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2-3 cups of coffee a day may reduce kidney injury risk by 23%

2-3 cups of coffee a day may reduce kidney injury risk by 23%
  • Researchers have investigated the effects of coffee intake on acute kidney injury risk.
  • They found that drinking any amount of coffee reduces the risk of acute kidney injury but that 2-3 cups per day is most beneficial.
  • They say that further research is needed to understand why this link may exist.

Coffee contains many beneficial compounds for health, including caffeine, diterpenes, and chlorogenic acid.

Studies show that habitual coffee consumption is linked to the prevention of chronic and degenerative conditions, including cancer, cardiovascular disorders, diabetes, and Parkinson’s disease.

Caffeine, the most commonly studied compound in coffee, exerts positive effects on kidney function, and daily coffee consumption is linked to a lower risk of chronic kidney disease.

Although other compounds in coffee are less studied, compounds such as chlorogenic acid and trigonelline are known to reduce generalized inflammation and oxidative stress.

Knowing more about how coffee consumption affects the incidence of other kidney-related conditions could help policymakers take steps to reduce people’s risk of developing progressive kidney disease.

Recently, researchers investigated the effects of coffee consumption on acute kidney injury (AKI), when the kidneys lose all or part of their function suddenly.

AKI represents a public health problem with around 0.25% of the general population experiencing AKI, which rises to 18% among individuals who are hospitalized annually.

From their analysis, the researchers found that higher coffee intake is linked to a lower risk of incident AKI.

The study was published in Kidney International Reports.

The most beneficial amount of coffee

For the study, the researchers used data from 14,207 adults ages 45 – 64 from the Atherosclerosis Risk in Communities (ARIC) study.

The researchers assessed the participants’ coffee consumption during their first visit via a food frequency questionnaire. In total, they found:

  • 27% never drank coffee
  • 14% drank less than a cup of coffee per day
  • 19% drank 1 cup per day
  • 23% drank 2-3 cups per day
  • 17% drank more than 3 cups per day

To define acute kidney injury, the researchers looked at rates of hospitalization, including an International Classification of Diseases code indicating AKI throughout a median period of 24 years follow-up. They noted 1,694 cases of incident AKI during the follow-up period.

After adjusting for demographic factors, they found that individuals who consumed any amount of coffee had an 11% lower risk of developing AKI compared to individuals who did not consume the beverage.

The researchers further noted a dose-dependent relationship between AKI and coffee intake, with those consuming 2-3 cups of coffee per day experiencing the most substantial risk reduction.

Coffee’s protective effects

When asked what might explain the potential protective effects of coffee for acute kidney injury, Dr. Matthew Weir, professor of medicine and the head of the Division of Nephrology at the University of Maryland, who was not involved in the study, told Medical News Today that the study did not offer clues.

“[The researchers] provide theories, but there are numerous problems with retrospective data review, which may confound the observations and limit the validity. At least there was no evidence of harm,” said Dr. Weir.

In the study, the researchers noted their findings might be the result of bioactive compounds in coffee that improve perfusion and oxygen utilization in the kidneys.

Dr. Kalie L. Tommerdahl, assistant professor of pediatric endocrinology at the University of Colorado, and Dr. Chirag Rohit Parikh, director of the Division of Nephrology at Johns Hopkins University, who were both authors of the study, told MNT that they conducted a companion study to further understand the potential mechanisms.

“We studied ten youths aged 12 to 21 years old with type 1 diabetes and aimed to assess the effects of a confirmed 7-day course of a single daily Starbucks cold brew (325 ml, 175mg caffeine) on [various measures of renal function],” they said.

“The study included a small sample size. While it confirmed that we can effectively assess these intrarenal measures in adolescents with type 1 diabetes, we did not find any differences in [renal function] following a short course of daily coffee consumption,” they added.

The researchers concluded that they needed to further evaluate the physiological mechanisms underlying the potentially protective effects of coffee consumption in larger studies of a longer duration.

What about other caffeinated beverages?

Dr. Weir noted that the study had many limitations that the authors readily accounted for in their paper.

When asked about these limitations, Dr. Tommerdahl and Dr. Parikh said the main limitation was that they used “a food frequency questionnaire that relied on participant recollection rather than direct measurement to assess average daily coffee consumption.”

“Coffee additives such as milk, half-and-half, creamer, sugar, or sweeteners could also influence outcomes and warrant further investigation,” they added.

They pointed out that other beverages may produce similar effects.

