Lychee's Role In Heart Health

Overview

Lychee (Litchi chinensis Sonn) is a subtropical fleshy fruit belonging to the soapberry family (Sapindaceae) - referred as the “king of fruits” in its native homeland for its delicious taste, nutritional value, and potential health benefits for individuals with chronic diseases.¹ 

The fruit itself is small and cordate, characterised by an inedible pinkish-brown leathery rind that is rough to the touch.² Once removed, the edible portion of the lychee is revealed, described as an almost translucent, white-creamy pulp that surrounds a dark brown, oblong-shaped seed in the centre. 

Lychee’s origin lies in southern China, specifically the provinces Kwangtung and Fukien, where the written history of its cultivation dates back 2300 years ago, often for their use in traditional Chinese medicine.² To this day, China remains the leading cultivator of Lychee around the world, with other subtropical regions such as India, Taiwan, Thailand, and Vietnam following closely behind. However, whilst the fruits are primarily consumed in south-east Asia, additional scientific backing over potential health benefits has increased popularity in westernised countries. 

Nutritional composition

Whilst the edible lychee pulp is mainly composed of water (~80%) and carbohydrates (~16.5%), the fruit remains packed with copious amounts of beneficial nutrients and active compounds that contribute to improved health.³ For example, a 100-gram serving (3.5 ounces) of fresh lychee pulp will contain - on average - the following main nutrients:³

• Carbohydrates:16.53g
  • The majority of carbs come in the form of sugars, mainly sucrose, fructose, and glucose, giving Lychee’s such a sweet flavour
• Protein: 0.83g
  • Primary amino acids: Methionine (0.009mg) and Tryptophan (0.007mg)
• Fiber: 1.3g
  • 46% Soluble / 54% Insoluble (indigestible) fiber⁴
• Fats: 0.44g
  • Although minor, the common fatty acids found in a Lychee are essential for adequate absorption of soluble vitamins in the body
• Vitamin C: 71.5mg
• Sodium: 1mg
• Potassium: 171mg
• Calcium: 5mg
• Copper: 0.148mg
• Iron: 0.31mg
• Magnesium: 10mg
• Phosphorus: 31mg
• Zinc: 0.07mg

Additionally, lychees are also known to be an abundant source of antioxidant plant compounds called polyphenols and flavonoids. These compounds are shown to protect against the development of chronic conditions through their anti-inflammatory, anti-cancer, hypoglycaemic, and lipid-lowering effects.⁵ 

Heart health and disease

The heart is a vital organ that pumps blood around the body, ensuring our organs and tissue are sufficiently supplied with resources (oxygen and nutrients) needed to function efficiently and equally removing waste products of metabolism at the same time.⁶

However, certain conditions or decisions we make can have a severe impact on our heart and circulatory system, increasing the risk of developing a debilitating or life-threatening ailment; referred to as a cardiovascular disease (CVD). These contributing factors are often split into two categories, modifiable (factors that can be controlled by an individual’s choices) and non-modifiable (factors that cannot be controlled), with examples shown in the following:⁷

Modifiable risk factors

• Smoking
• Physical inactivity
• Unhealthy diet 
• High blood pressure (hypertension)
• Being overweight or obese
• High cholesterol 

Non-modifiable risk factors

• Family medical history 
• Ethnicity
• Age
• Gender
• Air pollution

Cardiovascular disease

According to the latest data from the British Heart Foundation, CVDs cause around 1 in 3 deaths globally, totalling an estimated 20.5 million deaths alone in 2021, with future projections expected to rise further.⁸ There remains one disease that, before the coronavirus, was the single biggest killer for the last 30 years, responsible for 1 in 6 deaths globally, often referred to as coronary heart disease (CHD).

This ailment is caused by the gradual accumulation of fatty substances (cholesterol) on the walls of coronary arteries (vessels supplying blood to the heart), often referred to as atherosclerosis.⁹ Subsequently, over time the artery becomes partially obstructed, hindering blood supply to the heart. As a result, to maintain an adequate supply of blood around the body, the heart increases its workload (Pumps faster) and subsequently causes blood pressure to spike (hypertension).¹⁰

However, if the artery becomes completely blocked off by the atherosclerotic lesion, oxygenated and nutrient-rich blood supply to the heart's tissue is completely prevented, resulting in myocardial infarction (heart attack) and, if left untreated, death.⁹

Lychees benefit heart health 

Lychee consumption's direct effects on heart health have not been directly studied in humans to date, current clinical research - relying primarily on animal studies - suggests the fruit's nutritional components may protect against cardiovascular disease through the mechanism explored hereinafter.

Antihypotensive effects

A study by Rong et al., (2017)¹¹ discovered that the polyphenols in lychee also could reduce vascular oxidative stress (narrowing of blood vessels) by regulating the balance of endothelial nitric oxide (NO) production. This was determined through the use of apolipoprotein E deficient (ApoE-/-) mice - sometimes referred to as atherosclerotic-prone mice - genetically altered to ensure the development of hypercholesterolemia (accumulation of bad cholesterol) and subsequent promotion of atherosclerotic plaque formation.¹²

Researchers found that apoE-/- mice fed procyanidins, extracted from lychee, alongside their high-fat diet resulted in increased expression of endothelial NO synthase; the protein responsible for producing the vasodilator NO. As a result, NO bioavailability is restored, allowing endothelial-dependent relaxation to be maintained and lowering the risk of developing hypertension.¹¹

Furthermore, an additional study also found that the phenolic compounds in insert "lychee could modulate blood"lychee could modulate blood pressure through inhibition of angiotensin I-converting enzyme.¹³ This protein catalyses the conversion of angiotensin I (Ang I) into Ang II and the degradation of bradykinin, which collectively raises blood pressure through mediating vasoconstriction and sympathetic nervous stimulation.¹⁴ 

Antihyperlipidemic and anti-atherosclerotic effects

A study conducted in 2017 using high-fat-diet treated mice reported that lychee pulp extract could facilitate hyperlipidemia - a significant risk factor for atherosclerosis - by alleviating dyslipidemia.¹⁵ This was hypothesised to be because of phenols within the lychee pulp downregulating the expression of microRNA-33 and 122, which are known to regulate the expression of proteins that mediate fatty acid synthesis.

