BLOG BY Rhiannon Lambert

Nutrition & Fertility: Is There A Correlation?

Fertility, meaning the ability to produce healthy offspring, has been a source of concern from the beginnings of human existence. From the earliest time there was some understanding that foods eaten could affect this mysterious process. In many traditional cultures around the world, women would start eating special foods when they wanted to become pregnant. Nutrient-rich animal organs such as liver, bone marrow, adrenal glands and blood were particularly prized. In Scotland the wives of Gallic fishermen prepared crappit heid (fish heads stuffed with oats and chopped liver) to ensure ready fertility. Some plant foods were also recognised as having benefit. In Peru for example, American Indian women ate the root vegetable maca when they wanted to conceive.

The beginnings of Western medicine trace back to the Greeks. Trying a little sympathetic magic, they believed that my favourite fruit fresh figs would boost fertility because the shape of the ripe fruit represented womanhood. Certainly, their most famous physician, Hippocrates was familiar with the problem of female infertility. For conception, he advocated a special diet of: boiled pine twigs and white wine, with celery, cumin seed, and frankincense, accompanied by boiled puppy and octopus. Treatment moreover, was not just for the woman. Before trying for a child, the man was asked to be: sober and well-nourished with appropriate foods.

Now I could list the endless research and mythical dietary choices here but let me move on to what you can do today. In my clinic and online I have probably heard every food item being listed as good or bad for fertility, there are hundreds of pages online with suggestions, but what's really grounded in evidence and can actually help?

Weighty Issues

I want to raise this point immediately as it is well researched and documented that weight plays a role with hormones. Excessive fat stores can inhibit conception, trigger higher male hormones and effect the process of ovulation. The same is true for men, please don't forget it's a 50/50 matter when trying to conceive! Women of a healthy weight have higher fertility rates than those who are underweight or overweight. Significant weight-loss can disrupt the menstrual cycle while excess weight-gain can affect the hormones that regulate ovulation and pregnancy. Therefore, it is recommended that women achieve a healthy weight before they become pregnant.

High energy diets are also associated with a decline in male fertility via adverse effects on testicular physiology. The quality of diet will impact a female’s eggs and a male’s sperm so it’s really a team effort. If you think about it a women is born with all the eggs she will ever have and a man's sperm has a cycle of 74 days so ample opportunity to live well and create strong and healthy swimmers.

The Research Out There

Researchers from the Harvard T.H. Chan School of Public Health and Harvard Medical School have published a review of past studies that examined the impact of diet on fertility. They found that for women trying to become pregnant naturally (without “assistive reproductive technologies” such as in vitro fertilisation), the following vitamins and nutrients were linked to positive effects on fertility (1):

• folic acid

• vitamin B12

• omega-3 fatty acids

• healthy diets (such as the Mediterranean diet)

The research also found that antioxidants, vitamin D, dairy products, soy, caffeine, and alcohol appeared to have little or no effect on fertility. Now we must remember everyone is unique when it comes to nutrition but it does appear no single nutrient can create or hinder a miracle. Trans fat and “unhealthy diets” (those “rich in red and processed meats, potatoes, sweets, and sweetened beverages”) were found to have negative effects. Again, this doesn’t mean this is conclusive and therefore please don’t just focus on the above. There’s a whole body of conflicting evidence out there supporting the above but also literature that disproves it.

Conflicting Evidence

I discuss this a lot on the Rhitrition pages and the Food For Thought podcast but if you look hard enough you really will find research for and against everything. For example, sugar sweetened beverages have been linked to lower fertility in men and women, whereas diet drinks or fruit juice had little effect at all (2). Other studies have even found links to support high consumption of fast food and small amounts of fruit can result in a longer time period to get pregnant than those who have healthier diet! (3)

NUTRIENTS FOR FERTILITY 

Fats and Carbs

The Nurses’ Health Study II, which followed over 116,000 women (4), demonstrated that higher fertility rates in women were associated with diets rich in monounsaturated fats (rather than trans fats) vegetable protein (rather than animal protein) and based on fibre-rich low GI carbohydrates.

In men, consumption of long chain polyunsaturated fatty acids ( found in oily fish) is particularly important for sperm quality and quantity. Sperm production is improved with diets rich in omega-3 but reduced with diets rich in saturated and trans fats. Nuts are also said to be beneficial for sperm quality (5)

Iron and Selenium

Women of reproductive-age are often at risk of iron deficiency even before conception due to blood loss from menstruation, poor diet or multiple previous pregnancies. Iron can be found in lean meat and poultry. Data from the Nurses’ Health Study II indicated that women who consumed higher amounts of non-haeme iron (iron from plant-based sources) from foods like nuts, beans and vegetables are at decreased risk of ovulatory infertility.

A deficiency or indeed an excess of either iron or copper can lead to defective spermatogenesis, reduced libido, and oxidative damage to sperm with fertility impairment.

Selenium is yet another trace element that affect both male and female infertility. Selenium deficiency can be a particular problem in certain geographical areas which have very low levels of selenium in the soil. Selenium-rich foods include Brazil nuts, oysters, tuna and wheat germ.

