The battle of the sexes has been waging for centuries. We’ve fought over jobs, relationship demands, household responsibilities and driving ability. On reality shows, men and women are pitted against each other to see who is the best designer, chef and even survivalist.
But when it comes to health, the battle of the sexes is less of a “who’s better,” and more of a “what’s better.” Men and women’s bodies are clearly different, and what works well for one gender may not be as effective for the other.
And then there are those things that seem like they’d be universally effective, such as not smoking and eating more fiber. But, as it turns out, even those basics seem to have a gender preference.
Dietary Fiber and Heart Disease
It is widely accepted that fiber benefits your heart. Whether you are talking about soluble or insoluble fiber, you can count on dietary fiber to help lower cholesterol and reduce clotting risk, which in turns lowers your risk for stroke.
However, most of these studies have been performed in Western cultures. Given this, Japanese researchers questioned if fiber would also reduce the risk of cardiovascular disease in a Japanese population.
To answer this, they turned to the Japan Public Health Center-based prospective study, an ongoing study that focuses on cardiovascular disease and cancer. The study’s participants come from 27 different towns and cities served by nine separate public health centers in Japan.
There are two different cohorts for the study. The first was started in 1990 and consists of participants aged 40 to 59 years of age. The second cohort began in 1993 and includes participants aged 40 to 69 years of age. There is no overlap in participation between the two cohorts.
To determine the effects of fiber intake on cardiovascular disease, researchers looked at the food diaries of participants from both cohorts between the years 1995 and 1998. They ended up with more than 86,000 diaries (40,046 from men and 46,341 from women).
The food diaries include several nutrients and food groups, as well as some demographic and lifestyle factors, such as:
- Frequency of consumption
- Portion size
- Weight and height
- Smoking or not
- Alcohol consumption
- Exercise habits
- Medication use
- Mental stress
They found that, when it came to fiber, a few foods stood out. These included:
- Natto (fermented soybeans)
- Miso (fermented soybean paste)
- Shiitake mushrooms
Lastly, they looked at incidence of cardiovascular disease, which they defined as stroke and general heart disease. They noted deaths due to cardiovascular disease and stroke, categorizing the latter into three subgroups:
1. Ischemic stroke (blockage blood flow in an artery leading to the brain)
2. Intracerebral hemorrhage (blood vessel in the brain bursts)
3. Subarachnoid hemorrhage (bleeding between brain and the tissues that cover the brain)
Women Get More Out of Fiber
After following the participants for nearly 10 and a half years, researchers found a total of 3,237 cardiovascular issues, 684 of which were due to heart disease and 2,553 of which were strokes. Of the strokes, more than half (1,428) were ischemic strokes, while 766 were intracerebral hemorrhages and the remaining 359 were subarachnoid hemorrhages.
When they added fiber into the picture, researchers found that, when they adjusted for age, both men and women who had greater fiber intake had fewer cardiac incidents. They found a similar relationship in men and women who never smoked.
However, that’s where the similarities ended. Then it became all about the women.
When they looked at ALL women (not just adjusting for age), researchers found that women showed a significant association between intake of insoluble fiber (grains, seeds, nuts, etc.) and lower incidence of cardiovascular disease, total stroke, ischemic stroke and intracerebral hemorrhage. There was also an association with these same conditions and soluble fiber (oatmeal, legumes, most fruits, etc.), but it was weaker.
When it came to the men, there were no significant associations between fewer incidence of cardiovascular disease and fiber intake, regardless of type of fiber.
Not So Fast, Gentlemen
Does this mean that men no longer have to up their fiber consumption? Absolutely not. Remember, researchers found that both non-smokers and older adults — regardless of gender — benefited from higher fiber intake.
It’s just that women seem to gain even greater benefit from a high-fiber diet. While researchers don’t discuss this, we have to wonder if there is a hormonal issue at play.
Too much estrogen can increase a woman’s risk for heart disease, especially stroke. We learned this in the landmark 2002 JAMA study. Consequently, fiber helps to rid the body of excess estrogen.
Given this, I have to wonder if the high fiber/low heart disease and stroke association is more than a little related.
Regardless, I think the takeaway here is pretty clear: This is one area where both sides win in the battle of the sexes.
If you are male and smoke, quit. Today. (See A Surprising Way to Kick Your Cigarette Addiction.) And make sure to up your intake of fiber. Whether its whole grains, flaxseed, or lots of fruits and vegetables, get your fiber and get it often.
For women, the same advice goes for smoking. (See What to Do if You Can’t Stop Smoking.) And for fiber, it appears the key may be a bit more geared toward the insoluble variety. This means lots of whole grains, nuts, brown rice, root vegetables, broccoli, cauliflower, green leafy veggies and virtually all fruits.
Now that’s a plan we can all agree on!
 Kokubo, Y, et al. Dietary fiber intake and risk of cardiovascular disease in the Japanese population: the Japan Public Health Center-based study cohort. Eur J Clin Nutr. 2011;65:1,233-41.
 Rossouw, JE, et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA. 2002 Jul 17;288(3):321-33