In total, 69 plant species (identified at least to genus level) and 21 other treatments were identified. Nineteen plants and remedies mentioned by interviewed people could not be identified, but are listed with their local KiKongo names in (Additional file
1: Tables S1-S4). The species belong to 36 plant families but predominantly from Fabaceae (14 species) and Euphorbiaceae (10 species). None of the identified plants is listed as endemic to the area, but 11 are naturalised [
22]. Unless we focussed on plant species used to affect breast milk production, on occasion, the informants also recommended food and treatments, which were used. These are also listed and discussed in this study.
Increasing lactation
To increase or promote lactation, 39 plants (at least identified to genus level), 11 other edibles and medicines, and nine plants only known from their local name (Additional file
1: Table S1), were recorded in 61% of the 259 interviews. The 39 identified plants represent 25 different plant families.
In 57% of the interviews,
Manihot esculenta was mentioned as a galactagogue followed by
Arachis hypogaea L., (47%), and
Sesamum indicum L. (12%). Fish (7%),
Elaeis guineensis (7%), and
Saccharum officinarum L. (5%) were as well mentioned more frequently compared to other plants, food, and medicine (Table
1).
Table 1
The most frequently named plants, foods, and treatments to increase lactation or promote breast milk production
Manihot esculenta Crantz | Cassava | L, R | 148 | 0.568 |
Arachis hypogaea L. | Peanut | S | 95 | 0.367 |
Sesamum indicum L. | Sesame | S | 31 | 0.12 |
Fish | Fish | | 18 | 0.069 |
Elaeis guineensis Jacq. | Oil palm | S | 17 | 0.066 |
Saccharum officinarum L. | Sugar cane | St | 12 | 0.046 |
The treatments include a number of many different components, including the infusion of a bird’s nest, or the intake of minerals like salt. Furthermore, the decoction of a medical clay called Pemba, together with a bone, was recommended for women with poor breast milk production (Additional file
1: Table S1). In previous literature
Abrus precatorius [
26,
27],
Arachis hypogaea [
10],
Euphorbia hirta [
24‐
26],
Manihot esculenta [
10],
Milicia excelsa [
10,
24], and
Vitex doniana [
10,
24] have been reported as galactagogues.
The energy provided by most frequently cited plants and food can help the mother to meet the increased nutritional needs during lactation. The leaves and root tubers of
Manihot esculenta are used as important food in sub-Saharan African communities [
37]. The leaves are rich in protein, carotenoids, thiamine, riboflavin and minerals [
38], whilst the root tuber is rich in starch [
39]. The root is mostly consumed raw to promote or increase lactation. The plant produces linamarin, which can induce cyanide production. The leaves contain more linamarin than the root. Therefore, proper preparation is advised [
40] and the long term consumption of a low level of linamarin can cause goitre or kinds of neuropathy [
40,
41], but a good supply with S-containing amino acids is said to have a positive effect on the detoxification of cyanite in the body [
41]. The occurrence of linamarin in cassava could be the reason why it was mentioned in a few interviews (3%) as food, which should be avoided during lactation.
The seeds of
Arachis hypogaea are rich in fat (49 g) and protein (26 g). Of the total fat, 24 g in 100 g seeds are monounsaturated fatty acids, and around 16 g are polyunsaturated [
42]. Among other minerals and vitamins, peanuts contain thiamine, riboflavin, folate and vitamin B6 [
42] which are beneficial for the infant or the nursing mother [
9]. Arya et al. (2016) stated that the fat of peanuts provides healthy calories to malnourished infants and children [
43].
The seeds of
Sesamum indicum also contain a high level of proteins and fatty acids most of which are polyunsaturated [
44]. Sesame is the third most recommended galactagogue.
Contradictory statements exist about the effect of additional intake of proteins during lactation on the amount of protein in the breast milk [
45]. However, the proteins present in the breast milk are produced in the mammary gland and in the blood of the mother [
45]. The protein fraction of the mother’s milk additionally contains immunoglobulin, lactoferrin and lysozyme, which play an important role in the defence against pathogens [
31]. The dominant carbohydrate in the breast milk is lactose, which is synthesised by the mother. Nevertheless, maternal intake of carbohydrates seems not to affect the concentration in the breast milk [
45,
46].
