Evolution is all about fertility: the most beneficial adaptation in the world for gathering food, avoiding predators, or surviving disease is only evolutionarily useful if it helps the organism stay alive and reproduce, to pass its genes down to the next generation. Anything that helps us live long enough to raise children is technically useful for fertility, but when most people in the modern world think about fertility problems, they aren’t worrying about surviving into their 20s. They’re thinking of the most obviously relevant part of their anatomy: the reproductive system. Although other improvements to the human species have indirectly benefitted fertility, the reproductive system is most directly involved – and after several millennia of evolution, humans have developed sophisticated biological processes for keeping the species humming along.
Like everything else about us, though, our reproductive process developed in response to a certain type of environment – one that didn’t include cars, takeout pizza, or desk jobs. Think of a polar bear: it’s evolved a thick fur coat and a protective layer of fat in response to a specific environmental challenge (cold temperatures). It’s fantastically adapted to living in the Arctic, but if you took one to the Sahara, it would very quickly die. Humans are also adapted to a particular set of environmental circumstances – and when we replace our evolutionary environment with the modern world, we struggle to stay healthy.
Fertility is no exception to this rule. Biologists like to divide lifestyle situations into two categories: “fight or flight” and “rest and digest.” As the name implies, “fight or flight” involves stress and danger; in the modern world, we’re no longer being chased down by tigers, but chronic stress and poor nutrition can keep us stuck in “fight or flight” mode. Unfortunately, when your body is trying to make the choice between a battle and a sprint for your life, it doesn’t have much energy to spare for reproduction. Optimal fertility requires the second state, the “rest and digest” mode, when your body is not stressed, and is enjoying the benefits of plenty of nutritious food. As an evolutionary approach to health and nutrition, Paleo recreates the same kind of “rest and digest” environment that naturally increases fertility, as well as benefiting overall health and well-being.
Fertility and Nutrition: Micronutrients
One of the most fundamental reproductive adaptations that humans (especially women) have developed is a resistance to fertility during any kind of starvation: you can’t “rest and digest” if you haven’t eaten. This makes perfect sense: even if a woman could healthily carry a pregnancy to term while she was malnourished (which she usually can’t), the baby would be severely deficient in important vitamins and minerals, the birth would be very dangerous, and both mother and baby would have a lower chance of survival. This is why women with eating disorders and female athletes who overtrain very often lose their regular menstrual cycle. Any kind of fertility diet needs to be very nutrient-rich, to signal to the body that this is a time of plenty, when it’s biologically safe to expend the necessary energy for reproduction.
Thus, the first way a Paleo diet can improve your reproductive health is by providing all the beneficial micronutrients that a modern diet is often lacking. Traditional hunter-gatherer societies knew how important this is: as a form of population control, several traditional cultures restricted women from eating certain nutrient-rich foods, such as red meat, during pregnancy or menstruation. On the other hand, when the Inuit wanted to increase the fertility of women in their tribe, they fed them very nutrient-dense foods like organ meats.
Specific micronutrients important for female fertility seem to be iron, Vitamin E, B Vitamins including B6 and B12, Vitamin D, and the long-chain acids DHA and EPA. Because a woman’s body has to support a fetus for nine months, adequate levels of micronutrients are obviously important for the female reproductive system, but researchers are increasingly discovering that male fertility is also strongly affected by nutritional status. Deficiencies of Vitamins B12, C, and D, DHA and EPA, and zinc have been associated with damaged sperm or low sperm counts. Men might not need to support a growing baby, but a nutrient-rich diet is still important.
Those nutrients alone would be enough to fill a shelf with supplements, and the true list is probably much longer: scientists have not yet discovered exactly how all the different micronutrients affect fertility processes, but since reproduction involves creating an entirely new human being, it’s likely that every important micronutrient is somehow involved. But this doesn’t mean you should go out and buy every supplement on the shelf. Although almost every major vitamin manufacturer makes a supplement specifically for fertility and pregnancy, it’s always best to get a healthy balance of micronutrients from real foods instead: considering how little we truly know about pregnancy and nutrition, a varied and healthy diet full of nutrient-dense foods like liver, egg yolks, and cold-water fatty fish like salmon is probably the safest – and tastiest – way to go.
