Natto is a Japanese food that is fermented soybeans. For those of you who know me, you know I am not a soy fan but when soybeans are fermented most of soy's negative attributes are changed to be healing. During the fermentation process soy's toxic phytate and antinutrient levels are eliminated along with it's thyroid inhibiting qualities as well. Once fermented, soybeans are the most powerful bone building superfood on the planet. Samurai are said to have eaten natto everyday. But I will tell you now, if you don't already know, natto is slimy and smells foul and yet 7.5 billion packages of natto are consumed in Japan yearly. For those of us who are not used to it that's why I provide it in pill form for my patients.
Natto's superfood abilities comes from a high vitamin K2 concentration. So if you don't muscle test for the natto I then test you for a vitamin D3 and K2 supplement.
Habitual intake of natto was associated with a significant and beneficial effect on bone health in elderly men and this association is primarily due to vitamin K content of natto was concluded in Osteoporos Int. 2012: 23 (2).
Women who ate 4 packets of natto a week reduced bone mass loss on the thigh bone by 80% according to Journal of Nutrition 2006: 136
Those in the highest third of vitamin K2 intakes were 52% less likely to develop calcification of arteries according to Artherosclerosis. 1995: 226 Also Menaquinone (Vitamin K2) is associated with a reduced risk of coronary heart disease. Journal of Nutrition 2004: 134 (11)
Vitamin K is proven to help rebuild bone and protect against heart disease but there are two kinds. Vitamin K1 is the type found in dark leafy vegetables and for a long time I recommended them as a high source of vitamin K. However, studies show now that we only absorb 10% of K1 from dark leafy vegetables. Research has now turned to more effective vitamin K2. Vitamin K2 is hard to get from food other than natto so next time you are at a Japanese restaurant or section of the grocery store try it. It's an acquired taste as sometimes healthy things are!