“In addition, consumption of other caffeinated beverages such as tea or soda should also be considered a possible confounding factor. Further limitations include reliance on the inclusion of AKI on the problem list during inpatient hospitalization and the potential for confounding effects from differences in etiologies for participant hospitalization,” they said.


Is coffee bad for the heart or not?

Studies on coffee consumption variously claim that coffee harms the arteries, that it protects the heart, or that it has no effect on cardiovascular health. New research on thousands of participants weighs in again on the link between this favorite beverage and heart health.

coffee cup in a heart made from coffee beans
New findings suggest that even heavy coffee drinkers may have nothing to worry about when it comes to cardiovascular health.

Does coffee harm, protect, or have no effect on heart health and the vascular system?

For years, scientists have been trying to answer these questions, since coffee is such a favorite beverage around the world.

While some studies warn that drinking coffee can increase a person’s risk of cardiovascular events, others suggest that it can help maintain heart health and blood vessel function.

Some research has suggested that regularly drinking a lot of coffee contributes to aortic stiffness — this is when the aorta, which is the largest blood vessel in the human body, becomes less and less flexible. Aortic stiffness can contribute to the risk of cardiovascular disease.

At the same time, other evidence has indicated that drinking more than three cups of coffee a day can protect against atherosclerosis, a condition in which plaque builds up inside the arteries, preventing blood from flowing normally.

Now, a new study conducted by researchers from the Queen Mary University of London in the United Kingdom has found that even people who drink a significant amount of coffee each day do not experience arterial stiffness, meaning that coffee does not increase their risk of cardiovascular problems in this way.

Lead author Prof. Steffen Petersen and colleagues presented the study’s findings yesterday at the annual British Cardiovascular Society (BCS) Conference in Manchester, U.K.

The British Heart Foundation, a registered charity based in the U.K. that supports research about heart and circulatory conditions, funded the study.

Same results across all groups

In the new study, the research team analyzed the data of 8,412 participants recruited via the U.K. Biobank Imaging Study. At the BCS Conference, the team explained that the participants agreed to undergo cardiovascular magnetic resonance imaging and other specialist assessments to allow the investigators to determine the state of their cardiovascular function.

The participants also self-reported how much coffee they typically drank on a day-to-day basis. Following these reports, the investigators then categorized the participants into three groups, according to their coffee consumption habits:

  • people who drank one or fewer cups of coffee a day
  • those who drank between one and three cups of coffee per day
  • those who drank more than three cups of coffee per day

In their final analysis, Prof. Petersen and team excluded individuals who drank more than 25 cups of coffee per day, as well as those who had cardiovascular disease at baseline.

When comparing measurements of arterial stiffness between the three groups, the researchers found no differences between moderate and heavy coffee drinkers (those who drank between one and three or more than three cups of coffee per day, respectively) and those who had one cup off coffee or less per day.

These results, the investigators say, suggest that even drinking significant amounts of coffee is unlikely to have an ill effect on arterial health, so it may not negatively influence heart health and vascular function.

“Despite the huge popularity of coffee worldwide, different reports could put people off from enjoying it. Whilst we can’t prove a causal link in this study, our research indicates coffee isn’t as bad for the arteries as previous studies would suggest,” explains study coauthor Kenneth Fung.

These findings remained in place after the investigators adjusted for possible factors contributing to arterial stiffness, including age, biological sex, ethnicity, smoking status, alcohol consumption, height, weight, eating habits, hypertension (high blood pressure), high cholesterol, and diabetes.

What should and what shouldn’t we believe?

The researchers also noted that moderate and heavy coffee drinkers were more likely to be male, habitual smokers, and frequent drinkers of alcohol.

“Although our study included individuals who drink up to 25 cups a day, the average intake amongst the highest coffee consumption group was five cups a day. We would like to study these people more closely in our future work so that we can help to advise safe limits,” Fung also specifies.

Prof. Metin Avkiran, who is Associate Medical Director at the British Heart Foundation, and who was not involved in the current research, explains that such studies about the relationship between coffee consumption habits and heart health can help individuals make better-informed decisions.

“Understanding the impact that coffee has on our heart and circulatory system is something that researchers and the media have had brewing for some time. There are several conflicting studies saying different things about coffee, and it can be difficult to filter what we should believe and what we shouldn’t.”

Prof. Metin Avkiran

“This research will hopefully put some of the media reports in perspective, as it rules out one of the potential detrimental effects of coffee on our arteries,” Prof. Avkiran says.


What are the health benefits of bulletproof coffee?

Bulletproof coffee combines coffee, oil, and butter as a substitute for breakfast. Promoters of the drink claim it has a range of health benefits.

