Eating a diet high in antioxidants may protect against ischemic stroke, an Italian cohort study showed.
People who had a diet high in total antioxidant capacity — an index that takes into account several different antioxidants and their interactions — had a 59% reduced relative risk of ischemic stroke (HR 0.41, 95% CI 0.23 to 0.74), according to Nicoletta Pellegrini, PhD, of the University of Parma in Italy, and colleagues. But there was no such relationship with hemorrhagic stroke, they reported in the January issue of the Journal of Nutrition. In fact, the highest intake of the antioxidant vitamin E was associated with a greater risk of hemorrhagic stroke (HR 2.94, 95% CI 1.13 to 7.62).
Considering evidence suggesting that oxidative stress and systemic inflammation are involved in the pathogenesis of ischemic stroke, the researchers noted that “a high-total antioxidant capacity diet could be protective as a consequence of its ability to deliver compounds with antioxidant activity and with a demonstrated anti-inflammatory effect.” But, they acknowledged that the mechanism for such activity was unclear may “go beyond the antioxidant activity of the numerous total antioxidant capacity contributors present in foods and beverages.”
Pellegrini and her colleagues set out to explore the relationship between dietary total antioxidant capacity and the risk of stroke among 41,620 people participating in EPICOR, the Italian segment of the European Prospective Investigation into Cancer and Nutrition (EPIC). None had a history of stroke or MI at baseline. Dietary intake was assessed with a food frequency questionnaire. In the study population, more than half of the total antioxidants consumed came from coffee, wine, and fruit. Through a mean follow-up of 7.9 years, there were 112 ischemic strokes, 48 hemorrhagic strokes, and 34 other types of strokes. After adjustment for energy intake, hypertension, smoking status, education, nonalcoholic energy intake at recruitment, alcohol intake, waist circumference, body mass index, and total physical activity, individuals eating a diet in the highest tertile of total antioxidant capacity had a reduced risk of ischemic — but not hemorrhagic — stroke.
Looking at individual antioxidants, the researchers found that participants consuming the highest amounts of vitamin C had a reduced risk of ischemic stroke (HR 0.58, 95% CI 0.34 to 0.99). Controlling for vitamin C intake did not negate the overall association between antioxidants and ischemic stroke, which ruled out the nutrient as the sole driver of the relationship. High intake of vitamin E, on the other hand, was associated with nearly triple the relative risk of hemorrhagic stroke. However, “it must be stressed that the small number of cases observed in this population strongly limits the validity of statistical observations on hemorrhagic stroke,” noted the researchers, who called for further studies.
Aside from anti-inflammatory effects, it is possible that the association between antioxidants and ischemic stroke risk can be explained by the interaction between polyphenols — the major contributors to total antioxidant capacity — and the generation of nitric oxide from the vascular endothelium. That interaction leads to the vasodilation and expression of genes that may be protective for the vascular system, according to the researchers. In addition, coffee — the main source of antioxidants in the study population — reduces blood pressure, which is a recognized risk factor for ischemic stroke, the researchers wrote.
They noted some limitations of the study, including the low numbers of cases when different types of stroke were analyzed, the measurement of total antioxidant capacity at baseline only, and the inability to rule out confounding effects of other dietary components, like sodium and potassium.
Source: Del Rio D, et al “Total antioxidant capacity of the diet is associated with lower risk of ischemic stroke in a large Italian cohort” J Nutr 2011; 141: 118-123.
Two specific eating patterns increase the risk of death for older adults, a 10-year study finds.Compared to people who ate healthy foods, men and women in their 70s had a 40% higher risk of death if they got most of their calories from high-fat dairy foods or from sweets and desserts. University of Maryland researcher Amy L. Anderson, PhD, and colleagues monitored the eating patterns of 2,582 adults aged 70 to 79. They found that these diets fell into six patterns or clusters.
After adjusting for risk factors such as sex, age, race, education, physical activity, smoking, and total calories, “the High-Fat Dairy Products cluster and the Sweets and Desserts cluster still showed significantly higher risk of mortality than the Healthy Foods cluster,” Anderson and colleagues found.
The six dietary patterns were:
- Healthy Foods: Higher intake of low-fat dairy products, fruit, whole grains, poultry, fish, and vegetables. Lower intake of meat, fried foods, sweets, high-energy drinks, and added fat.
