Let’s take a closer look at what they are and how they may affect health and fertility.

Sue Bedford (MSc Nutritional Therapy)

Eating the right fats is not only good for your health, it’s essential! ‘Good’ fats are important for your health and play a role in the healthy functioning of our brains, our cardiovascular systems and hormonal functioning, including fertility.

Research about the possible benefits and harmful effects of dietary fat is always evolving. There has been much debate over the years as to whether reducing our fat intake and following a low- fat diet is healthier than a diet that contains a higher amount of fat such as saturated fat. There is still further research needed to clarify exactly how much saturated fat is actually needed by the body to remain ‘healthy’, but it is also important to acknowledge that the human body needs fat to function effectively and that everyone is different (biochemical individuality) and so different people will need different amounts of saturated fat dependant on age, sex, activity levels etc. There are several different types of fat which complicates the issue! Over the next few weeks we will look at some of the different types of fats and how they may impact on health and fertility more closely.

A growing body of research is indicating that when it comes to dietary fat, the focus should be on eating more of the ‘healthy’ fats such as omega 3 fatty acids along with monounsaturated and polyunsaturated fats (as well as some saturated fat) and less of other, not so ‘healthy’ fats such as the trans fats. 

We do all need a certain amount of fat in our diet in order to function, so the focus needs to be on the amount and quality of fat that we consume.

Fat is important in our diet for a variety of reasons including:

  • Energy
  • Insulation
  • Healthy skin
  • Cell membranes
  • Absorption of fat -soluble vitamins (A, D, E and K)
  • To provide the essential fatty acids
  • Brain development
  • Control of inflammation
  • Blood clotting
  • Production of oestrogen and other hormones

What are the main groups of fats?

Saturated fats

This is a type of fat that comes mainly from animal sources of food, such as red meat, poultry, coconut butter and full-fat dairy products. It can also come from biscuits, cream, ice cream, savoury snacks etc A small amount in our diets is needed but too much can increase cholesterol levels so it is important to be mindful of how much you are consuming. Generally, people are consuming too much saturated fat and as a guideline, men should not consume more than 30g per day and women no more than 20g per day.

Trans fats

Trans fats are liquid oils that have been turned into solids by a process called hydrogenation and are in thousands of pre-prepared foods to give texture and a long shelf life. There have been studies recently linked trans fats to many adverse health conditions – we will explore this further in our next article.

Examples of some popular foods that may contain trans fats (check the label for hydrogenated fats):

  • Biscuits
  • Margarine
  • French fries/some chips
  • Piecrust
  • Most things that have been battered or fried
  • Cake mixes
  • Some ice creams
  • Frozen microwave meals

Monounsaturated fatty acids

This is a type of fat found in a variety of foods and oils such as olive oil, avocados and nuts such as Brazil nuts. Studies show that eating foods rich in monounsaturated fatty acids improves blood cholesterol levels, which can decrease your risk of heart disease. Research also shows that these fatty acids may benefit insulin levels and blood sugar control, which can be especially helpful if you have type 2 diabetes or PCOS.

Polyunsaturated fatty acids

Our bodies cannot make Polyunsaturated fats. This is a type of fat found mostly in plant-based foods and oils found in some fish and oil, such as sunflower oil. Evidence shows that eating foods rich in polyunsaturated fatty acids improves blood cholesterol levels, which can decrease your risk of heart disease. These fatty acids may also help decrease the risk of type 2 diabetes. The word ‘polyunsaturated’ refers to their chemical structure, as ‘poly’ means many and ‘unsaturated’ refers to double bonds.

Omega 3 fatty acids:

One type of polyunsaturated fat is made up of mainly omega 3 fatty acids and may be especially beneficial to your heart and fertility as well as other health conditions (we will explore further in another article). Omega 3, found in some types of fatty fish, appears to decrease the risk of coronary artery disease and also helps reduce inflammation in the body. There are three main omega 3 fatty acids; alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

Omega 6 fatty acids:

Like Omega 3 fatty acids Omega 6 are a type of polyunsaturated fatty acid and cannot be made by the body. They are an important source of energy for the body. The most common omega 6 fatty acid is linoleic and if too much of it is consumed it can become pro inflammatory. The problem is that in the western world we consume too much omega 6 and not enough omega 3 and so the ratios are ‘out’. The typical intake of omega-6 in western countries is high, and the ratio of the omega-6: omega-3 fatty acids in the UK are now thought to be greater than 10:1 and even as high as 25:1 in some adult diets. Many years ago the omega-6: omega-3 ratio dietary intake of primitive man was closer to 1:1. Examples of omega 6 rich foods are corn, sunflower oil, safflower oil, firm tofu, peanut butter, cured meats.