In this article, we look at what bulletproof coffee is and how to make it. We also examine its potential health benefits, its downsides, and who might benefit from drinking it.

What is bulletproof coffee?

bulletproof coffee
Bulletproof coffee is a mixture of coffee, oil, and butter.

Bulletproof coffee is a drink that combines coffee, oil, and butter. It is a creamy coffee served warm and looks similar to a latte. The original recipe comes from Bulletproof health blog.

People who promote bulletproof coffee claim that it has a range of benefits, including:

  • maintaining energy levels throughout the morning
  • preventing hunger
  • improving mental focus

Because bulletproof coffee is a relatively new product, there has not been any scientific research into whether it benefits or harms health. The United States Food and Drug Administration (FDA), who are responsible for assessing the safety of food, medication, cosmetics, and other products, have not yet evaluated bulletproof coffee.

How do you make bulletproof coffee?

There are four steps to making bulletproof coffee:

  1. Using freshly ground coffee beans, brew 1 cup of coffee, using a French press.
  2. Add 1 tablespoon (tbsp) of a medium-chain triglyceride (MCT) oil, which usually derives from coconut oil.
  3. Add 1 to 2 tbsp of grass-fed, unsalted butter or a non-dairy alternative
  4. Mix in a blender for 20 to 30 seconds.

The coffee mix should look foamy and creamy. People usually drink it warm.

Health, diet, and lifestyle benefits of bulletproof coffee

smiling woman drinking coffee in the morning
A person may feel more awake after a morning coffee.

Drinking coffee in moderation has a range of health benefits and may reduce the risk of death from heart disease and several cancers. Drinking coffee may also lower the likelihood of developing conditions, such as liver disease, Parkinson’s disease, and type 2 diabetes. However, the reasons for these health benefits need further research.

Coffee in the morning can improve mental focus and help a person to feel more awake and alert. This effect usually lasts for a maximum of a few hours.

The bulletproof coffee recipe uses a coconut-derived MCT oil. MCT oil contains a medium-length chain of triglyceride fats. The shorter the chain of fats, the more quickly the body can break them down.

2015 review of scientific evidence found that MCTs may be more useful for weight loss than long-chain fats, which most other fats and oils contain. However, the authors concluded that there is not enough research to determine whether MCTs are safe and effective as a food supplement.

The ketogenic diet

Usually, the body converts carbohydrates into energy before using fat. If there are not enough carbohydrates available, then the body uses its fat stores as an alternative source of energy. When the body uses its fat reserves, it produces ketones.

A ketogenic diet is low in carbohydrates and high in fat. Promoters of bulletproof coffee claim that it fits into a ketogenic eating plan because it contains fat but no carbohydrates, and the body converts MCT oil into ketones.

However, there is currently a lack of scientific research into the potential health benefits and risks of the ketogenic diet.

Type 2 diabetes

Some studies state that a low-carbohydrate diet may be beneficial for some people with type 2 diabetes.

A low-carbohydrate diet may help a person with diabetes to:

  • reduce their risk of heart attack or heart disease
  • lose weight if needed
  • lower their blood sugar level

Doctors usually recommend following a low-carbohydrate diet for a short time only.

Reducing hunger

One of the reasons for drinking bulletproof coffee is to prevent hunger during the morning. Adding butter and oil to coffee may make a person feel less hungry than if they drank coffee alone. Everyone is different, but some people may still feel hungry during the morning if they have not eaten a meal for breakfast.

Downsides of bulletproof coffee

The American Heart Association (AHA) recommend people limit the amount of saturated fat in their diet. The organization state that only 5 to 6 percent of calories should come from saturated fat, which is around 13 grams (g) of saturated fat per day.

According to the United States Department of Agriculture, 1 tbsp of unsalted butter contains around 7 g of saturated fatty acids. A bulletproof coffee can contain 2 tbsp of butter. This totals 14 g of saturated fatty acids, which is more than the AHA’s recommended daily allowance.

Consuming large amounts of saturated fat can raise the level of cholesterol in the blood. High cholesterol increases a person’s risk for stroke and heart disease.

However, not all saturated fats are the same. Although high in saturated fat, MCTs may be more healthful than long-chain fats.

The idea is to drink bulletproof coffee as an alternative to breakfast. However, replacing a meal with a drink can leave a person short of the nutrients they need each day.

Bulletproof coffee does not contain the right balance of essential nutrients. Coffee, oil, and butter do not contain carbohydrates, protein, fiber, or many of the other vitamins and minerals that a person needs. Choosing a breakfast that includes a balance of nutrients is a more healthful way to start the day.