- High-Fat Dairy Products: Higher intake of ice cream, cheese, and 2% and whole milk and yogurt. Lower intake of poultry, low-fat dairy products, rice, and pasta.
- Sweets and Desserts: Higher intake of doughnuts, cake, cookies, pudding, chocolate, and candy. Lower intake of fruit, fish and other seafood, and dark green vegetables.
- Meat, Fried Foods, and Alcohol: Higher intake of beer, liquor, fried chicken, mayonnaise/salad dressings, high-energy density drinks, nuts, snacks, rice/pasta dishes, and added fat. Lower intake of low-fat dairy products, fiber/bran breakfast cereal, and other breakfast cereal.
- Breakfast Cereal: Higher intake of fiber/bran and other breakfast cereals (especially the latter). Low intake of nuts, refined grains, dark yellow vegetables, and dark green vegetables.
- Refined Grains: Higher intake of refined grains (such as pancakes, waffles, breads, muffins, and cooked cereals such as oatmeal) and processed meat (such as bacon, sausage, ham, and other lunchmeats). Lower intake of liquor, breakfast cereals, and whole grains.
Several of the groups got an unusually large amount of their total calories from just one food group:
The sweets and desserts cluster got 25.8% of its total energy from sweets.The refined grains cluster got 24.6% of its total energy from refined grains.The breakfast cereal group got 19.3% of its total energy from cold cereals other than those full of fiber and bran.The high-fat dairy products group got 17.1% of its total energy from higher-fat dairy foods.
Overall, people in the healthy foods cluster had more years of healthy life and a lower death rate than all other groups. Moreover, their blood tests came back with significantly more indicators of health than the other groups.
But not all of the study findings were so predictable. “Unexpectedly, in this and in several other studies, a [dietary] pattern higher in red meat was not significantly associated with increased risk of mortality,” Anderson and colleagues note. It's also not entirely clear why the Meat, Fried Food, and Alcohol cluster didn't have a significantly higher death risk, as most diets warn people to limit or avoid such foods.
“In our study, the Meat, Fried Food, and Alcohol cluster did have a slightly higher percentage of total energy from vegetables, fruit, and whole grains than both the High-Fat Dairy Products and Sweets and Desserts clusters, which showed higher risk of mortality,” Anderson and colleagues suggest.
This was by far the most common eating pattern seen in the study: 27% of participants were in the meat, fried food, and alcohol cluster. But Anderson and colleagues do not recommend such a diet. Instead, they point to the fact that 14.5% of study participants were in the healthy foods cluster. “Adherence to such a diet appears a feasible and realistic recommendation for potentially improved survival and quality of life in the growing older adult population,” Anderson and colleagues conclude.
The study appears in the January 2011 issue of the Journal of the American Dietetic Association.
The paper directly compared findings from two separate studies: 'The Diets of British Schoolchildren' conducted by the Department of health (DH) in 1983 (Department of Health 1989); and the National Diet and Nutrition Survey (NDNS) from 1997 (Gregory & Lowe, 2000).
Gibson's analysis found that total sugar intake averaged at 115g/day in 1983, compared with 113g/day in 1997. Allowing for exclusions of low and high energy reporters, intake levels were 122g/day (1983) and 127g/day (1997), showing a marginal and insignificant increase over the study period. Contrastingly, mean body weight increased significantly during the period of the DH and NDNS surveys, showing a rise of 1.9kg for 10-11 year olds and 3.4kg among 14-15 year olds. BMI increased from 17.9 to 18.6 units in the younger group, and 20.2 to 21.3 units in the older group. According to these calculations, the prevalence of being overweight (plus obesity), as defined by the International Obesity Taskforce (IOTF) cut-offs (91st percentile) rose from 13% to 21-22% between surveys. Gibson concluded that the slight increase in consumption of total sugars did not account for the significant increase in BMI, equivalent to 2-3 kg over the review period.
During the same period, Gibson found that mean energy intake (EI) was 3% lower in 1997 than in 1983, mainly as a result of lower fat intake. This change in overall energy consumption meant that sugars represented a higher proportion of daily energy intake in 1997 (23.6% versus 22.3%), despite total sugar consumption remaining relatively static in comparison. The review surmises that the most likely cause for the increased BMI is a decline in energy expenditure.
