Browsing your phone before bed may not just be a habit that affects sleep quality; A new study suggests that exposure to light at night may also be linked to changes in heart structure and function.
The study, published in the European Heart Journal, found that exposure to night light exceeding 3 lux was associated with left ventricular hypertrophy, that is, an abnormal increase in the thickness of the main heart chamber responsible for pumping blood. Exposure to higher levels of light was also associated with a slight decrease in the heart's ability to contract.
How was the study conducted?
According to the Eating Well website, researchers from Tulane University analyzed data from 11,71 participants in the UK Biobank, who wore a device on the wrist equipped with a light sensor for 7 consecutive days between 2013 and 2015. The device recorded ambient light levels around the clock, including during each participant's circadian nighttime period.
The exposure level in question was more than 3 lux, a level that previous research indicated may be sufficient to inhibit the hormone melatonin, which regulates sleep and helps set the body's internal clock. For comparison, a completely dark room is usually less than one lux, while a smartphone placed at arm's length may emit several lux in a dark room, depending on the brightness level.
Participants were free of cardiovascular disease at the beginning of the study. About three years later, they underwent cardiac magnetic resonance imaging, which provides precise measurements of the heart's structure and function. The researchers then compared nighttime light exposure to 24 different indicators of heart structure and function.
What did the study find?
Participants who were exposed to the highest levels of light at night showed a consistent pattern of unfavorable changes in the heart, compared to those who were not exposed to levels exceeding 3 lux, most notably:
Left ventricular mass increased by 2.4 percent, and mean wall thickness increased by 1.5 percent, a pattern consistent with myocardial hypertrophy.
The efficiency of myocardial contraction decreased by 1.9 percent.
Reduced various indicators of myocardial stress by about 2.7 to 2.9 percent.
Similar patterns appeared in the right ventricle and left atrium, indicating that the potential effects were not limited to one chamber of the heart.
Although these changes were relatively small, all associations showed a linear, dose-dependent relationship; That is, increased exposure to light at night was associated with increased changes in the structure of the heart, but researchers did not specify a specific level at which this effect stopped.
Sleep may explain part of the relationship
The researchers found that sleep duration explained an important part of the relationship between exposure to light at night and cardiac changes, as night light may suppress melatonin and lead to shorter sleep duration.
Sleep duration explained about 24 to 49 percent of the relationship observed by the study, indicating that sleep disturbance may be one of the factors behind the results. However, a significant portion of the association remained even after sleep duration was taken into account.
Does night light prove to be harmful to the heart?
no. The study was observational, so it cannot prove that exposure to light at night directly causes changes in heart structure or heart disease.
Also, the light measurements were based on a single 7-day period and may not reflect the participants' usual long-term exposure level. Most participants were older, white adults in the UK, which limits the generalizability of the findings to the entire population.
How can you reduce light while sleeping?
Exposure to light at night can be reduced through simple steps, including:
-Use blackout curtains or an eye mask, especially in areas exposed to street lighting or car lights.
-Place the phone with its screen facing down or take it out of the bedroom.
-Turn off or cover small indicator lights in devices such as electrical routers and streaming devices.
- Dim the TV brightness or use a timer to turn it off while sleeping.
-When a night light is needed, red or amber light can be chosen instead of white or blue light, because it has less effect on inhibiting melatonin.
If you're trying to diet to lose weight, you've probably heard of both keto and intermittent fasting. Both common eating patterns can support metabolic health and help with weight control, but they work in different ways.
Choosing the system that is most suitable for you depends on several different factors.
Which two systems are better for losing weight?
Both intermittent fasting and the keto diet can help you lose weight. However, on the face of it, one system does not appear to be more effective than the other; Rather, the effectiveness of dietary patterns varies from one person to another.
This means that choosing a regimen that best matches your daily habits, food preferences, and nutritional needs may increase your chances of staying on it and succeeding.
In intermittent fasting, you only eat during specific hours of the day, making it more likely that you will consume fewer calories than you burn. Intermittent fasting also helps keep insulin levels low for a longer period, which may enhance fat burning. Some people may find intermittent fasting easier to adhere to, because it allows them to eat a wider range of foods.
