September 24, 2018
The Perfect Diet for a Mother-To-Be Through a Macronutrient Lens - Part III Fats.
Fats are the third major macronutrient and are found in nature in animals and plants as the major storage form of energy. Fat provides many vital functions for humans including the provision of an energy source, organ insulation, cell membrane fluidity, and a storage site for toxins until the body has the ability to metabolize and clear them.
Fats are a very important part of the human diet and have been the subject of some vilification over the last 50 years because of questionable science quality that ushered in an era of low fat foods in order to protect against heart disease. This unfortunately produced a whole supply of sugar, salt and flour laden foods to replace the flavorful fats that disappeared from the market. While well intentioned, the end result of these changes to the American food supply has been associated with a worsening of obesity, diabetes and heart disease nationally.
Pregnancy is a unique metabolic time for a female human as the physiologic changes are rapid and very different than the pre-pregnancy state. The demands for fat are higher and fat has become misunderstood by the general populace. In order to understand this we need to break fats down into a few types: 1) monounsaturated 2) polyunsaturated 3) saturated. Each type is important and they are each distinguished from the other by a slight change in chemical structure. Then we can try and draw conclusions on what is best for mom with regard to fat.
Monounsaturated fats are found in olives, avocados, sunflower seeds, nuts and canola oil. They are the least controversial and a significant part of the heart and pancreas healthy Mediterranean diet. The intake of olive oil in particular continues to be associated with better health outcomes especially for cardiovascular disease. (Estruch et. al. 2018)(Martinez-Galiano et. al. 2018) A google scholar search also finds significant studies in animal models related to reduced inflammation in pregnancy.
Polyunsaturated fats are very important and broken up into two subgroups: omega 3 and omega 6. The omega 3 fat type is found predominantly in cold water oily fish like sardines, mackerel and salmon as well as flax seeds and walnuts. The omega 6 variety is found in vegetables and their oils. Examples are oils from corn, soy, nuts and seeds. The omega 3 variety contains the fatty acids DHA and EPA that are critical for immune and brain function of mom and baby. The infant's brain's cell membranes are significantly made up of DHA which is obtained entirely through the placenta. Mom's dietary omega 3 intake dictates this fat deposition for her babe. This has been found to be so critical that omega three fats are now in all formulas for newborns and often recommended to pregnant mothers.
The omega 6 variety is also necessary but has the effect on the body in a pro inflammatory way which is great if you are ill or have an injury. The real problem with the omega 6 fats is thought to be that we get too many of them and the end result appears to be increased inflammation from the processed American foods that are loaded with the omega 6 oils and excess sugars. This is hotly debated with research on both sides of the fence. (Akerele et. al. 2016)(Coletta et. al. 2010)(Greenberg et. al. 2008)(Haghiac et. al. 2015)(Innes et. al. 2018)(Koletzko et. al. 2007)(Mennitti et. al. 2015)(Zhang et. al. 2011)
The truth with polyunsaturated fats is likely at the balance point. We historically ate much less omega 6 fats and more omega 3 types and likely rarely in combination with refined carbohydrates. With the advent of processed vegetable oils and their addition to many foods, the ratio has swung toward the omega 6 side potentially creating a problem in certain individuals. (Blasbalg et. al. 2011) I think that rebalancing this ratio makes prudent sense.
Saturated fats are found in animal products like red meats, dairy and palm or coconut oils. They are currently the topic of much debate regarding their health and safety. One camp completely believes that they are unhealthy and promoting heart disease and other issues while another camp disagrees and believes that these fats are good and necessary in moderation. As with most things the answer is likely in the middle somewhere. Unfortunately, when researching saturated fats and pregnancy, I could not find any data worth sharing.
The general human health data noted that some reviews have come out showing that replacing saturated fat with omega-6 fats has a heart healthy effect. (Mozaffarian et. al. 2010) Others have shown no difference to mortality, heart disease and diabetes risk. (DeSouza et. al. 2015)
Yet again, I am frustrated with the lack of quality science to answer these questions in general let alone for pregnancy or infancy. We are left extrapolating backwards from the general population data. Regarding saturated fat, I believe that it comes down to volume. It is highly unlikely that animal fats are inherently bad for us. Looking at the Tsimane Indians and the Blue Zone populations, they did consume saturated fats but in very small volumes and that this dietary pattern seemed to be associated with the greatest longevity.
There is a very good article on saturated fat by Dr. David Katz at this link for you to read.
There is not even clear evidence as to the percentage of fat necessary per day during pregnancy. Ranges are from 10-25% of total intake.
What we do know is that fats are a necessary major macronutrient that pregnant women need in their diet. The omega 3 variety from fish seems to have a critical function to play in the infants brain health. Having a balanced intake of fats leaning towards monounsaturated fats like olive oil makes epidemiological sense. Saturated fats are likely good in moderation.
What to do?
1) Consume fats daily as high quality whole unprocessed foods. Vegetables, avocados, nuts and seeds are great fat sources.
2) Aim for high quality monounsaturated fats from olives and olive oil to put on salads and in dishes as the data is pretty clear that this food stuff is healthy.
3) Omega-3 fats are very important during pregnancy. Eat wild caught oily cold water fish like salmon, mackerel, sardines and trout. Flax seeds, chia seeds and walnuts are also reasonable sources depending on your FADS2 gene makeup.
4) Look for grass fed meats for a better fatty acid profile when you do eat red meat. Try to limit it to a few times a month.
5) Limit the intake of saturated fats as animal products as the data is leaning towards less is more. Plant based saturated fats from coconut and dark chocolate are healthy in moderation.
6) I do not think that large volumes of vegetable oils are good for us especially when they are combined with refined carbohydrates.
Dr. M
Tsimane Indians
Blue Zones
In Defense of Food
The American Journal of Clinical Nutrition Butte Article
Proceedings of the Nutrition Society Clapp Article
The American Journal of Clinical Nutrition Moses Article
The American Journal of Clinical Nutrition Zhang Article
Journal of Nutrition and Intermediary Metabolism Akerele Article
Reviews in Obstetrics and Gynecology Coletta Article
Reviews in Obstetrics and Gynecology Greenberg Article
Prostaglandins Leukotrienes and Fatty Acids Innes Article
British journal of Nutrition Koletzko Article
The Journal of Nutritional Biochemistry Mennitti Article
New England Journal of Medicine Estruch Article
Nutrients Martinez-Galiano Article
PLOSone Haghiac Article
Google Scholars Search for Olive oil and Pregnancy
American Journal of Clinical Nutrition Blasbalg Article
PLOSmedicine Mozaffarian Article
British Medical Journal DeSouza Article
Huffington Post Katz Article