Omega 9 fatty acids:

These fatty acids are monounsaturated and can be made by the body. Oleic acid is a main example of an omega 3 fatty acid and in found in avocado’s, olives, nuts and seeds, some meats such as chicken and beef, eggs, milk, sunflower seeds and cheese. There have been links in studies to omega 9 fatty acids benefitting health: including reducing inflammation and improving insulin sensitivity.

Fats and fertility

There has been research carried out which has indicated that consuming fat is important when it comes to fertility- but the right fat and the right amount!

Body fat cells produce oestrogen which is needed to maintain cholesterol levels, healthy bone formation, gene expression, and to regulate the menstrual cycle. Research has indicated that there is a balance to be had as consuming too much fat can lead to obesity and this can lead to fertility problems. Conversely women who have a low BMI (or not an adequate amount of body fat) may not be ovulating and have irregularities in the menstrual cycle.

Consumption of trans fats can lead to obesity which may impact on fertility by affecting ovulation, increasing insulin resistance and by increasing inflammation. Trans fats seem to amplify the symptoms of PCOS (Poly Cystic Ovary Syndrome) and may cause endometriosis in some women.

Researchers from Harvard Medical School investigated 18,800 women and looked at the effect of trans fats on fertility. They discovered that a consumption of 2% trans fats in the diet doubled the risk of infertility (Chavarro et al 2007). The study also looked at the effects of high and low- fat dairy on female fertility. It found that an increase of just one serving of low-fat dairy food per day was associated with an 11% greater risk of infertility.

It was also discovered from this research that eating high fat dairy was associated with a reduction in the risk of infertility. For instance, it was found that the addition of one serving of whole fat milk per day was associated with a 50% drop in infertility risk. Increased intake of calcium and vitamin D were also associated with a lesser risk (and dairy products containing fat are more likely to contain these substances).

Researchers concluded that the negative impact of low- fat dairy on fertility was likely to be a result of IGF-1 levels. Studies have shown that milk consumption can increase IGF-1 levels (which can negatively affect fertility) and it is thought that low fat milk in particular might drive this association.

The research team also concluded that the association between the consumption of high fat dairy and improved fertility has a couple of likely explanations.

High fat dairy products have more oestrogen than their low-fat counterparts, and oestrogens decrease IGF-1 levels (and so improve fertility). There is also evidence that high fat dairy products may improve insulin sensitivity. Further research is still needed on this topic to validate it’s conclusion.

 Some nutrition ideas:

– Eat organic free range eggs as they are an excellent source of vitamins A, D, and E, along with EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid) and choline.

– Include 2-3 portions of oily fish into your diet each week, such as wild salmon, mackerel, sardines and herring. These foods contain essential fatty acids which can be helpful for female infertility due to their anti-inflammatory properties. Fish oil is also highly beneficial for maintaining a healthy pregnancy and the DHA found in fish oil is crucial to building your baby’s brain.

– Choose healthy foods that contain fat choices that are beneficial to fertility, pregnancy and overall health including olives, olive oil, nuts, seeds, avocado, rapeseed oil and flax seed/flax oil.

– Research is leaning towards the fact that we should all include some saturated fat in our diet but further studies are being carried out into exactly how much is to be recommended (at present 30g for men and 20g for women per day). Good sources are butter, full fat milk, cream and red meat.

Further reading

Chavarro, J., Rich-Edwards, J., Rosner, B. and Willett, W. (2007) Dietary fatty acid intakes and the risk of ovulatory infertility. American Journal of Clinical Nutrition, Vol. 85, No. 1, pp231-237.

Missimer, S. et al.,(2010) Trans fats linked to increased endometriosis risk and omega-3-rich food linked to lower risk. European Society of Human Reproduction and Embryology.

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