Getting knocked up just isn’t as easy as it used to be.
In 1960, the global average births per woman was 4.92. In 2010, it was 2.45—a reduction of just over 50%.
Here in the United States, we saw a 42% drop in births per woman during that same period. Women were having an average of 3.65 children in 1960, and 2.1 in 2010. This declined further to 2.06 in 2012.
Western Europe has been hit even harder, with just about every nation currently below the “replacement rate” of 2 children per woman (when the birth rate drops below this threshold, populations decline over time). Experts predict that European populations will dramatically shrink over the next 50 years if this statistic remains.
While the number of children people ultimately have is affected by various non-health things like education levels, finances, and living standards, there’s been a very clear decline in women’s physical ability to naturally conceive.
The big question, of course, is why is this happening, and what does it mean for the future?
Well, much more research is going to have to be done to conclusively answer those questions.
“The truth is that we are still speculating about the causes, but it appears certain that it is changes in our modern environment, whether this be chemical exposures or our changing lifestyle or both,” said professor Richard Sharpe of the MRC Centre for Reproductive Health, University of Edinburgh, UK.
The medical answer to the infertility issue is drugs such as Clomid and forms of a sex hormone known as gonadotropins, and in-vitro fertilization, a process whereby a woman’s egg is removed, artificially inseminated, and then inserted into her uterus.
While these interventions do improve chances of pregnancy, they come with serious dangers.
Research has shown that pregnancies achieved with the use of fertility drugs increases the risk of ovarian and breast cancer and multiple fetuses, which carries its own risks, such as increased chances of premature birth, stillbirth, placenta complications, and low birth weight.
Pregnancies achieved with IVF are even dicier. Research has shown that IVF significantly increases the chances of stillbirth, preterm delivery, low birth weight, birth defects, placenta previa, placental abruption, preeclampsia, and several other pregnancy complications.
Considering the very real, and potentially disastrous consequences of these assisted reproductive technologies (as they’re known), conceiving naturally is not just preferable, but vital for many women.
In this article, I want to talk about how diet alone can impair female fertility, and how you can make simple changes in the way you eat to improve the likelihood of conception.
Trans fat is a scientifically modified form of saturated fat used to extend the shelf life of food and improve palatability. The most common forms of trans fats added to foods are hydrogenated and partially hydrogenated oils (oils that have hydrogen atoms added to them). Any food that contains “hydrogenated oil” or “partially hydrogenated oil” contains trans fats.
Many processed foods contain trans fats, such as baked goods, breakfast cereals, bread and crackers, breaded fish products, frozen pizzas and pastries, “healthy” snack bars, margarine, shortening, microwave popcorn, nondairy creamers, peanut butter, puddings, ramen noodles, sauces, and tortillas.
In women, eating trans fats can be devastating to fertility. In a 2007 Harvard study involving 18,555 married, premenopausal women, it was found that women obtaining just 2% of their daily energy from trans fats rather than monounsaturated fats were at more than double the risk of ovulatory infertility.
Researchers believed that there were two primary reasons for the association between trans fats and infertility.
Even when eaten at normal levels of human consumption, trans fats reduce insulin sensitivity. This, in turn, can negatively impact female fertility. Consumption of trans fats has been associated with systemic inflammation in women, which may negatively affect fertility as well.
Avoiding trans fats isn’t as simple as finding foods with labels claiming them to be trans fat free. To meet the FDA’s definition of “zero grams trans fat per serving,” food doesn’t have to contain no trans fats—it must simply contain less than one gram of trans fats per tablespoon, or up to 7% by weight, or less than .5 grams per serving. So if a bag of cookies contains .49 grams of trans fat per serving, the manufacturer can claim it’s trans fat free on the packaging.
“Since the [FDA has] recommended that the amount of trans fat intake be ‘as low as possible,’ in other words, less than 1 percent of total calories or less than 2 grams per day, it’s not hard to see how the ‘fake-zero’ foods could create problems in an otherwise healthy diet,” said Dr. Carlos Camargo of Harvard Medical School.
The amount and quality of carbohydrates that women eat has been associated with changes in fertility.
Another Harvard analysis of the 18,555 women found that when carbohydrates were increased at the expense of naturally occurring fats, the risk of infertility rose. To be specific, women that were getting 60% of their daily energy from carbohydrates were at a 78% greater risk for ovulatory infertility than those getting 40% of their daily energy from carbohydrates (and more from naturally occurring fats).
It was also found that consumption of high-glycemic foods like cold breakfast cereals, white rice, potatoes, and French fries was associated with a greater risk for infertility, especially in women without children. The association between the consumption of high-glycemic foods and infertility has been found in other research, too.
