Let’s talk about cholesterol. In clinical practice, we are often faced with the challenge of analyzing blood test results for breastfeeding women. Increasingly, we are seeing breastfeeding mothers at a more advanced age and, therefore, more likely to have comorbidities. Dyslipidemia is one of the most frequent in our context.

Blood cholesterol during lactation

We have carried out a literature review of the studies published on cholesterol levels during lactation.

During pregnancy, plasma cholesterol and triglyceride levels increase progressively from the first trimester of pregnancy and may reach peak levels around 35 and 37 weeks (1).

Cholesterol is an essential part of cell membranes for the synthesis of steroid hormones, such as progesterone, and a precursor of metabolic mediators. It is, therefore, essential for fetal growth and development. The fetus obtains cholesterol endogenously (by synthesizing cholesterol) and from the mother through maternal lipoproteins transported across the placenta (2).

Although we are aware that blood cholesterol levels increase during pregnancy, we still do not have enough studies to establish normal or acceptable cholesterol levels at this stage. Therefore, it is not routinely measured in pregnancy control, nor is it treated. Some authors have estimated a mean value of around 260 mg/dL of total cholesterol at the end of pregnancy (3,4).

In the weeks after giving birth, during the postpartum, cholesterol levels decrease, although it is estimated that normal levels are not established until 6 weeks after birth (5).

Human milk contains cholesterol, and it is estimated that 20% is produced in the mammary gland itself, while the remaining 80% comes from the maternal bloodstream (6). Therefore, breastfeeding could help to establish total and LDL cholesterol levels after birth as it represents a physiological excretion pathway for triglycerides and cholesterol (7). This release of large amounts of cholesterol into breast milk could reduce maternal blood cholesterol concentrations. Some authors have measured up to an excretion of 15-20 mg of cholesterol per 100 mL of milk, which would be equivalent to approximately 150 mg of cholesterol per day (8), but these studies were performed in the 1980s, and we do not have recent studies to confirm this estimate.

In addition, during lactation, there appears to be increased catabolism of very low-density lipoproteins (VLDL and LDL) and the generation of a greater number of high-density lipoprotein (HDL) components (9), improving the maternal blood lipid profile after pregnancy, although again, we do not have more recent studies to confirm these hypotheses.

Kallio et al. 1992 demonstrated that maternal blood cholesterol levels decreased in women who exclusively breastfed between two and six months of lactation, from six months onwards, cholesterol levels remained consistently low and returned to normal levels after weaning (10). This study reinforces the hypothesis that breastfeeding helps to re-establish the abnormal metabolic changes produced during pregnancy, in this case, hyperlipidemia. Still, again, there are no recent and more robust studies to confirm these findings.

Conclusions

In conclusion, total cholesterol levels are expected to increase during pregnancy and decrease after birth. Breastfeeding could help to restore cholesterol levels to normal.

More research and studies on this subject are extremely necessary in order to establish normal values for total cholesterol, LDL, and HDL cholesterol in pregnant and lactating women so that these parameters can be routinely measured and real cases of hyperlipidemia can be treated.

 

References

1. Bartels Ä, Egan N, Broadhurst DI, Khashan AS, Joyce C, Stapleton M, et al. Maternal serum cholesterol levels are elevated from the 1st trimester of pregnancy: A cross-sectional study. J Obstet Gynaecol (Lahore). 2012 Nov;32(8):747–52.
2. Cantin C, Fuenzalida B, Leiva A. Maternal hypercholesterolemia during pregnancy: Potential modulation of cholesterol transport through the human placenta and lipoprotein profile in maternal and neonatal circulation. Placenta [Internet]. 2020 May 1;94:26–33.
3. Contreras-Duarte S, Carvajal L, Fuenzalida B, Cantin C, Sobrevia L, Leiva A. Maternal Dyslipidaemia in Pregnancy with Gestational Diabetes Mellitus: Possible Impact on Foetoplacental Vascular Function and Lipoproteins in the Neonatal Circulation. Curr Vasc Pharmacol. 2017 Nov 20;17(1):52–71.
4. Leiva A, Salsoso R, Sáez T, Sanhueza C, Pardo F, Sobrevia L. Cross-sectional and longitudinal lipid determination studies in pregnant women reveal an association between increased maternal LDL cholesterol concentrations and reduced human umbilical vein relaxation. Placenta. 2015 Aug 1;36(8):895–902.
5. DM J, M P, J R-C, MA R, H M, F G. Longitudinal study of plasma lipids and lipoprotein cholesterol in normal pregnancy and puerperium. Gynecol Obstet Invest. 1988;25(3):158–64.
6. Ontsouka EC, Albrecht C. Cholesterol Transport and Regulation in the Mammary Gland. J Mammary Gland Biol Neoplasia. 2014;19:43–58.
7. Perrine CG, Nelson JM, Corbelli J, Scanlon KS. Lactation and Maternal Cardio-Metabolic Health. Annu Rev Nutr. 2016 Jul 17;36:627.
8. Kallio MJ, Siimes MA, Perheentupa J, Salmenperä L, Miettinen TA. Cholesterol and its precursors in human milk during prolonged exclusive breast-feeding. Am J Clin Nutr. 1989 Oct 1;50(4):782–5.
9. IA Q, XR X, YR L, HY B, MI C. Hyperlipidaemia during normal pregnancy, parturition and lactation. Ann Acad Med Singapore. 1999 Mar 1;28(2):217–21.
10. Kallio MJT, Siimes MA, Perheentupa J, Salmenperä L, Miettinen TA. Serum cholesterol and lipoprotein concentrations in mothers during and after prolonged exclusive lactation. Metabolism. 1992 Dec 1;41(12):1327–30.