Researchers keep finding new reasons to make sure you’re getting adequate amounts of vitamin D. The latest focus? Your blood vessels. Growing evidence links vitamin D with improved vascular health, including recent research by Tufts’ Jennifer S. Buell that associated vitamin D levels with improved vascular health specifically in the brain.
Now an analysis of data from the National Health and Nutrition Examination Survey (NHANES) finds vitamin D may help prevent peripheral artery disease. Associated with decreased blood flow in the legs, peripheral artery disease (PAD) affects 8 million Americans and is linked with other serious health conditions.
Publishing their findings in Arteriosclerosis, Thrombosis, and Vascular Biology, lead researcher Michal L. Melamed, MD, MHS, of the Albert Einstein College of Medicine and colleagues analyzed data from 4,839 NHANES participants. The large, diverse study sample was described as nationally representative, with participants’ average age at just over 61 — since the risk of PAD is higher among older people.
Researchers divided the sample into four groups, according to subjects’ blood levels of vitamin D. The study found that increasing levels of the vitamin were associated with a lower prevalence of PAD. The occurrence of PAD dropped from 8.1% in the group with the lowest vitamin D levels to 5.4%, 4.9% and 3.7% as vitamin D levels rose in each quartile.
After adjusting for age, sex, race and co-existing health problems, the researchers calculated that PAD risk was 80% higher in the lowest-level group as compared with those with the highest levels of vitamin D. In fact, for each 10 nanogram/milliliter drop in blood levels of vitamin D, subjects’ risk of PAD rose by 35%.
Vitamin D is a fat-soluble nutrient that is naturally present in only a few foods. Fortified foods — like milk, orange juice and commercial breakfast cereals — provide most of the vitamin D in the American diet. Vitamin D refers to two precursors: D3 (cholecalciferol), which is produced in the skin upon exposure to sunlight, and D2 (ergocalciferol), which comes from dietary sources, especially oily fish, egg yolks and liver.
But not everyone agrees about the need to turn to supplements to increase the intake of vitamin D.
“We recommend eating a balanced diet,” said Dr. Melamed, suggesting that in addition to foods that naturally contain the nutrient, people eat more vitamin D-fortified foods. “We would not recommend that people start taking vitamin D supplements without talking to their doctors.”
The researchers also pointed out that their study does not prove a causal relationship between Vitamin D and reduced artery disease — that is, the study does not prove that vitamin D, in and of itself, lowers PAD risk. It’s possible, they wrote, that higher vitamin D levels may simply be evidence of a healthy diet and lifestyle practices.
TO LEARN MORE: Arteriosclerosis, Thrombosis, and Vascular Biology, online before print at <atvb.ahajournals.org/cgi/content/abstract/ATVBAHA.108.165886v1>.
To help reduce your risk of diabetes, eat like a Mediterranean. That’s the suggestion of a new Spanish study, which linked following a Mediterranean-style diet to sharply lower rates of developing type 2 diabetes.
The findings, by lead author Miguel Martinez-Gonzalez, MD, PhD, of the University of Navarra and colleagues, are consistent with the scientists’ previous research associating a Mediterranean-style diet with reduced risk of metabolic syndrome, a precursor of diabetes. Other studies have reported that such a dietary pattern might be beneficial against mortality from heart disease and some cancers.
Though there’s no such thing as a “Mediterranean diet” per se, these studies suggest that the traditional eating habits of people living around the Mediterranean Sea might be a good pattern for protection against some chronic diseases. The Spanish researchers pointed out that such a diet is highly palatable, so people are more likely to stick with it. A Mediterranean-style diet is characterized by the use of olive oil as the major culinary fat and high intake of fruits, nuts, legumes and fish, with relatively low consumption of meat and dairy.
Dr. Martinez-Gonzalez emphasized the importance of olive oil in this diet. He noted that diets high in monounsaturated fats — such as olive oil — and low in saturated fats improve lipid profiles as well as insulin resistance and glycemic control in diabetes patients.
The latest study followed 13,380 men and women, initially free of diabetes, for an average of 4.4 years. Researchers assessed participants’ diets using a 136-item food-frequency questionnaire, then scored the responses on a nine-point scale for adherence to a Mediterranean-style diet.
Although only a few subjects developed diabetes during the course of the study, those with the highest adherence to a Mediterranean-style diet were 83% less likely to be among those developing diabetes. Even moderate adherence was associated with a 59% relative reduction in risk. Every two-point increase in adherence saw a 35% risk reduction.
