Do you enjoy coffee? If so, you should know that taking certain supplements within two hours of drinking a cup of coffee may reduce their physiological effects. This is particularly true for specific types of supplements.

Vitamin D

Caffeine in coffee inhibits the absorption of vitamin D in the small intestine. It does this by reducing the secretion of vitamin D receptors, preventing the body from absorbing the amount of vitamin D it needs. A 2007 study observed that women consuming more than 300 mg of caffeine daily showed lower expression of vitamin D receptors in osteoblast cells, which are crucial for bone formation (1). However, caffeine does not directly block vitamin D absorption in the bones. Instead, the reduced levels of vitamin D caused by caffeine can have an indirect effect on bone health. Overall, caffeine can interfere with both the absorption and metabolism of vitamin D, highlighting the importance of timing your coffee intake when taking vitamin D supplements.

1) The Journal of Steroid Biochemistry and Molecular Biology
Volume 103, Issues 3–5, March 2007, Pages 368-371
The Journal of Steroid Biochemistry and Molecular Biology
Caffeine decreases vitamin D receptor protein expression and 1,25(OH)2D3 stimulated alkaline phosphatase activity in human osteoblast cells
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Prema B. Rapuri, J.C. Gallagher, Zafar Nawaz

Iron

Caffeine binds with iron before it can be absorbed, causing it to form a compound that is excreted through urine, reducing absorption by up to 80%. Found in coffee and tea, caffeine interferes with iron absorption, which is already a challenging process in the small intestine. Caffeine’s unique chemical structure allows it to bind directly with non-heme iron in the stomach, forming a chelate. When iron encounters caffeine before absorption, they attach and are eliminated from the body. This reduction in iron absorption can lead to decreased oxygen transport and lower energy production. Additionally, coffee and tea contain polyphenols and tannins, which further inhibit iron absorption by forming insoluble complexes with it. To ensure better iron absorption, it’s essential to be mindful of the timing of your caffeine intake.

Water-soluble vitamins (B, C)

Caffeine affects certain vitamins, primarily water-soluble ones like vitamins B and C, due to its diuretic effect. By increasing the frequency of urination, caffeine accelerates the excretion of these vitamins through urine.

Water-soluble vitamins, such as B-complex and vitamin C, are not stored in the body. They dissolve in water and are easily eliminated through urine. Caffeine speeds up this natural process, potentially reducing the time the body has to absorb and utilize these nutrients.

Additionally, caffeine promotes faster fluid elimination, limiting the body’s ability to retain water. Over time, this can lead to deficiencies if the intake of water-soluble vitamins is insufficient to compensate for the loss. While the body only excretes excess water-soluble vitamins once its needs are met, caffeine’s diuretic effect increases the amount expelled, further depleting these essential nutrients. Similarly, minerals like calcium, which are also excreted through urine, should not be taken with caffeine. Caffeine increases the excretion of minerals through urine, decreasing their availability to the body.

It’s best to wait at least two hours after drinking coffee before taking these supplements.