The inspiration for writing this post has come from my post-grad nutrition and metabolism subject last semester at university, even though I complained quite a lot about the general structure and teaching style of the subject, it sure taught me a lot and really cleared up quite a bit of dietary confusion for me, especially around fats! The subject was unlike most nutrition subjects in that it didn’t teach you all about the biochemistry of macronutrients and micronutrients and how to write meal plans for people, but rather it took us through all the main quality studies in nutrition on various topics. The second module was all about dispelling popular myths that are propagated online without adequate scientific backing. There is simply so much information on the internet, and often when enough people say the same thing over and over again, we begin to believe it without checking the sources for ourselves. The most common myths that I hear propagated in the women’s hormone/fertility space are that “saturated fats are the best fats for hormone balance” and that “polyunsaturated fats are inflammatory” and therefore harmful to general health and fertility. For a while, I agreed with some of these claims, at least in part, but was completely shocked to discover what the evidence really had to say. I wanted to share a little bit of information about the best and worst fats for hormones and fertility.
I am sure it comes as no surprise that trans fats are the absolute worst for health. The consumption of trans fats has decreased significantly in recent years in most countries as awareness of the negative health impacts has increased and regulators have restricted the use of trans fats in most foods. In Australia there is a ban on using high trans fats in our food products (which gives me peace of mind) There are two types of trans fats, naturally occurring trans fats found in meat and dairy and unnatural trans fats found in hydrogenated vegetable oils (the process of making a liquid vegetable oil solid). The is little evidence that naturally occurring trans fats found in animal products are all that harmful (1); however, unnatural trans fats are definitely harmful to human health on many levels. For fertility, in particular, trans fats have been found to increase the risk of an-ovulation when compared to all other fats as well as dietary carbohydrates (3). Trans fats have traditionally been found in baked goods like doughnuts and pastries etc thankfully the use of trans fats has diminished significantly but care should still be taken to avoid trans fats as much as possible.
I have heard saturated fat being promoted as the best fat for hormone balance because it is the most heat-stable, and therefore the least likely to oxidise and cause inflammation. While it is true that saturated fats have a much higher smoking point and are less likely to oxidise or go rancid, this is not the only factor involved in an inflammatory response when consuming fats or oils. In fact, saturated fat has been found to be the most inflammatory fat when compared to polyunsaturated and monounsaturated fats (8) It is thought to promote inflammation by mimicking the actions of liposaccharides which is an endotoxin that promotes inflammation, whereas both mono and polyunsaturated fats have been found to be anti-inflammatory (8). I have also heard it be promoted as the best fat because our cells and hormones need saturated fat as building blocks. While there is some evidence surrounding the benefits of saturated fats the long-term quality health studies simply do not support the notion of high saturated fat consumption for overall human health (read my other article on fats for female hormones here ) Saturated fat intake is well-established as an independent risk factor for cardiovascular disease, the leading cause of death among women today. In terms of hormone health and fertility, high saturated fat consumption was shown to reduce the number of good-quality eggs and ovarian aging in women undergoing IVF (4). We also know that from the large Nurses Health Study that meat intake (particularly red meat which is one of the highest sources of saturated fats) increases the time to conception (5). Saturated fats are found predominately in meat and dairy. The only plant foods that contain significant amounts of saturated fats are coconut, coconut oil, palm oil and palm kernel oil and to a lesser degree cacao butter. Nuts and seeds also contain some saturated fats but in very minimal amounts. The general recommendation is to keep saturated fat consumption to 10% or lower of total fat consumption. On a plant-based diet, this is much more easily maintained providing coconut products, particularly coconut oil not to excess. Although coconut oil hasn’t been shown to be quite as harmful to cardiovascular disease risk as animal-based saturated fats, it has still been shown to raise both good and bad cholesterol (7). Personally, I do not stress the use of plant-based saturated fats in my diet because being plant-based I know my consumption is low. I also enjoy the other benefits of coconut products like being antimicrobial etc. However, some women that are prone to high cholesterol etc may like to minimise plant-based sources of saturated fat as well.
Monounsaturated fats (MUFA’s) are found in high amounts mostly in olives, olive oil as well as avocados and avocado oil as well as good quality canola oil. They are also found in reasonable amounts in most nuts and seeds. MUFAs are associated with lower rates of ovulatory infertility. (4) The same study that identified saturated fats to reduce the number and quality of ovarian egg follicles also showed that people who eat a diet rich in monounsaturated fats have almost 3.5 times higher odds of successful IVF procedures (4).