As anyone with malabsorptive digestive problems knows, dietary intake of nutrients doesn’t do any good unless your body can use them. This means that, along with a high micronutrient intake, it’s also important to take care of your gut flora and eat plenty of healthy fats – since many vitamins and minerals are fat-soluble, you need to eat them with fat to help your body use them properly. Saturated fat is especially important for both men and women because of its effects on hormone levels (estrogen and testosterone). It’s also important to maintain a balance between other types of fat and PUFAs: in one study, women with menstrual irregularities had a higher intake of PUFAs and a lower intake of saturated fat than women with normal menstrual cycles. By eating plenty of healthy fats, and limiting PUFA intake, you can get the most out of all those delicious micronutrients you’re so carefully including in your diet.
Fertility and Nutrition: Metabolism
Your intake of specific micronutrients isn’t the only dietary factor affecting fertility: the health of your metabolism also matters. Metabolic extremes (starvation and obesity) have negative consequences for reproductive health – this has a lot to do with the number of calories consumed, but recent research indicates that it is also related to other nutritional factors, and closely tied to the hormone leptin. While researchers do not fully understand the link between metabolism, fertility, and diet, the hormones leptin, insulin, and ghrelin (all of them regulated by the metabolic system) seem to be clearly connected to fertility.
Maintaining a healthy metabolism is another signal to your body that there is no scarcity of food, and that it’s safe and healthy to reproduce. To achieve the optimal metabolic balance, a moderate intake of carbohydrates seems to be important. “safe starches” get bad press among low-carb advocates for the very same reason that they’re so important for reproductive health: they raise the metabolic rate. The attitude of Dr. Ron Rosedale, a diehard low-carbohydrate advocate, is revealing in this respect. Rosedale explicitly claims that a very low-carb diet is “unnatural” because it isn’t in line with our evolutionary imperative to survive and reproduce. His diet is designed to optimize longevity, but at the expense of fertility. A moderate level of dietary carbohydrates, on the other hand, promotes healthy thyroid function (important for fertility because thyroid dysfunction often affects the reproductive system), raises your metabolic rate, and boosts reproductive function.
Adequate calories, high levels of micronutrients, and plenty of carbohydrates and healthy fats signal to your body that food is plentiful, and that you have enough energy to spare for reproduction. For women especially, it’s also helpful to avoid intermittent fasting, since it can be a serious stressor on your metabolism. The potential dangers of IF don’t seem to be as severe for men – possibly because successful reproduction doesn’t require men’s bodies to be as well-nourished as women’s – but if you’re having trouble conceiving on IF, it’s always worth a try.
Although a moderate carbohydrate intake is very beneficial for fertility, it’s also important not to go too far in the high-carb direction, because reproductive disorders and metabolic syndrome are very closely related. In men, excess body fat can lower testosterone levels and negatively affect sperm production. In women, insulin resistance and metabolic syndrome are linked to PCOS (Polycystic Ovary Syndrome, a hormone-related disease that causes infertility and menstrual irregularity). In fact, the connection is so strong that some researchers speculate that PCOS and diabetes might be nothing but two sides of the same insulin-resistant coin.
The metabolic upshot for fertility is that, as in so many other areas of life, moderation is king. Some carbohydrates are helpful – and possibly even necessary – for peak fertility; too many can lead to insulin resistance and metabolic syndrome, which can impair reproductive health just as much as starvation.
Fertility and Nutrition: Avoiding Toxins
For health of any kind, it’s important to avoid harmful foods as well as getting plenty of healthy ones. This is just as true for fertility as for anything else – especially for women, since a fetus in utero has very few defences against any toxic chemicals or medications that the woman might be exposed to. Many of the food and other toxins that are so harmful for all of us also have measurably negative effects on reproductive health; they’re not good for anyone, but they’re especially problematic for fertility.
