Shea butter is an off-white or ivory-colored fat extracted from the nut of Shea tree (Vitellaria paradoxa formerly Butryspermum paradoxum, B. parkii and B. paradoxa) [1]. Shea tree is native to the dry savanna belt of West Africa, where it grows wild across a 5000 km wide belt of savanna [2,3]; inhabiting West African countries of Senegal, Burkina Faso, Côte d’Ivoire, Mali, Ghana, Togo, Benin, Nigeria, Cameroon, Niger, and further east into Sudan, Uganda and Ethiopia [4,5]. The West African trees are classified as the subspecies “paradoxa” and the East African one as “nilotica” [6-8].

Shea butter is solid at room temperature with a good buttery consistency. It is edible and is used in food preparation in Africa [9,10] and as a substitute for cocoa butter in chocolate industry [3], although the taste is noticeably different [11]. Shea butter is also renowned for its use as a component of cosmetic formulations [9,12]. There are no reports of allergic reaction owing to consumption of Shea butter or its produce [13,14].

Margarine is a butter mimicry used for spreading, baking and cooking [15]. While butter is made from butterfat of milk, margarine is made principally from vegetable oil and water, and may also contain milk. Like butter, margarine, consists of a water-in-fat emulsion, with tiny droplets of water dispersed uniformly throughout a fat phase which is in a stable crystalline form [16]. Margarine has a minimum fat content of 80%, the same as butter, but unlike butter, reduced-fat varieties of margarine can also be labeled as margarine.

Margarine was formulated in the 19th century as a replacement for butter because of inability of the low class to afford dairy butter [17]. Although the raw material for the original margarine formulation was beef fat, shortages in beef fat supply combined with advances in the hydrogenation of plant materials led to its replacement with hydrogenated vegetable oils [18].

In recent decades, the composition of margarine has changed significantly in efforts to increase its healthfulness; notably in relation to cardiovascular disease. Hydrogenation of vegetable oils has consequently been severely discouraged as it leads to the generation of trans-unsaturated fatty acids which increase levels of LDL, lower levels of HDL and therefore increases the risk of coronary heart disease [19], the leading cause of death [20]. The use of tropical vegetable oils including palm oil, palm kernel oil and coconut oil, which are rich in saturated fatty acid, is progressively reducing hydrogenation in margarine production. Shea butter is a stable solid at room temperature, even in the warm tropics unlike other tropical oils, and will therefore require no hydrogenation for production of margarine. This work therefore presents Shea butter as a more suitable raw material for margarine production than other tropical oils.

Dietary Lipid and Cardiovascular Health

Cardiovascular diseases are the leading cause of global death [20], and are projected to remain the single leading cause of death till 2030 [21]. Cardiovascular diseases are multi-factorial and several risk factors have been identified. These risk factors include: gender, age, physical inactivity, unhealthy diet, family history of cardiovascular disease, tobacco use, excessive alcohol consumption, obesity, raised blood pressure (hypertension), raised blood cholesterol (hyperlipidemia), raised blood sugar (diabetes mellitus), psychosocial factors, poverty and low educational status and air pollution [22-25]. While some of these risk factors such as age, gender or family history are immutable; many important cardiovascular risk factors are modifiable by social change, lifestyle change, drug treatment and prevention of hyperlipidemia, hypertension, and diabetes.

Of the risk factors that can be modified to improve cardiovascular health is healthy dietary lipid [26]. It has become clear that it is the composition and not the total amount of fat intake that affects cardiovascular health [27,28]. While it is evident that the dynamics of cholesterol homeostasis and development of cardiovascular disease are extremely complex and multifactorial [29], researchers maintain that cholesterol intake increases the risks of cardiovascular diseases [29-31]. Also, dietary saturated fatty as well as trans-unsaturated fatty acids increases the risks of cardiovascular diseases as they both raise levels of LDL cholesterol and lower levels of HDL cholesterol [26,27,32-34].

It is also clear that different type of saturated fatty acids contribute differently to cardiovascular disease [35]. An isotope labeling study in humans [36] concluded that the fraction of dietary stearic acid (18:0) that oxidatively desaturates to oleic acid (18:1) is 2.4 times higher than the fraction of palmitic acid (16:0) analogously converted to palmitoleic acid (16:1). This demonstrates that dietary palmitic acid (16:0) contributes to progression of cardiovascular disease than stearic acid (18:0). Also, in a systemic review of clinical and epidemiological studies [37], dietary Stearic acid (18:0) was found to be associated with lower LDL and directionally lower total cholesterol/HDL cholesterol ratio compared to any other saturated fatty acid. Substitution of Stearic acid (18:0) for trans-unsaturated fatty acid also decreased LDL cholesterol, increased HDL cholesterol and decreased the total cholesterol/HDL cholesterol ratio. However, when compared with unsaturated fatty acids, Stearic acid raised LDL cholesterol, lowered HDL cholesterol, and increased the total cholesterol/HDL cholesterol ratio. It was thus concluded that Stearic acid (18:0) is a reasonable substitute for trans-unsaturated fatty acids and cholesterol-raising saturated fatty acids for solid fat applications.