The American Academy of Nutrition and Dietetics recommend including carbohydrates, protein, and fruits or vegetables in a breakfast meal. Some people may choose to have a hot drink rather than food first thing in the morning. However, a homemade smoothie can be a healthier option than skipping breakfast altogether. Try blending fruit, a few berries, and a banana with milk.

Who might benefit from bulletproof coffee?

People who are following a ketogenic or low-carbohydrate diet for health reasons may benefit from drinking bulletproof coffee in moderation.

Drinking a version of bulletproof coffee alongside a healthful breakfast from time to time is unlikely to be harmful to health. A person could reduce the amount of butter and oil they add to the drink to cut down on saturated fat.


healthful breakfast of fruit and granola
Bulletproof coffee does not contain the nutrients of a healthful breakfast.

Bulletproof coffee is a growing diet trend that combines coffee, oil, and butter as a substitute for breakfast. Promoters of the drink claim that it prevents hunger and provides lasting energy and better mental focus. However, there is not yet enough evidence to confirm its potential health benefits or risks.

Drinking coffee in moderation is not harmful and may even have health benefits. But, adding large amounts of saturated fat to coffee may be damaging to long-term health.

Bulletproof coffee as a meal replacement does not provide all the nutrients a person needs. Eating a balanced and healthful breakfast is the best way to start the day mentally focused and to feel full until lunch.


Can you be allergic to coffee?

Coffee is the morning drink of choice for many people around the world. It provides caffeine, which helps to stimulate the body and mind and be alert and ready for the day.

People who have a coffee allergy will have a reaction when they are exposed to the bean. Someone who is sensitive to or has an intolerance to caffeine or something else in coffee may also experience symptoms. It is important to know the difference between these conditions.

Doctors can help people with suspected allergies or sensitivities to coffee find a solution to their specific problems.

Prevalence and causes

coffee beans being roasted
An adverse reaction can be caused by the dust from coffee beans before they are roasted.

Allergic reactions to drinking coffee are very rare.

According to a study posted to International Archives of Allergy and Immunology, the dust from green coffee beans causes an allergic reaction in some of those who work with the beans. No recent medical literature mentions allergic reactions to drinking coffee, though rare cases have occurred in the past.

An allergic reaction caused by food, such as coffee beans, is actually due to an immune system response. The immune system recognizes compounds in the cells of coffee as invaders.

The immune system then responds to coffee in a similar way to how it would respond to pathogens, such as bacteria and viruses. It releases protective compounds, such as histamine, to isolate and destroy the intruding coffee. The symptoms of a coffee allergy are the result of this process.


Symptoms of a coffee allergy

A true coffee allergy can cause serious symptoms in the body, usually within the first hours after it has been drunk. Symptoms can affect many areas of the body and will usually get worse over time.

Symptoms of an allergic reaction to coffee include:

  • skin rashes, such as hives or blotches of red skin
  • nausea and vomiting
  • trouble swallowing
  • shortness of breath or difficulty catching a breath
  • a wheezing cough
  • stomach or abdominal cramps
  • diarrhea
  • reduced color in the skin
  • weak pulse or a sudden drop in blood pressure
  • dizziness or loss of consciousness

Severe allergic reactions may lead to anaphylaxis, which can be life-threatening if left untreated. Anaphylaxis can cause swelling of the throat and mouth, blocking off the airways, while also adversely affecting the heart rate and blood pressure.

Anyone who experiences any of these symptoms should get medical attention right away. People who have a coffee allergy and have taken antihistamine medications or epinephrine should still seek medical attention to avoid any potential complications.

Coffee allergy vs. coffee sensitivity

Many people with coffee sensitivities mistakenly think that they are allergic to it. Sensitivity to coffee can create its own problematic symptoms, but they are usually not life-threatening.

closeup of hands indicating anxiety
Feelings of anxiety, unease, or irritability after drinking coffee may indicate a coffee sensitivity.

Symptoms of a coffee sensitivity can include:

  • feelings of jitteriness and unease
  • irritability
  • anxiety or nervousness
  • trouble sleeping or insomnia
  • upset stomach
  • abdominal cramps
  • elevated heartbeat or blood pressure
  • involuntary muscle spasms

Symptoms caused by sensitivity to coffee will usually go away if the person stops drinking coffee.

