Is coffee good or bad for your health?

"Coffee may reduce dementia risk". "Coffee combats inflammation-related heart disease". "Study links caffeine with pregnancy-loss".

These are the kind of headlines that have been published over the last year looking at the link between coffee and health, often leaving people confused as whether they should be drinking the beverage and how much of it.

In recent years, there has been intense scientific interest in examining the effects on coffee consumption – and more accurately the effects of caffeine.

In the space of five years, more than 1000 studies on the subject have been registered on PubMed – the database comprising 26 million citations for biomedical literature.

IBTimes UK takes a look at the most common questions this type of research has tried to answer.

What are the benefits of drinking coffee?

The good news is that most of the recent studies tend to highlight the benefits of coffee, rather than the risks associated with it.

Caffeine tends to improve people's concentration, energy, alertness and feeling of sociability, and studies have often backed this up.

It's important to take into account however that when scientists look at the effects of caffeine on specific conditions, these studies are often conducted on a small number of participants and on the short-term. Additionally, they often rely on self-report of coffee consumption and do not distinguish well between what types of coffee people drink. Thus, their conclusions may be limited.

Below are some of the conditions for which most of the evidence has been gathered.

1) Parkinson's disease

A higher caffeine intake has been associated both with slightly lower incidences of the disease and improved symptoms – patients saw motor benefits from drinking more coffee.

2) Liver disease

The evidence for liver disease has been more robust. The relationship was first noted with alcoholic liver disease, but coffee was then found to correlate with a decreased risk of liver-associated enzyme elevations, hospitalisations and mortality in cirrhosis.

One study has for instance shown that drinking coffee has a beneficial impact on non viral hepatitis related cirrhosis mortality, while another showed that coffee and tea consumption are associated with a lower incidence of chronic liver disease in the United States.

3) Type 2 Diabetes

A recent study has indicated that long-term habitual coffee drinking could have a positive impact against type 2 diabetes onset. The anti-inflammatory effect of several coffee components may be responsible for this protection.

Another Harvard study revealed that people who drink about three to five cups of coffee a day may be less likely to die prematurely from some illnesses than those who don't drink or drink less coffee. Drinkers saw benefits with both caffeinated and decaffeinated beverages, such as a lower risk of death from cardiovascular disease, neurological diseases, type 2 diabetes.

However, it it is to soon to rush to the conclusion that coffee can prevent type 2 diabetes – especially since some people add sugar and cream to their coffee which can cause other health problems.

4) Cardiovascular disease

This is perhaps the area of research where most controversy arise. However, most recent studies have shown no link between coffee consumption and heart disease.

A systematic review published in 2013 even suggested that moderate coffee consumption was significantly associated with lower incidence of cardiovascular disease.

Another more recent points out that there is actually little evidence that chronic coffee intake consumption raises blood pressure and drinking coffee it is considered safe for the heart. Coffee is thought to have a protective effect against inflammatory mechanisms associated with ageing and the chronic diseases that come with it.

The bottom line of all this research is that coffee consumption can have a range of health benefits, providing individuals have otherwise healthy lifestyles and people drink it in moderation.

What's the effect of coffee on sleep?

Caffeine is a central nervous system stimulant and it has the effect of increasing wakefulness – this has given rise to concerns that it could cause insomnia.

The human body absorbs caffeine relatively quickly. However, it also gets rid of it fairly quickly – after 8 to 10 hours, most of it is gone from the body. So if you take a cup of coffee in the morning, it is unlikely to affect the way you will sleep at night.

Drinking coffee closer to your bedtime however may disrupt your sleep, increase nervousness and lead to gastrointestinal upset.

Should pregnant women avoid coffee?

A number of studies have suggested that pregnant women may be at risk of miscarriage or may harm the foetus if they drink too much coffee. However, there is little evidence that this is the case, providing women remain cautious not to drink huge amounts of the beverage.

The European Food Safety Authority states that habitual caffeine consumption up to 200mg per day by pregnant women does not give rise to safety concerns for the foetus. There again, the idea of drinking coffee in moderation is key.

Can I become addicted to coffee?

Caffeine is considered the world's most popular psychoactive drug. It has been recognised as chemically addictive for the past two decades, and can lead to withdrawal symptoms like other drugs – although they are far less serious, with health impacts that are less severe. Withdrawal symptoms include fatigue, headaches, irritability and being less alert.

A large review of scientific literature has found that caffeine produces behavioural and physiological effects similar to those produced by other drugs of dependence. Furthermore, a disorder known as caffeine-use disorder is now included in the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM5), referring to people who are unable to reduce consumption, despite knowing that drinking too much might not be good for them.

That being said, talking of an addiction like you would do for a cocaine or heroin addiction might be far-fetched and people rarely put themselves in mortal danger by drinking a few cups of coffee a day.

Can I overdose on coffee?

You can, but you would have to drink a really large amount of coffee. The lethal dosage of caffeine for 50% of the population stands at 10g for oral admission. That's between 50 and 200 cups.

Acute coffee poisoning can occur at large doses with early symptoms including tremor and restlessness. This can be followed by nausea, vomiting, tachycardia, and confusion. Serious intoxication may cause delirium, seizures, and hyperglycemia.