“The new thing is that we have been able to assess adherence to a [Mediterranean-style] diet and the incidence of diabetes in people who were initially healthy,” Dr. Martinez-Gonzalez told Reuters news service. “We didn’t expect such a high reduction.”
Of particular interest, he added, was the fact that the benefit applied equally to older people, smokers and those with a family history of diabetes. “These higher-risk participants with better adherence to the diet, however, had a lower risk of diabetes,” the researchers wrote, “suggesting that the diet might have a substantial potential for prevention.”
Publishing their findings initially on the British Medical Journal’s Web site, the researchers cautioned that the study was limited by the small number of new diabetes cases. They called for further prospective observational studies and trials to confirm their results.
TO LEARN MORE: BMJ, online before print at <dx.doi.org/10.1136/bmj.39561.501007.BE>. American Diabetes Association: “Making Healthy Food Choices” <www.diabetes.org/diabetes-prevention/nutrition/healthyfoodchoices.jsp>.
According to the American Cancer Society, diets high in vegetables and fruits have been associated with lower risk of colon cancer, while diets high in processed and/or red meats have been linked with a higher risk. To reduce your risk, the cancer society recommends:
- Eat a healthy diet, with an emphasis on plant sources.
- Choose foods and beverages in amounts that help achieve and maintain a healthy weight. Obesity raises the risk of colon cancer in both men and women, but the link seems to be stronger in men.
- Eat five or more servings of a variety of vegetables and fruits each day.
- Choose whole grains rather than processed (refined) grains.
- Limit consumption of processed and red meats.
- Get at least 30 minutes, preferably 45 to 60 minutes, of physical activity on five or more days of the week.
Casting a wide net in the effort to prevent cancer, scientists have found that eating fish-and the omega-3 fatty acids found in fish oil — may reduce the risk of colorectal cancer. Lead author Megan N. Hall, ScD, RD, of Columbia University and colleagues studied 21,376 men participating in the Physicians’ Health Study over a span of 22 years. The researchers found that the men who ate the most fish had a 40% reduced risk of colorectal cancer. Similarly, those with the highest dietary intake of omega-3s from fish had a 26% lower risk of colorectal cancer, compared to the men with the lowest intake of omega-3s.
“Fish is the main dietary source of long-chain n-3 ['omega-3'] fatty acids, which have been suggested to play a protective role in colorectal cancer development in laboratory and animal studies,” Hall explains. “Our results from this long-term prospective study suggest that intakes of fish and long-chain n-3 fatty acids from fish may decrease the risk for colorectal cancer.”
The men’s fish consumption, and in turn their omega-3 intake, was calculated from food-frequency questionnaires. Over the course of the study, 500 subjects were diagnosed with colorectal cancer.
It’s not clear why the protective effect apparently was greater for fish consumption in general than for omega-3s in particular. “We can’t know for sure, but there could be another component of fish — for instance, vitamin D, which is found in fatty fish-that exerts a protective effect,” says Hall. “It could also be an issue of additional measurement error in the assessment of omega-3 fatty acid intake from fish.”
The findings, published in Cancer Epidemiology, Biomarkers & Prevention, add to a growing body of evidence linking fish and omega-3s to protection against colorectal cancer. A meta-analysis by scientists at Wageningen University in the Netherlands recently suggested that increasing fish consumption could cut the incidence of colorectal cancer by 12%, and that each additional serving of fish reduced the risk by 4%.
In 2005, the Journal of the National Cancer Institute published an analysis of data from 1 million participants in the European Prospective Investigation into Cancer and Nutrition (EPIC) trial. The study found that people averaging less than a half-ounce of fish a day had a 40% higher relative risk of colorectal cancer than those eating the most fish, more than 1.75 ounces daily.
Hall cautions, however, that other studies have not shown protective effects of fish intake, saying additional research is needed.
Worldwide, colorectal cancers kill some 492,000 people annually. In the US, according to the American Cancer Society, cancers of the colon and rectum are the third most common type of cancer and cause of cancer death among both men and women. Colorectal cancers are expected to strike more than 101,000 Americans this year, and to result in almost 50,000 deaths.
TO LEARN MORE: Cancer Epidemiology, Biomarkers and Prevention, May 11, 2008; abstract at <cebp.aacrjournals.org/cgi/content/abstract/ 17/5/1136>. American Cancer Society: Learn About Colon and Rectum Cancer <www.cancer.org/ docroot/lrn/lrn_0.asp>.
