we have moved so far away from our natural environment. But there is a tremendous amount of evidence that humans evolved eating some animal products. While B
₁₂
is not needed in large amounts, it may take more than can be picked up from unwashed produce to sustain optimal levels. That’s especially true during pregnancy and lactation, when a woman needs to consume enough B
₁₂
for her own needs and to pass on to her baby.

In fact, adding small amounts of animal products to the diet has been shown not to cure B
₁₂
deficiency. At least one study showed that some lacto-ovo vegetarians may have vitamin B
₁₂
status that is similar to that of vegans when neither group supplemented.
¹¹
If consuming small amounts of animal foods doesn’t improve vitamin B
₁₂
status, then it is unlikely that inadvertently ingesting B
₁₂
from unwashed produce would be enough to sustain vegans through the life cycle in a pre-vitamin-supplement culture.

Paleontology student Robert Mason, who writes the PaleoVeganology website, says this about the evolution of human diets: “This touches on the issue of how vegans should handle the caveman argument. Many of us are tempted to strain credulity and torture the evidence to ‘prove’ humans are ‘naturally’ vegan. This is a trap, and one into which carnists (especially paleo-dieters) would love us to fall; the evidence isn’t on our side. There’s no doubt that hominids ate meat.... The argument for veganism has always been primarily ethical, and ought to remain that way. It’s based on a concern for the future, not an obsession about the past.”
¹²

And Tom Billings, who writes the Beyond Veg website, says, “Further, if the motivation for your diet is moral and/or spiritual, then you will want the basis of your diet to be honest as well as compassionate. In that case, ditching the false myths of naturalness presents no problems; indeed, ditching false myths means that you are ditching a burden.”
¹³

We agree that it just doesn’t matter whether a vegan diet is our historical way of eating or not. The fact is, it makes sense
now
to choose a vegan diet. And whose diet is really natural, anyway? The assumption that there is one natural prehistoric diet, which can be approximated today and would be optimal for modern humans, is dubious at best.

Today’s commercial plant foods and meats are different from the foods available in prehistoric times. We eat hybrids of plants and we feed foods to animals that they would not normally eat. Additionally, the U.S. food supply is routinely fortified with a host of vitamins and minerals. Even those people who strive to eat a more “natural” diet as
adults have normally benefited from fortified foods as children. It is quite unlikely that anyone is eating a natural diet in today’s world.

Taking a daily vitamin B
₁₂
supplement is a small thing that can make all the difference in your health as a vegan. Based on our current knowledge of vitamin B
₁₂
requirements and sources, supplementation is not a subject for debate. Vitamin B
₁₂
supplements or fortified foods are an essential part of a well-balanced and responsible vegan diet at all stages of the life cycle.

For most of human history, people got their calcium from plants, primarily wild, leafy greens. Dairy foods didn’t become part of the human diet until around 10,000 years ago and even then they were consumed only in some parts of the world. Calcium-rich greens were so abundant in early diets that some nutritional anthropologists speculate that people consumed as much as 3,000 milligrams per day of calcium from these foods, or about three times our current recommended intakes.
¹
The cultivated greens that are available to vegans today are lower in calcium than the wild vegetables available to our ancestors, but they can still make a significant contribution to calcium intake. Vegans can also get calcium from some legumes and nuts, and from fortified foods.

There is no question about whether vegan diets can provide enough calcium. They can. But that doesn’t mean that they do. In studies of vegans, average calcium intakes often fall well below recommendations.
²
One unanswered question has to do with calcium needs of people who eat plant-based diets. Do vegans need less calcium? You’ll see that it’s not so easy to figure this out.

While bones might seem solid and static, they are actually quite dynamic. The skeleton acts as calcium storage, providing a steady supply of calcium to the blood where it is needed for muscle relaxation, nerve cell transmission, and a host of other functions. Some of this calcium is regularly lost in the urine and must be replaced by dietary sources. As a result, bones are in motion—breaking down to release calcium to the blood and then taking up new calcium and rebuilding. Getting enough calcium is important for bone health, but reducing the amount that is lost through the urine could be important too.