Avocados, in particular, are a high source of monounsaturated fat and a known fertility food. They contain certain plant phenols that are thought to help boost progesterone and balance estrogen. They also contain lots of vitamins and minerals including vitamin E which is known to support ovarian egg quality as well as increase blood flow to the corpus luteum and therefore increase progesterone production (9). Avocados have been identified as the best type of monounsaturated fat in the Harvard study mentioned above.
Canola oil has a very high monounsaturated fat content and although it has been demonised it is actually considered one of the healthiest oil, especially for cardiovascular health (10). Unfortunately, the majority of canola plants are genetically modified made mostly so that they are resistant to herbicides and pesticides. In Australia, about 20% of all the canola is GMO (11), but in countries like the USA, about 90% is GMO. For this reason, I am a little cautious with canola oil, but a good quality organic canola oil may prove to be beneficial.
Polyunsaturated fats are essential fats (meaning we need to consume them and our body can not make its own) are usually found in nuts, seeds, vegetable oils and fish or other seafood. There are two main classes of polyunsaturated fats: omega 6 found in nuts and seeds and omega 3 found predominately in fish, flax seeds, walnuts, chia and pumpkin seeds. In recent times I have seen polyunsaturated fats get an increasingly negative reputation, especially in the hormone space. The main reason for this is the idea that PUFAS are inflammatory due to the presence of linoleic acid. The thought is that linoleic acid found in PUFAs becomes pro-inflammatory in the body by converting to arachidonic acid or other compounds that can cause inflammation. A systemic review of randomised control studies (the highest quality studies we have) on linoleic acid found in PUFAs concluded that there was virtually no evidence that PUFAs increase inflammatory markers in the body (12). Although PUFAS are involved in some essential inflammatory processes in the body, the idea that they contribute to widespread inflammation is speculative and not well supported in the research. In fact, linoleic acid has actually been proven to be anti-inflammatory, especially when used to replace animal-based saturated fats.
Despite a general understanding that PUFAs are good fats, it is generally agreed that the ratio between omega 6 and omega 3 fats consumption is unbalanced due to the excessive use of omega 6-rich oils in processed and fast foods. Greater attention needs to be taken to increase omega-3 fats in the body. This can be achieved simply by lowering processed and deep-fried fast food intake and by increasing the consumption of omega-3-rich foods.
In terms of fertility and hormone health and PUFA consumption, the evidence is largely inconclusive, especially on women with normal fertility (most research is conducted in an IVF setting). However, a study comparing all fats found that PUFA’s were most associated with decreased risk of anovulation as well as increased progesterone production and a small increase in testosterone (13). A 2012 study found omega-3 supplementations to help increase ovarian reserve and slow down reproductive aging (14).
I think PUFAs are the most confusing to women trying to balance their hormones or achieve a pregnancy and healthy menstrual cycle because many hormone experts promote PUFAs and encourage things like “seed cycling” while others tell people to stay away from PUFA’s because they are inflammatory and lead to hormone imbalance. Overall the general evidence for PUFAs is very positive however care needs to be taken to ensure adequate omega 3 in relation to omega 6. This is especially important to pregnancy when the conversion of plant-based omega 3 (ALA) to active omega 3 forms (EPA and DHA) is very low. Although eating fish can be one way to achieve this, it is difficult to get adequate omega-3 from fish/seafood without also being exposed to toxins like mercury, which becomes even more dangerous during pregnancy (this is why fish consumption is limited in pregnancy). Personally, I focus on eating lots of nuts and seeds, in my opinion, nuts and seeds were the greatest things I added to my diet to help nourish my very malnourished self and balance my hormones. , I include flax seeds and chia seeds almost daily in my diet for the omega 3 and opt for a vegan EPA and DHA source from algae that, unlike many fish oils, is not contaminated with toxins. My favourite is taking a phytoplankton capsule. Phytoplankton gives the equivalent omega 3 of an algae oil but is also loaded with many other essential nutrients including the daily requirements for vitamin b12 which is usually always lacking on a vegan/plant-based diet.
Overall I hope this article has helped clear up some confusion around dietary fats and female hormones and fertility. To sum up: Trans fats are bad, monounsaturated and polyunsaturated fats are good (with special emphasis on omega 3 sources) and saturated fats are mostly inflammatory to the ovaries and ovarian hormones although not quite as bad as trans fats. Keeping total saturated fat consumption to 10% of intake is currently recommended based on the available scientific research on fats and human health.