What about calcium?
People ask this question fairly often, and it's actually two questions: A) Where do I get calcium if I don't drink milk and B) I've heard that a high protein diet will cause my bones to become weak; is this true? Let's tackle both, shall we?
First of all, where do we get calcium in a low carb diet, since we don't drink milk? Well, first you need to be aware that an 8 oz glass of milk contains only about 1/4 of your calcium requirement for one day ("about" because requirements vary). The same is true of a cup of yogurt. Accordingly, a whole lot of people who have a glass of milk or a cup of yogurt every day, and figure that their calcium needs are taken care of, are sadly mistaken. You need between 800 and 1500 mg. of calcium every single day. So where will we get it?
We can, of course, have cheese on our low carb diets, in moderation. (Both Doc Atkins and the Eades recommend that you hold it to no more than 4 ounces a day, and I think that's a good idea, too. People who eat a ton of cheese seem to have a harder time losing. Don't know if it's the few carbs that cheese contains, its caloric density, or some other factor; just know it's so.) We can get some calcium there, for sure -- hard cheeses, like cheddar and parmesan, have in the neighborhood of 180-200 mg per ounce, while softer, moister cheeses have less. Why? Because they're diluted with water, of course.
Almonds are a fair-to-middlin' source of calcium, with 66 mgs. in one ounce. Those sunflower and pumpkin seeds I mentioned earlier have some, too -- 3 1/2 ounces of sunflower seeds contains 120 mgs. of calcium, and 3 1/2 ounces of pumpkin seeds contains 51 mgs. Actually, these seeds pretty good sources of minerals in general. So are sesame seeds, if you buy them unhulled -- you'll have to go to a good health food store for these. Unhulled sesame seeds taste the same as the hulled ones you pay inflated prices for in little jars at the grocery store, but they're cheaper and far better for you. On the other hand, I don't generally sit around and snack on sesame seeds. They're good on or in things, though.
Many dark green leafy vegetables are good sources of calcium, and they're some of the lowest carb vegetables around. Two-thirds of a cup of cooked broccoli has 88 mgs, and just a half a cup of cooked collards packs 203 mgs, while mustard greens have 138 mgs. Kale, beet greens, and turnip greens are good, too. Iceberg lettuce -- the type most often used in the US -- has 35 mgs. in 3 1/2 ounces, while the same amount of romaine, which I much prefer, has 68 mgs in the same size serving, and butterhead has 70 mgs. Fresh parsley, which I adore in salads, has 203 mgs. of calcium in 3 1/2 ounces -- and you thought it was just for garnishing! Chopped fresh parsley is a fine addition to all kinds of foods. Spinach is a pretty good source of calcium, but it contains a chemical called oxalic acid which tends to inhibit calcium absorption. Eat spinach for its other nutrients, but not for its calcium.
One egg has about 26 mg. of calcium, the vast majority of which will be found in the "evil, high fat, high cholesterol" yolk, by the way. That means I'm getting 78 mgs. of calcium with my breakfast every day, along with all the other vitamins and minerals -- and the protein -- that eggs have to offer.
Soybeans are a pretty good source of calcium, so if you're using tofu in your low carb diet, you're getting some calcium there. If you enjoy canned sardines, they're a terrific source of calcium, because the bones are eaten The same is true of canned salmon, assuming you don't pick the bones out, but rather crush them up.
Which leads us to an important point: One of the greatest sources of calcium in the human diet, historically, has been bones. Meat was cooked with the bones in it much of the time, and bones were gnawed on to get every last scrap. Calcium! Too, meat with bones in it that was cooked in an acidic medium, such as wine, vinegar, or tomatoes, would leach some calcium out of the bones, into the surrounding meat and the sauce. More calcium! And this bone-form calcium is the most absorbable kind -- the most cutting-edge calcium supplements on the market use "hydroxyapatite", which is the technical name for bone-form calcium!