Keto works in a different way. In this system, there are greater restrictions on the types of foods you eat, as you consume a greater percentage of fat and protein, which helps you feel full and eat fewer calories. The body may also begin burning fat for energy when it enters a stage known as ketosis. Therefore, some people may notice a faster change in weight, especially during the first weeks of following the diet.
Benefits of intermittent fasting
Intermittent fasting, or time-restricted eating, focuses more on the timing of eating than eliminating specific foods. The most common methods of intermittent fasting are:
16:8 diet: Fast for 16 hours and eat within an 8-hour period.
5:2 diet: Eat normally five days a week, cutting calories on two days.
Fasting day by day: Fasting one day and eating normally the next day.
The body usually gets energy from glucose, or sugar, found in food. When fasting for a period of time, the body's glucose stores run out, and it begins to burn fat for energy. This shift can help with weight loss and other health benefits.
During the fasting period, you can drink water, black coffee, and unsweetened tea. Intermittent fasting may help reduce your total calorie intake and improve the way your body uses insulin. Research suggests that intermittent fasting may help:
Promote weight loss.
Help control blood sugar levels.
Improve heart health when followed with balanced meals.
Although intermittent fasting does not exclude certain foods, it is important to eat healthy, nutrient-rich foods during eating periods, to ensure that the body gets the elements it needs to maintain general health.
Benefits of following the keto diet
The ketogenic (keto) diet is high in fat and very low in carbohydrates. People who follow keto typically eat foods such as meat, fish, eggs, cheese, nuts, seeds, oils, and low-carb vegetables.
On a traditional keto diet, about 90 percent of calories come from fat, 6 percent from protein, and only 4 percent from carbohydrates. Followers of the diet avoid or reduce foods rich in carbohydrates, such as bread, rice, pasta, and most fruits and starchy vegetables.
When eating less than about 50 grams of carbohydrates per day, the body enters a state known as ketosis. During this condition, the liver converts fats into ketones, which the body uses for energy instead of sugar from carbohydrates.
The keto diet can help you lose weight quickly at first, mostly due to water loss, and then fat loss over time. Studies indicate that keto may help:
Support weight loss.
Improve control of blood sugar levels.
Reducing epileptic seizures in people with epilepsy.
Improving some heart disease risk factors, such as triglyceride levels and high-density lipoprotein (HDL) cholesterol.
Which of the two systems is better for long-term health?
Although both diets can be effective for weight loss, there are some considerations about continuing with them for long periods.
The dangers of following keto for a long time
Staying on the keto diet for a long time may increase the risk of:
Nutrient deficiencies: Keto excludes many foods that provide fiber and important nutrients, such as whole grains, legumes, most fruits, and some vegetables. This may increase the possibility of not getting enough vitamins and minerals.
High cholesterol: Eating large amounts of fat for a long time can cause high levels of low-density lipoprotein (LDL) cholesterol in some people, which may increase the risk of heart disease.
Kidney stones: Keto can affect the balance of minerals and fluids in the body, which may increase the risk of kidney stones.
Weight fluctuation: Many people find it difficult to adhere to keto for long periods, which may lead to weight loss and then regaining it. Repeated weight loss and regain may be associated with an increased risk of high blood pressure, high cholesterol, and kidney or liver problems.
Long-term risks and benefits of intermittent fasting
Committing to intermittent fasting for long periods is also associated with a number of benefits and risks, including:
Improving metabolic health: Studies indicate that intermittent fasting may improve insulin sensitivity, blood pressure, and cholesterol levels when eating healthy meals during eating periods. These changes may help reduce the risk of heart disease and type 2 diabetes.
Accelerating cell repair: Fasting stimulates a process known as autophagy, which is a process in which the body dismantles damaged cells and recycles their components. This may help support healthy aging, but researchers are still studying its long-term effects in humans.
Risks to heart health: Studies indicate that eating less than 8 hours a day may be associated with an increased risk of death related to heart disease in some people, especially those with heart disease or cancer.
Can intermittent fasting and keto be combined?
Following intermittent fasting and keto together can help the body enter a state of ketosis faster, and may lead to faster fat loss in the short term. Combining the two may be safe for a short period, but it may increase the risk of side effects, such as:
Fatigue.
