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May 2014

Topics:

Grain fiber lowers chance of 2nd heart attack
Heme iron (meat) raises heart risks
Dietary resveratrol and mortality
Inactivity and heart risks in women
General Information

Grain fiber lowers chance of 2nd heart attack

Researchers looked at data from two large prospective studies, the Nurses’ Health Study and the Health Professionals Follow-Up Study, to evaluate the effect of dietary fiber on mortality, including cardiac mortality. Of those who were free of cardiovascular disease, stroke, or cancer at enrollment, 2258 women and 1840 men survived a first heart attack (MI) during follow-up. They also filled out dietary questionnaires before their MI and at least once afterwards. (Li S et al., Dietary fiber intake and mortality among survivors of myocardial infarction: prospective cohort study. BMJ. 2014 Apr 29;348:g2659. doi: 10.1136/bmj.g2659.)

The researchers then evaluated dietary fiber intake post-MI and changes in fiber intake from before to after MI. They correlated this information with the subsequent risk of cardiovascular and all-cause mortality. They adjusted their evaluations for drug use, medical history, and lifestyle habits. They categorized subjects in quintiles of the highest to the lowest fiber intake. Men in the highest quintile averaged 37 grams of fiber a day, and women averaged 29 grams. These are about the recommended amounts, although most Americans get far less than that. The native African diet that Denis Burkitt studied in the 1950s averaged nearly 100 grams of fiber per day, and consisted of potatoes, bananas, corn meal, and beans as the staples.

In this study, those who consumed the most fiber had a 25 percent lower risk of mortality from all causes. Those with the highest intake of cereal fiber (grains such as oatmeal, barley, and whole wheat) had an even better outcome, with a 27 percent lower mortality over the course of the study. Those who responded to their heart attack by increasing their fiber intake compared to pre-MI had a 31 percent lower mortality rate than those who did not. This suggests that the idea that “carbs” (such as grains) are harmful does not take into account the difference between whole and refined grains. Refined carbs (white flour, sugar) are harmful, but whole grains are beneficial.

Practical guidelines:

By all means, avoid refined carbohydrates, such as sugars, white flour (for example, virtually the entire range of pastries and breads that you see at the supermarket), and white rice, but not unrefined, complex carbohydrates. Include a variety of whole grains, fresh fruits, and vegetables in the diet. The grains might include whole wheat, millet, brown rice, whole corn (only organic is not genetically modified), barley, rye, and quinoa. Buckwheat is not a true grain, but has many of the nutritional properties of whole grains (Japanese soba noodles are made from buckwheat). Other fiber sources include legumes (peas and beans), seeds, and nuts.

Heme iron (meat) raises heart risks

Iron is a critical nutrient for many physiological functions, the most commonly known one being the formation of hemoglobin to carry oxygen. The “heme” part of hemoglobin is a complex molecule with iron at its center (it is almost the same as chlorophyll, which has magnesium at its center instead of iron, making it green instead of red). In 1992, a study from Finland showed that high stored iron (as reflected in serum ferritin levels) was associated with a greater risk of heart attacks. (Salonen JT, et al., High stored iron levels are associated with excess risk of myocardial infarction in eastern Finnish men. Circulation. 1992 Sep;86(3):803-11.)

They also found a similar association with dietary intake of iron. Those with the highest iron (ferritin level or dietary iron) had double the risk of heart attacks than those with the lowest levels. Because iron stimulates production of hydroxyl- free radicals, it is a stimulant of peroxidation of lipids, and in their study, the relationship of iron to heart disease was strongest among those subjects with the highest LDL-cholesterol levels, which is vulnerable to such oxidation. Doing the study in Finland meant that the bulk of dietary iron came from red meat, and a number of researchers suggested that the iron source itself might be the problem.