The fat component is the most variable component of the breast milk and is related to the nutritional status of the mother. The milk of well-nourished mothers has a higher fat content than that of other mothers [
45,
47]. It is widely proven that the maternal intake has an influence on the fatty acid composition of the breast milk [
48]. To identify whether a woman’s breast milk has a good quality, four informants from different municipalities recommended to put a cockroach into a pot with breast milk to test the quality. If the cockroach is still alive after 5–30 min (the time varies depending on the informant) the milk has a good quality. There is no scientific explanation for it and we have not tested it either.
Only a small number of studies have been undertaken to examine the effect of herbal galactagogues on human breast milk production and the effect on mother and infant [
15,
49]. Therefore, the effect for most galactagogues herbs on the breast milk production has not been proven, and reasons for the use of the identified plants remain speculative. Furthermore, herbals as well as chemical drugs should be used with caution during lactation to avoid overdosing and as a result to be protected against unwanted side-effects [
50].
It is striking, that the galactagogues most frequently used by informants have a high nutritional value, but the effect of additional intake of carbohydrates and proteins even for malnourished women on the breast milk quantity is not adequately clarified.
Cleaning breast milk
As no equivalent scientific expression is available for the term “cleaning the breast milk” that is frequently used by women, we asked for a definition. According to the interviewees, the breast milk needs to be cleaned when it appears to be watery because this provokes diseases like diarrhoea.
In 220 interviews informants were asked about “milk-cleaning” plants, food, and treatments. We could identify 33 plant species that were thought to clean maternal milk. For three plants that could not be identified only the local name is available.
Spondias mombin L. (36%),
Vernonia amygdalina (11%),
Carica papaya L. (7%), and
Elaeis guineensis (7%) were the plants and medicines most frequently named in the interviews to “clean” aqueous or diarrhoea-causing breast milk (Table
2).
Carica papaya and
Momordica charantia L. are the only plants previously recorded as breast milk “cleaning” plants used by mothers in this area [
51]. Additionally, Göhre et al. (2016) recorded
Euphorbia thymifolia L. as a plant used by the local population to “clean” diarrhoea causing breast milk [
52].
Table 2
The most frequently named plants, foods, and treatments to clean the breast milk production
Spondias mombin L. | Yellow mombin | L, B | 80 | 0.364 |
Vernonia amygdalina Delile | Bitter leaf | L | 24 | 0.109 |
Carica papaya L. | Papaya | L | 15 | 0.068 |
Elaeis guineensis Jacq. | Oil palm | S | 15 | 0.068 |
Morinda morindoides (Baker) Milne-Redh. | – | L | 10 | 0.045 |
Abrus precatorius L. | Jequirity bean | L | 9 | 0.046 |
The composition of breast milk varies over time and always fits the specific needs of the child. Especially the concentration of protein, fat, minerals and other components changes from the beginning to the end of the lactation period [
31,
53]. The foremilk, which is secreted in the first minutes of every breast meal, has a high water content to quench the child’s thirst [
31]. Therefore, this milk can be described as aqueous. Nevertheless, this milk should not cause diarrhoea. Several reasons may exist for diarrhoea in infants such as viruses or bacteria that can be easily transmitted by faecal residuals on surfaces, or by other people’s skin parts like the mother’s breast. In general, breast milk does not cause diarrhoea in infants. Other reasons for acute diarrhoea can be drugs, or poisons, or the immediate onset of hypersensitivity reactions. The reasons for chronic or persistent diarrhoea vary from parasite infections over food allergies, autoimmune disorders or other infections, to specific enzyme defects [
5]. Malnutrition can contribute to the outbreak of diarrhoea [
6].