Unsurprisingly, the first food on the danger list is gluten. Numerous studies have linked both subclinical and severe Celiac Disease to all kinds of reproductive disorders in both men and women. Furthermore, the gut irritation caused by eating gluten can prevent you from absorbing adequate levels of micronutrients, compounding the problem. Eating a lot of gluten is also often accompanied by eating too many carbohydrates, leading to metabolic disorders that can further stress your body. Although it’s a good idea for anyone to avoid gluten, it’s especially necessary for couples trying to conceive.
Gluten is one toxin to avoid, but it’s hardly the only one: environmental toxins can do just as much damage by leeching into your food, water, and air from various different sources. A particularly harmful kind of environmental toxins for fertility is environmental estrogens: these are chemicals that mimic the effects of estrogen, the main female sex hormone. There’s nothing wrong with estrogen itself (in fact, it’s necessary for both men and women), but ingesting too many environmental estrogens throws off the natural and healthy balance of your own hormones. For women, this essentially sends the hormonal system into overdrive, causing problems like early puberty and very heavy and painful periods. For men, environmental estrogens can slow or prevent normal sexual development – the best-known example of this is probably the feminized fish that scientists have increasingly discovered in modern waterways. Environmental estrogens are ubiquitous in the modern world: plastic is a major source of them, but so are any common chemicals, building materials, and industrial and agricultural pollution. This makes them very tough to avoid, and probably impossible to escape altogether, but it’s important to take whatever steps you can.
Another diet-related problem frequently linked to male and female infertility is oxidative stress, a type of cellular damage caused by physical stressors (free radicals) that exceed your body’s ability to respond to them. As this diagram shows, oxidative stress impairs healthy reproductive function in both men and women by damaging cellular DNA. Since the primary purpose of egg and sperm cells is to carry DNA, this causes problems with the entire reproductive process, and reduces the chances of fertilization, implantation, and viability (whether or not a fertilized egg actually has the ability to develop into a fetus). Oxidative stress also contributes to female infertility by damaging the follicles and endometrium (the lining of the uterus), preventing the embryo from implanting, and disrupting the woman’s normal hormonal cycle; it’s linked to disorders including PCOS, endometriosis, and preeclampsia. To avoid oxidative stress and help your body heal from it, make sure to get plenty of antioxidants (including Vitamins C and E), and avoid food toxins.
Lifestyle and Fertility
Nutrition (both getting plenty of beneficial micronutrients and avoiding harmful food toxins) definitely plays a role in the difference between “fight or flight” and “rest and digest.” But it’s not the only factor. Exercise can be a wonderful way to stay healthy and energetic, and in men, the increase in bone density caused by strength training can help raise sperm production. On the other hand, overtraining can signal your body that you’re constantly in danger and need to conserve all available energy to keep yourself alive, rather than expending your precious resources on reproduction. In women, this is one part of the so-called female athlete triad (disordered eating, amenorrhea, and osteoporosis), a group of three problems that commonly affect women who train too hard and don’t eat enough. Excessive exercise can also lead to oxidative stress in both men and women.
As with carbohydrate intake, the answer to this is moderation. Some exercise is healthy and normal – even for pregnant women. Too much exercise sends your body into “fight or flight” mode, putting fertility on the back burner. Especially for women who are currently pregnant, lighter and low-impact exercises like walking and swimming have the added benefit of being very gentle on your bones and joints, which are already under a heavier load than usual. Heavy weightlifting and extreme endurance sports, on the other hand, can even contribute to miscarriage: 6 months into your pregnancy is not the time to go for a personal best on the squat rack!
