In the news: ‘Multi’ Use & Risk of Stroke Death: Vitamin K Supports Artery Function

Multivitamin Use & Risk of Death from Stroke

February’s issue of Staying Healthy described the results of a study looking at multivitamin and mineral use among participants in the U.S. National Health and Nutrition Survey Exam. That study found a 35% reduction in the risk of death from cardiovascular disease (CVD) among women supplementing for over 3-years compared to non-users of multi supplements.

A link between multi use and CVD risk has again been reported – this time in research from Japan, published in the American Heart Association’s journal Stroke (1).

Over 72,000 men and women free from CVD at the study’s start were followed for about 19 years by investigators, who also collected information about the participants’ multivitamin supplement use.

After taking into account other factors affecting stroke risk, multi use was associated with a 20% lower risk of death from ischemic stroke – stroke that is caused by a clot blocking blood flow to the brain. The link was not seen for hemorrhagic stroke, which occurs when an artery in the brain leaks or ruptures. About 80% of all strokes are the ischemic type.

Among those who ate fruits and vegetables less than 3 times daily, multi use was linked to lower risk of dying from both total and ischemic stroke. This association was stronger for regular multi use vs. casual use.

Vitamin K Basics

There are two forms of fat-soluble vitamin K: K1 or phylloquinone, and vitamin K2, the menaquinones.

Our diet supplies Vitamin K1 through vegetables (green leafy ones especially), vegetable oils, and some fruits. Meat, dairy, and eggs contain low levels of K1 and modest amounts of vitamin K2. Fermented foods like natto (from fermented soybeans) have high levels of menaquinones, and fermented cheeses are a source as well. The bacteria in our GI tract also produce menaquinones, though it’s not clear how much is absorbed.

In plants, chlorophyll-containing cells tightly hold K1, making it less well absorbed than K1 from oils or supplements. Eating veggies at the same time as fat – dressing spinach salad with olive oil for instance – ups absorption of K1 from veggies.

Vitamin K is needed for blood to clot, and by a bone-building protein. It’s also required by a protein (matrix GLA-protein) that may play a role in the prevention of vascular calcification – the depositing of calcium in the middle or inner lining of arteries. One hypothesis is that inadequate vitamin K affects the function of matrix GLA-protein leading to greater artery calcification.

Vascular calcification is one risk factor for coronary heart disease because it reduces artery elasticity. Healthy, flexible arteries can expand and briefly store blood from each heartbeat to help move blood to all areas of the body. Both K1 and K2 are needed for good health, but recent population-health studies suggest that consuming adequate levels of K2 may be important for artery health.

K2 Findings from Observational Studies

Several population-health studies published in the past decade have reported that higher intake of the mena-quinones (though not phylloquinone) is linked to lower coronary calcification or risk of coronary heart disease in women (2,3).

A recent 10-year follow up study also found that a higher intake of menaquinones and good vitamin K levels overall are associated with a lower occurrence of metabolic syndrome – a cluster of symptoms associated with a greater risk of CVD (4).

Note: If you take Coumadin, be sure to inform your doctor before increasing vitamin K intake through foods or supplements. Maintaining consistent intakes of vitamin K is important for this drug to work properly.

References

1. Dong J-Y, et al. Multivitamin use and risk of stroke mortality. Stroke. [Epub March 31, 2015].
2. Beulens JW, et al. High dietary menaquinone intake is associated with reduced coronary calcification. Atheroscler. 203:489-93, 2009.
3. Gast GCV, et al. A high menaquinone intake reduces the incidence of coronary heart disease. Nutr Metab Cardiovasc Dis 19:504-10, 2009.
4.  Dam V, et al. The association between vitamin K and the metabolic syndrome: a ten-year follow-up study in adults. J Clin Endocrinol Metab. [Epub Apr 2, 2015].