Parts of
Spondias mombin L., but especially the leaves, were mentioned in 36% of the interviews in relation to milk “cleaning” plants and in 3% of the interviews about galactagogues. In one interview, the participants did not recommend this plant for nursing mothers but in former studies, it had a positive effect on the initiation of breast milk secretion in West African dwarf (WAD) ewes [
54]. The plant should not be used in high dosage over a long period, because it might cause hepatic and renal injury. This effect was reported in a study investigating the toxicological effects of
Spondias mombin in adult male Wistar rats [
55]. This finding can be related to the doctor’s statement that some women show signs of poisoning after they treated themselves with this plant. On the other hand, the leaf extract of
Spondias mombin shows antimicrobial [
56,
57] and antiviral activity [
58]. In Nigeria, it is also used as a treatment for diarrhoea [
59]. This might explain the high frequency of uses for this species to “clean” the breast milk.
The antimicrobial activity of some plants could explain the use of these plants for milk “cleaning” purposes. For instance, extracts of
Carica papaya [
60],
Spondias mombin [
56,
57],
Euphorbia hirta [
61] or
Azadirachta indica A. Juss [
62] show antimicrobial properties among others. Further studies are needed to explore whether some of their antimicrobial substances are transferred in the breast milk and have an antimicrobial effect against several pathogens inside the infant.
To avoid
Complementary to the former aspects of treatments in 236 interviews the informants were asked about plants, food, and treatments, which should be avoided during breastfeeding periods. In 42% of the interviews, in total 32 plants (29 identified, three unidentified) and 11 other food and habits were mentioned that should be avoided during lactation period (Additional file
1: Table S3).
Dried fish was named in 16.1% of the interviews, followed by
Mangifera indica L. (7.2%), and
Salacia erecta (G.Don) Walp. (5.1%, Table
3). Dried fish was often described to cause watery milk and diarrhoea in children. In fact, many of the plants, foods, and treatments described were assumed to cause watery milk and diarrhoea in the child. According to the information provided, breast milk will dry up when the mother consumes
Monodora myristica (Gaertn.) Dunal or
Salacia erecta.
Table 3
The most frequently named plants, foods, and treatments which should not be eaten or applied during lactation period
Fish | Fish | | 38 | 0.161 |
Mangifera indica L. | Mango | F | 17 | 0.072 |
Salacia erecta (G.Don) Walp. | – | L | 12 | 0.051 |
Elaeis guineensis Jacq. | Oil palm | F, O | 10 | 0.042 |
Goat | Goat | | 10 | 0.042 |
Cucurbita spec. | Pumpkin | L, F | 9 | 0.038 |
Similarly rated was the consumption of goat meat supposedly having a negative effect on the child, eventually causing its death. In addition, the consumption of many animal products like eggs, pork or the meat of antelope, birds, chicken, goat, or fish was not recommended for lactating women as well as removing birds’ nests and the consumption of bitter plants, salt, or meat with vegetables.
Several studies showed, that phytochemicals can be transmitted from the mother to the child by breast milk and have an effect on the infants’ health [
63,
64]. However, phytochemicals can also be toxic for other organisms than for the producing one – and thus also for humans [
65]. Nevertheless, only few adequate studies are available, which observe the risk of herbal treatments during lactation for the infants health [
15,
49,
66]. The plants mentioned in this study are probably avoided because they also reduce milk production (e.g.
Monodora myristica,
Salacia erecta). The prohibition of the consumption of several foods and plants can also have traditional reasons explained later.
Reduce lactation
In 124 interviews, the informants were asked about information on plants, foods, or treatments, which are used to reduce the breast milk production. The informants recommended 17 identified plant species, 3 unidentified plants, 4 habits and the consumption of fish (Additional file
1: Table S4).
Monodora myristica was named in three interviews (2.4%) and is therefore the most commonly used remedy for breast milk reduction. Other common remedies are
Abrus precatorius L.,
Saccharum officinarum, and
Salacia erecta (Table
4).
