Beans are another functional food. As one of the high potassium foods they lower blood pressure and increase bone density and reduce the chance of kidney stones when part of a high potassium diet. Of course you need to get 4700 mg of potassium and less than 1500 mg to 2300 mg of sodium a day. In addition the legumes provide more protein than most other plant food, are low in fat, have plenty of fiber, especially soluble fiber, and have polyphenols to fight free radicals.
An epidemiological study (1) showed that legumes were predictive of lower mortality in studies of 5 groups from Japan, Sweden, Greece and Australia. The study is part of an ongoing study of long-lived elderly groups – the Food Habits in Later Life (FHILL). There was a 7 to 8% reduction in mortality hazard ratio for every 20 gm increase in daily legume consumption in these groups. The researchers statistically corrected for many factors. But as with many of these multicultural studies, there may have been other factors that were not corrected for. Nonetheless it is a good indication of how beans may be helpful, and is consistent with many other high potassium food studies.
The health benefits of beans go beyond their high potassium content. They have higher protein content than most other plant foods reaching 20 to 25% of calories. They are low fat unless fried or refried. They are filled with fiber which helps push food through the intestines. And they have large amounts of soluble fiber to reduce LDL cholesterol.
Their micronutrient, vitamin and phytochemical content also contribute to their healthful effects. They have a wide variety of minerals, including magnesium and often selenium. They are folate rich which counters high homocysteine levels, lowering the chance of heart disease. Their polyphenols fight free radicals. Polyphenols have been shown to reduce inflammation, increase nitric oxide production and produce higher antioxidant levels.
How beans are handled is important to their effect on health. If fried, the saturated fat level will be markedly raised, removing one healthful aspect. Also many canned beans have a high sodium content which reverses the favorable effect of their high potassium content.
For a table of macronutrient values and potassium content, see the post here. For a list of multiple posts, many of which have tables of the potassium content of various foods, look here.
1. Legumes: the most important dietary predictor of survival in older people of different ethnicities. Darmadi-Blackberry I, Wahlqvist ML, Kouris-Blazos A, Steen B, Lukito W, Horie Y, Horie K. Asia Pac J Clin Nutr. 2004;13(2):217-20.