The Hidden Side Effects of MCT Oil

MCT oil is a dietary supplement derived from medium-chain triglycerides, a type of fat that is rapidly absorbed and converted into energy. It is typically sourced from coconut oil or palm oil, though it is more concentrated in MCT oil than in whole food sources.

Unlike long-chain fats, which require bile and enzymes for digestion, MCTs are processed directly by the liver, making them a quick source of fuel. The most common types of MCTs are caprylic acid (C8) and capric acid (C10), which have distinct metabolic effects. While MCT oil is widely used as part of high-fat, low-carb diets, research on its long-term benefits and risks is ongoing.

MCT oil can cause digestive discomfort, including stomach cramps, diarrhea, and nausea, particularly for those who are new to using it or consume large amounts at once.

This occurs because MCTs are rapidly absorbed and processed by the liver, sometimes overwhelming the digestive system and leading to loose stools or irritation. One review on MCT oil’s role in athletic performance found that high doses could cause significant GI distress.

In one study, participants who consumed an excessive amount of MCTs reported digestive distress, leading researchers to suggest that keeping intake below 30 g per day may help minimize these effects. To avoid discomfort, it’s best to start with a small amount (1 teaspoon) and gradually increase intake as the body adjusts.

While some people find that MCT oil helps them feel full, others may experience the opposite effect. The body’s response to MCT oil can vary, with some research suggesting that MCT oil may increase ghrelin, a hormone that stimulates hunger. This increase in ghrelin signals the brain to eat, potentially leading to an uptick in appetite.

Some experts speculate that this effect may be due to how quickly MCTs are metabolized—because they are burned for energy rather than stored, the body may compensate by increasing hunger cues.

If your appetite increases after taking MCT oil, adjusting the timing of intake—such as consuming it with meals rather than on an empty stomach—may help regulate hunger levels.

Non-alcoholic fatty liver disease occurs when excess fat accumulates in the liver, potentially leading to inflammation and long-term liver damage.

While MCT oil is a type of saturated fat, it is metabolized differently from long-chain saturated fats found in foods like butter and red meat. Unlike those fats, MCTs are more readily used for energy rather than stored. However, excessive intake—especially when combined with a high-fat diet—may still contribute to liver strain over time.

Some research suggests that the liver prioritizes metabolizing MCTs, which could lead to increased fat storage from other dietary sources. To minimize potential risks, it’s best to consume MCT oil in moderation and as part of a balanced diet.

MCT oil is calorie-dense, providing approximately 120 calories per tablespoon. While some people incorporate it into their diet for potential weight management benefits, consuming too much can lead to unintended weight gain.

Unlike long-chain fats, MCTs are metabolized more quickly for energy, which may slightly increase calorie burning. However, this does not negate the impact of excess calorie intake.

If MCT oil is used as part of a weight loss plan, it’s important to balance overall calorie consumption by adjusting portion sizes of other fats and oils. Moderation is key—most experts recommend limiting intake to one to two tablespoons per day to avoid excess calories.

Though rare, people with sensitivities to coconut or palm oil may experience an allergic reaction to MCT oil. While pure MCT oil is often refined to remove proteins that trigger allergies, trace amounts may still be present, particularly in lower-quality products.

Symptoms of an allergic reaction can range from mild irritation to more severe responses. If you develop symptoms like rash, itching, swelling, or difficulty breathing after taking MCT oil, stop using it and consult a doctor promptly.

Those with known coconut or palm allergies should consult a doctor before using MCT oil to assess their risk and consider alternative supplements.

Unlike coconut and palm oil, researchers suggest that MCT oil does not significantly impact LDL (“bad”) cholesterol, HDL (“good”) cholesterol, or total cholesterol.

However, some studies indicate that it may cause a slight increase in triglycerides, a type of fat found in the blood. While moderate triglyceride levels are normal, persistently high levels can contribute to arterial hardening, increasing the risk of heart disease, heart attack, and stroke.

Individuals with conditions such as diabetes, metabolic syndrome, or hypothyroidism—where triglyceride levels are already a concern—should use MCT oil cautiously.

MCT oil is often used in ketogenic diets, but it may intensify some of the initial side effects of transitioning into ketosis. The keto flu is a set of temporary symptoms that can occur as the body shifts from using glucose to burning fat for fuel.

Some people experience brain fog, headaches, fatigue, nausea, irritability, constipation, or difficulty sleeping within the first week of starting a ketogenic diet. While MCT oil does not cause keto flu, its rapid digestion can contribute to dehydration and electrolyte imbalances, which may make these symptoms more pronounced.

Staying hydrated, replenishing electrolytes, and gradually introducing MCT oil into the diet may help minimize discomfort during this transition.

MCT oil is generally safe for many people, but certain individuals should exercise caution or avoid it altogether. Because MCT oil is processed by the liver, those with liver conditions—such as fatty liver disease or other hepatic disorders—may need to limit their intake, as excessive consumption could place additional strain on liver function. Additionally, MCT oil can raise triglycerides, which may be problematic for individuals with heart disease or metabolic disorders.

Like all supplements, MCT oil has the potential to interact with medications, though research on specific interactions remains limited. If you are taking prescription medications, particularly those for cholesterol management, diabetes, or liver conditions, consult a healthcare provider before adding MCT oil to your routine.

Pregnant or breastfeeding individuals should also avoid MCT oil, as its safety during these stages has not been well studied. Lastly, those with allergies to coconut or palm oil should avoid MCT oil due to the risk of an allergic reaction.

MCT oil is generally well-tolerated, but starting with a gradual approach can help minimize side effects. To avoid digestive discomfort, begin with half a teaspoon per day and slowly increase the amount over time. Taking MCT oil with food may further reduce the risk of stomach upset.

For individuals managing heart conditions, liver concerns, or metabolic disorders, consulting a doctor before use is essential, especially if taking prescription medications. If you experience persistent side effects, such as nausea or gastrointestinal distress, adjusting the dosage or discontinuing use may be necessary.

Moderation is key—excessive intake can lead to unwanted effects, including digestive issues and unintentional weight gain. Used responsibly, MCT oil can be a useful dietary addition, but it’s important to tailor its use to individual health needs.