Table 4
The most frequently named plants, foods and treatments to reduce the breast milk production
Monodora myristica (Gaertn.) Dunal | Calabash nutmeg | S | 3 | 0.024 |
Abrus precatorius L. | Jequirity bean | L | 2 | 0.016 |
Saccharum officinarum L. | Sugar cane | St | 2 | 0.016 |
Salacia erecta (G.Don) Walp. | – | L | 2 | 0.016 |
Clean the body | – | | 2 | 0.016 |
Reduced food intake | – | | 2 | 0.016 |
Common herbs, which are used to decrease lactation in other countries, are peppermint, sage and parsly [
50]. In only 19% of the interviews, respondents recommended plants, food, or treatments at all.
Monodora myristica, the plant that mentioned most frequently, is only recommended in 2.4% of the interviews. This indicates the minor importance of plants, foods, and treatments to reduce breast milk production. Additionally, the four most recommended plants are also mentioned in other use categories but with higher frequency. In 1.6% of the interviews, a reduced food intake was recommended to decrease lactation. A decrease of milk in animals by reducing the energy supply could be documented in some studies, but the reduction of energy intake in lactating mothers is not adequately investigated yet [
53].
Ethnological perspective
Little research has been conducted with respect to the cultural habits of the local population in the study area. An important exception is Laman’s study of the Bakongo people in the Lower Congo region. In his research, although concentrating on an area outside of our study region, Laman reports many cultural habits of the BaKongo people in the Lower Congo region [
67‐
69]. As an example, women lacking milk production after birth drink a mixture that includes nzeke-nzeke [
68]. This plant most probably is similar to
Craterispermum spec., in our study called nseka-seka, and identified inter alia for increasing or promoting lactation. The consumption of salt, pepper and other tasty things is also recommended for women with lactation problems [
68]. In two interviews, salt was mentioned to promote or increase lactation. Additionally, five galactagogue plants were suggested to be taken or prepared together with salt. In contrast, Laman also notes that coarse salt should not be eaten by nursing mothers because the milk will be curdled and the child will fall ill [
69]. Compared with our findings, salt is more often recommended to increase or promote lactation, instead of the opposite.
Due to prohibitions which are part of the BaKongo culture, several plants, foods, and treatments are forbidden for a certain person or a group of people [
67‐
69]. However, in other cultures, restrictions especially for nursing mothers exist as well [
70,
71].
Pork, for instance, plays a special role in the local culture. The meat is prohibited for many people because it is assumed to have negative effects on the body. For example, it is said that if the mother eats pork, the child will fall ill [
69]. While in one interview, pork was reported as a food that should be avoided during the breastfeeding period, three other persons, recommended pork as a galactagogue. In fact it does have nutritional benefits for the nursing mother because of its high content in protein, fat, iron, zinc and B vitamins like Thiamin [
72], but can also be contaminated by parasites, which has a negative effect on the mothers’ well-being [
73].
Laman documents, that the Nkabi-antelope or other striped or spotted animals are often banned for women or certain families as they are said to cause ringworm rash or similar eruptions [
67]. He also notes that the consumption of eggs during pregnancy is forbidden for both the wife and her husband because it will affect the appearance of the child. The consumption of goat and chicken is also not recommended for pregnant women. Generally, for women it is often forbidden to eat the best parts of mammals and fish [
67].
Some of these traditional nutritional taboos may have been preserved and influence the eating habits of the Bakongo people today. This could explain why the consumption of pork, salt, patterned antelope, eggs, and feathered animals like chicken are not recommended for consumption during breastfeeding, which was noted in some interviews. The most common food restriction was the abdication of eating fish noted in 16% of the interviews. In a survey conducted by Kouser Banu et al. (2016) in Tamilnadu (India), fish is also reported as a prohibited food during pregnancy and lactation [
74]. The consumption of fish does have some risk, especially if the fish is not fresh or prepared properly, or is contaminated with bacteria during processing. On the other hand, fish is rich in Group 1 micronutrients like vitamin D, iodine and riboflavin and several Group 2 micronutrients like iron, calcium and zinc [
75]. The amounts of Group 1 micronutrients in the breast milk depend on the intake of these nutrients by the mother. The secretion of Group 2 nutrients into the mother’s milk does not depend on the dietary intake of the mother, but a maternal supplementation with these nutrients is beneficial for her [
75]. Therefore, it is not surprising that fish is also the fourth most common galactagogue recommended in this study (Table
2).
