What Is Bitter Orange, and Does It Aid Weight Loss?

The bitter orange plant thrives in subtropical regions but can withstand adverse environmental conditions like frost for short periods (2).

Oval or oblong in shape, the fruit is red-orange when ripe and has a distinctively thick, dimpled skin. True to its name, it’s very bitter (2).

There are 23 cultivars of the fruit, the most prominent of which is Bergamot. You can expect some varieties to be more bitter than others.

Bitter orange contains several potent plant compounds that are sometimes extracted from the dried peel to make dietary supplements. The patented extract of bitter orange, p-synephrine, is sold in capsule form as the herbal weight loss supplements Advantra Z and Kinetiq (4).

Essential oils and powdered and liquid supplement forms are available as well.

Summary

Bitter orange is a citrus fruit with dimpled skin and potent plant compounds that are extracted and used in a variety of supplements.

The plant compounds in bitter orange, which are called protoalkaloids, have been used for over 20 years in supplements for weight loss, athletic performance, skin care, appetite control, and brain health, as well as perfumery (1, 2, 3, 5, 6, 7, 8).

Synephrine (p-synephrine)

P-synephrine, the main extract from bitter orange, has a similar structure to ephedrine, the main component of the herbal weight loss supplement ephedra (8).

This supplement was banned by the U.S. Food and Drug Administration (FDA) because it raised blood pressure, increased heart rate, and caused heart attacks and stroke among some consumers (1, 3, 7).

In addition, p-synephrine is structurally similar to your flight-or-fight hormones, epinephrine and norepinephrine, which also increase your heart rate (1, 4).

As such, the safety of bitter orange extract has been called into question.

However, several studies have shown that bitter orange extracts and the plant’s natural uses neither harm your heart and nervous system nor excite nervous system activity, as some stimulants do (3, 4, 5, 6, 7, 9).

Furthermore, at least one study has claimed that p-synephrine shouldn’t be classified as a stimulant (4).

P-synephrine is also found in other citrus fruits and their juices, such as mandarins and clementines (4, 7).

Limonene

Like other citrus fruits, bitter orange provides limonene — a compound shown to have anti-inflammatory and antiviral properties (10, 11, 12).

Population studies suggest that limonene may prevent certain cancers, namely colon cancer. However, more rigorous human research is needed (13).

An ongoing study is also exploring the use of limonene as a treatment for COVID-19. However, the results are not yet known. Bear in mind that limonene cannot prevent or cure COVID-19 (12).

Octopamine (p-octopamine)

Another protoalkaloid found in bitter orange is p-octopamine. However, little to no p-octopamine exists in bitter orange extracts. Moreover, it’s thought to be metabolized very rapidly in your liver when consumed from the whole fruit (3, 5).

Likewise, it doesn’t appear to exert any beneficial or adverse effects on your body.

Other compounds

The leaves of the bitter orange plant are rich in vitamin C, which acts as an antioxidant. What’s more, its peel has a high content of flavonoids, which are potent antioxidants with high medicinal value (2, 14).

Antioxidants are substances that may protect your body from disease by preventing cell damage. They work by deactivating free radicals, which are unstable compounds that damage your cells, increasing inflammation and your disease risk (15, 16).

Summary

Protoalkaloids are plant compounds found in bitter orange that have anti-inflammatory and antiviral properties. They have been shown to be safe for consumption.

Bitter orange and other citrus varieties show potential for weight loss, but there’s limited evidence on their effectiveness (1, 5, 6, 8, 17, 18).

Many weight loss supplements use bitter orange extracts in combination with other ingredients. However, scientific studies have not thoroughly examined the composition of these supplements to determine which ingredient, if any, supports weight loss.

Notably, p-synephrine has been shown to increase fat breakdown, raise energy expenditure, and mildly suppress appetite, all of which may contribute to reduced weight.

Yet, these effects occur at high doses that are discouraged due to the lack of safety information (4, 8, 18).

Thus, more studies on bitter orange’s weight loss properties are needed.

