Rumor has it that drinking tea will cause calcium loss? The truth is here!

For tea drinkers, you have more or less heard the saying: "Drinking tea will cause calcium loss."

Is this rumor true or false?

Let’s find out!

1
  Calcium metabolism in the human body

Calcium is one of the important elements that make up the human body, accounting for about 2% of human body weight. Most calcium in the body is stored in bones.

Calcium absorption occurs throughout the gastrointestinal tract and is primarily absorbed in the intestines.

(1) Effects of calcium deficiency on the body

The skeleton is the most basic scaffold for vertebrates and the main organ for calcium metabolism in vertebrates. It controls the balance of calcium in the internal environment together with the kidneys and intestines. When the body's calcium intake is insufficient, calcium is released from the bones and the risk of diseases such as osteoporosis increases.

(2) Factors leading to calcium loss

Calcium in the human body mainly comes from food. The bioavailability of calcium can be affected by many endogenous factors such as age, disease, hormones, physiological conditions (pregnancy, lactation, menopause, etc.) and intestinal microorganisms. It can also be affected by dietary intake. Affected by exogenous factors such as other nutrients.

Age factor: From birth to old age, the metabolism of calcium in the human body changes greatly. During the growth period, the bones gradually mature and the amount of calcium in the bones gradually increases. Generally, bone metabolism is in dynamic balance after the age of 20. After the age of 40, bone metabolism shows negative growth and the amount of bone calcium decreases.

Hormonal factors: The human body mainly uses three hormones, parathyroid hormone (PTH), calcitonin (CT) and vitamin D, to regulate blood calcium concentration to maintain calcium homeostasis.

Disease factors: When the calcium in the blood circulates to the kidneys, part of it must be filtered out from the glomerulus. Then, under the influence of hormones related to calcium metabolism, most of it is re-entered through the renal tubules according to the needs of the body's calcium balance. absorbed and returned to the blood circulation. Therefore, the amount of urinary calcium excretion is closely related to the two processes of glomerular filtration and renal tubular reabsorption. When you suffer from kidney and other diseases, electrolytes will be disturbed, resulting in the loss of calcium, phosphorus, etc.

2
  Rumors and truth

Rumor 1:

The oxalic acid in tea forms a precipitate with calcium ions in the intestines, thereby inhibiting calcium absorption.

the truth:

The oxalic acid content in tea per gram is 1.6-6.8 mg. The human body's absorption rate of oxalic acid in tea is very low, only 2.4%. But tea also contains calcium. The calcium content per gram of tea is 3.1-8.0 mg. Even if oxalic acid can combine with calcium and precipitate, the tea itself has enough calcium to react with oxalic acid, so drinking tea will not interfere with other food sources. Calcium absorption.

Swiss medical scientist Paracelsus once pointed out: "Everything contains toxins. Nothing is completely non-toxic. The dose is the key to determining the toxicity of the substance." Compared with spinach, amaranth, strawberry, etc., the oxalic acid content in tea is rich in toxins. For foods containing oxalic acid, there are relatively few.

Rumor 2:

The caffeine in tea increases urinary calcium excretion and may reduce bone density.

the truth:

The amount of urinary calcium excretion is closely related to the two processes of glomerular filtration and renal tubular reabsorption.

Early studies on the risk of calcium loss caused by high caffeine intake focused on coffee as the main source of caffeine. Caffeine accounts for about 3% of tea, but it contains more tea polyphenols, tea polysaccharides, theanine, tea pigments, minerals, vitamins, etc. Their mechanisms of action on bone health are not exactly the same.

And most studies show that as long as the daily calcium intake is normal, drinking tea or coffee has nothing to do with calcium loss.

3
  scientific experimental demonstration

Scientific research shows that drinking tea can positively regulate blood calcium, improve bone density, and prevent osteoporosis.

(1) Drinking tea improves bone density

In 2017, the team of Professor Sheng Jun of Yunnan Agricultural University published "Pu-erh Tea Extract Ameliorates Ovariectomy-Induced Osteoporosis in Rats and Suppresses Osteoclastogenesis In Vitro" in the journal. The experiment used the ovariectomized (OVX) rat model (to study postmenopausal bone quality in women). The best animal model of porosis) studied the effect of Pu'er tea extract (PTE) on ovariectomy-induced osteoporosis and in vitro osteoclastogenesis in rats. The results showed that: ① Pu'er tea extract maintained the balance of calcium and phosphorus. homeostasis, and improved other blood biochemical parameters to varying degrees; ② significantly inhibited osteoclast differentiation without cytotoxicity; ③ inhibited the expression of key osteoclast-specific genes and proteins. Therefore, drinking tea has a positive impact on bone health and may prevent osteoporosis.

A 2024 meta-analysis study on the relationship between tea drinking and bone health, "Tea consumption and risk of bone health: an updated systematic review and meta-analysis", showed that people who drink 2-3 cups of tea a day have lower lumbar spine bone density. The growth rate is faster than that of people who do not drink tea every day. Tea drinking may have a protective effect on fractures, osteoporosis, hip joints, femurs, lumbar spine and increasing bone density.

(2) Drinking tea regulates blood calcium

In a study "Observation of the Effect of Pu'er Tea Powder on Blood Lipids and Blood Calcium in Diabetic Patients", 65 patients were recruited, including 36 males with an age of 55.5±10.3 and 29 females with an age of 56.9±7.4. The disease duration was 1-15 years. All patients had varying degrees of dyslipidemia and normal serum calcium at the time of enrollment. Drink 3-10 grams of Pu'er tea powder every day. While observing, you should eat a reasonable diet and exercise appropriately. At the same time, continue the original drug treatment unchanged. After 3 months, take blood to measure blood lipids and blood calcium concentration. The results showed that blood lipids decreased significantly and blood calcium increased significantly compared with before drinking, and there were statistical differences.

(3) Functional components in tea that regulate calcium and phosphorus metabolism and bone health

Flavonoids: protect bone health through five possible mechanisms: i) reducing bone loss through the action of antioxidants, ii) attenuating bone loss through anti-inflammatory effects, iii) by enhancing osteoblastogenesis, iv) by inhibiting osteoclasts cell generation, v) through osteoimmune effects.

Tea polyphenols: can inhibit the differentiation and generation of osteoclasts: epigallocatechin gallate (EGCG), as a type of tea polyphenols, can regulate the metabolism of bone cells, osteoblasts and osteoclasts. And by regulating receptor activator of nuclear factor-b ligand (RANKL), it promotes osteogenic differentiation and inhibits the occurrence of osteoclasts. In vitro studies have shown that EGCG can inhibit the formation of calcium oxalate crystals in the kidney.

Minerals: Tea is rich in minerals such as calcium and phosphorus, which can regulate bone metabolism.

Vitamins: Tea also contains essential vitamins, including vitamin C and vitamin K, which have been shown to reduce the risk of bone fractures.

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  Recommendations for preventing calcium loss