Two recent meta-analyses of studies show that the problem with iron is primarily from heme iron, not from plant-based sources. In one review of six prospective studies with a total of 131,553 participants, combined results showed that those with the highest heme iron intake had a 31 percent increased risk of coronary heart disease, compared to those with lower intake. (One study from Japan was a statistical “outlier,” in which the results were far different from all the others. Excluding this one study from the analysis changed that increased risk to 46 percent.) (Yang W, et al., Is heme iron intake associated with risk of coronary heart disease? A meta-analysis of prospective studies. Eur J Nutr. 2014 Mar;53(2):395-400. doi: 10.1007/s00394-013-0535-5.)

The other meta-analysis found 21 prospective studies with a total of 292,454 participants followed for an average of 10 years. Heart disease incidence (but not mortality in this analysis) was directly associated with heme iron intake and related body iron stores. Those with the highest heme iron intake had a 57 percent increased risk compared to those with the lowest intake. However, total iron intake had an inverse relationship to heart disease incidence. Those with high total iron intake from food and supplements had a 15 percent lower risk than those with the lowest intake. (Hunnicutt J, et al., Dietary iron intake and body iron stores are associated with risk of coronary heart disease in a meta-analysis of prospective cohort studies. J Nutr. 2014 Mar;144(3):359-66. doi: 10.3945/jn.113.185124.)

One reason for this discrepancy between the effects of heme iron and non-heme iron could be that heme iron is 37 percent absorbed, while plant-source (non-heme) iron is only 5 percent absorbed. It is possible, of course, that other components of meat could be responsible for the heart risks, but a number of other studies also suggest that iron is at least part of the problem. A recent prospective study evaluated 36,882 Swedish men aged 45-79 years who had no history of coronary heart disease, stroke, diabetes, or cancer at baseline. They were followed for 11.7 years.

During follow-up 678 fatal and 2593 non-fatal heart attacks were registered. Those subjects in the highest quintile of heme iron intake had a 51 percent higher risk of heart death than those with the lowest heme iron intake. (Kaluza J, et al., Heme iron intake and acute myocardial infarction: a prospective study of men. Int J Cardiol. 2014 Mar 1;172(1):155-60.) Non-heme iron intake was not associated with either fatal or non-fatal heart attacks.

Interestingly, a high intake of other minerals can reduce these effects. Calcium, magnesium, and zinc can inhibit the absorption of iron. The increased heart risk was confined to those men who had low dietary (or supplemental) levels of these minerals. For men in the below-average intakes of calcium, magnesium, and zinc, but high heme iron intake, their risk of fatal heart attacks was almost triple that of those men who had the lowest heme iron intake.

Practical guidelines:

As some of the news reports pointed out, these studies do not establish a cause-and-effect relationship between meat consumption and heart attacks, just a correlation, but it is a very strong correlation. Around the globe, iron deficiency is one of the most common nutritional disorders. Supplements are a good source of iron and are not associated with heart disease.

Our iron needs are 8 mg (adult males) to 18 mg (pre-menopausal adult women). Good plant-based sources of iron include pumpkin seeds (1 oz, 4.2 mg), quinoa (4 oz, 4 mg), lentils (4 oz, 3 mg), cooked spinach (1/2 cup, 3.2 mg), tofu (2 oz, 3.2 mg), chickpeas and black-eyed peas (1 cup 4.5 mg), cooked Swiss chard (1 cup, 4 mg), kidney beans, black beans, and pinto beans (1 cup, 3.6-4 mg), potato (1 large, 3.2 mg), and tahini (2 Tbsp, 2.7 mg). A daily serving of a few of these foods will satisfy daily iron requirements for men, while women will need about double that. Also, be sure to consume adequate magnesium, zinc, and calcium from food or supplements.

Dietary resveratrol and mortality

Resveratrol is a polyphenol component of red wine that has had a number of studies suggesting a correlation with reduced mortality. In addition to red wines, resveratrol is found in grapes, chocolate, peanuts, and some berries, but in smaller quantities. Most studies on its benefits have used larger quantities as supplements, mostly derived from Japanese knotweed (Polygonum cuspidatum). However, a recent study suggested that resveratrol might not have any beneficial effects in humans (in quantities that are commonly consumed in red wine in the Chianti region of Italy).

