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Does nutrition really matter for fertility? Truths and myths about the "fertility diet"

Does nutrition really matter for fertility? Truths and myths about the "fertility diet"

6 min read

When it comes to nutrition, everyone and their mother has an opinion about what you should eat. The realm of fertility is no exception.

Catchy phrases like “fertility foods” and “fertility diet” are tossed around like hot potatoes, begging the question: How much of an impact does nutrition actually have on reproductive health? Is there really a "fertility diet" and, if so, which one is the real one?

Spoiler alert: Yes, nutrition does impact fertility. But that’s not the whole story. With so much hype out there in the Google-sphere, when you hear “fertility diet,” it’s often best to take what follows with a grain of salt.

Here, we’re going to debunk some myths and dive into the dos and don’ts of the “fertility diet.” But first, there are two important things to keep in mind:

  1. The so-called “diet” is not really a diet: Optimal fertility is not achieved through overly restrictive, extreme diets (like keto, for example). Instead, it’s the result of healthy, balanced eating — which happens to include a (mostly) Mediterranean style. Though the style is often called the “Mediterranean diet,” it's less a diet and more a way of life.
  2. Nutrition is only one piece of the puzzle: For those struggling with conditions like endometriosis or polycystic ovary syndrome (PCOS), nutrition remains an important element, but the puzzle gets much more complex. The following guidelines are to be considered within the full picture of your health and well-being — they’re not prescriptive or curative.

What is the “fertility diet”?

The “fertility diet” originated from a team of researchers at the Harvard School of Public Health. In 2007, Drs. Jorge Chavarro, Janet Rich-Edwards, Bernard Rosner, and Walter Willett reviewed eight years of food diaries from over 17,000 women, all in the baby-making years of life. Each participant received a score based on how well they adhered to the researchers’ prescribed “fertility diet.”

Long story short, those who had the highest scores were 66% less likely to struggle with ovulatory infertility. (Note the specification of ovulatory fertility issues — they weren’t expecting nutrition to impact infertility due to structural issues like blocked fallopian tubes.)

Here are the nutritional tenets of Harvard’s fertility diet:

1. Fats:

  • Eat more monounsaturated fats, like olive oil and avocados.
  • Eat less trans fats (look for partially hydrogenated oils on the ingredients lists of crackers, baked goods, peanut butters, and other packaged foods that perplexingly never seem to spoil).

2. Protein:

  • Eat more protein from vegetable sources.
  • Eat less animal protein (think more beans, less red meat).

3. Carbohydrates:

  • Eat more fiber from vegetables, beans, lentils, and whole grains.
  • Eat less blood sugar-spiking refined carbs (like white bread, pasta, ciabatta, and sweets).

4. Dairy:

  • Eat more high-fat and full-fat dairy (yes, you read that right).
  • Eat less nonfat or low-fat dairy products (if fertility is the goal at hand and you’re a dairy eater, go for the whole-milk versions).

5. Supplements:

  • Take a prenatal multivitamin with folic acid daily up to a year before conception and then throughout the first trimester.

But what does the latest research say about the “fertility diet”?

As a savvy reader, you’ll likely notice that the Harvard research dates back over a decade, which may have you wondering if the conclusions still hold true. Good question.

A 2018 review published in the American Journal of Obstetrics & Gynecology compiles the findings from the last decade. While upholding the overall dietary patterns of the original “fertility diet,” this review digs deeper into the role of specific nutrients — helping to tease apart truth from myth. Let’s dive in.

MYTH: Vitamin D is your ticket to ride

Discovery of vitamin D receptors on the ovaries, endometrium, and placenta spurred a flurry of hype. However, results from human and animal studies trying to better understand the relationship between vitamin D intake and fertility have been all over the map.

If you’re a woman living in the northern hemisphere who wears sunscreen, chances are high that your vitamin D levels are deficient. The best next step is to talk to your provider about getting your vitamin D levels tested.

If you are deficient in vitamin D, getting your levels up to normal is likely to be helpful for conception, as well as for your overall health. Vitamin D and calcium work together in the body to promote the development of bones and teeth — and vitamin D helps with calcium absorption. Developing babies need calcium and vitamin D during pregnancy, so having adequate levels of both are important.

If you’re not deficient, there isn’t enough evidence yet to recommend taking vitamin D for the sole purpose of fertility.

MYTH: Soy is an anti-thyroid estrogen bomb

Rumor has it that soy is a scary hormone disruptor. Yes, soy does contain phytoestrogens —  compounds that weakly mimic the structure of estrogens. This does not mean, however, that eating soy increases your estrogen levels. In reality, research doesn’t back up threats that eating soy causes or exacerbates endocrine issues. Some evidence even suggests that taking soy isoflavone supplements while undergoing artificial reproductive technology (ART) can improve outcomes.

