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Human and animal studies show that a group of genes called the major histocompatibility complex (MHC) can influence odor. In general, females prefer the odor of mates with a dissimilar MHC -- but this effect is reversed in women on oral contraceptive pills.

A study found that that single women preferred the odor of MHC-similar men, but women in relationships preferred the opposite. This means that that the use of contraceptive pills could influence mate preference.

According to FYI Living:
"The women on pills preferred men with similar MHC genes. Studies indicate that, 'women consider the olfactory domain to be an important factor in their assessment of potential partners.' Thus, due to serious alterations in odor preference, the use of oral pills could influence partner choice."
Dr. Mercola's Comments:

This is something that most people would rarely ever consider, but according to researchers, women who are on birth control pills may inadvertently be misled to select less compatible long-term partners than women who aren't on the Pill... Whether or not this is of any real concern to most is debatable, but contraceptive pills may also wreak havoc in your life in more direct ways, which I'll review in a moment.

How the Pill May Influence a Woman's Choice of Partner

It's a fairly well-known fact that odor plays an important role when selecting a partner. This includes the scents that you cannot consciously detect, such as pheromones. (A few years ago, researchers discovered that a specific olfactory nerve, dubbed "Nerve O," appears to be the route through which pheromones are processed. Nerve "O" has endings in your nasal cavity, but the fibers go directly to the sexual regions of your brain. Because Nerve O bypasses your olfactory cortex, it does not register a conscious smell, but rather identifies chemical sexual cues.)

Humans, like animals, also have major histocompatibility complex-associated (MHC) odor preferences that influence their choice of mates. Researchers have discovered that women, in general, prefer the body odor of men with dissimilar MHC. It is believed that this may be part of a natural selection process to prevent and control genetic inbreeding. When partners have similar MHC, their chances of successfully reproducing are diminished.

However, when a woman is on the Pill, her odor preferences change. The Pill essentially mimics pregnancy, and when a woman is pregnant, she tends to prefer the scent of men with similar MHC as her own - perhaps as a biological cue to now seek out and bond with supportive family members as opposed to potential mates.

What this means is that when you're taking a hormonal contraceptive, you interfere with your biology and risk producing a hormonal imbalance that might make you more attracted to men with similar chemical makeup. If you were on the pill when you met your mate, you might, therefore, feel less attracted to him when you stop taking it - or worse, you may have greater trouble getting pregnant. Needless to say, either of these scenarios could cause problems within the relationship...

However, there's another issue that may be of even greater importance, and that is the health effects that birth control pills have on the female body.

Artificially controlling your menstrual cycle with synthetic hormones may certainly seem like an ideal method of a highly effective, relatively inexpensive and easily reversible birth control. And contraceptive pills are a convenient way to prevent pregnancy ... but that's where their benefits end. Birth control pills are linked to numerous very serious health risks, so it's important to carefully weigh the benefit of convenience against its considerable risks.

Artificially Manipulating Your Hormones is a Risky Proposition

Most birth control pills, patches, vaginal rings, and implants contain a combination of the derivatives of the hormones estrogen and progestin. They work by mimicking these hormones in your body to fool your reproductive system into producing the following effects:

  • Preventing your ovaries from releasing eggs
  • Thickening your cervical mucus to help block sperm from fertilizing an egg
  • Thinning the lining of your uterus, which makes it difficult for an egg to implant, should it become fertilized
However, your reproductive system does not exist in a bubble ... it is connected to all of your other bodily systems, and therefore the Pill is capable of altering much more than your reproductive status.

Well-Documented Risks of Synthetic Estrogen and Progestin

If you're on one of the hormonal birth control methods (whether it's the pill, patch, vaginal ring or implant), it is important to understand that you are taking synthetic progesterone and synthetic estrogen -- something that is clearly not advantageous if you want to maintain optimal health.

These contraceptives contain the same synthetic hormones as those used in hormone replacement therapy (HRT), which has well-documented risks, including an increased risk of blood clots, stroke, heart attack, and breast cancer. In fact, studies have found that HRT increases post-menopausal women's breast cancer risk by at least one percent per year, and HRT with progestin increases your risk by eight percent per year, potentially going as high as 30 percent after just four years of use!

So, what are the risks for women who start taking synthetic hormones at an early age and stays on them for up to 15 years or longer?

