The domestic coffee market is becoming more and more vigorous. It is common for many people to have one or two cups of coffee every day, but many people still have many health doubts about coffee, such as whether drinking coffee often will be addictive? Can coffee cause palpitations? And today’s Xiaobian to crack the misunderstanding that drinking coffee can lead to calcium deficiency!
1. Can oxalic acid in coffee inhibit calcium absorption?
The most common reason why coffee can inhibit calcium absorption is that coffee contains oxalic acid, which will combine with calcium to reduce calcium absorption. Some people even suggest that coffee should be taken separately from high calcium foods such as milk. For example, latte is not recommended to avoid reducing the absorption rate after calcium is bonded. Next, let’s see what oxalic acid is?
Oxalic acid, also known as oxalic acid, structurally means that two carboxyl groups are connected together, so oxalic acid has two negative charges and can just combine with two positively charged calcium ions (Ca2 +) to further reduce calcium absorption.
In the past research, scholars used the method of isotopic calibration of calcium to let experimental animals ingest calcium oxalate or spinach with high oxalic acid (containing high oxalic acid and calcium). Compared with calcium chloride (CaCl2) in the control group, the absorption rate of calcium has been greatly reduced by 90%, which proves that oxalic acid can inhibit calcium absorption!
2. But is coffee high in oxalic acid?
Oxalic acid and calcium are divalent ions, which are theoretically 1:1 combined. Therefore, if calcium absorption is to be greatly inhibited, it is bound to contain a large amount of oxalic acid. The oxalic acid content of coffee beans is not low, and each 100 grams of raw coffee beans (dry weight) contains 200 mg of oxalic acid.
However, factors such as baking, brewing and usage should also be considered to affect the oxalic acid content of coffee solution. In fact, coffee “solution” itself is not a food rich in oxalic acid. The oxalic acid content per 100 grams of coffee solution is only 0.9 mg (link), which is only 2 mg for a large cup of coffee. How can we combine the large amount of calcium in milk?
3. Does caffeine in coffee inhibit calcium absorption?
In addition to oxalic acid, caffeine may also affect calcium absorption? But caffeine doesn’t have any charge. How does it affect calcium absorption? To understand this problem, we must first understand how calcium is absorbed. The human body has two calcium absorption mechanisms:
4. Low dietary calcium content and low intestinal calcium concentration:
At this time, calcium is absorbed through two channel proteins on both sides of intestinal cells. Calcium will first enter intestinal wall cells from intestinal cavity. A protein in the cells is called calcium binding protein (calbidin), which will bind calcium and help calcium to be absorbed into the body through channel proteins on the other side. Calbidin is regulated by vitamin D, The regulatory mechanism is that vitamin D binds to vitamin D receptor (VDR) in cells to further promote the production of calbidin.
5. High dietary calcium content and high intestinal calcium concentration:
Through calcium channel protein directly and passively transported through intestinal cells to the body, this channel protein may also be regulated by vitamin D.
It can be seen that these two absorption mechanisms may be related to vitamin D. in the past, studies have reported that caffeine can inhibit the expression of vitamin D receptor (VDR), but there is no research that vitamin D receptor (VDR) in the intestine can also be affected by caffeine. Therefore, there is no way to confirm that caffeine can reduce calcium absorption in the intestine through this mechanism.
However, some scholars believe that as long as 1-2 spoons of milk a day, you can ignore the decline in calcium absorption caused by caffeine!
6. Can coffee cause bone calcium loss? The focus is on getting enough calcium
Although the oxalic acid and caffeine of coffee are not enough to affect the absorption of calcium, studies have found that caffeine does affect the VDR protein expression of bone and affect bone calcium deposition, and caffeine also promotes the activity (connection) of osteophagocytes, allowing osteophagocytes to release bone calcium into blood calcium.
So, the focus is on getting enough calcium or dairy products, not coffee itself! As mentioned above, oxalic acid and caffeine in coffee will not affect calcium absorption. Therefore, if you are worried about your lack of calcium, drinking latte coffee will be a good choice. You can not only get the flavor and nutrition of coffee, but also supplement calcium to avoid the risk of bone!