Written by Crystal Karges, DTR, CLEC
With the growing concern of obesity in the United States, the implications for breastfeeding women are not completely understood. The frequency of obesity of adult women in the United States, particularly of those women who are considered to be within the reproductive age (20-39 years old), is increasing rapidly. A recent study has analyzed how a high fat diet may alter lactation outcomes, revealing possible complications for mothers who consume high-fat diets during pregnancy or who are overweight or obese.
Several studies have demonstrated the negative effects of obesity on various physiological pathways. Such outcomes resulting from excessive weight gain during pregnancy include increased risk of developing breast cancer, increased birth weights in offspring, augmented probability of developing obesity or metabolic syndrome in their lifetime, development of gestational diabetes, and the possibility of delayed lactogenesis (failure to lactate for more than 72 hours postpartum). This is particularly important for the breastfeeding mother, as delayed onset of lactogenesis has also been correlated with overall shorter duration of breastfeeding. While it has been determined that obesity is a contributing factor to the interference of normal lactation cycles in mothers, the mechanisms within mammary glands that trigger delay of lactogenesis are yet to be understood.
In this recent study by Hernandez et al, the possible mechanisms by which high fat diets effect lactation outcomes were explored on rodent models. These researchers discovered that the mammary glands of rats ingesting a high fat diet had a significant reduction in the number of intact alveolar units within the mammary glands, which are critical for lactogenesis to occur normally. Additionally, it was also concluded from this study that within the mammary gland itself, there was a decline in genes corresponding with the uptake of glucose and development of milk proteins (an essential step for the synthesis of lactose), along with the increase in genes linked with the inflammatory process (a response activated by obesity). Based on these results, authors were able to determine that the consumption of a high-fat diet inhibits the normal functional ability of mammary parenchymal tissue, hindering its capability of manufacturing and secreting milk.
This information would be relevant to discussing with patients/clients in the prenatal period, particularly in encouraging pregnant mothers to consume a relatively low-fat diet with the goal of optimizing initiation and long-term duration of breastfeeding.
How does this information affect your scope of practice as a Lactation Consultant?
To be directed to the original study, please continue reading here.
Citation: Hernandez LL, Grayson BE, Yadav E, Seeley RJ, Horseman ND (2012) High Fat Diet Alters Lactation Outcomes: Possible Involvement of Inflammatory and Serotonergic Pathways. PLoS ONE 7(3): e32598. doi:10.1371/journal.pone.0032598
This study didn’t specify what KIND of fats these women were consuming or specify whether the issues with lactation were due to obesity itself or a combination of both. We know that there are several cultures around the world that consume traditional fats as a large portion of their diet and they do not have, as far as we know, the same issues with lactation. However, they are also not obese. Obesity alone has its own cyclical cycle of inflammation within the adipose tissues, so, I’m assuming that it’s either the kind of fats these women are consuming or, more than likely, the fact that they are obese from the start. I wonder what the outcome of the study would have been if the two issues (HFD and obesity) were separated?
This study is meaningless without clearly defining what is meant by “high fat” diet beyond breaking it down in terms of macronutrient percentages. I couldn’t find any mention in this study of the types of fat these rodents were fed, but I would hazard an educated guess that their “high fat” diet contained large amounts of vegetable seed oils (and possibly trans fats). These polyunsaturated oils are high in omega 6 fats, which displace omega 3s in the body and are highly detrimental, to humans as well as rodents. The scientific consensus is that the overall omega 6 to omega 3 ratio is important to human health.
The types of fats consumed during pregnancy and lactation affect the types of fats in human breastmilk (though not necessarily the percentage of fat). The fetus and infant need healthy fats (the good saturated fats, monounsaturated fats and adequate omega 3s) to promote brain growth in particular. Fats are necessary for the absorption of fat-soluble vitamins such as D, E and K.
In my view it would be irresponsible to advocate a low-fat diet either during pregnancy or lactation — even for an obese woman — without paying much more attention to types of fat consumed. All fats are not created equal.
I really don’t see how this study can be interpreted so broadly. Fat is commonly vilified in our society, but the research does NOT support wholesale “low fat” options for pregnant and nursing moms. Fat is very necessary for hormone function in many systems, and wholesale limiting of “healthy” fat would be more problematic than helpful. Yes, of course we want to encourage moms to maintain healthy weight, but limiting fat is not necessarily the answer to obesity. I think this post should have been more carefully worded.
I recently read that lab animals are often fattened up with added sugar. This article suggests these animals had a high fat diet. The jury is still out about “low fat” diets and associated products on store shelves that humans ingest. We might be wise to help women read ingredients in packaged products. Often “low fat or “no fat” products have other taste enhancers that encourage more to be consumed. Before we suggest that women start lowering fat content I think we should consider the types and amount of fat and other foods they are ingesting as well as the fructose and HFCS they are taking in, in “foods” and drinks.
Did the study differentiate the effects of processed foods and their hydrogenated fats from healthy omega 3s and saturated animal fats unmixed with sugars, starches and additives?
I’m quoting someone else here but this is exactly how I feel. That you are perpetuating the myth that fat causes you to be fat. The real issue with obesity is overly processed man made foods. We need more paleo/primal/whole food diets. shame…..
” Unfortunately the wrong conclusions were drawn from the data presented in this article. Giving rats very high fat chow ( which is also high calorie) is a way researchers induce obesity in rats. This was done 6 weeks before the rats got pregnant–so they were obese before pregnancy and lactation. The study found that in this obese rat model, it took longer for the milk to come in–but it did come in, and that the milk producing cells looked different. As others have said–this was done in rats, not humans–but also, what was studied here was obesity in rats, not necessarily high fat diet. Had the 2 sets of rats consumed the same amount of CALORIES on low or high fat diet, we could draw conclusions about dietary fat’s impact on lactation in rats. However, the high fat diet rats consumed more calories –and were obese before they even got pregnant, so we can’t generalize this to say pregnant or lactating women should eat a low fat diet. The only thing we can say is that in rats, obesity impacts lactation.” Jennie Bever on Kellymom FB post
What kind of fat wete rhe rats fed? Corn oil? Industrial oils? Thats my bet. Now tell me this – if i eat 3 avocados, a bunch of spinach, some full fat yogurt and almost a pound of salmon – is that a hifh-fat diet? Oh yeah!!! Any industrial oils like canola in that? Nope. Name your fat if you want people to take the article seriously.
“Thank you to the many who pointed out weakness in the interpretation of this study and the ability to draw conclusions on high-fat diets. Please see our follow up comments