As a result, the levels of low-density lipoprotein-cholesterol (bad cholesterol) within the blood are decreased whilst simultaneously increasing levels of high-density lipoprotein-cholesterol (good cholesterol), thereby alleviating dyslipidemia and subsequently reducing the risk of atherosclerotic plaque development. 

In addition, another study found that procyanidins could alleviate hypercholesterolemia and subsequently ameliorate atherosclerosis in ApoE-/- mice fed on a high-fat diet, by more effectively regulating lipid metabolism.¹⁶

This was determined to be the procyanidin effect on the expression of critical genes involved, namely increasing lipid homeostasis regulators (farnesoid X receptor and its small heterodimer partner) and ATP-binding cassette transporter-1 (which modulates cholesterol efflux) whilst simultaneously decreasing an enzyme that mediates cholesterol biosynthesis (3-hydroxy-3-methylglutaryl-coA-reductase).

As a result, these collective mechanisms lead to more effective lipid metabolism, alleviating hyperlipidemia and atherosclerosis risk.

Incorporating Lychee into a heart-healthy diet

Although the specific cardiovascular benefits lychees provide remain undetermined, the current scientific research remains promising and should not be overlooked. Regardless, it’s clear that this exotic fruit is packed full of nutrients, harbouring many of the essential vitamins and minerals required to live a healthy lifestyle. To obtain all the benefits, current experts suggest you consume two cups of fresh lychee daily, with one cup typically equating to 190-grams (13.4 ounces).¹⁷ 

Note: If you have or are suspected of heart disease - or any other ailment - and want to use lychee to aid symptoms, please consult with a healthcare provider first to ensure you know the precautions and potential adversities associated with its use.

Precautions

Lychee is known to interact with certain medications negatively. It’s recommended to exercise caution if you’re taking any of the following:¹⁸

• Anticoagulants (E.g., Warfarin)
• Antiplatelets (E.g., Clopidogrel)
• Non-steroidal anti-inflammatory drugs (E.g., Ibuprofen)
• Anticancer agents
• Antivirals
• Cardiovascular agents
• Cholesterol or lipid-lowering agents
• Immune-modulating agents
• Pain relievers
• Herbal supplements (E.g., Ginkgo biloba)

In addition, insufficient evidence supporting lychee safety during pregnancy, breastfeeding, or infancy. Therefore, medical advice should be sought before consuming. 

Potential adverse effects

When consumed in accordance with the recommended daily intake mentioned previously, lychees are not known to have any adverse health effects. However, in some rare cases, frequent or overconsumption can lead to pruritus (itchy skin) that develops into urticaria (rash), swelling of the lips or in the throat, dyspnea (shortness of breath), and diarrhoea.¹³ 

In scarce or infrequent circumstances, lychee may cause a severe, life-threatening allergic reaction referred to as anaphylaxis.¹⁹ Nevertheless, it's important to note that, whilst a risk remains, there have only ever been a few cases reported in the scientific literature.^20,22

However, two of these cases reported cross-reactivity - an allergic reaction to the fruit of the same or unrelated families - with the perennial plant mugwort (Artemisia vulgaris). Therefore, if an individual is aware of their allergic reactivity to mugwort or antigens of the Umbelliferae family, it is strongly suggested that they should avoid lychee in all forms.

Furthermore, they should seek consultation with a healthcare professional to be made aware of additional dietary allergens and cross-reactors that may threaten them. They will also likely be advised to carry an emergency kit - consisting of epinephrine, antihistamines, and corticosteroids - at all times in case of an unexpected anaphylactic reaction.¹⁹ 

Lastly, although this only applies to the consumption of immature (unripe) lychee in a malnourished state, outbreaks of hypoglycemic encephalopathy - brain injury due to prolonged periods of low blood sugar (<4 mmol/L) - among children in India were reported in 2014; leading to acute neurological effects (E.g., seizures) and even death.²³

This was later determined to be due to the high concentration of the amino acid hypoglycin-A in the pulp of immature lychee, which disrupts the body's ability to generate the sugar glucose (gluconeogenesis), causing blood sugar levels to drop significantly and subsequent injury to the brain. 

Fortunately, if you are lucky enough to be in a well-nourished and healthy state, with the option to eat ripe lychees, this ailment poses little risk. However, as lychees may lower blood sugar levels, individuals on medications for diabetes should exercise caution or seek medical advice before consumption.

Summary

The subtropical fruit lychee is exotic in appearance, sweet and flowery in taste, and packed full of nutrition. Although current scientific research hints towards the fruit's cardiovascular benefits, further research is required before firm conclusions can be made.

Regardless, delving into a few cups of fresh lychee a day will provide you with most of the vitamins and minerals needed to live a healthy life. However, due to our limited understanding of the fruit, it’s best to consume it in moderation and exercise caution.