Hint, you will need a calculator
Recently, my doctor recommended I start taking calcium supplements. As medical advice is often general in nature, I had to wonder if this advice was well-founded in research and whether it would be applicable to my specific circumstances, which include a very precisely crafted diet. As is often the case, the general answer was “it depends.” For some people, calcium supplements are a great idea. For others, not so much. What I can say is that no general rule like “more is better” or “less is more” applies when it comes to calcium. This is because the intricate and ongoing chemical balancing within the body, along with its inability to fully absorb most nutrients we ingest cause this matter to be quite complex.
Calcium phosphate gives bones their strength. It makes bones hard and resistant to damage. However, every cell in the body needs calcium to function properly. Calcium that is stored in the bones can become immediately available to the cells.
When it comes to calcium, cell needs take priority over strong bones.
As the blood runs through the parathyroid gland, the parathyroid gland assesses whether the level of calcium in the blood is adequate for cellular needs. If not, it releases a hormone to cause calcium to move from the bone to the blood.
Calcium and phosphorus in the blood should be balanced appropriately. The need to constantly top up blood calcium and to balance calcium and phosphorus in the blood give rise to the general recommended daily allowance (RDA) for adults of 1000 mg of calcium and 700 mg of phosphorus. The RDA for calcium assumes an absorption rate of 30%.
If all sources of calcium were absorbed by the body at the rate of 30%(bioavailable) and there were no factors that impeded absorption, then consuming 1000 mg of calcium would typically satisfy an adult’s daily requirements. However, this is not the case as bioavailability differs significantly depending upon the food consumed and food combinations.
Considerations Affecting the Absorption of Calcium
Oxalic acid, phytic acid, and tannins (OPT) naturally occur in plants. OPTs bind with calcium and research generally indicates that they impede the body’s ability to absorb calcium. Studies have shown that only between 24 percent and 69 percent of the calcium in foods high in OPTs is bioavailable.
Other factors that impair calcium absorption include low levels of estrogen (whether from menopause in women or a variety of health conditions), consuming protein along with calcium and high fiber - low fat diets.
Accordingly, if the goal is to maximize the body’s absorption of calcium, it is recommended that calcium be consumed two hours before or after foods containing OPTs or protein are consumed. Obviously, in many cases, it is not possible to separate eating calcium and protein.
Sodium and alcohol tend to flush calcium out of the body. Regular alcohol consumption can reduce bone mass by up to 50 percent as it dramatically impairs the body’s ability to absorb calcium. For those who regularly consume alcohol, I recommend discussing calcium-related concerns with a physician as prescription sources of calcium and other nutrients may be necessary to maintain bone strength.
To reduce the risk of calcium flushing due to sodium consumption, a leading researcher suggests that for every 100 milligrams of extra sodium above the RDA (1500 mg for most adults), one milligram of calcium is flushed.
It is fairly well-known that caffeine decreases calcium absorption. Studies have shown that the extent of this impact is 6.4 mg of calcium for every ounce of coffee that contains caffeine. In other words, for every 10-ounce coffee or other similarly caffeinated beverage, increase your calcium intake by 64 mg. If you are drinking espresso, soft drinks or energy drinks, you should include these drinks in your calculations, with any necessary adjustments to account for a higher or lower proportion of caffeine in those drinks.
The caffeine content per ounce of energy drinks is more-or-less equivalent to the caffeine content in regular coffee. Therefore, increase your calcium intake by 64 mg for every 10-ounces of an energy drink.
Sodas contain approximately one-third the caffeine of a regular coffee. Therefore, from a calcium perspective, sodas can generally be disregarded unless you are consuming a number of them each day. If so, consider adjusting your soda intake rather than your caffeine intake since soda poses a number of health concerns, including impacting the body’s calcium-phosphorus balance.
For an espresso drink, knowing the amount of espresso in the drink will be critical to computing your calcium adjustment. In general, calcium intake should be increased by 12 mg per ounce of espresso.
Approximating the Amount of Calcium Absorbed on a Given Day
It is highly likely that calcium will be ingested in circumstances that impede its absorption. Accordingly, the total amounts ingested should be adjusted in order to make food and supplement decisions that will avoid creating a blood calcium deficit or excess.
Regular blood tests can determine your blood calcium level. However, without also having a test to confirm that your bone calcium is being maintained, they do not tell you to what extent your blood calcium is attributable to calcium being moved from the bone to the blood.
Currently, the best plan for managing blood calcium levels is using a good food tracker app that reflects the amount of calcium ingested per food item. With that general information, knowledge of which foods you consume contain high levels of OPTs and an understanding of your entire day’s intake, you can make the appropriate adjustments to estimate whether or not you need to use supplements to ensure an appropriate blood calcium level.
I propose that to obtain a more accurate view of your daily calcium absorption, the following reductions should be made to total calcium ingested as per your food tracker:
- 60 percent of calcium intake through foods containing high levels of OPTs
- 60 percent of calcium from dairy
- 60 percent of calcium ingested within 2 hours of ingesting foods with high levels of OPT, dairy or protein
- 6.4 mg per ounce of caffeinated coffee or energy drink
- 12 mg per ounce of espresso
- 1 mg for every 100 mg of sodium in excess of the RDA
As actual bioavailability varies widely by source, it would be preferable to be more precise by using the specific calcium bioavailability percentage for each item of food consumed.
Here is an example of how you might use these general guidelines to adjust your calcium intake and determine whether or not you should take a supplement:
Maintaining Adequate Calcium Levels
Ingesting the necessary amount of calcium is just the first step. In order for calcium to be absorbed by the body, calcium and phosphorus must be balanced and other nutrients must be present to maximize the body’s ability to absorb, store and properly use the calcium. These nutrients include vitamin D, boron, magnesium, and vitamin K. Each of these may be viewed as a co-factor for calcium.
Adequate magnesium and vitamin D levels will enable vitamin D to be activated throughout the day which encourages both calcium and phosphorus to be absorbed from the digestive tract. Where there is insufficient boron, Vitamin D or magnesium, the body is unable to use the calcium ingested. Vitamin C, taken with calcium, increases the absorption of calcium. All of these mechanisms help ensure that blood calcium levels are maintained.
Magnesium encourages calcium to be retained, and phosphorus to be excreted, by the kidneys. Therefore, a certain level of excess phosphorus can be addressed where adequate magnesium is present. This should negate the pulling of calcium from the bone to balance the phosphorus in the blood.
Too little boron (for which there is no RDA) increases calcium excretion and decreases magnesium uptake. Studies suggest that approximately 3 mg is a sufficient boron intake for a day. f you are eating a plant-based diet you are unlikely to need to supplement your boron intake.
Vitamin K helps to bind calcium in the bones, keep blood vessels elastic and direct calcium within the body. This, along with maintenance of proper levels of the other nutrients mentioned above generally prevents calcium from ending up in the muscles or soft tissue.
Unfortunately, the complexities do not end here. The levels of the various co-factors can be impacted by the excess or lack of other nutrients.
Loading up on calcium supplements to avoid doing this analysis is a bad idea. Existing bone can only store so much calcium and the blood will only carry so much calcium. Excess calcium will first be used by the body to replace existing bone. Therefore, excess calcium triggers a breakdown of existing bone. Unfortunately, the body has a greater capacity to breakdown bone than replace it so ongoing excess calcium can lead to weakened bones. When the excess calcium cannot be used to grow replacement bone and it is not needed in the blood, it may accumulate in the arteries which could lead to cardiovascular disease.