Researchers said their findings have two likely explanations.
First, as carbohydrate intake increases, so does insulin response to meals, which can reduce insulin sensitivity over time.
Second is the fact that research has shown that fats, both saturated and unsaturated, can have beneficial effects on the menstrual cycle. By reducing your intake of healthy fats, you may impair fertility.
Another Harvard study published involving the same group of women found that consumption of soda, both diet and those sweetened with fructose, and other sugared drinks was associated with increased risks of infertility. The negative association of soft drinks and female fertility has also been noted in other studies.
While the reasons for this weren’t totally clear, researchers believed that it had to do with the fact that soft drink consumption has been linked to a reduction in insulin sensitivity.
Animal vs. Plant Proteins
Yet another Harvard analysis of the same group of women revealed that replacing animal sources of protein with plant sources may reduce infertility risk.
Adding just one serving of meat (red meats, chicken, turkey, processed meats and fish) per week was associated with a 32% greater risk of infertility. On the other hand, increasing the daily intake of vegetable protein in the place of animal protein or carbohydrates was associated with reductions in infertility risk (43% and more than 50%, respectively).
Researchers suspected two underlying mechanisms explaining these findings.
Meat consumption has been shown to elevate insulin levels and glucose response more than vegetable sources of protein. Over time, regular consumption of meat could negatively affect insulin sensitivity.
In women, eating meat has been shown to increase levels of a hormone known as insulin-like growth factor 1 (IGF-1). Research has suggested that elevated IGF-1 levels increases the risk of infertility.
High- and Low-Fat Dairy
Another significant finding from the Harvard analysis of those 18,555 women is the effects of high- and low-fat dairy on female fertility.
The study found that an increase of just one serving of low-fat dairy food per day was associated with an 11% greater risk of infertility.
On the flip side, 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 likely had to do with IGF-1 levels. Studies have shown that milk consumption can increase IGF-1 levels (which can negatively affect fertility, as you know), and it’s suspected 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 estrogen than their low-fat counterparts, and estrogens decrease IGF-1 levels (thus improving fertility). There is also evidence that high-fat dairy products may improve insulin sensitivity.
Iron is found in many types of food, including red meat, beans, poultry, fish, leafy vegetables, tofu, and types of peas. The color of our blood is due to an iron-containing protein called hemoglobin, and many biological functions rely on iron-containing enzymes and proteins.
Iron deficiencies are particularly common among young women, and research has found that this can greatly reduce their fertility.
Another finding of the Harvard researchers was that women that supplemented with iron were up to 70% less likely to suffer from ovulatory infertility than those that didn’t.
This study also found that eating meat-derived iron increased risk of infertility, whereas eating plant-based iron reduced it. The women that ate the most meat-derived iron were 31% more likely to experience fertility issues than those that ate the least. And the women that ate the most plant-derived iron had a 40% lower risk of ovulatory infertility than those that ate the least.
The role of iron status in reproduction isn’t totally clear, but research has suggested that iron-transporting proteins play an essential role in ovum development.
The Woman’s “Fertility Diet”
Harvard’s extensive research into female fertility prompted them to release a study in 2007 that analyzed the effectiveness of what they called a “fertility diet.
They followed a group of 17,544 women for 8 years as they tried to become pregnant or became pregnant.They scored diet based on factors they found associated with higher fertility (higher consumption of monounsaturated rather than trans fats, vegetable rather than animal protein sources, low glycemic carbohydrates, high fat dairy, multivitamins, and iron from plants and supplements) as well as lifestyle information.
Increasing adherence to a “fertility diet” pattern was associated with a lower risk of ovulatory disorder infertility. A combination of five or more low-risk lifestyle factors, including diet, weight control, and physical activity was associated with a 69% lower risk of ovulatory disorder infertility.
Researchers concluded with the following:
“Following a “fertility diet” pattern may favorably influence fertility in otherwise healthy women. Further, the majority of infertility cases due to ovulation disorders may be preventable through modifications of diet and lifestyle.”
Use the following table to help you make better dietary choices for your fertility.
FOODS ASSOCIATED WITH FEMALE FERTILITY
FOODS ASSOCIATED WITH FEMALE INFERTILITY
Olives and olive oil
Cake mixes and other packaged foods
Frozen food like pot pies, waffles, and pizzas
Baked goods such as cookies and donuts
Whole-fat dairy foods
Plant sources of protein such as peas, beans, tempeh, and quinoa.
Chips and crackers
Sugary breakfast cereals and energy bars
Low-fat dairy foods
Whole wheat bread