Eric Garza

Musings on food, energy and adaptation

Investing in Nutrient Dense Foods: Parting Thoughts

BlueberriesAs I polish off my series on investing in nutrient dense foods, and few final caveats are in order. First is an acknowledgement that the number of foods I looked at for each vitamin or mineral were limited, and were also biased. I don’t do well on grains, so generally didn’t include grain-based foods in my analysis as I wanted the list to have practical value for me. It’s also true that grains, as well as many seeds don’t have much bioavailable minerals or vitamins anyway, so I don’t think there was much information lost here. I also didn’t include a huge number of dairy products, nor did I include manufactured foods with the exception of the hamburger in Making Good Food Affordable. I figure if readers are interested in how their favorite foods stack up, they’re welcome to do the calculations for themselves based on the foods’ nutritional content and its cost.

Another important caveat is that nutrient content varies tremendously from food to food, even within a single food type. A head of lettuce grown in New Jersey will have a different nutrient profile than one grown in California or Vermont, and the same variety of lettuce grown on different farms just a few miles apart will also vary. Soil quality and type matters, as does pest pressure, microclimate, and myriad other factors. So the nutrient estimates I extracted from USDA’s National Nutrient Database are only rough estimates, and the estimates of cost per unit of nutrient I presented throughout this series should have very wide error bars around them, although I don’t have a way to calculate how wide those error bars should be. And, of course, market prices for different foods vary too, so that adds another layer of uncertainty. Hopefully the series sparked some critical thought about how we invest our food expenditures.

A last note is the issue of wild foods, including wild game and fish and wild plant foods and fungi. These foods are typically far more nutrient dense than domesticated animal foods – even animal organs – and are certainly far more nutrient dense than cultivated plant foods. Another benefit is that they cost little beyond the time required to forage or hunt for them, so for those who have extra time on their hands and are flustered by the rapid increase in food prices you might consider investing some time learning wildcrafting. Not only can you access more nutrient dense foods at a lower cost, it’s also a nice excuse to spend time outdoors, get some sun and make some vitamin D.

Investing in Nutrient Dense Food: Magnesium

The last nutrient I’ll focus on in this series is magnesium. Magnesium, like iron and calcium, is a mineral rather than a vitamin, and it serves a range of purposes in our bodies. Among them, magnesium serves as a cofactor in hundreds of enzyme systems that regulate a range of biological processes, including protein synthesis, muscle and nerve function, blood sugar control and blood pressure regulation, among others [1]. It also contributes to the structural development of bones and teeth, and aids in the transport of calcium and potassium across cell membranes. Magnesium deficiencies have been linked to high blood pressure, heart disease and diabetes, among other ailments [2].

Magnesium is present in a wide range of foods of both plant and animal origin. The graph below shows the cost of meeting a daily allowance of 400 mg of magnesium from several foods, with data on nutrient contents taken from the USDA’s National Nutrient Database and prices recorded from recent visits to my local farmers’ market and grocery cooperative [3]. These prices reflect certified organic produce, and grass fed and pasture raised animal foods.


Based on USDA data the most cost-effective sources of magnesium are plant-based, including almonds, potatoes, spinach, cabbage and sweet potatoes. All of these sources provide a daily allowance of 400 mg magnesium for less than $10. Animal derived foods like organ and muscle meats are far more costly per unit magnesium, as are fruits. As with calcium though, the data provided by the USDA doesn’t tell the whole story. Many factors influence the degree to which our bodies can absorb magnesium from the food we eat. The presence of anti-nutrients such as phytate in seeds like almonds reduces the availability of magnesium and other minerals, making these foods less of an ideal source than a simple mineral analysis might initially suggest [4]. As with calcium though, resistant starch increases the absorbability of magnesium.

It’s also true that, in pursuit of higher yields for many fruits and vegetables, nutrient density of foods have declined in the US and elsewhere [5]. This reality is exacerbated by decades, if not centuries, of abusing prime agricultural soils such that many are depleted in magnesium and other minerals, making it all but assured that food grown in or animals raised on those soils will be depleted of the nutrient. Given this reality, it can be helpful to supplement our magnesium intakes with non-food sources of magnesium, and one such source is bathing in mineral salts, particularly epsom salts (magnesium sulfate). Although I make a point to eat a wide array of fresh vegetables that offer resistant starch to help maintain a good magnesium status, I also take baths in epsom salts a few times each week as a mineral supplement since magnesium is readily absorbed through the skin [6]. A cautionary note on this habit though: those who take this method too far and supplement daily with large quantities of epsom salts, particularly when taken as a gargle, risk overdose [7]. So be cautious with supplementation, not just of magnesium but with any mineral.