Summary

Although bitter orange extracts are often included in weight loss supplements, there’s limited evidence to support their effectiveness.

Bitter orange and its extracts are used in Traditional Chinese Medicine (TCM) to treat indigestion, diarrhea, dysentery, and constipation. In other regions, the fruit is used to treat anxiety and epilepsy (3).

Nonetheless, there’s limited evidence to support these uses.

There’s also insufficient evidence to support any uses for symptoms of premenstrual syndrome (PMS) (1).

Although a study in older rats suggested that flavanone compounds in citrus fruits and juices may improve thyroid function, it cannot be assumed that they’ll exert the same effects in humans (19).

All the same, given the high vitamin C content of bitter orange, it’s presumed that this fruit may improve skin health. Vitamin C’s role in wound healing and collagen formation is well established (16).

Another study noted that the bitter orange compound p-synephrine may improve athletic performance though by increasing total reps and volume load, or your ability to train harder (20).

Summary

There’s insufficient evidence to support the effectiveness of bitter orange and its extracts for its numerous medicinal uses.

There’s conflicting information about whether synephrine, one of bitter orange’s natural compounds, should be considered a stimulant. A stimulant is a substance that increases your heart rate and blood pressure (1).

Several sports organizations, such as the National Collegiate Athletic Association (NCAA), list synephrine as a stimulant. Thus, it’s regarded as a banned substance in athletics (1, 21).

Furthermore, one study determined that bitter orange juice contains furanocoumarin, a compound that may cause the same medication interactions as grapefruit juice (22).

Therefore, people taking decongestants or those who have high blood pressure, an irregular heartbeat, or glaucoma should avoid the juice and fruit of bitter oranges. It’s unclear whether bitter orange supplements pose this risk (5).

Summary

Despite numerous studies showing that bitter orange extracts are not stimulants, widespread controversy exists, and the NCAA has listed it as a banned substance. Bitter orange may also interact with certain medications.

Generally, bitter orange extracts in dietary supplements are safe to consume in doses of 50–98 mg per day (1, 23).

One study showed that 40 mg of synephrine combined with 320 mg of caffeine is a safe dose of these combined ingredients (3).

In another study, eating a whole bitter orange containing 30.6 mg of p-synephrine revealed no interactions with medications (24).

Still, people who are pregnant or breastfeeding should avoid bitter orange due to a lack of safety information (1).

summary

Bitter orange is likely safe in doses ranging from 30.6 mg of synephrine in the fruit itself to 98 mg in dietary supplements, although additional research is required.

Bitter orange is quite tart and unlikely to be eaten raw.

Naturally high in pectin, a gelling agent, the fruit’s primary culinary application is for making marmalade (2, 25).

Bitter orange oil is also used as a flavoring or additive for the following:

• preservatives (jellies)
• candy (chewing gum, hard candy, and candied fruit)
• desserts (ice cream, pies)
• sauces and chutneys
• salad dressing
• fermented wine

The juice of the bitter orange can be used as a marinade to flavor fish and meat. In some regions, it’s used similarly to vinegar (2).

What’s more, the extracted oils give a distinctive flavor to liqueurs like Grand Marnier (2).

In China, bitter orange is used to make herbal teas and medicines.

Other uses

Bitter orange has several other household uses outside of the kitchen. These include (2):

• soap substitutes
• essential oils (including neroli and petitgrain)
• perfumery
• traditional medicine (such as antiseptics and hemostatics)

Summary

Bitter orange is a citrus fruit with several household and industrial uses, ranging from food additives to perfumery. It’s primarily used to make marmalades and jellies due to its high pectin content.

Bitter orange is a citrus fruit that’s often processed into an extract. It has several culinary uses as well, though it’s rarely eaten whole.

Although bitter orange supplements are widely considered safe at common doses, there’s inconclusive evidence for their efficacy for weight loss, thyroid health, and skin care.

You may want to avoid this fruit and its extracts if you have high blood pressure, an irregular heartbeat, or glaucoma. Likewise, bitter orange supplements are banned for NCAA athletes.