Another lifestyle factor that contributes to infertility is stress. Technically, poor nutrition and overtraining are also stressors, but when most people think of stress, they conjure up images of their demanding boss, their frantic morning commute, or the mounting pile of bills in their inbox. This kind of chronic stress causes higher levels of the hormone cortisol, which reduces fertility in women through a variety of channels. In men, cortisol may also lower testosterone, with negative consequences for overall fertility and sex drive.
In sum, a Paleo diet is wonderful for fertility, but diet is not the only benefit involved: the Paleo lifestyle (plenty of rest and relaxation, moderate exercise, and lower stress levels) is also an important part of the overall picture. Activities like prenatal yoga or special meditation techniques aren’t harmful in this regard – if you enjoy them, there’s no problem with them – but they also aren’t necessary. Getting moderate exercise of any kind and making an effort to reduce the stress in your life will have most of the same benefits, keeping you in “rest and digest” mode.
Mother’s Diet, Baby’s Health
As any woman who’s ever suffered through a miscarriage knows, conception is only half the battle. Once a woman is pregnant, the same nutritional or lifestyle stressors that can prevent her from conceiving can cause her body to spontaneously abort the baby for the same reasons. At any point during pregnancy, if a woman’s body doesn’t think the pregnancy is safe for the mother, it’s much more likely to cause a miscarriage. From an evolutionary perspective, this makes perfect sense – it’s better for a woman to miscarry and survive than continue with a pregnancy that’s likely to kill both her and the baby, leaving any other children she has without a mother and less likely to survive.
Thus, for optimum fertility, it’s important that a woman also eat well during pregnancy. In general, the same nutritional advice applies to women who are already pregnant as to women who are trying to conceive. Micronutrients are just as important for a healthy pregnancy as they are for successful conception. A healthy metabolism is also crucial, although this becomes slightly more complicated during pregnancy because many pregnant women do naturally become slightly insulin resistant. There’s even a name for the extreme version of this problem – gestational diabetes is a type of diabetes that occurs during or is triggered by pregnancy, and often disappears after birth. From an evolutionary perspective, this may actually be an advantage (slight insulin resistance in the mother can ensure that the fetus gets adequate levels of glucose), but for an individual woman it can pose an irritating health problem. Fortunately, gestational diabetes is rarely a long-term issue – often it disappears after birth, and it rarely becomes as serious as other types of diabetes. Women who develop insulin resistance or gestational diabetes need to monitor their blood glucose levels carefully, but most don’t need insulin or other medication.
Men, obviously, don’t need to support a growing fetus for nine months, but that doesn’t mean nutrition isn’t important. Raising a family is a joint project, and eating a nourishing, healthy diet will leave you more energetic and better equipped to handle any curve balls life might throw at you before and after birth. Needless to say, it’s also good to support your partner as she tries to maintain the best diet she possibly can.
Health and Contraception
One of the great ironies of fertility is that, for every family that spends a huge amount of time and energy trying to conceive, there’s another family spending just as much time and energy trying not to conceive. Managing fertility is a two-way street – some people aren’t ready to have children yet, or never plan to have them at all, and need safe, effective, and minimally laborious methods of birth control that don’t undo all the health benefits of a Paleo diet.
Contraception has probably existed since human beings first figured out where babies come from – but this is one case where most people emphatically don’t want to imitate actual Paleolithic societies: one of the most common methods of birth control was to simply kill unwanted babies, a method that might not do any harm to the mother, but certainly isn’t acceptable to a modern sense of morality.
More modern contraceptive techniques are broadly classified as either hormonal (i.e. methods that work by changing the balance of a woman’s hormones) or non-hormonal (methods that work by physically preventing the egg from meeting the sperm). Hormonal birth control methods – the Pill, the patch, the NuvaRing, Depo Provera shots, the implant, or a hormonal IUD – generally contain the same types of hormones (synthetic versions of estrogen and progesterone, the two major hormones governing the female reproductive system). They deliver the hormones in different amounts, and through different mechanisms, but all of them raise similar concerns: introducing so many artificial hormones into the delicate balance of your endocrine system can have serious side effects. Like environmental estrogens, the hormones in these contraceptives can make a woman more prone to various types of cancers, blood clots, and a laundry list of other symptoms. Some of these problems can also lead into a positive feedback cycle: for example, artificial estrogens lower thyroid function, which can in turn cause further reproductive dysfunction.