People who are sensitive to coffee may have a gastrointestinal upset or symptoms connected to other issues may be getting worse. For example, coffee can make heartburn and symptoms of gastroesophageal reflux disease (GERD) worse. The caffeine in coffee can relax the sphincter at the lower end of the food pipe, causing stomach acid to leak up and irritate it.

Symptoms of too much caffeine vs. allergy symptoms

Allergies may be confused with the symptoms caused by having too much caffeine or sensitivity to caffeine. Many people who get sick from drinking coffee are simply seeing the effect of caffeine sensitivity.

Typically, the recommended caffeine consumption for adults is limited to 400 milligrams (mg) per day. This is around 4 small cups of home-brewed coffee. After that, many people will start experiencing symptoms.

People who do not have caffeine regularly, or those that are sensitive to caffeine, may experience symptoms after relatively small amounts of caffeine, such as 1 cup of coffee or tea. If a person is not used to caffeinated drinks, symptoms may occur because their body is not used to caffeine’s effects and struggles to process and eliminate the caffeine from the system.

Too much caffeine is associated with similar symptoms to those of a coffee sensitivity. In addition to these symptoms, too much caffeine in someone who is caffeine-sensitive may cause symptoms, such as:

  • chest pain
  • heart palpitations
  • mood swings, anger, or depression
  • numbness in the extremities
  • muscle pains
  • shortness of breath
  • headaches or migraines
  • delusions or hallucinations
  • cold sweats
  • flu-like symptoms
  • panic attacks

Although very rare, it is also possible to be allergic to caffeine itself. Some people may experience allergic reactions to the compound, which can lead to anaphylaxis.

Any new symptoms should be reported to a doctor or allergist immediately to discuss a plan of action.

Other causes

Other ingredients in the coffee can also cause an adverse reaction.

Coffee beans contain many different substances that may cause a reaction in some people. For example, the beans may have come into contact with pesticides or chemicals during their growing and transportation.

Any of these factors could potentially cause an allergic reaction or intolerance in certain people.

People who drink coffee with milk or cream may be having a reaction to dairy. Heavily sweetened beverages may cause a reaction to sugar. Flavored syrups can also contain many other ingredients, which could be the culprit behind allergy or intolerance symptoms.

A recent study posted to Journal of Toxicology and Environmental Health found that various green coffee bean samples were contaminated with mycotoxins, which come from fungi on the beans. These toxins may survive the roasting process and be present in coffee, causing an allergic reaction.

Researchers noted that mycotoxin exposure is a health concern. Further studies will need to look into ways to limit exposure to these toxins.

It may help anyone who is uncertain about their allergies or sensitivities to keep a food journal, logging what they eat and drink and how they feel throughout each day. Over time, this journal can help people work out which foods to avoid.

Foods to avoid

People who have a reaction to coffee need to avoid the bean in all of its forms. This includes drinking it, eating it, or being exposed to the beans before roasting.

coffee and chocolate
If a person is sensitive to caffeine, they may need to avoid foods such as chocolate and some energy bars.

People with sensitivity to caffeine need to avoid consuming the compound. Caffeine is found in:

  • coffee
  • various teas including black, green, Oolong, Pu’er, and white tea
  • energy drinks
  • some soft drinks and sodas
  • some workout bars or meal bars
  • cocoa
  • chocolate

Decaf coffee or tea may still contain a small amount of caffeine. In a person who is highly sensitive to it, this may be enough to cause a reaction.

Anyone with severe caffeine sensitivity will need to check labels carefully. Caffeine is added to many products, such as candy, gum, and even vitamins.

Some pain treatment medications also have caffeine in them. These must be avoided, and a doctor should be told of caffeine sensitivity before any medication is prescribed.

Coffee substitutes

For those who are allergic or intolerant to coffee itself, some teas might be a good alternative. Tea leaves have less caffeine than coffee beans, but can still be a source of energy in the morning.

If a person enjoys coffee but caffeine upsets their system, there are alternatives made from chicory or roasted grains that can satisfy their morning habit and provide the same roasted flavor as a cup of coffee. Non-caffeinated herbal teas of any kind can replace coffee for many people.

When to see a doctor

Anyone experiencing new symptoms, or symptoms which get worse after drinking coffee, should see a doctor or allergist. They can help by administering tests and checking for any other influential factors.

Doctors may recommend an elimination diet, or recommend that someone keep a food journal of everything they eat and drink and records how they are feeling. Doing so can help identify any reactions that would normally go unnoticed.

Many people who experience negative reactions to coffee can work with a doctor or allergist to find a way to alleviate symptoms and avoid allergic or intolerance reactions to coffee.