A bit of a minefield? I couldn’t agree more, let me break it down into some easy to digest evidence based advice and take home nutrition tips.

Folate

In women, a preconception diet rich in folate also seems to be important for oocyte quality and maturation mediated by the effects of folate in curbing total homocysteine levels and reducing reactive oxygen species. Folate is found in dark green leafy vegetables like broccoli and spinach and in many different kinds of legumes.

Vitamin D

In recent years, evidence has also accumulated about the importance of numerous micronutrients in fertility and conception. One example is Vitamin D, a lipid-soluble vitamin that can have significant effects on fertility.

In women, its importance was first indicated when receptors for this vitamin were detected in the ovaries, placenta and endometrium. Subsequent studies suggest that the main effects on fertility may be mediated through the endometrium, not the follicle or the oocyte.

In men, the vitamin D receptor is present in the testicles and sperm and vitamin D may be involved in the actions of acrosine that are critical for fertilisation. Vitamin D is largely obtained by sun exposure but can also be found in some foods including sardines, beef liver and egg yolks.

Fertility For Men

Food and nutrition affects sperm quality in men. Sperm quality governs how well sperm swim and how readily they are able to fertilise an egg. Spermatogenesis, the 70-90 day process of developing sperm and increasing sperm count, is affected by nutrition. What a man eats today will determine his sperm quality and quantity in 70-90 days. Therefore, it is important for men to eat a healthy diet for many months before trying for a baby.

Two nutrients that are essential for healthy and abundant sperm are zinc and folate. Zinc is required for spermatogenesis and sperm motility. Good sources of zinc include oysters and lean red meat as well as nuts, sesame seeds, beans and whole grains. Folate is required for the synthesis of genetic information, or DNA, that is found in sperm. Good sources of folate include fruits and vegetables, particularly green leafy vegetables, and cereal products.

Sperm also needs to be protected once they are formed. They are easily damaged by free-radicals that circulate around the body and damage cells. Antioxidants are molecules that can protect against this damage by neutralising the free-radicals. Antioxidants include nutrients such as vitamin C, vitamin E and selenium and a large number of other compounds found in fruits, vegetables and whole grains. (6)

Researchers in the Netherlands found that a combined zinc and folate supplement taken under medical supervision increased the sperm count in men. Due to lack of sufficient evidence (i.e. studies with relatively small samples, and/or potential bias that has not been addressed), these findings are yet to be translated into specific recommendations that can be made by health professionals (7)

Why Nutrition?

• May help with egg and sperm health

• Optimise the chances of conception

• May reduce the risk of miscarriage

• May reduce the time it takes to conceive

• Ensure the healthiest possible environment for a pregnancy

Key Factors That Don't Help

• Stress

• Lack of Sleep

• Extreme weight loss/weight gain

• Predisposing medical factors

• Low Immunity

• Poor Digestion

• Smoking

Top Diet Tips For Women

1. Pregnant women are advised to take folic acid supplements before conception and during pregnancy to lower the risk of neural tube defects in the fetus (400 µg), which should be continued with until the 12th week of pregnancy. In women, a pre-conception diet rich in folate also seems to be important for oocyte quality and maturation mediated by the effects of folate in curbing total homocysteine levels and reducing reactive oxygen species. Folate is found in dark green leafy vegetables like broccoli and spinach and in many different kinds of legumes.

2. Women who are pregnant or planning a pregnancy are advised to stop drinking alcohol altogether and if you smoke stop straight away.

3. Try and follow the basic dietary advice and eat a varied balanced diet, I am an advocate of the mediterranean diet

4. My 2 Q’s; Quality and Quantity of food!

Top Diet Tips For Men

1. Excessive alcohol intake may affect sperm quality and men are advised not to drink more than the Department of Health's recommendation of 3 to 4 units per day.

2. Men who smoke are more likely to have reduced semen quality and stopping smoking may also reduce the impact of passive smoking for their partner. Stopping smoking can increase the chances of conceiving and will improve general health.

3. Obese men (BMI over 30 kg/m2) may also have reduced fertility and should aim for a healthy body weight to improve their chances of conception.

4. It is also important for men to eat a healthy, varied diet with the 2 Q.s. For example, selenium is needed to make healthy sperm, zinc is needed to ensure healthy testosterone levels and long-chain omega-3 fatty acids found in oily fish help produce prostaglandins, which are important for making sperm.

Rhiannon has a pre and post natal qualification from Monash University and has included some useful references below. If you wish to learn more tune in to the Food For Thought podcast on Fertility with Dr Zoe Williams here

References

1.https://www.ncbi.nlm.nih.gov/pubmed/2884482

2.https://journals.lww.com/epidem/Abstract/2018/05000/Intake_of_Sugar_sweetened_Beverages_and.8.aspx

3.https://academic.oup.com/humrep/article/33/6/1063/4989162

4.The Nurses Study 2 https://www.nurseshealthstudy.org/about-nhs/history

5.https://www.sciencedaily.com/releases/2018/07/180704112048.htm

6.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5203687/

7.https://www.ncbi.nlm.nih.gov/pubmed/11872201

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