For many of us, the day does not really begin until the coffee is ready. And because the morning is also when most people take their vitamins, the two often go down together. Mostly that is fine. But coffee has a few real effects on how your body handles certain nutrients, and a small change in timing can make your supplements work better.
First, the good news about coffee
Large observational studies have linked moderate coffee drinking, roughly three to four cups a day, with lower rates of several health problems, including type 2 diabetes, Parkinson's disease and liver disease. These studies show associations rather than proof, but they are reassuring for coffee lovers. For most healthy adults, the FDA says up to about 400 mg of caffeine a day, roughly four or five cups of brewed coffee, is not generally linked with harmful effects. Pregnant people are usually advised to stay under about 200 mg a day. MedlinePlus has a good overview of caffeine.
Iron: the biggest interaction
Coffee and tea contain compounds called polyphenols that bind to iron from plant foods and supplements, making it harder to absorb. Studies have found a cup of coffee with a meal can reduce iron absorption significantly.
What to do: If you take an iron supplement or are trying to raise your iron levels, take iron at least an hour before coffee, or a couple of hours after. Taking it with vitamin C, such as a glass of orange juice, improves absorption. See iron supplements: who needs them.
Calcium
Caffeine slightly increases the amount of calcium lost in urine. For most people who get enough calcium, moderate coffee is not a problem. If your calcium intake is low or you are at risk of osteoporosis, make sure you are getting enough calcium from food or supplements, and consider adding milk to your coffee. See calcium and bone health.
Zinc and magnesium
Coffee may modestly reduce absorption of some other minerals, such as zinc. The effect is smaller than with iron. If you take a mineral supplement, spacing it away from coffee is a simple precaution.
B vitamins and water-soluble vitamins
Coffee is a mild diuretic, so some people worry it flushes out water-soluble vitamins. For regular coffee drinkers, this effect is small, and the body adapts. There is no need to worry about B vitamins or vitamin C as long as your diet is reasonable.
Vitamin D
Some research has suggested caffeine might affect vitamin D receptors, but the evidence is limited and inconsistent. The more practical issue is that vitamin D absorbs better with a meal containing fat, and black coffee on its own is not a meal. Take vitamin D with breakfast or another meal. See how to take supplements with or without food.
Caffeine-containing supplements
Many pre-workout powders, energy supplements and weight loss products contain caffeine, sometimes a lot of it, along with green tea extract or guarana, which also contain caffeine. Add these to your coffee and you can easily go over 400 mg a day. Too much caffeine can cause jitters, a racing heart, anxiety, stomach upset and poor sleep. Check labels carefully.
Coffee and medications
Caffeine can interact with some medicines, including certain antibiotics, thyroid medicine and some asthma and heart medicines. Thyroid medicine, levothyroxine, is a common example. Coffee can reduce its absorption, so it is usually taken on an empty stomach with water, 30 to 60 minutes before coffee or breakfast. Ask your pharmacist about your medicines. See supplement and drug interactions.
Coffee and sleep
Caffeine can stay in your system for many hours. If you have trouble sleeping, try having your last cup before noon or early afternoon. Poor sleep affects energy far more than most supplements can fix.
A simple morning plan
- Wake up and drink a glass of water.
- If you take thyroid medicine, take it now with water.
- If you take iron, take it now with a little vitamin C, or save it for later in the day.
- Have your coffee.
- Take your multivitamin, vitamin D, fish oil and other supplements with breakfast.
The bottom line
Coffee is fine for most people and may even be good for you. The main thing to watch is iron, which should be kept away from coffee by at least an hour. Take fat-soluble vitamins with food, keep an eye on caffeine in supplements, and separate thyroid medicine from your morning cup.