Can we use calcium from dairy products?

A few weeks ago when I entered Aunt Gayle’s hospice room, the gathered family had a nutrition question for me: can humans absorb the calcium found in milk and other dairy products? I was fairly confident that dairy is a good source of calcium and is well absorbed. If not, the government and the dairy industry’s been doing us a huge disservice for decades.

Then my mother-in-law raised the same question this weekend. Her doctor had recommended leafy greens as a calcium source. Again, I was fairly confident that most leafy greens are a good source of calcium, though not necessarily as well absorbed.

So what's the deal? Should one consume dairy products for the calcium? My newly purchased textbook, Krause’s Food and Nutrition Therapy, by L. Kathleen Mahan and Sylvia Escott-Stump (Saunders-Elsevier, 2008), offers two reasons to do so. First, dairy products are the most concentrated calcium sources, and second, lactose enhances calcium absorption, probably even in those with lactose intolerance (104, 106).

A cursory glance at a Google Scholar search related to lactose-enhanced calcium absorption reassured me that this reason was probably valid.And while "most concentrated" sounded about right, I was curious as to how exactly that played out.

I started calculating the concentration of calcium in some foods, both dairy and non-dairy to get some numbers. I began by calculating milligrams of calcium per calorie, but that didn’t result in dairy being uniformly more concentrated:

Food	Calcium (mg)	Kcals	Mg Ca per kcal
Yogurt, plain, low fat, 1 cup (245g)	448	154	2.9
Milk, 2%, 1 cup (144g)	286	122	2.3
Cheddar cheese, 1 oz (28g)	202	113	1.8
¼ block firm tofu (81g)	163	57	2.9
Kale, 1 cup cooked (130g)	94	36	2.6
Broccoli, 1 cup cooked (156g)	62	54	1.2
Almonds, 1 oz (28g)	75	169	0.4

Tofu stands eye-to-eye with yogurt, a cup of kale beats a cup of milk - what's going on? I switched to milligrams of calcium per gram, which still didn’t yield the results I expected:

Food	Mg Ca per gram
Cheddar cheese, 1 oz	7.2
Yogurt, plain, low fat, 8 oz	1.8
Milk, 2%, 1 cup	1.2
Almonds, 1 oz	2.7
¼ block firm tofu	2.0
Kale, 1 cup cooked	0.7
Broccoli, 1 cup cooked	0.4

Here, water content plays a big role - generally the more water, the heavier the food is. Cheddar is the leader by far, since cheese is basically milk wrung of water. This time, almonds are doing pretty well, and tofu is still a champ. NOTE: These calculations are based on calcium-set tofu, not the silken type, which has about 80% less calcium. Straight-up cooked soybeans have about 0.6 mg Ca per kcal, and 1.0 mg per gram.

Bottom line – the author of the statement "Cow's milk is and dairy products are the most concentrated sources of calcium" has a different understanding of “concentrated sources” than I do.

Next up: the relationship between protein and calcium.

Photo Source: UMN Extension

Childhood (Mis)conceptions

Every morning this week, I've showed up at the U of M's student organic farm. I stick around for a couple of hours, helping out with the tasks at hand: transplanting pansies, harvesting chives and cilantro, weighing the produce, thinning the turnips.

My mind often turns to images formed of farming in my childhood by the Little House on the Prairie books and even The Boxcar Children. Of course, we've got a Prius and more water sources than you can shake a stick at, but I hoof it an awful lot and watering, although it doesn't involve lugging water buckets, can still be tedious.

And then there's thinning plants. You may recall that in the first Boxcar Children novel, back when they were actually living in a boxcar, the Alden children do yard work for Mr. Henry. One task was to thin the carrots. I really had no idea what this meant: I imagined Jessie pulling out a carrot, running it between her fingers to "thin" it, and putting it back in the ground. Why would anyone pull out perfectly good carrots? When Jessie asks to take home the pile of thinned carrots (apparently they didn't all make it back into the ground), I always imagined a heap of pale, pinched roots, ready to wilt at a second glance.

The reality is less laborious. Thinning involves only the removal of the smaller plants, no size-reduction at all. We ended up with a healthy pile of turnip greens that destined for the Campus Club. No humble junkyard stew pot for these organic roots.

Photo source: http://mysticdomestica.blogspot.com/2009/07/boxcar-kid.html

Program reciprocity

This essay for a scholarship for HECUA's Environment and Agriculture program answers the question of what I thought I could contribute to and receive from the program, and how my participation would benefits myself and others. Bottom line: I want my kids to know that Brussels sprouts are a fall vegetable and delicious with mustard.

Environment, Agriculture, and Brussels sprouts

My mother grew up with a kitchen garden in the backyard and canned vegetables in the basement. I grew up helping her shop at the co-op and shucking corn from the farmers’ market. So it surprised both of us when one summer afternoon in my teenage years, I could not say if Brussels sprouts were in season. My mother had assumed that I had a clear conception of seasonality, but all I really knew was that citrus fruits were somehow “in season” in the winter. Not long after this, I launched in the study of nutrition, working my way from Introductory Chemistry to Physiology to Medical Nutrition Therapy. Missing from my classes, however, has been a comprehensive look at how healthy food, the foundation of nutrition, gets to our plates. This Environment and Agriculture program promises to flesh out my understanding, cobbled together through reading books and articles on my own, so that I can more effectively work toward just and sustainable food systems in Minnesota.

To this program, I can contribute thoughtful discussion and openness to new ideas. Before attending the University of Minnesota, I spent two years at Lawrence University, a liberal arts college in Wisconsin. Small class sizes and a tight-knit community fostered thoughtful discussion. There, I learned how to prepare well for class and lead discussions. Later, after a semester abroad, I became more open to new ideas that challenged my previously held beliefs. I came to realize that no idea, no matter how great it sounds, comes without drawbacks and should be weighed carefully. As much as I want to see issues in black and white – organic good, pesticides bad – I realize that life is painted in shades of gray.

Environment and Agriculture will surely give as well as receive. I believe I will gain much from this program, both personally and academically. I do want to know where my food comes from and how to grow it, but often these tasks seem overwhelming. I’m not prepared to interrogate each farmer at the farmers’ market or figure out how much light my backyard gets or what the soil pH is. I believe this program will help me take strides forward in this arena, giving me the vocabulary and confidence to talk with farmers and, through an internship, getting my hands in some dirt. These strides will help me achieve my goal to become a registered dietitian who considers the impact a diet will make not just on the health of her client, but also on the health of the soil it came from and the people who harvested it. Academically, I look forward to breaking away from lectures and professors, and learning from my peers and food system actors.

The benefits of this program will not be confined to my own personal and academic goals. I anticipate great benefits for the issues that I care about – school lunch, food deserts, and animal cruelty. I look forward to meeting and building relationships with local farmers because I want to be an able implementer of farm-to-school programs around the state. With a deeper understanding of food system politics and economics, I could contribute to or evaluate plans for eliminating food deserts in urban and rural neighborhoods. I need to see farmers treat their livestock with compassion to balance out the images of animal cruelty I’ve seen over the years. I plan to use everything I learn on this program to help me be a more better advocate for sustainable food systems.

There are others who will benefit from my experience in with Environment and Agriculture – my future children. I want to be happy to have them eat school lunch. I want them to always be within walking distance of a grocery store. I want them to know that drumsticks come from a bird that has feathers and a personality. I want them to know the work that farmers do and appreciate truly healthy food is. And, I want them to know they have to wait until fall for Brussels sprouts.