It's important to understand that the dramatic heart-related effects of vegetables depend on dosage. You can't just eat a carrot and call it a day. To really make an impact, the recommended amount of vegetable servings per day is five to 13, depending on your size, with a serving equaling about a cup (for lettuce, a serving is two cups) [source: Harvard]. That's a lot of vegetables. Most of us only eat about three servings a day [source: Harvard]. But it's worth the effort to increase your vegetable intake. It makes more of a difference than you might think.
Dietary fiber is divided into two types: soluble (meaning it dissolves in water) and insoluble. Both types of dietary fiber are important. They resist digestion and help you feel full, naturally decreasing your hunger and food intake and keeping weight and body fat down. But the insoluble type doesn't have a direct effect on the heart. It aids in weight control and insulin regulation, which certainly helps the heart tremendously, but the effect isn't as direct as with soluble fiber.
The soluble fiber in carrots and other foods helps keep arteries clean primarily by lowering LDL ("bad") cholesterol. LDL cholesterol helps plaque form in the arteries, narrowing the passageways and restricting blood flow to the heart. The process is fairly straightforward, and it starts with bile acids.
Bile acids are molecules in the body that aid in the formation of molecule clusters called micelles. Micelles are a necessary component in the reaction that takes cholesterol from the food we eat and integrates it into our bodies. When we consume soluble fiber, it binds to bile acids, preventing them from participating in the reactions necessary to form micelles. With micelle formation reduced, the body's absorption of cholesterol is reduced.
And with cholesterol absorption reduced, less plaque ends up building up in the arteries. Fiber can be as good as drugs like Lipitor at lowering cholesterol; if you eat the daily recommended amount of fiber, you could lower your cholesterol by up to 20 percent. [source: BNET].
Fiber isn't the only reason to eat vegetables, of course. Carrots are the greatest source of beta-carotene, a substance that acts as both an antioxidant and a pro-vitamin. Antioxidants can counter cell damage, which slows aging and disease processes and can help prevent death by heart disease and cancer. Pro-vitamins are chemicals the body can convert into vitamins. In the case of carrots, this pro-vitamin is beta-carotene, which the body converts into vitamin A. Vitamin A helps the immune system work most effectively, allowing it to fight off disease and infection.
With all of the health benefits of vegetables, they do have one big problem: Lots of people hate eating them. Enter drinks like V8, and countless powders sold in health food stores that claim to let you have your vegetables without actually eating them. Can it really be that easy? Unfortunately, no -- the fiber in vegetables is mostly lost when they're made into juices and powders. Fiber lives primarily in the skin and cell walls, which tend to be left behind in the juicer [source: CSPI]. Plus, drinks like V8 have so much sodium, the health effects of any good stuff that does make it into the drink are pretty much counteracted by all the salt [source: CSPI].
On the upside, dousing a head of lettuce in low-fat dressing so you can't taste the green stuff doesn't decrease its health benefits.
For more information on vegetables, heart health and related topics, look over the links below.
Related HowStuffWorks Articles
More Great Links
- Another Win for Vegetables. Time.com. http://www.time.com/time/health/article/0,8599,1807344,00.html
- Carrots. The World's Healthiest Foods. http://www.whfoods.com/genpage.php?tname=foodspice&dbid=21
- Fiber. American Heart Association. http://www.americanheart.org/presenter.jhtml?identifier=4574
- Lost in Translation: Why real fruits and vegetables beat juices, powders and purees. Center for Science in the Public Interest. http://www.cspinet.org/nah/12_07/special.pdf
- Type of Vitamin A Found to Cut Heart Disease. The New York Times. November 14, 1990. http://query.nytimes.com/gst/fullpage.html?sec=health&res=9C0CEFDF1F3 AF937A25752C1A966958260
- Use of dietary fiber to lower cholesterol. American Family Physician. April 1989. http://findarticles.com/p/articles/mi_m3225/is_n4_v39/ai_7609823
- Vegetables and Fruits: Get Plenty Every Day. Harvard School of Public Health. http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/vegetables- full-story/index.html