Other documented traditions, like the ban on listening to the wind soughing in bunches of bananas and melon-tree [
69] to prevent the milk from coagulation or child illness, or the consumption of tiba-bananas and binsakulu-tomatoes by the mother along with others, were not mentioned by our informants.
Laman’s research provides an insight into traditional uses of plants, foods, and treatments. However, the recorded prohibitions and food regulations in this study could also have other reasons. Some plants have names, which are related to their usage or their characteristics. For example, “Kimvumina” is the KiKongo word for mother’s milk but also the name of several plants such as
Gongronema latifolium Benth. and
Euphorbia hirta L.. The naming may have its origin in the production and secretion of a white milk sap that is strikingly similar to regular milk, or due to its effect on breast milk production. The use of
Euphorbia hirta as a galactagogue was recorded once in our study but also known from previous studies [
11,
24,
26] and mentioned as a milk “cleaning” plant as well. The latter application could be related to its antidiarrhoeic activity [
76] and antibacterial effects against some gram-positive bacteria, causing enteric infections [
61].
G. latifolium is used in the same way for both as a galactagogue and to “clean” the breast milk. The leaves can be used as a source for important nutrients like proteins [
77] and especially the ethanolic extract of the leaves again has shown antimicrobial activity against some bacteria [
77,
78].
The use of
Azadirachta indica as a milk “cleaning” plant may also be related to its name. Its Portuguese name is “Curatudo”, which can be translated as a cure-all. Therefore, it might be used by local people for many health-related problems. Indeed,
Azadirachta indica is used by many people historically and today for many different applications [
79]. This includes the treatment of diarrhoea and cholera by Indian people [
80], diabetes in Bali (Indonesia) [
81], or stomach pains by locals in the province Uíge in Angola [
51]. The leaf extract has shown antimicrobial activity [
62] even against some multi-resistant microorganisms [
82].
Qualitative analysis of statements made by medical staff
The interviews included four with nurses, and one with a doctor. All medical persons had completed a professional medical training. The nurses stated that the medical resources at their disposal were not sufficient. For several diseases like malaria, they have neither medical tests, nor a microscope for simple testing. They do have the authorisation to prescribe medication and tests. The nurses did not see a problem in the use of traditional medicine, and even knew several of them. The interviewed doctor in the hospital in Uìge, however, saw problems with the traditional treatments applied by women. He experienced cases of slightly poisoned children after the consumption of Spondias mombin leaves. He noted that the wrong dosage of medicinal plants can cause many negative effects on the mother and the child.
The nurses stated that women do not have many problems with lactation. The doctor supported this assessment. He said that most women breastfeed their children very often and over a long period. Furthermore, in cases when the mother does not have enough breast milk, this is often caused by a chronic disease such as hepatitis, or other diseases like breast cancer or mastitis. In these cases, the infant receives a therapeutic breast milk substitute, such as F75 [
33], which was mentioned by the nurse in the hospital. One male nurse recommended Amodiaquin to clean the breast milk. Amodiaquin is a remedy used as a treatment against malaria. The informant testified that malaria is the most common cause of child death in this region.
There is a clear difference between the interviews conducted with the hospital staff members and the local nurses in the villages. The doctor pointed out that the nutrient supply of children is deficient, while for the nurses in the villages malnutrition is not a major problem in this area of the country.
The doctor stated that an unbalanced diet of the mother has an impact on breast milk quality. This can lead to the malnutrition of children who consequently suffer from many diseases that eventually are lethal. Additionally, many childbirths take place in unsanitary conditions, which also has an impact on the high child mortality rate. According to the doctor, a lack of prenatal examinations leads to many children with disabilities.