This doesn’t mean that hormonal birth control is universally wrong. The choice to go on or off any method of birth control is very personal, and almost always influenced by factors beyond the potential side effects. However, non-hormonal methods are less invasive, and generally preferable – and fit just as well into most people’s lifestyles.
Many non-hormonal methods of birth control have a long history – methods attested from the ancient world include withdrawal, douching, and various methods of physically preventing sperm from passing the cervix. While most women today don’t want crocodile dung (a common ingredient in ancient birth control recipes) anywhere near their bodies, modern variations of these techniques include commercially available douches, condoms, and diaphragms (female condoms, which are made either with or without spermicide). A non-hormonal intrauterine device (IUD) is a more recent option: a small, T-shaped piece of copper and plastic inserted into the uterus, an IUD prevents pregnancy because the copper acts as a natural spermicide.
Another minimally invasive method is fertility awareness. This technique works because every woman is actually fertile for only a few days during her menstrual cycle. A woman who practices fertility awareness keeps very close track of her cycle, and abstains from vaginal sex only for a few days every month, when she runs the risk of becoming pregnant. Although this method is possibly the least invasive of all, it isn’t for everyone: women with irregular periods, or women who tend to be absent-minded should probably avoid it.
Birth control is a very complicated and personal topic: before you decide on any particular method, it’s a good idea to talk it over with your partner and possibly your doctor. This series of articles on birth control provides a much more in-depth introduction to the various methods available (both hormonal and non-hormonal). For anyone interested in learning more about non-hormonal birth control, this chart also provides a very useful overview of the most commonly available options.
Paleo and Libido
The discussion of birth control also brings up another aspect of any healthy adult’s sex life: pleasure. Many people do find that a Paleo diet increases their sex drive – this isn’t so much due to any one specific food as to the cumulative effect of diet and lifestyle on sex hormones. Testosterone is the main hormone governing sex drive in both men and women; the key to a healthy sex drive is a balance of testosterone (too little will lower your sex drive through the floor; too much will send it out of control, and an imbalance of estrogen and testosterone can cause serious fertility problems in women). As with all things hormonal, the main organ involved is the thyroid: a large number of people have undiagnosed thyroid problems, and, since a Paleo diet is very beneficial for thyroid health, it can get straight to the root of any hormone imbalances that might be affecting libido. While a Paleo diet isn’t specifically designed to have any particular effect on the sex drive, it’s often a great side effect of better hormone balance and thyroid health!
Of course, it’s also common that the overall health improvements on a Paleo diet contribute to increased sex drive along with everything else. Any diet that suddenly improves your mood and energy levels – not to mention your appearance – will probably tend to increase your sex drive along with it. The side effects of the modern diet are far from arousing; many people didn’t know they had so much energy for sex until they stopped filling their bodies with toxins and started eating the way they were designed to.
Fertility is a very complicated subject – no one article could touch on every aspect of diet and reproductive health. In general, however, a diet that optimizes fertility is the kind of diet we should all be eating anyway: a diet low in toxins and rich in micronutrients, with adequate calories and a healthy balance of protein, carbohydrates, and healthy fats. Women with gestational metabolic problems may face specific issues, but in general, it’s not necessary to completely overhaul your regular Paleo eating plan for a special “fertility diet.” For further information, Chris Kresser’s Healthy Baby Code is a wonderful resource geared towards Paleo parents-to-be. As always, it’s important to find what works for you (and if you have any serious medical conditions, to address them directly with your doctor), but a Paleo diet and lifestyle can go a long way toward helping you conceive a healthy, vibrant cave baby of your very own.