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Kalonji, also known as Nigella sativa, black seed, and black cumin, is a flowering plant native to Southern Europe, North Africa, and Southwest Asia.

Its seeds have long been used in herbal medicine to treat a variety of diseases and conditions ranging from diabetes to arthritis (1).

More recently, the herb has gained popularity for its purported weight loss benefits.

This article explores whether kalonji can help you lose weight and provides an overview of its health benefits, safety, and side effects.

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What is kalonji?

Kalonji is an annual flowering plant that can grow 8–35 inches (20–90 cm) tall (2).

Its fruits contain numerous black seeds that have been used traditionally in Southeast Asian and Middle Eastern countries to treat diseases and conditions like diabetes, pain, and digestive tract problems (1).

The Prophet of Islam, Muhammad, even believed the seeds to be a remedy for all diseases except death (2).

Today, it’s known that kalonji seeds and oil contain active compounds called phytochemicals, including phytosterols. These have demonstrated a wide range of therapeutic benefits, including weight loss (1).

Kalonji seeds and oil contain active compounds that have demonstrated a wide range of therapeutic benefits, including weight loss.

Can it help you lose weight?

The exact mechanisms through which kalonji promotes weight loss is unclear.

It’s suggested that the active components in kalonji seeds boost weight loss by affecting the expression of specific genes related to appetite control and fat loss (3, 4, 5).

A review of 11 studies in 783 participants with obesity or overweight found that kalonji powder and oil reduced body weight by an average of 4.6 pounds (2.1 kg) and waist circumference by 1.4 inches (3.5 cm) over 6–12 weeks, compared with a placebo (6).

However, these effects were only significant when participants combined kalonji with diet and lifestyle modifications, suggesting that the herb supplements alone aren’t effective for weight loss.

Another review of 13 studies with 875 participants showed that kalonji powder and oil reduced body weight by 4 pounds (1.8 kg) but had no significant effect on waist circumference over 6–13 weeks, compared with placebo (7).

Thus, while kalonji is likely ineffective for weight loss on its own, it may aid weight loss when combined with a low calorie diet.

Indeed, one 8-week study found that women combining a low calorie diet with 3 grams of kalonji oil daily lost 4.6 pounds (2.1 kg) more and shaved an additional 1.2 inches (3.1 cm) from their waistline compared with women receiving a low calorie diet and placebo (8).

It should be noted that physical activity levels weren’t assessed in many of the studies, which potentially also influenced the results.

As such, additional high quality research — like randomized controlled trials (RCTs) — that includes controls for variables like physical activity and diet is necessary to confirm kalonji’s potential weight loss benefits.

Studies suggest that kalonji can aid weight loss when combined with a low calorie diet, but more research is needed to confirm these findings.

May decrease heart disease risk

In addition to its promising weight loss benefits, kalonji contains plant compounds that may benefit heart health.

A review of 5 RCTs found kalonji powder and oil supplements significantly decreased levels of C-reactive protein (CRP) — an indicator of inflammation and heart disease risk — in people with obesity based on body mass index (BMI) (9, 10).

The herb may also reduce heart disease risk through its beneficial effects on blood pressure and blood fat levels.

A review of 11 RCTs demonstrated that kalonji powder and oil significantly decreased blood pressure in people with both high and normal blood pressure after 8 weeks of treatment, compared with placebo (11).

Another review of 17 RCTs found that kalonji oil was effective at significantly reducing LDL (bad) cholesterol, while the powder increased HDL (good) cholesterol in healthy participants and in people with conditions like diabetes, obesity, and high blood pressure (12).

This review also noted that the supplements significantly reduced triglycerides, a type of fat in the blood which in elevated levels increases heart disease risk (13).

Collectively, these findings suggest that kalonji may benefit heart health in a variety of ways.

Kalonji may reduce the risk of heart disease by lowering inflammation and blood pressure, and by improving blood levels of fats like cholesterol and triglycerides.

May promote healthy blood sugar levels

Kalonji may promote healthy blood sugar levels in people with type 2 diabetes.

Type 2 diabetes is a condition where your body doesn’t produce enough of — or can’t efficiently use — a hormone called insulin, which is produced by your pancreas to lower blood sugar levels.

Unmanaged blood sugar levels in people with type 2 diabetes can increase the risk of diseases of the heart, eyes, and kidneys (14).

Kalonji is thought to improve blood sugar management by increasing the action of insulin and delaying the absorption of sugar into the blood (15, 16).

A review of 17 RCTs in people with type 2 diabetes showed that kalonji powder and oil significantly reduced levels of fasting blood sugar, as well as hemoglobin A1c, a marker of 3-month average blood sugar levels (15).

Other reviews have similarly demonstrated significant improvements in blood sugar control in people with type 2 diabetes who took the powder and oil supplements (16, 17, 18).

Still, many of the studies included in these reviews failed to control for factors related to diet and exercise, which may have influenced the results.

Kalonji may help people with type 2 diabetes manage their blood sugar levels by increasing the action of insulin and slowing the absorption of sugar into the blood.

Side effects and dosage

Several studies have assessed the safety of kalonji.

One study in 114 people with type 2 diabetes found no adverse side effects on kidney or liver function in a group that consumed 2 grams of the powder daily for 1 year in addition to their regular medications (19).

Studies have also failed to find adverse side effects on kidney or liver function with the oil in doses of 3–5 mL per day for 8 weeks (8, 20).

However, mild side effects like stomachaches and nausea have been reported with both the powder and oil supplements (6, 7).

In either case, people taking medications for diabetes or a thyroid problem who wish to try kalonji should speak with their medical provider first, as it may interfere with the effectiveness of those medications (21).

Dosing

An effective dose of kalonji for weight loss appears to be 1–3 grams per day of the powder or 3–5 mL of the oil (6, 7).

These doses have also been shown effective for heart health and managing blood sugar levels (12, 15).

There doesn’t appear to be a difference between kalonji seed powder or oil in terms of weight loss effectiveness.

However, the powder appears to be more effective than the oil for increasing HDL (good) cholesterol, possibly related to the powder’s higher concentration of heart healthy fats (12).

Kalonji seed oil and powder are likely safe in doses that have been shown effective for weight loss, heart health, and blood sugar control.

The bottom line

Kalonji is a plant from which the seeds have been traditionally used for the treatment of diabetes, pain, and digestive tract problems, among other diseases and conditions.

It may be effective for weight loss when combined with a low calorie diet.

It may also promote heart health, as well as lower blood sugar levels in people with type 2 diabetes.

While more research is needed to confirm these promising health benefits, kalonji appears to be safe for most people.