Dizziness.
Headache.
Constipation.
When you limit the time you eat and the types of foods you eat at the same time, it may become difficult to get enough fiber, vitamins and minerals daily. Also, combining the two systems may be more restrictive and difficult to maintain over time.
Before starting to combine keto and intermittent fasting, it is recommended to talk to a doctor or nutritionist.
Coconut oil is widely popular as a natural and healthy cooking option, and over the past years it has been associated with claims about its benefits for the heart, cholesterol and metabolism. But its nutritional composition puts it in a more complex area; It contains a very high percentage of saturated fat, which can raise levels of harmful cholesterol, while some research indicates different effects on other types of cholesterol.
Why is coconut oil controversial?
Coconut oil contains a high percentage of saturated fat, amounting to about 80-90 percent of its total fat, according to Harvard Health. The main problem is that saturated fats can raise levels of low-density lipoprotein (LDL) cholesterol, known as bad cholesterol, which is one of the factors associated with increased risk of cardiovascular disease.
In contrast, coconut oil also contains lauric acid, a type of saturated fatty acid that can raise levels of high-density lipoprotein (HDL) cholesterol, known as the good cholesterol. This effect is one of the reasons why coconut oil has a healthy reputation, but higher HDL alone does not necessarily mean a lower risk of heart disease.
What do studies say about cholesterol?
A systematic review and meta-analysis of intervention trials showed that coconut oil intake was associated with higher levels of total cholesterol and LDL than a number of other vegetable oils, while also resulting in a limited increase in HDL.
In another analysis published by Harvard Health, which included 16 trials and 730 participants, coconut oil raised LDL by about 10 points on average compared to other vegetable oils, such as olive, canola, soy, and safflower oil.
These results support the general recommendation to focus on the type of fats that replace saturated fats, and not simply adding coconut oil to the diet without modifying the rest of the fat sources.
Is virgin coconut oil different?
There is some evidence that virgin coconut oil may affect some indicators of heart health differently than conventional coconut oil, but these results are not enough to say that it protects the heart.
A systematic review and meta-analysis published in December 2025, including 14 randomized trials and 1,049 participants from 11 countries, found that virgin coconut oil led to significant reductions in triglycerides and higher HDL. However, the duration of the interventions ranged from two to 24 weeks, and the study did not prove that these changes lead to an actual reduction in the incidence of heart attacks or strokes.
This is important because some studies showing potential benefits of coconut oil rely on short-term laboratory indicators, while evaluating the effect of any food on heart disease risk requires longer, more comprehensive clinical evidence.
Should I stop eating coconut oil?
The evidence does not suggest that coconut oil should be treated as a toxic substance or as a food that should be completely eliminated. But its image as a “heart-healthy oil” does not match the totality of the available evidence.
Harvard Health points out that coconut oil can be used in small quantities and from time to time, especially because of its distinctive flavour, but it is better not to regularly replace vegetable oils rich in unsaturated fats, such as olive oil.
The difference is important: using a small amount of coconut oil as part of a balanced diet is completely different from relying on it as the main source of fat every day.
The alternative may be more important than the oil itself
When evaluating the effect of fats on heart health, it's not just a matter of whether a particular oil raises or lowers one index, but rather what it replaces in the diet.
Replacing saturated fats with unsaturated fats can help improve cholesterol levels and reduce cardiovascular risks. Liquid vegetable oils, nuts, seeds, and fatty fish are important sources of trans fats.
Therefore, if coconut oil is replacing butter or other saturated fats, the result may be different than using it in place of olive or canola oil, which are higher in trans fats.
Conclusion
Current evidence suggests that coconut oil is not a “superfood” for heart health, nor is it necessarily a food that should be avoided completely. However, its high saturated fat content makes using it in large quantities or regularly a less suitable option for heart health compared to oils rich in trans fats.
There may be some limited benefits of virgin coconut oil in indicators such as triglycerides and HDL, but current evidence does not prove that it reduces the risk of heart disease. For long-term heart health, focusing on a balanced diet and replacing saturated fats with trans fat sources remains the most evidence-supported approach.