Furthermore, bones were not simply discarded, but were saved and boiled for soup. I do this -- all my chicken bones, unless they're from a strongly seasoned dish, go in a bag in my freezer. When I have a bag full, I boil them up for soup -- and get a delicious, high calcium meal from the discards of my previous dinners! Talk about something for nothing. I'm quite aware that boneless, skinless chicken breasts are the hot-selling form of chicken these days -- as I've mentioned, that's the reason I get chicken legs and thighs so darned cheap! I know that the boneless, skinless breasts are fast and easy to cook. But be aware that you're paying far more, for less nutritious food. (Me, I love the skin, too!)
So that should give you a pretty good idea where the calcium can be found in a low carb diet. Do I believe that you're going to carefully construct your diet to be sure that you get your 800-1500 mgs of calcium a day? No, anymore than I believe that most people who aren't on a low carb diet do that! I recommend that you eat the good, low carb sources of calcium, but I also strongly recommend that you take calcium supplements, especially if you're female. I take about 1000 mgs a day on top of what I get from my food. Osteoporosis is no joke, and my mom has been treated for it already.
(Men, there is some new research that suggests that excessive calcium, and in particular, drinking a lot of milk, may correlate with prostate cancer. Get your 800-1000 mgs a day, but don't go overboard. This is one of those things where a little is good, but a whole lot may not be better.)
Now, about the question of a low carb/high protein diet causing calcium loss. Is it true? I've done a lot of reading on the subject, and the conclusion I've come to is: Dunno.
The research is conflicting, you see. There is some research which shows that women who have adult onset diabetes are less likely to have weak bones, which suggests that insulin may help deposit calcium -- but do we want all the horrible health consequences that come with diabetes, in the name of preventing osteoporosis?
I've seen an article from The American Journal Of Clinical Nutrition (1983, June) which concludes that eating a diet high in meat protein does not lead to calcium loss, and another from the Journal of Nutrition (1988, June) which reaches the same conclusion. Further, many other things seem to contribute to bone loss, from excessive phosphorus found in soft drinks, to aluminum-containing antacids, to alcoholism.
On the other hand, we know that the Chinese, who eat both less protein and less calcium than Americans, have less osteoporosis. On the other other hand, they eat more vegetables, get phytoestrogens from soy foods, drink less high-phosphorus soda pop, and get a whole heck of a lot more exercise than your average member of a Western industrialized culture.
We know that paleolithic hunter-gatherers were tall, with strong bones and teeth, and we're relatively certain that they ate primarily meat and vegetables, like us. And we know that when various people developed agriculture, and switched to eating grains and beans, their stature dropped, and their bones became weaker. But are we certain why this is? Was it because of the reduction in protein intake? Did phytates in the bran on the grains -- phytates are a chemical found in bran that inhibits calcium absorption (Which means, by the way, that if you, like I, eat bran crackers, you need to be that much more certain you get your calcium) -- cause the problem? Or was it the lesser number of bones that were gnawed on? Or that farming was less exercise than hunting and gathering? From the distance of tens of thousands of years, the best we can do is make educated guesses.
So the question of whether a low carbohydrate diet, rich in protein, increases the risk of osteoporosis is not settled, but it does not seem to me to be a huge factor, either way. However, we know some things for certain. We know that plenty of people, especially women, who are not on low carb diets develop osteoporosis. We know that making sure that you get enough calcium, whether through your food, or through supplements, can dramatically slow bone loss. We know that exercise, too, is crucial to maintaining strong bones -- and that people who feel well are more likely to exercise; so if you feel more energetic on a low carb diet, as I do, that's likely to be a plus. We know that replacing estrogen and progesterone (yes, progesterone, and preferably natural progesterone) is very beneficial in preventing bone loss in women. If we do these things -- get our calcium, get some exercise, especially resistance (weight-bearing) exercise, and pay attention to our hormone balance if we're women -- osteoporosis does not seem to be a major threat to us.
We also know that far more people die every year of diseases associated with carbohydrate intolerance/hyperinsulinemia (high insulin levels) -- heart attack, high blood pressure, diabetes, breast cancer, the whole ugly list. Life is always, to some degree, a matter of playing the odds. Bet on the right horse!