Coffee: Daily pleasure or hidden risk?

Coffee is one of the most popular beverages in the world. Millions of people enjoy it every day — not only for its taste, but especially for its energizing effect.

At the same time, coffee is one of those drinks surrounded by very conflicting opinions.
So which is it: healthy or unhealthy?

Let’s take a closer look at what the scientific evidence actually shows.

The Positive Health Effects of Coffee

• Mental alertness

As most of us know, the caffeine in coffee can improve concentration and mental alertness.

• Rich in antioxidants

Coffee is an important source of antioxidants, which help protect cells from damage. They can reduce inflammation and are associated with a lower risk of various diseases.

• Type 2 diabetes

Regular coffee consumption appears to be linked to a lower risk of developing type 2 diabetes. Interestingly, one possible explanation is that coffee inhibits iron absorption.¹

What does iron have to do with diabetes?

The risk of type 2 diabetes increases as ferritin levels in the blood rise. Ferritin reflects the body’s iron stores — so the higher your iron stores, the higher your diabetes risk.²

In fact, people with diabetes who donated blood several times in a study showed improved blood sugar levels.³

• Parkinson’s & Alzheimer’s

There is growing evidence that coffee may help protect against certain neurodegenerative diseases such as Parkinson’s and Alzheimer’s — likely due to its caffeine content and antioxidant properties.

Here too, reduced iron absorption may play a role.⁴ ⁵

• Liver health

Coffee consumption is associated with a lower risk of liver diseases, including fatty liver and liver cancer.

When all existing studies are analyzed together, people who drank the most coffee had only half the risk of liver cancer compared to those who drank the least.

But What About the Negative Effects of Coffee?

• Sleep

Caffeine can disrupt your sleep cycle and lead to insomnia. One study examined coffee consumption 6, 3, and 0 hours before bedtime and found that even a (admittedly high) dose of 400 mg of caffeine — which may still be normal for many people — significantly impaired sleep when consumed 6 hours before bed.⁷

• Digestive issues

For some people, coffee’s acidic and laxative properties can cause heartburn or gastrointestinal discomfort.

• Pregnancy

Pregnant women are often advised to limit coffee intake, as high caffeine consumption may increase the risk of miscarriage and low birth weight.⁸

Currently, up to 200 mg of caffeine per day is considered safe.⁹

However, it’s hard to know exactly how much caffeine is in that cup of coffee you drank this morning — it depends on the type of beans, brand, and brewing method.

As a rough guideline:

• Filter coffee per 100 ml: 40–66 mg
  

• Espresso per 100 ml: 100–120 mg
  

• Instant coffee per 100 ml: ~40 mg

• Blood flow

Caffeine appears to impair blood flow to the heart muscle during physical exertion — even in healthy individuals, and especially in people with heart disease.¹⁰

Interestingly, caffeine consumed in the form of tea seems to have the opposite effect, significantly improving blood flow in the coronary arteries.¹¹

• Iron absorption

We’ve already seen that reduced iron absorption from coffee may lower the risk of type 2 diabetes, Parkinson’s, and Alzheimer’s.

However, if you tend toward low iron levels, it’s important to drink coffee either one hour before meals or at least two hours after eating.¹²

You can also lessen coffee’s impact on iron absorption by consuming vitamin C–rich foods at the same time — such as citrus fruits, kiwi, berries, or vegetables like bell peppers, broccoli, and kale.¹³

Black or with Milk?

Did you know that adding cow’s milk to coffee significantly reduces the absorption of coffee’s antioxidants? This is likely due to casein, a protein found in animal milk.¹⁴ ¹⁵

But what about plant milk, such as soy milk?

Good news: plant milk does not negatively affect antioxidant absorption from coffee. While soy protein initially binds to coffee compounds, they are later released by beneficial gut bacteria and can still be absorbed.¹⁶

So if you don’t like your coffee black, soy milk is definitely the better choice.

Final Thoughts

In summary, coffee does offer several well-documented health benefits — but its potential downsides shouldn’t be ignored.

And remember: every cup of coffee is also a missed opportunity to drink an even healthier beverage — green tea.

Take a look at the health benefits of green tea here and maybe you’ll find yourself swapping your coffee for green tea more often in the future. ☺️

References for further reading:
1 Inhibiton of iron absorption
2 Iron and diabetes type 2
3 Type 2 diabetes and high-ferritin
4 Iron and diseases of aging
5 Iron and Alzheimer's
6 Coffee and liver cancer
7 Caffeine and sleep
8 Coffee consumption and health
9 Safety of caffeine
10 Caffeine and blood flow
11 Black tea coronary flow
12 Iron absorption
13 Iron from breakfast
14 Antioxidants in coffee
15 Coffee and milk
16 Coffee and soymilk

Want to go deeper?
If you’d like to learn how to integrate these principles step by step into your everyday life — without diets or complicated plans — you’ll find more resources here on the blog and in my free ebook and online course.