In this and in subsequent entries, I will respond to some of the questions received following the lecture Paleolithic Nutrition: What is the Evidence? The lecture will also be given at noon on Friday, May 6 at The Medical Center of Aurora, North Campus.
Adults considering Paleolithic nutrition worry about getting enough calcium if the cut out dairy products. Their main concern is preventing osteoporosis, a thinning of the bone that can lead to fractures, disability, and in the elderly, even death. (Calcium metabolism in children is a separate issue and will not be considered in this entry. After all, Paleolithic young were likely breast fed for 5 or 6 years.)
The modern diet, also referred to as the Western diet, is not favorable to healthy calcium metabolism. As Staffan Lindberg notes in Food and Western Disease:
For the average Westerner, roughly one-fourth of their energy intake is provided by food that is lacking in calcium (primarily oil, margarine, and sugar). Cereals, which provide an additional 25%, contain relatively little calcium. Hence, it should come as no surprise that the calcium intake among many hunter-gatherer societies is estimated to have been higher than among modern Westerners.
Fruits and vegetables, which form the base Paleolithic food pyramid, are important sources of calcium. As Loren Cordain states in The Paleo Diet:
One of the greatest – and least recognized – benefits of fruits and vegetables is their ability to slow or prevent the loss of bone density, called osteoporosis, that so often comes with aging.
Referring to dairy milk –
Hunter gatherers never drank milk. They did not have bone-mineral problems because they ate lots of fruits and vegetables – which gave them enough calcium to build strong bones.
In regards to cheese -
Surely eating a lot of cheese can help prevent osteoporosis? The answer is a bit more complicated. One of the great ironies of the low-carbohydrate, high-fat diets is that even though they allow the consumption of unlimited quantities of high-calcium cheeses, they almost certainly will be found to promote bone loss and osteoporosis in the long run. How can this be? Because getting a lot of dietary calcium from cheese, by itself, isn’t enough to offset the lack of fruits and vegetables.
However, adequate calcium intake is not enough, it has to be absorbed. Although dairy products found in the modern diet provide calcium, grains and beans inhibit calcium absorption. According to Lindberg:
The absorption of calcium in the intestines (i.e. its bioavailability) is affected by certain dietary factors, of which the most quantitatively important one is probably phytic acid in cereals and beans. Through the process of chelate bonding, phytic acid forms insoluble salts, phytates, with calcium, iron, zinc and magnesium, which effectively prevent their absorption.
The amount of calcium available for healthy bone metabolism depends not only on its absorption, but also its excretion. Here the acid-base balance of the diet is important. Again, Dr. Cordain:
The main factor that determines calcium loss is yet another kind of balance - the acid-base balance. If your diet has high levels of acid, you'll lose more calcium in your urine; if you eat more alkaline foods, your retain more calcium.
This is another area in which fruits and vegetable excel: a study 459 men and women published in the New England Journal of Medicine revealed "diets rich in fruits and vegetables (these are alkaline foods) significantly reduced urinary calcium loss." (Cordain)
Futhermore, the calcium-to-phosphorous ratio is also important. Cordain points out that “Few realize that cereal grains and legumes are catastrophic for your bone health." Their "unfavorable calcium-to-phosphorous ratio can speed up bone loss."
Thus, obtaining adequate intake, promoting absorption and decreasing urinary excretion are all essential for healthy calcium metabolism. The trick to protecting your bones is to eat plenty of fruits and vegetables and no grains or legumes. However, most of us have spent years (decades!) eating the modern diet. (I was born above a bakery and was a high bread consumer!) For many, supplementation with calcium and important co-factors such as magnesium, Vitamin K2, and Vitamin D3 is needed to reverse, or at least stabilize, the effects of decades of the standard diet.
Take home point: To maintain sturdy bones like those of your Paleolithic ancestors, eat plenty of fruits and vegetables and avoid cereals and beans. The sooner you start, the better.