In addition, Gibson's paper found that basal metabolic rate (BMR) increased by approximately 3% between surveys as a result of higher body weights, and it is estimated that EI in relation to basal requirements was even lower at 6%. Gibson found that the paradox of rising BMI, despite a 2-3% rise in BMR and an EI that is static or falling, pointed to declining energy expenditure as an important factor in the change.
The Gibson analysis showed that the key sources of sugars in the diet have changed with a marked shift away from table sugar and smaller falls in consumption of sugars through milk, biscuits and cakes, counterbalanced by a significant increase in sugars consumed in soft drinks and, to a lesser extent, fruit juice and breakfast cereals.
A conclusion of Gibson's reanalysis of data from the DH and NDNS studies, that consumption of total sugars remained relatively static during the period, providing an estimated 22% of energy, is supported by findings from a repeated cross sectional study of children's food and drink intake, conducted in Northumberland in 1989, 1990 and 2000 which looked at trends in children's food and drink intake.
Sigrid Gibson, the paper's author, said: “There are very few studies that have assessed trends in sugar intake over time and particularly over such an extended period. The findings of the reanalysis strongly contradict widespread assumptions that sugar levels in the diet are responsible for rising obesity levels. With dietary sugar intakes relatively static, and overall energy consumption showing decline, increased BMI levels cannot be attributed to sugar consumption.”
Beta-carotene is the precursor to vitamin A and gamma-tocopherol is a common form of vitamin E. Lutein is found in dark green leafy vegetables and is important in vision and healthy skin. All three compounds are oil soluble vitamins.
Antioxidants are of interest because oxidized low-density lipoproteins (LDL) are implicated in inflammation and plaque buildup inside blood vessels. Antioxidants should prevent LDLs from oxidizing, migrating into the blood vessel walls and causing inflammation.
“Currently, studies on antioxidants do not show major benefits,” said Kris-Etherton. “Maybe we are not studying people long enough. Maybe there is something in the food that travels with the antioxidants. The antioxidant story is very disappointing to the scientific community.”
The reason for the disappointment is that studies on specific antioxidants currently do not show health benefits, but epidemiological studies seem to indicate benefits. Many people feel that we have not figured out antioxidants yet, said Kris-Etherton.
If antioxidants are important, then pistachios fit the bill as antioxidant-laden food.
The researchers conducted a randomized, crossover design, controlled feeding experiment to test the effects of pistachios on antioxidant levels when added to a heart healthy moderate-fat diet. Controlled feeding experiments provide all the food eaten by study subjects for the duration of the study period.
The participants began the study by eating a typical American diet consisting of 35 percent total fat and 11 percent saturated fat for two weeks. They then tested three diets for four weeks each with about a two-week break between each diet. All three diets were variations on the Step I Diet, a cholesterol-lowering diet in general use. The diets included, as a control, a Step I Diet with no pistachios and about 25 percent total fat and 8 percent saturated fat. The pistachio-enhanced diets were Step I Diets with 10 and 20 percent of the energy supplied by pistachio nuts, respectively. The 10 percent pistachio diet had 30 percent total fat and 8 percent saturated fat and the 20 percent pistachio diet had 34 percent total fat and 8 percent saturated fat.
The actual amounts of pistachios included in each diet were 1.5 ounces and 3 ounces for the 10 and 20 percent diets, respectively.
Both pistachio diets produced higher blood serum levels of beta-carotene, lutein and gamma-tocopherol than the typical American diet. Compared to the pistachio free Step I Diet, the pistachio-enhanced diets produced greater blood plasma levels of lutein and gamma-tocopherol. After eating both pistachio-enriched diets, the participants had lower oxidized-LDL concentrations in their blood than after the control Step I Diet.
When the researchers controlled for the change in LDL-cholesterol produced by the pistachio-enhanced diets, increases in beta-carotene and gamma-tocopherol were still associated with decreased oxidized-LDL for the 3-ounce pistachio-enhanced diet.
“Our results suggest that a heart-healthy diet including pistachios contributes to a decrease in serum oxidized-LDL levels, in part through cholesterol lowering, and also due to an added benefit of the antioxidants in the pistachios,” said Kris-Etherton.
Other researchers in the study include Sheila West, associate professor of biobehavioral health, Penn State; Sarah Gebauer, U.S. Department of Agriculture, Beltsville, Md. and Colin D. Kay, lecturer, University of East Anglia.
The Western Pistachio Association supported this work. Partial support also came from the NIH- supported General Clinical Research Center at Penn State.