Bones grow through the first three decades of life, becoming longer, heavier, and denser. By their late twenties or early thirties, most people have achieved
peak bone mass
, and their skeleton is as heavy and dense as it is going to get. There is some evidence that peak bone mass determines bone health and risk for osteoporosis in later years.

Beginning at age forty-five or so, there is a shift in metabolism and bone mass begins to decline. Efforts to slow calcium losses from the body and provide enough calcium to keep bones strong are important for preventing osteoporosis, especially for women, who can begin to lose bone rapidly after menopause.

Good bone health depends on a complex interplay of factors that affect both absorption of calcium and calcium losses from the body. Diet, lifestyle, and genetics all play a part in calcium balance. Figuring out how these factors interact and affect calcium needs has been an ongoing subject of debate among researchers, and some of the issues may be especially important for vegans.

Calcium is different from other nutrients in that it isn’t associated with an acute deficiency disease. With most nutrients, if your intake is too low, you’ll get sick. That’s not true for calcium because levels in
the blood are very tightly controlled. Even a small change in those levels can be life-threatening, so the body utilizes stored calcium in the bone plus the filtering system of the kidneys to keep calcium concentrations within strict boundaries. You can’t ascertain calcium status by measuring blood levels of this mineral because those levels are always the same. But while a low calcium diet doesn’t cause an acute nutritional deficiency, a chronically low intake can raise the risk for osteoporosis later in life.

Osteoporosis is a crippling and debilitating disease of severe bone loss—as much as 30 to 40 percent of total bone—that affects an estimated 10 million Americans. Eighty percent of Americans with osteoporosis are women.

When nutrition scientists look at the relationship of diet to bone health, they look at both bone density and fracture rates. And the findings are anything but clear. How much calcium humans need and the extent to which varying intakes affect bone health are topics of intense research. Many large epidemiologic studies fail to show that high calcium intakes protect against bone fractures.
^3
,
4
The balance of evidence suggests, however, that calcium and vitamin D together are protective.
⁵

A couple of decades ago, studies of bone health among people in different countries revealed an interesting pattern. Rates of hip fracture (which is often used as a marker for bone health) were highest in countries with the highest intakes of animal protein, even though calcium intake was also high.
⁶
The findings suggested that too much protein was worse for bones than too little calcium. And, in fact, there is a biological explanation to back this.

High intakes of certain proteins increase the blood’s acidity, kicking off a chain of reactions to bring blood back to a more neutral pH. A release of calcium from the bones is one part of the process. The
more acidic the blood, the greater the loss of calcium from bones. Meat proteins are among the most acid-producing foods, followed by proteins from grains and dairy. Diets high in fruits and vegetables are the least acidic.

Based on this, it seems to make sense that people who eat animal protein should need more calcium to replace what is constantly being leached from their bones. Conversely, wouldn’t vegans, whose diets contain no animal proteins, have lower calcium needs? This sounds like an obvious conclusion, but it’s not quite that straightforward.

First, the studies comparing different populations have limited usefulness. These are ecological studies, and we saw in Chapter 1 that they provide only weak evidence. There are just too many cultural and genetic variations among people of Asian, African, and Caucasian backgrounds for us to make direct comparisons about their protein intakes and bone health. For example, people of African descent have a genetic predisposition toward stronger, heavier bones.
⁷
And a slight genetic advantage in hip anatomy among Asians protects against fracture.
⁸

There are cultural differences too. Asians tend to have better balance, so they are less likely to fall and break a bone. And in some cultures, elderly people rarely leave their home without a younger family member at their side and are therefore less likely to fall. In fact, while Asian populations fare well in comparisons of hip-fracture rates, their spinal bone health is similar to westerners’.
⁹
This suggests that there is something in their genes or lifestyle that is specifically protective against hip fracture but doesn’t affect other parts of the skeleton. If diet were the protective factor, the benefits would show up in all parts of the skeleton.

As a result, these cross-cultural studies might tell us more about culture and genetics than about diet, which means that these comparisons don’t tell us a whole lot about how much calcium western vegans might need.

It’s better to look at clinical research, where the effects of protein are directly observed and measured. Findings from clinical studies show the following:

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.

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.