Q: Can the vitamin K in green, leafy vegetables help people with diabetes?
A: There are obviously a lot of good reasons to eat vegetables, and this just adds one more. It turns out that vitamin K may be a nutrient important for glucose regulation—hence a benefit for diabetes. There are two main forms of vitamin K: phylloquinone, also known as phytonadione and called vitamin K1, and menaquinones, called vitamin K2. Vitamin K1 is found in green, leafy vegetables such as lettuce, spinach and broccoli and makes up about 90 percent of the vitamin K in a typical diet; K2 can be synthesized in the gut by microflora.
A recent human study gave some interesting results on the subject of vitamin K and diabetes. Researchers recruited 355 non-diabetic men and women (60 percent women) between the ages of 60 and 80. The participants were randomly assigned to receive a daily vitamin K1 supplement (500 mcg/day of phylloquinone) or placebo for 36 months. At the end of the study, it was found that supplemented men (but not women) benefited with a statistically significant reduction in insulin resistance compared to placebo (meaning that their regulation of glucose or blood sugar improved).4
A question remains as to why the effect was just seen with men. A larger study might have shown effects with women, or there may be a subset of women who are vitamin K-deficient and need extra amounts of the vitamin—hence, the supplemented vitamin K in this study just may have brought body levels up to normal versus beneficial amounts in deficient women. Previous research showed that vitamin K may have an effect on diabetes development via the vitamin K-dependent bone protein osteocalcin. Apparently, osteocalcin helps regulate the cells that both produce insulin in the pancreas and release it into the bloodstream.5
No matter what, whether you are a man or woman, and particularly if you are diabetic, making sure you are eating plenty of green, leafy vegetables and getting a reasonable amount of vitamin K in your multiple vitamin seems like a good idea.
Q: A customer asked about a link between coffee and the risk of developing breast cancer. I'm confused. Can you help?
A: This is a great question and really requires a paper to answer. It's a bit complicated. First, the good news for coffee drinkers: It's thought that coffee, caffeinated tea and caffeine in general may play a role in the inhibition of breast-tumor growth. Large epidemiologic studies have suggested that coffee consumption is not associated with increased breast-cancer risk and, in fact, may show a slightly decreased risk. A study in Sweden, which has the highest coffee consumption per capita in the world, reported that women drinking four or more cups of coffee per day had a very slight decreased risk of developing breast cancer compared to women who reported drinking one cup a week or less.6 The study did not clarify whether the coffee was caffeinated or decaf. Another large study in the United States (the Nurses' Health Study) looked at coffee consumption (caffeination again unspecified) for 22 years. They also found a small protective effect for coffee as well as caffeine-containing beverages, with a decreased risk of postmenopausal breast cancer.7
One study, hospital-based and case-controlled, directly addressed the caffeinated versus decaffeinated coffee question.8 It was conducted to evaluate the role of regular coffee, decaffeinated coffee and black tea in breast-cancer etiology. Study participants included 1,932 cases with primary breast cancer and 1,895 controls. Among premenopausal women, consumption of regular coffee was associated with an overall linear decline in breast-cancer risk; consumers of fewer than four cups per day experienced a 40 percent risk reduction. No clear associations between intake of black tea or decaffeinated coffee and breast cancer risk were noted. In opposition to the Nurses' Health Study, among postmenopausal women, breast-cancer risk was not associated with consumption of coffee, tea or decaffeinated coffee. The researchers concluded that findings support a protective effect of coffee intake on premenopausal, but not postmenopausal, breast-cancer risk.
There are a variety of compounds in coffee—e.g., caffeine, diterpenes, caffeic acid and polyphenols—that may alone or together be associated with decreased breast-cancer risk, but it's not really clear. Coffee consumption seems to have a modest risk reduction in a number of cancers besides breast cancer, including cancer of the liver, kidney and colon.9
Now for the complications. A recent study looked at consumption of caffeine and caffeinated foods and beverages and risk for breast cancer. They again found a small protective effect. However, in women with benign breast disease, a borderline significant positive association with breast-cancer risk was observed for those women who drank the highest amount (more than four cups daily).10 Benign breast disease (BBD), also referred to as fibrocystic breast disease, is a common condition marked by benign (noncancerous) changes in breast tissue that include irregular lumps or cysts and breast discomfort and tenderness. So the bottom line is, women who have a history of BBD should refrain from drinking much regular coffee at all. This is generally a good idea anyway, as women with BBD often get better when they remove caffeine from their diet.11
Q: Is pycnogenol useful for arthritis symptoms?
A: It depends on what type of arthritis you are asking about—rheumatoid (an autoimmune disease characterized by pain, stiffness, inflammation, swelling and, sometimes, destruction of joints) or osteoarthritis (a chronic disease affecting the articular cartilage of synovial joints, including pathophysiological changes in the synovial fluid, the underlying bone and overlying joint capsule). There seem to be a variety of nutritional supplements that help with osteoarthritis (OA), with glucosamine sulfate the most well-studied. However, you are correct that newer research on pycnogenol, an extract derived from the bark of the French maritime pine tree, has also shown positive results with OA.
A number of studies have shown pycnogenol to have strong antioxidant and anti-inflammatory properties,1 so researchers decided to look at osteoarthritis to see if the nutrient would have a clinical effect on this disease. One study looked at 100 adults with mild knee OA. For three months, half of the participants took 150 mg/day of pine bark extract, and the other half took a daily placebo. Researchers found significant improvement in pain scores in the pycnogenol group.2 Another slightly larger knee OA study used 100 mg/day of pycnogenol and found the same results.3 Both studies also found that those taking pycnogenol significantly decreased their use of anti-inflammatory drugs while those on placebo did not. So yes, pycnogenol might be a good supplement for people with OA.
Natural Foods Merchandiser volume XXIX/number 13/p. 32,34