  1. Magnesium: Fact Sheet for Health Professionals. National Institutes of Health, United States Department of Health and Human Services.
  2. A. Rosanoff, et al. (2012) Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutritional Review, Vol. 70, Pgs. 153-164.
  3. National Nutrient Database for Standard Reference. United States Department of Agriculture, Agricultural Research Service.
  4. C. Coudray, et al. (2003) Effects of dietary fibers on magnesium absorption in animals and humans. The Journal of Nutrition, Vol. 133, Pgs. 1-4.
  5. B. Halweil (2007) Still No Free Lunch: Nutrient Levels in U.S. Food Supply Eroded by Pursuit of High Yields. Report for The Organic Center.
  6. R. Waring, et al. Report on Absorption of Epsom Salts (Magnesium Sulfate) Across the Skin. Report for the Epsom Salts Council.
  7. R. Birrer, et al. (2002) Hypermagnesemia-induced fatality following epsom salt gargles. The Journal of Emergency Medicine, Vol. 22, Pgs. 185-188.

Investing in Nutrient Dense Food: Calcium

This post’s focus is on calcium, the single most abundant mineral in the human body. Calcium plays many roles in our bodies, including supporting the proper function of muscles, nerves and muscled organs like the heart, as well as providing some of the mineral structure that underlies the strength and resilience of bone and teeth [1]. Interestingly enough, the concentration of calcium in our blood doesn’t vary all that much; our bones and teeth are used as reservoirs of calcium, and the mineral is removed from and redeposited to these stores as needed [2].

One interesting fact I uncovered in doing research for this post is that consuming lots of calcium won’t necessarily build strong bones; the body must sense the need for additional bone mass, necessitating an active lifestyle for calcium to be absorbed from food and purposed towards building bones and teeth. As many know, Vitamin D plays a vital role supporting the body’s absorption of calcium as does magnesium, so those with chronic deficiencies of these nutrients may struggle to maintain adequate stores of the mineral.

We can get calcium from a range of foods, including dairy products like milk and cheese, deep green leafy vegetables like kale and cabbage, as well as broths made from the bones of animals like cows and chickens. The following graph shows the cost associated with consuming a daily allowance of 1,000 mg of calcium from a range of different foods. Calcium contents for these foods were sourced from the USDA’s National Nutrient Database, while costs were recorded at my local farmers’ market or grocery cooperative and reflect prices for grass fed or pastured animal products and certified organic produce [3].

CalciumThe milk price used for the above graph was $10 per gallon, which is what it costs me to source 100% grass fed milk from a local raw dairy, while the price I used for cheese was $15 per pound, which is what I pay for cheddar cheese made from unpasteurized milk. Despite these high prices, milk and cheddar cheese still represent the most cost-effective sources of calcium, followed by the green leafy vegetables cabbage, spinach and kale. It’s worth noting there’s an inverse relationship between a vegetable’s oxalic acid content and the absorbability of its calcium, so spinach, while calcium rich, might not be a particularly good source of the mineral because of its high oxalic acid content [4]. This is the only graph presented so far where organ meats didn’t feature prominently among cost-effective sources of a nutrient, and my guess is the only reason pork made the graph is because the cut I gathered data on was cooked bone-in and some of the calcium leached into the meat during the cooking process.

Bone broth is likely also a good source of calcium, although I wasn’t able to find any research articles quantifying levels of calcium in the broth nor have I ever seen bone broth available commercially so that I can figure it’s price. Bone broth is easy enough to make, simply buy bones – often marketed as marrow bones or soup bones – from animals like cows, goats or sheep or from a whole chicken, immerse them in water and simmer ever so gently for a few, or even several, hours. One article I did find suggested that the concentration of calcium in bone broth water stabilizes after about an hour, suggesting little value in cooking bone broth for hours or days, at least as far as calcium leaching goes [5]. The study also found no evidence that adding vinegar to bone broths aided the extraction of calcium into solution. Regardless, I drink a fair amount of home made bone broth, and find it to be quite nourishing.

Calcium absorption, bioavailability and bioconversion is a hugely complex topic, one I can’t remotely do justice to in this short blog post. One point I uncovered worth finishing this post with is that prebiotics – among them inulin – seem to enhance calcium absorption from plant foods [6, 7]. Inulin, as some may know, is a type of soluble fiber often termed resistant starch, a hot topic in health circles these days as people gain a better appreciation for the value it adds to diets. On a personal level, I’m banking on my modest consumption of raw dairy products, bone broth, leafy green vegetables and prebiotics to provide adequate calcium intake.


  1. Calcium and Bone Health. Centers for Disease Control and Prevention, United States Department of Health and Human Services.
  2. Calcium Dietary Fact Sheet. National Institutes of Heath, United States Department of Health and Human Services.
  3. National Nutrient Database for Standard Reference. United States Department of Agriculture, Agricultural Research Service.
  4. C. Weaver, et al (1997) Calcium bioavailability from high oxalate vegetables: Chinese vegetables, sweet potatoes and rhubarb. Journal of Food Science, Vol. 62, Pgs. 524-525.
  5. R. McCance (1934) Bone and vegetable broth. Archives of Disease in Childhood, Vol. 9, Pgs. 251-258.
  6. K. Kashman (2002) Calcium intake, calcium bioavailability and bone health. British Journal of Nutrition, Vol. 87, Pgs. S169-S177.
  7. K. Kashman (2003) Prebiotics and calcium bioavailability. Current Issues in Intestinal Microbiology, Vol. 4, Pgs. 21-32.