The K Connection

The K Connection

If you’re concerned about the health of your bones, or if you’ve been diagnosed with osteopenia (a condition that precedes osteoporosis), then you’ll find plenty of helpful information in the e-Alert “Rags to Riches” (1/25/07), which offers details about supplements that help promote bone strength. “Rags to Riches” is available at this link:

In that e-Alert, I reviewed recommendations from Jonathan V. Wright, M.D., and HSI Panelist Allan Spreen, M.D., about vitamin D, calcium, and magnesium. Today we’ll look at a study that underlines the importance of another vitamin that’s a key player in bone health: K2.

Keeping the ball in the socket

Among vitamin K’s various forms, K1 and K2 are the two basics. Almost all of our intake of this vitamin comes in the form of K1, which is mostly found in dark, leafy green vegetables, broccoli, asparagus, tomatoes, avocados, olive oil, whole wheat, butter, and green tea. Vitamin K1 is converted into K2 in the intestine, but we get some amount of K2 directly from meat, liver, egg yolk, and fermented products such as yogurt and cheese.

According to researchers at the University of Maastricht in the Netherlands, vitamin K acts as a manager in the synthesis of proteins that regulate bone metabolism. Last month, the Maastricht team published the results of a new vitamin K study in the journal Osteoporosis International. Their study was designed to determine how bone mineral content (BMC) and femoral neck width might be affected by high intake of vitamin K.

The femoral neck is a narrow section of the femur (thigh bone) located just below the ball-and-socket hip joint. When the femoral neck is fractured, the femur is often disconnected from the ball.

STUDY PROFILE Researchers recruited 325 postmenopausal women, without osteoporosis, who were divided into two groups – one group received 45 mg per day of vitamin K2, while the other group received a placebo

  • The intervention period lasted three years
  • A technique known as dual x-ray absorptiometry was used to assess BMC and hip geometry throughout the course of the trial
  • Results showed that BMC and femoral neck width increased in the K2 group, but not in the placebo group
  • Bending strength, compression strength, and impact strength all improved in the K2 group, but not in the placebo group
  • Strength of hip bones didn’t change in the K2 group, but decreased significantly in the placebo group
  • Researchers noted that the supplement dosage used in the study is quite a bit higher than the recommended daily allowance (RDA) of 90 mcg for women and 120 mcg for men. But they also noted that vitamin K levels are quickly depleted, even when three 15 mg doses are taken over the course of a day.

One and two but not three

In his Nutrition & Healing newsletter, Dr. Wright has noted that supplementing with K is a good idea if there’s a family history of osteoporosis or a family history of arteriosclerosis. Dr. Wright recommends 5 to 15 mg of vitamin K per day – less than the dosage in the University of Maastricht study, but still considerably higher than the RDA.

If you talk to your doctor about supplementing with K, keep these basic guidelines from Dr. Spreen in mind: “The synthetic form (K3, or menadione) has caused some liver toxicity and, rarely, a form of anemia when taken in high doses. There’s also K2 (or menaquinones), but K1 and K2 are fine. As usual, it seems best to avoid synthetic forms, if possible. If the individual is on coumadin (blood thinner), he needs to talk with his doctor, as vitamin K can interfere with its effect.”

Dr. Spreen also notes that a study from the 1940s showed that vitamin K is helpful in preventing tooth decay.