The researchers followed 783 men and women 65 years of age or older, and followed them from 1998 to 2009. At the start of the study (and only at the start) they measured resveratrol by-products in participants’ urine. By the end of the study, 34 percent had died, 27 percent developed heart disease, and 4.6 percent developed cancer. They found no difference in disease or mortality rates in subjects in the lowest or highest quartile of urinary resveratrol byproducts. (Semba RD, et al., Resveratrol levels and all-cause mortality in older community-dwelling adults. JAMA Intern Med. 2014 May 12. doi: 10.1001/jamainternmed.2014.1582. [Epub ahead of print].)

There have been some critiques of this study, and nobody has suggested starting or giving up red wine based on this report. Supplements of resveratrol are usually standardized, while wine resveratrol content is quite variable. Having only one urine sample at the start of the study would ignore changes in consumption over the nine years of the study. Because these metabolites are very short-lived, one test does not reflect long-term consumption of wine. The alcohol in red wine could be detrimental to the health of the participants, depending on the quantity consumed, and this might skew the results.

Resveratrol is an antioxidant that inhibits free radical production and the oxidation of LDL cholesterol. It also inhibits inflammation and platelet aggregation, both risk factors for cardiovascular disease. Supplements of resveratrol typically contain 10 to 20 times as much as is found in red wine. One of the study critics, Bill Sardi, noted that the participants who consumed the most wine in this study were more than three times as likely to be smokers, which could account for the reported lack of benefits from resveratrol.

Practical guidelines:

I have no objection to moderate wine consumption, although I do not think the data is clear enough that it is beneficial for long-term health, suggesting that if you do not already consume wine, there is no strong health reason to start. I do think it is worth taking standardized supplements of resveratrol, based on animal studies and lab studies of its effects on risk factors. Typical doses of supplements contain 10 to 50 mg of resveratrol. (I take a daily capsule, derived from Japanese knotweed, that contains 37 mg of resveratrol.)

Inactivity and heart risks in women

A new study from Australia highlights the importance of physical activity to prevent heart disease. The study was on women in 15 age groups, ranging from 22-27 at the start of the study to 85-90 at the end of the study. The researchers evaluated the contribution of different risk factors to cardiac mortality, including smoking, hypertension, body mass index (BMI), and physical inactivity.

The study group sizes ranged from 3901 subjects in the oldest group to 9608 in the youngest group. They analyzed data from a long-term study that followed Australian women from 1996 to 2011. For the youngest women, smoking was the greatest contributor to the development of heart disease. For women under 30, even though heart disease is rare, smoking led to a more than 6-fold increase in the risk of heart disease. (Brown WJ, et al., Comparing population attributable risks for heart disease across the adult lifespan in women. Br J Sports Med. 2014 May 8. doi: 10.1136/bjsports-2013-093090. [Epub ahead of print].)

However, over age 31, all the way up to 90, the greatest risk factor was physical inactivity, outweighing smoking, high BMI, and hypertension. The highest BMI (overweight or obese women) was found in the middle range of ages, but still was not as significant a risk factor as inactivity. In an interview with Reuters Health, the lead author noted that even one hour of moderate physical activity per day could delay death for over 2600 women.

Heart disease is the leading cause of death in women, in both the United States and Australia. Getting even a moderate amount of physical activity can reduce the risk. Of course, physical activity also influences the other risk factors, lowering BMI and helping to control blood pressure.

Practical guidelines:

Physical activity is a critical component of a complete health program that includes a healthy diet and relaxation, as well as dietary supplements. You don’t need to run marathons to get healthy. Even climbing more stairs instead of using elevators and parking at the far end of the parking lot can help. Household chores, gardening, and bicycling to the post office would be beneficial. If you spend time reading, or even watching TV, you can do it while riding a stationary bicycle. Every little bit helps. I like a daily hour walk on the beach, if the weather permits, and otherwise I’ll use a treadmill at the gym.

General Information

 


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Information herein is not medical advice or direction. All material in this newsletter is provided for information only. Its contents should not be used to provide medical advice on individual problems. Consult a health care professional for medical or health advice.

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