Dairy is a relatively recent addition to the human diet. How did early humans get enough calcium to develop and maintain healthy bones?
Dairy is a relatively recent addition to the human diet. How did early humans get enough calcium to develop and maintain healthy bones?
RESEARCH CITED
Calcium in Evolutionary Perspective
The roles of calcium and vitamin D in skeletal health: an evolutionary perspective
Nutrition Diva is hosted by Monica Reinagel, MS, LDN. Transcripts are available at Simplecast.
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Hello and welcome to the Nutrition Diva podcast, a show where we take a closer look at nutrition research, headlines, and trends so that you can make informed choices about what you eat. I’m your host, Monica Reinagel, and today’s topic was suggested by an email from Ann.
Unfortunately, Ann has been diagnosed with osteoporosis and her doctor has told her that she needs to get 1,200 mg of calcium a day. Fairly standard advice.
But Ann raises an interesting question.
“I have been researching which foods contain calcium and it sure seems that the only cultures where people consume anywhere near this amount are those that consume significant amounts of dairy. But, historically, many cultures evolved without consuming a lot of dairy. So how do these cultures get anywhere near the 1,200 mg of calcium necessary to develop and maintain healthy bones?”
It’s true that dairy products are very concentrated sources of calcium, and the calcium that they contain is very well-absorbed in the body. Cultures whose dietary patterns include a lot of dairy products are likely to get a large proportion of their calcium from dairy.
Humans didn’t really start consuming dairy products until they started keeping ruminant animals (such as sheep and goats), for the purpose of consuming their milk–usually, fermented or cultured into yogurt, kefir, or cheese, which would extend its shelf-life
After Europeans colonized North America, we were mostly an agricultural society. As industrialization drew people from the farms into the cities, agriculture gradually became an industry of its own, with a lot fewer farmers providing food for a lot more people–a process that continues to this day.
Because a lot of the land on our continent is better suited to grazing than to plowing, dairy has always been a big part of our agricultural industry. And dairy has traditionally been the primary source of dietary calcium in the North American diet, providing about 70% of the calcium in our diets.
Our dietary guidelines, which up until very recently considered dairy products to be a distinct food group, definitely reflect the fact that we are a dairy-producing and dairy-consuming nation. After all, the USDA, which is in charge of establishing our dietary guidelines, is also in charge of supporting our agricultural economy.
Some have even suggested that we don’t need as much calcium as we’re told and that the recommended intake of 1,000 to 1,200 mg a day is really just a ruse to get us to drink more milk.
I wouldn’t go that far. There are decades of research to support the individual nutrient recommendations that make up the Dietary Reference Intakes. However, that research and those recommendations are definitely influenced by and reflect our lifestyle.
For example, if the North American diet were a lot higher in vitamin D, K, folate, fiber and other nutrients, and if we all engaged in a lot more weight-bearing and muscle-building activity, we might be able to take in significantly less calcium without negative consequences on our bone health. But our diets typically aren’t higher in those nutrients and our lifestyle tends to be very sedentary.
I think this is a mistake we often make when we decide to emulate the diets of other people (either contemporary or historical) who seem to be healthier or live longer or have lower risks of various diseases (such as osteoporosis). We forget that diet and nutrients do not operate in a vacuum.
We can try to replicate the diet of a Paleolithic human, but it’s a lot harder to replicate the rest of the Paleolithic lifestyle: the amount and intensity of physical activity, the amount of sleep, the amount of exposure to artificial light and its effects on circadian rhythms, the fact that we sit in chairs instead of squatting by the campfire, or that we live in climate controlled environments, not to mention the fact that we may live until we’re 90 or 100–and spend the 30 or 40 years prior to that worrying about how we’re going to save enough money to live that long!
I think you get my point. Our health and longevity are determined by a lot more than just our diet and nutrition. And, for better or worse, our dietary recommendations reflect the realities of our modern lifestyle.
There’s one other aspect that I should mention. The U.S. dietary recommendations are also based on data gathered primarily from white individuals and don’t necessarily account for genetic variations that affect our nutrient needs. Due to differences in skeletal structure and calcium metabolism, those of European ancestry may require more calcium than those of African or Asian ancestry.
It’s certainly possible to meet even our relatively high calcium recommendations without consuming dairy products (or taking supplements). But I will grant you that it is a bit more challenging. And you’d better like eating your greens!
Vegetables in the cabbage family, including broccoli, kale, bok choy, cabbage, mustard and turnip greens are all good sources of calcium that’s very bioavailable. Cabbages and leafy greens are also good sources of folate and vitamin K, nutrients that also help build strong bones. A half cup of Chinese cabbage or a cup of bok choy provides almost as much absorbable calcium as a glass of milk.
Tofu is another good source of calcium–but not because soybeans are particularly high in calcium. Rather, it’s because tofu is usually made with calcium sulfate as a setting agent. But soybeans and tofu are rich in soy isoflavones, which contribute to strong bones
Canned fish such as sardines and canned salmon are also good sources of calcium because they contain tiny bones that are so soft you’d never notice them, but that are a potent source of calcium. As a bonus, these fish are also among the few natural food sources of vitamin D–which helps us absorb that calcium better.
So, it’s possible to meet the recommendations without dairy. But Ann’s question made me curious to see if I could find any data on the typical calcium intake of hunter-gatherer populations who would probably not have consumed dairy products. What I found may surprise you.
Researchers estimate that hunter-gatherer humans would have consumed something like 2,400 mg of calcium per day–which is twice the recommended intake for modern North American women over 50.
The diet of hunter gatherer societies did not typically include dairy products but it did include lots of leafy greens, nuts, roots, and tubers, all of which are relatively calcium rich. But apparently, most of the calcium in their diets came from the bones of animals, including small mammals, birds, fish, and reptiles. In addition to being rich in calcium, bones also contain magnesium, phosphorus, aminoglycans, osteocalcin and other compounds that promote bone formation.
Not surprisingly, archeological evidence suggests that hunter gatherers had much higher bone mass and density than we typically do today, and lower rates of osteoporotic disease. But again, their high calcium intake is only part of that picture.
As I said, it is possible (although challenging) to get 1,200 mg of calcium a day from foods, without consuming dairy. But to be honest, I suspect that those recommended intakes could actually be lower, if we took a more holistic view of bone health–and placed as much emphasis on the effects of exercise and other lifestyle factors, as well as all the other nutrients that contribute to (or detract from) bone formation–instead of being so singularly focused on calcium.
But thanks, Ann, for the invitation to go spelunking through the literature on calcium in evolutionary diets! I’ll include a couple of links in the show notes for anyone who might be interested in taking a deeper dive.
Calcium in Evolutionary Perspective
The roles of calcium and vitamin D in skeletal health: an evolutionary perspective
If you have a question you'd like me to answer, you can email me at nutrition@quickanddirtytips.com You can also leave me a message at 443-961-6206
I’d also like to invite you to check out my other podcast. It’s called the Change Academy, where we explore the art and science of creating positive behavior change, both in our own lives, and in our workplaces and communities. You can find it on all the major podcast platforms. Just search for Change Academy.