In exchange for the convenience of preventing pregnancy (which you can do naturally just as well, and I'll explain how below), you are putting yourself at risk of:
  • Cancer: Women who take birth control pills increase their risk of cervical and breast cancers, and possibly liver cancer as well.
  • Thinner bones: Women who take birth control pills have lower bone mineral density (BMD) than women who have never used oral contraceptives.
  • Heart disease: Long-term use of birth control pills may increase plaque artery buildups in your body that may raise your risk of heart disease.
  • Fatal blood clots: All birth control pills increase your risk of blood clots and subsequent stroke. And if your prescription contains the synthetic hormone desogestrel, your risk of fatal blood clots nearly doubles!
  • Impaired muscle gains: A recent study found that oral contraceptive use impairs muscle gains from resistance exercise training in women.
  • Long-term sexual dysfunction: The Pill may interfere with a protein that keeps testosterone unavailable, leading to long-term sexual dysfunction including decreased desire and arousal.
  • Migraines
  • Weight gain and mood changes
  • Yeast overgrowth and infection
Newer Hormonal Birth Control Methods May be Even Riskier

Two of the newer hormonal contraceptives - the hormone-releasing vaginal ring, NuvaRing, and the combination pills Yaz and Yasmin, which also contain the hormone drospirenone in addition to estrogen and progestin - may be of even greater concern than the older "classics."

The NuvaRing is a flexible vaginal ring that is replaced once a month. It releases estradiol and etonogestrel. The latter is known as a "third generation" progestin desogestrel, which has been linked to serious health concerns and may double your risk of blood clots when compared to second generation contraceptives. The NuvaRing delivers a relatively high dose of this hormone.

Other types of birth control also contain this third generation hormone, including some implants.

More than 4,000 lawsuits have also been filed against Bayer for serious side effects suffered by women taking the newer birth control pills Yaz and Yasmine. The four most common adverse effects are blood clots, gallbladder disease, heart attack and stroke. The first trial is scheduled to begin in September, and according to some legal estimates, the number of lawsuits filed may at that point reach 30,000.

Safer Options Exist - Top Eight Natural Birth Control Methods

Because the health risks of hormonal contraceptives are so significant, and other safer options exist, I strongly advise against them. Nearly all patients who visit my Natural Health Center are asked to stop using hormonal contraceptives like birth control pills as soon as possible.

Many women opt for hormonal contraceptives because they're unaware of the other effective birth control methods out there. The following options, which include both natural family planning and barrier methods, are effective ways to prevent pregnancy without damaging your health.

  • Male condoms: Condoms have a 98 percent effectiveness rate when used correctly. A water-based lubricant will increase the effectiveness; do not use an oil-based lubricant, however, as they break the latex.
  • Female condoms: These thin, soft polyurethane pouches fitted inside the vagina before sex are 95 percent effective. Female condoms are less likely to tear than male condoms.
  • Diaphragm: Diaphragms, which must be fitted by a doctor, act as a barrier to sperm. When used correctly with spermicidal jellies, they are 92 to 98 percent effective.
  • Cervical cap: This heavy rubber cap fits tightly against the cervix and can be left in place for 48 hours. Like the diaphragm, a doctor must fit the cap. Proper fitting enhances the effectiveness above 91 percent.
  • Cervical sponges: The sponge, made of polyurethane foam, is moistened with water and inserted into the vagina prior to sex. It works as a barrier between sperm and the cervix, both trapping and absorbing sperm and releasing a spermicide to kill them. It can be left in for up to 24 hours at a time. When used correctly, the sponge is about 89-91 percent effective.
Aside from these barrier methods, there are also natural family planning (NFP) tools that a woman can use to track her ovulation. Many women feel empowered by NFP because it allows them to get in touch with their fertility cycle.

Some of the most popular NFP methods include:

  • Calendar Method: Abstention from sex during the week the woman is ovulating. This technique works best when a woman's menstrual cycle is very regular. However, it may not work very well for couples who use it as the sole means of contraception, as its success rate is only around 75 percent. You can boost its effectiveness by combining it with the temperature and mucus methods described below.
  • The Temperature Method: This is a way to pinpoint the day of ovulation so that sex can be avoided for a few days before and after. It involves taking your basal body temperature (your temperature upon first waking) each morning with an accurate "basal" thermometer, and noting the rise in temperature that occurs after ovulation.
    Beware that illness or lack of sleep can change your body temperature and make this method unreliable by itself, but when it is combined with the mucus method, it can be an accurate way of assessing fertility. The two methods combined can have a success rate as high as 98 percent.
  • The Mucus Method: This involves tracking changes in the amount and texture of vaginal discharge, which reflect rising levels of estrogen in your body. For the first few days after your period, there is often no discharge, but there will be a cloudy, tacky mucus as estrogen starts to rise. When the discharge starts to increase in volume and becomes clear and stringy, ovulation is near. A return to the tacky, cloudy mucus or no discharge means that ovulation has passed.
As you can see, there are many alternatives to the Pill and other hormonal contraceptives out there, and my advice to women is to seriously evaluate the risks versus benefits before taking any type of birth control pills.

Recommended Reading

I encourage you to become actively involved in fertility awareness, and embrace natural family planning or barrier methods that will not interfere with your hormones and health.

Some excellent reading to get you started on this path include:
  1. The Ovulation Method: Natural Family Planning, by John J. Billings
  2. Taking Charge of Your Fertility: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health, by Toni Weschler
  3. Honoring Our Cycles: A Natural Family Planning Workbook, by Katie Singer