Composition and Properties of Shea Butter

In addition to a stearic and oleic acids rich saponifiable fraction, Shea butter contains an unsaponifiable fraction composed of bioactive substances that are responsible for its medicinal properties [38]. These bioactive compounds are majorly triterpene alcohols, with some hydrocarbons, sterols, and other minor components such as vitamin E [39-42]. The saponifiable triglyceride fraction of Shea butter constitutes about 90% by mass of the butter [39-43] and is composed primarily of stearic and oleic acids with lesser amounts of palmitic, linoleic and arachidic acids [44]. While Shea butter has about 50% of its fatty acid saturated, about 83% of the saturated fatty acid is made up of stearic acid [44], the least deleterious of the saturated fatty acids [37] (Table 1).

Table 1: Chemical composition of Shea butter; Source: [41,45,46].

Shea butter has a relatively high melting point compared to other vegetable oils. When contrasted with highly unsaturated vegetable oils like grape seed oil, olive oil, canola oil and soybean oil that have saturated fatty acid fraction less than 20% [47-50], the elevated melting point of Shea butter can be attributed to its high saturation [51]. However, Shea butter melts between 51°C and 56°C; a temperature much higher than the melting points of highly saturated tropical vegetable oils like palm oil (35°C), palm kernel oil (24°C) and Coconut oil (24°C). This is because the saturated fatty acid fraction of Shea butter is majorly constituted by stearic acid while that of palm kernel oil, palm oil and coconut oil is majorly constituted by lauric, palmitic and lauric acids respectively [49]. Lauric and palmitic acids are of shorter carbon chains, hence have lower melting points, than stearic acid [52,53].

The high melting point of Shea butter can also be in part due to its high content of unsaponifiables which make up 8-10% of Shea butter [38]. These unsaponifiables are majorly triterpene alcohols and sterols [39-42], which have high melting points [54].

Margarine and its Ingredients

Margarine is basically a water-in-fat emulsion [16] made from vegetable oil or animal fat, mixed with skim milk, salt, and emulsifiers like lecithin [55,56]. The vegetable oils are hydrogenated by passing hydrogen through the oil in the presence of a nickel or palladium catalyst, under controlled conditions [57]. The hydrogenation process increases the melting point of (“Harden”) the oil by reducing the unsaturated bonds (alkenic double C=C bonds) to saturated C-C bonds [58]. While the Soft vegetable fat spreads and Margarines in bottle can circumvent hydrogenation by making use of tropical oils like palm oil, coconut oil and palm kernel oil that are naturally rich in saturated fatty acids and are semi-solid at room temperature, hard margarines, used for cooking and baking, unavoidably requires hardening to increase its melting point [59].

Shea Butter versus Other Tropical Oils as Raw Material for Margarine

While the manufacture of margarine requires a vegetable fat that is solid at room temperature, most vegetable oils are liquid at room temperature. Increasing the melting point of such oils through partial hydrogenation leads to the generation of trans unsaturated fatty acids which increases the risk of cardiovascular diseases [19]. To reduce hydrogenation in margarine production, tropical oils like palm oil and palm kernel oil, with high melting points are increasingly gaining application in margarine production [60]. However, while this tropical oils which are semi solid at room temperature, are saturated enough to eliminate the need for hydrogenation in the production of softer tub margarines, the production of solid block margarines that are required for cooking and baking, requires further saturation [59]. Hence hydrogenation is unavoidable even with the use of such oils.

Shea butter, by contrast, is a stable solid at room temperature and will remain a solid even at a temperature as high as 50°C [61]. The use for Shea butter for the production of margarine will therefore require no further hardening. Hence no generation of trans unsaturated fatty acids. This will consequently eliminate the risk of cardiovascular disease associated with the consumption of trans unsaturated fatty acids in margarine. Albeit, the mechanisms through which trans unsaturated fatty acids contribute to cardiovascular disease are still poorly understood, research has shown that trans unsaturated fatty acids are more deleterious to cardiovascular health than the highly denounced saturated fatty acids [37,62,63].

Also, stearic acid, which constitutes the saturated fraction of Shea butter [49], is considered the least deleterious of the saturated fatty acids [36,37]. Therefore, the use of Shea butter for the manufacture of margarine will not only eliminate trans unsaturated fatty acids from the product but will also make use of the healthiest saturated fatty acid as a source of “hardening” in the product. Another edge Shea butter has over other tropical vegetable oil with regards to cardiovascular health is that it is exceptionally high in unsaponifiables and these unsaponifiables have been credited for anti-hypercholesterolemic activities in experimental animals [64,65].

Finally, looking from the manufacturers’ point of view, Shea butter as a raw material for margarine production will reduce cost of production as it does not require hardening. The cost of hydrogenation will thus be eliminated (Table 2).

Table 2: Shea butter versus other tropical oils as raw material for margarine.

Due to its high stearic acid concentration and high melting point, Shea butter as a raw material for margarine production is healthier, as regards to cardiovascular health, than other vegetable oils because it eradicate the presence of the much criticized trans unsaturated fatty acids from the product while it making use of the least deleterious saturated fatty acid. The unsaponifiable fraction of Shea butter also contributes to cardiovascular health. The exclusion of hydrogenation process, which is otherwise used for “hardening” vegetable oils, will reduce the cost of production of margarine from Shea butter.

A huge thank you goes to Pastor David Adebayo his encouragement and kindness. The guidance of Professor OB. Ajayi is highly appreciated.