In particular, a joint study by Creighton University in Nebraska and the University of Miami, Florida, found that caffeine reduced the expression of vitamin D receptors on the cells in our bodies responsible for producing bone.
Vitamin C & B vitamins
Why vitamin C and B vitamins are important:
There’s not much that vitamin C can’t do. It helps the body produce collagen, a protein used to make cartilage, ligaments, skin and blood vessels. Vitamin C also helps with wound healing and is a potent antioxidant, which protects your body’s DNA from damaging free radicals.
Meanwhile, B vitamins help your body’s cells (skin, blood and brain cells) to develop and convert food into energy.
Why you shouldn’t mix caffeine with vitamins B or C:
While they have very different functions, B vitamins (thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folate, and cobalamin) and vitamin C are all classed as water-soluble vitamins, meaning that your body can’t store them so they are easily lost through urine.
Given caffeine is a stimulant, it also increases the production of urine so some vitamins and minerals don’t absorb as well before being flushed out. Rhian points out that “because caffeine has a diuretic effect, it can increase the excretion of B vitamins and vitamin C,” before your body has had a chance to absorb their benefits.
So you may want to think twice about taking a biotin-rich hair supplement with your morning espresso.
Magnesium & potassium
Why magnesium and potassium are important:
Magnesium and potassium belong to an umbrella family known as electrolytes – minerals found in the body, which carry a positive or negative charge when they’re dissolved in water. “Given our bodies are about 60% water, nearly every fluid and cell we have will contain electrolytes,” says Rhian. “They are vital to many key functions in our body because they regulate chemical reactions, maintain proper fluid balance, are involved in muscle contraction, and are critical to our nervous system.”
Magnesium, in particular, is needed for at least 400 reactions in the body. It helps to improve brain function and sharpens your focus. It is often referred to as the ‘calming mineral’ because of its role in supporting the nervous system. “It mediates our stress response,” says Rhian. “Because of this, it’s been shown to boost mood.”
Magnesium can also improve sleep “by regulating the body’s level of the hormone melatonin [responsible for our sleep-wake cycles],” says Dr Harry Jarrett, head of science and research at Heights.
Meanwhile, potassium is most well-known for supporting heart health, as well as your muscles and nervous system, and for moving nutrients around the body.
Why you shouldn’t mix caffeine with magnesium or potassium:
According to Rhian, the diuretic effects of caffeine can have a big impact on electrolytes. In particular, it can affect how much magnesium and potassium is absorbed before being flushed out.
How should you take your vitamin supplements?
Ideally, take your vitamin supplements with a glass of water. If you’re a coffee lover, Lucy Goff, founder of Lyma, recommends “leaving 30 minutes before or after caffeine” to take your supplement.
The exception is iron. “It’s important to leave a one to two hour gap between your iron supplements and your cup of coffee or tea,” Rhian notes. And try knocking them back with orange juice, as vitamin C helps the body to absorb iron better.
You can also replenish your magnesium and potassium levels by adding electrolytes to a glass of water. Good options include Artah Cellular Hydration and Ancient + Brave True Hydration Jar. And remember, ground coffee typically contains more caffeine than instant coffee.
Disclaimer: Vitamin supplements are not a replacement for a healthy balanced diet. Before supplementing, it’s best to consult with your doctor and/or a registered dietitian.
For more from Fiona Embleton, GLAMOUR’s Associate Beauty Director, follow her on @fiembleton.