Preventive Medicine and Nutrition
against Menstrual Pain
Neal D. Barnard, M.D.
Menstrual pain is significant in about half
of women, and in up to 10 percent it is severe enough to interfere
with work and other activities for one to two days every month.
Sometimes it diminishes after childbirth, but for many it
In the 1960s, it became clear that chemicals
called prostaglandins are a central part of the problem. These
chemicals are made from the traces of fat stored in cell membranes
and that they promote inflammation. They are also involved in
muscle contractions, blood vessel constriction, blood clotting,
Shortly before your period begins, the
endometrial cells that form the lining of the uterus make large
amounts of prostaglandins. When these cells break down during
menstruation, the prostaglandins are released. They constrict the
blood vessels in the uterus and make its muscle layer contract,
causing painful cramps. Some of the prostaglandins also enter the
bloodstream, causing headache, nausea, vomiting, and diarrhea.2
Researchers have measured the amount of
prostaglandins produced by the endometrial cells in women with
menstrual pain and found that it is higher than for other women.3
The concentration of prostaglandins circulating in the blood is
higher, as well.2
This helps explain why nonsteroidal
anti-inflammatory drugs work for menstrual pain. Ibuprofen
(Motrin), naproxen (Anaprox), and other NSAIDs reduce the
production of prostaglandins.
There may be a more fundamental approach.
Rather than focus on the prostaglandins themselves, it may help to
focus on the cellular "factories" that make them. After all, we
know that birth control pills reduce menstrual pain, and they
apparently do this by reducing the growth of the endometrial cell
layer. The smaller this layer of cells is, the less tissue there
is to make prostaglandins.
In every monthly menstrual cycle, the amount
of estrogens in a woman's body rises and falls. Estrogens are
female sex hormones. You can think of them as a sort of hormonal
fertilizer, making the cells of your body grow. Estrogens are
responsible for breast development at puberty, and each month,
they cause the lining of the uterus to thicken in anticipation of
If you were to measure the amount of
estrogens in a woman's bloodstream as her period ends and a new
cycle begins, you would find that it is gradually rising. For
about two weeks, it rises toward a peak and then falls quickly
around the time of ovulation. It rises again in the second half of
the month and then falls just before her next period. The uterus
sheds its lining in a menstrual flow, accompanied by crampy pain.
The amount of estrogen in your blood is
constantly being readjusted. Some foods push hormone levels up.
Others bring them down.
Here's how it works: Fat drives estrogen
levels up. Any kind of fat will do it: chicken fat, fish fat, beef
fat, olive oil, canola oil—you name it. It does not matter if it
is animal fat or vegetable oil; the more of it there is in your
diet, the more estrogen your body makes.
If you cut the amount of fat in your diet,
the amount of estrogen will be noticeably reduced within the very
first month. Cancer researchers have taken a great interest in
this phenomenon, because lowering the level of estrogen in your
blood helps reduce the risk of breast cancer. Less estrogen means
less stimulation for cancer cell growth.
If a woman eating a Western diet cuts her
fat intake in half, her estrogen level will be about 20 percent
lower.4 If you cut the fat even more, your estrogen
level will drop further. That is a good change. If your hormone
level does not rise too high, it will have less effect on your
I hypothesized that a change in estrogen is
what gets the credit for the newfound comfort that many women
experience when they change their diets. In a research study,
published in Obstetrics & Gynecology in February 2000, we
found that a low-fat, vegan diet significantly reduces pain and
PMS for many women.
The diet change was designed to do two
things. First, it eliminated all animal fats and nearly all
vegetable oils. Less fat in the diet means that less estrogen is
produced, which is a good thing.
Second, plant foods also increase the amount
of plant roughage (fiber) in your diet, which helps your body to
get rid of excess estrogens. Estrogens are normally pulled from
the bloodstream by the liver, which sends them through a small
tube, called the bile duct, into the intestinal tract. There,
fiber soaks them up like a sponge and carries them out with the
wastes. The more fiber there is in your diet, the better your
natural "estrogen disposal system" works.
Animal products never have any fiber at all.
If fish, chicken, yogurt, or other animal products make up any
substantial part of your diet, there will be less fiber in the
digestive tract. The result is disastrous. The waste estrogens,
that should bind to fiber and leave the body, end up passing back
into the bloodstream. This hormone "recycling" increases the
amount of estrogen in the blood. But you can block it with the
fiber in grains, vegetables, beans, and other plant foods that
keep waste estrogens headed toward the exit.
So, by avoiding animal products and added
oils, you reduce estrogen production. And by replacing
chicken, skim milk, and other fiberless foods with grains, beans,
and vegetables, you will increase estrogen elimination.
Foods to Work
You can do this yourself. The key is to
follow the diet exactly, so that you can see the effect it
has for you.
whole grains, such as brown rice, whole grain
bread, and oatmeal
vegetables: broccoli, spinach, carrots, sweet
potatoes, Swiss chard, Brussels sprouts or any other
legumes: beans, peas, and lentils
animal products of any type: fish, poultry,
meats, eggs, and dairy products
added vegetable oils: salad dressings,
margarine, and all cooking oils
any other fatty foods: doughnuts, french
fries, potato chips, peanut butter, etc.
This sounds like a significant change, and
it is. However, we have found that, while everyone feels a bit at
sea for the first several days, virtually everyone makes the
change in about two weeks. Those who have the best time with it
are those who experiment with new foods and new food products and
who enlist the support of their friends or partners at home.
As the benefits kick in—reduced menstrual
cramps, incredibly easy weight loss, and increased energy—the diet
change is so rewarding that you will only wish you had tried it
It is important to avoid animal products and
oily foods completely. Even seemingly modest amounts of
them during the course of the month can cause more symptoms at the
end of the month.
Be sure to have your foods in as natural a
state as possible, choosing brown rice instead of white rice and
whole grain bread instead of white bread in order to preserve
Give this experiment a careful try for just
one cycle, and you will see what it can do for you. You will very
likely start to look at the power of foods in a very different
1. Merskey H, Bogduk N (eds). Classification of
Chronic Pain, 2nd edition. Seattle: IASP Press, 1994, pp. 164-6.
2. Chan WY. Prostaglandins and nonsteroidal
antiinflammatory drugs in dysmenorrhea. Ann Rev Pharmacol Toxicol
3. Ylikorkala O, Dawood MY. New concepts in dysmenorrhea.
Am J Obstet Gynecol 1978;130:833-47.
4. Prentice R, Thompson D, Clifford C, Gorbach S, Goldin B,
Byar D. Dietary fat reduction and plasma estradiol concentration
in healthy postmenopausal women. J Natl Cancer Inst
This factsheet is drawn from Dr. Barnard's
book Foods That
here for a downloadable version of this fact sheet.