Soy also gets slammed as a perpetrator of thyroid imbalances. Again, myth busted. Here’s the real deal: It’s true that eating copious amounts of soy can block iodine uptake, and that iodine is required to make thyroid hormone. The rest of the story, however, is that if you eat enough iodine, like most people in the modern industrialized world, soy is not going to make a discernible impact on your iodine levels. A substantial body of research zeroing-in on this issue concludes that soy is an unlikely culprit in most cases of thyroid malfunction.

TRUTH: You should consider taking folic acid

Recommendations are well established for women of childbearing age to take 400 micrograms (mcg) per day of folic acid for the prevention of neural tube defects. If you’re a strict vegetarian or vegan, have a history of seizure disorder, are a heavy drinker, or have certain genetic predispositions, you might need more than the typically recommended amount. There is also a body of emerging research that suggests up to 800 mcg/day for enhancing chances of conception and preventing miscarriage. Talk to your provider about the appropriate dose for you.

TRUTH: Antioxidants make strong swimmers

Has someone in your life insisted that your fertility depends on taking antioxidants like vitamin E, carnitine, selenium, and/or CoQ10? These recommendations are not total woo-woo.

Antioxidants are protective compounds, found in healthy foods like blueberries and almonds, that mitigate the damaging effects of oxidative stress (like egg damage). So, it’s not a crazy leap to assume that supplementing with antioxidants can boost fertility.

However, studies looking specifically at fertility among women who take antioxidants don’t corroborate these assumptions. We don’t have enough scientific evidence to support blanket recommendations for otherwise healthy women struggling with infertility to drop dollars on antioxidant supplements.

For sperm producers, antioxidants hold more promise. The research suggests that male antioxidant supplementation may give a modest boost to semen quality and pregnancy rates.

The takeaway: It’s widely accepted that a high-antioxidant diet (think copious amounts of fruits and vegetables) is good for you, and thus, good for your reproductive health. But that doesn’t mean that more (in the form of supplements) is better. For people with sperm who are undergoing fertility treatments, antioxidants could be helpful. For people with ovaries in the same boat, supplementation may not be the best use of limited resources. As always when considering any supplement, run it by your provider first.

TRUTH: Sugar is not a fertility friend

We’re not going to make outrageous claims that sugar is toxic and the cause of all your ailments. We’re also not here to shame anyone — sweet treats are part of a balanced, delicious life. Healthy eating is not perfect eating. Read the following to empower yourself with knowledge, not to fuel your guilt over enjoying sweets.

One clear finding from the Harvard researchers’ review of thousands of food records was that keeping blood sugar balanced appears to be a critical element of preventing ovulatory infertility.

Here’s why: Over time, perpetual spikes in blood sugar can cause a condition called insulin resistance (if PCOS is in your health history, this likely rings a bell). Insulin is a hormone that, when chronically elevated, can cause the ovaries to produce excess androgens (male hormones). (Take a deep dive into insulin resistance and PCOS.)

So, what causes your blood sugar levels to spike, triggering this cascade of hormone imbalance? You guessed it — sugar. Well, technically, simple carbohydrates (aka high-glycemic foods), including white or refined carbs, as well as sweets. It may be intuitive that candy corn raises your blood sugar. Maybe less intuitive is that cereal, crackers, pasta — even local, artisan baguette — are all just as easily broken down by your digestive enzymes into a simple sugar, spiking insulin production.

From a fertility perspective, this doesn’t mean you have to treat sugar like toxic waste. It does mean making balanced choices and monitoring your hormone levels (thankfully, Modern Fertility’s test makes staying informed easier than ever).

So, what’s for lunch? You do you

If cutting back on gluten, sugar, carbs, animal products, and other dietary changes is what helps you feel more in control of your fertility, do it. But these extremes are not a silver bullet to fertility — and not the best (or easiest) choice for everyone.

From a nutrition perspective, eating for fertility can be boiled down to this: Eat a colorful abundance of fresh fruits and vegetables, with tons of fish, seafood, nuts, seeds, whole grains, and healthy fats (including high-fat dairy). Nutrition is not the full fertility story, but unlike so many health factors, food is one area where you have some control. Take the reins where you can (and checking in with your hormones with the Modern Fertility test is just one of the ways you can do that!).

This article was written by Anna Bohnengel, MS, RD, LD, co-founder of Alavita Nutrition. Learn more about her practice here.

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Anna Bohnengel, MS, RD, LD

Anna, MS, RD, LD is co-founder of Alavita Nutrition. With clinical training from the NIH, she teaches women how to nourish themselves so they can take control of their health. alavitanutrition.com

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