Updated: Feb 13, 2019
With the release of the new Canada's Food Guide, the emphasis has been taken off "Dairy" as a category. The previous guide (and what many of us have grown up with), put a focus on getting our daily calcium intake (for an adult female, it use to be 2 servings a day), through "milk or powdered milk, canned evaporated milk, fortified soy beverage, yogurt, kefir or cheese. These previous suggestions in the Food Guide (and what our parents and advertising have told us for years, that milk builds strong bones) that these are the only options when it comes to calcium rich foods.
Let's back up a minute
No matter how much calcium we ingest, our body does this neat thing where it will balance the calcium in our blood and inside our cells on its own (yes, it's doing it RIGHT NOW!). To help this out, we have some ability to control the proportion of calcium absorbed through food, to alter the amount lost in using and if necessary, take it from our bone stores. Calcium intake in tandem with calcium loss is known as calcium balance.
We reach our peak bone mass in our early 30's. We're gaining this mass during our growing years (45% by age 8, and another 45% in the next 8). Right now as an adult, you should have between 2.2 and 3.3 pounds of calcium in your body. In those growing years (the first 16), we need to maintain a positive calcium balance by taking in more than we lose. By getting a good base in the first few decades of life you can set a good precedent for long-term bone health. Generally speaking, we absorb the most of the calcium from our diets when we need the most - during pregnancy, lactation and growing!
Children may absorb up to 75% of daily calcium, young adults 20-40% and adults 15-20%
When the input and losses are roughly equal, you have balance. This is a good goal during our adult years. After about age 45, bone mass can decline up to 0.5% in a year, and in the decade after menopause, can be as high as 5% loss PER YEAR before slowing down. Our diet and lifestyle choices can help keep our bones strong by maximizing absorption, minimizing loss and helping us retain the calcium we have. (And it isn't just important for bones - if you are experiencing muscle cramps or spasms, tooth decay, high blood pressure, heart disease, insomnia, acid reflux, digestive problems, obesity, diabetes, cancer or PMS - you may have a calcium deficiency!)
If adults are looking at a 15-20% absorption rate, what can we do to help increase this?
when our needs increase, vitamin D steps into action and absorption also increases. So make sure you have enough of this Sunshine Vitamin.
we absorb calcium more efficiently when small amounts are eaten throughout the day rather than all in one sitting. You're gut can only process and absorb so much at once, so spread it out!
certain substances in foods, particularly oxalates (spinach, swiss chard, rhubarb, beet greens), can bind calcium; essentially, we can only absorb a small amount from the calcium available in these foods. Yet, similar "greens" such as kale, collards, broccoli and turnip greens - we can absorb 40-70% of the calcium because they have minimal amounts of oxalates. Phytates in food (think wheat bran) can also have the same effect, but not to the same levels as oxalates.
There are two major calcium stealers - protein and sodium.
Research shows that for every gram of dietary protein above 47 grams per day, we lose out 0.5mg of calcium through the urine. The byproduct of protein breakdown is sulfate from sulfur-containing amino acids, which makes our blood more acidic, so our bodies rely on calcium reserves to balance our pH. All dietary protein contributes to urinary calcium loss, but people with diets high in animal protein (those sulfur amino acids) are more likely to need more calcium that those who are plant-based.
High sodium intake decreases our kidneys' ability to reabsorb the calcium that passes through it. For every 1000mg of sodium in our diets, we lose between 20-40mg of calcium. Note that only about 15% of our salt intake comes from what we add to our foods during cooking or at the table - the processed foods we are so very fond of are a more significant source! In fact, 75% of North Americans sodium intake comes via processed foods.
If your calcium intake is already low, you may also want to stay away from coffee and anything with phosphoric acid - so cola beverages. Phosphoric acid can increase calcium excretion (just another reason why you should kick the habit!)
So, if you can only absorb so much from your food, and you're overdoing the protein or salt, you can see where you start getting into a calcium deficit - and as with everything, it's about finding balance!
Hormones play a role in bone health as well. Estrogen appears to aid in calcium absorption and also help our bones retain the calcium. Note that vegetarians tend to have lower lifelong serum estrogen for a multitude of reasons; and while this may be an advantage when it comes to cancer, it may increase the risk of osteoporosis, so vegetarians needs to be extra careful on their calcium balance.
Because the body will pull from bone stores when it needs calcium to balance, you can't find out through a blood test if you are deficient. Just know that repeated withdrawals from your calcium bank will leave you broke.
What to do about it?
One of the best things you can do for your bones is to exercise. Exercise communicates a strong message to the bones to preserve calcium and keep the bones strong. Apart from diet, there is nothing we can do that is more valuable to our bones. Weight bearing exercise here is the way to go - so think of walking, running, cycling or dancing, along with adding some resistance exercise. If you don't use them, you do loose them.
The ideal ratio appears to be 16mg of calcium for every gram of protein we eat in our diet. You have to be aware of excess calcium as well, as those can lead to kidney stones - which will be a problem if you are consuming high-oxalate plant foods (spinach, swiss chard, beet greens and rhubarb) - remember, the oxalate in these prevents the calcium from being absorbed, and it has to go somewhere! But don't let this stop you from eating these amazing foods - just don't rely on them as your calcium source! High calcium intake may also interfere with our absorption and use of other minerals such as iron, zinc, magnesium and phosphorus.
Cow's milk has an excellent calcium to protein ratio, and your body can absorb roughly 32% of the calcium, but there are even better options in the low-oxalate greens (kale, collards, broccoli, turnip greens, boy chow). Milk comes with it's own set of concerns; saturated fat, hormones, environmental issues and the impact of animal agriculture, lactose intolerances....but it 100% isn't true that you have to drink milk to get your daily calcium intake! Greens are among the our best bone builders for reasons beyond their unbeatable calcium absorption. They're high in vitamin K - which helps our bone-building team perform their task. They also contribute plenty of potassium to the team. Almonds are also particularly rich in calcium! Even blackstrap molasses is a rich source of minerals that was in the original plant, including calcium - just make sure to go organic because otherwise you may be looking at a concentrated form of pesticides and other sprays. And don't forget to add black turtle and white beans!
It's clear that we can readily absorb calcium from many foods, not just from dairy products! So maybe the cow's were lying to you your entire life (after all, where do they get their calcium?)