For The Love of Food

Welcome to Friday’s For The Love of Food, Summer Tomato’s weekly link roundup.

This week vitamin C fights colds for real, working out less may be more and why you’re eating more than you realize.

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Links of the week

• Vitamin C Is Beneficial Against the Common Cold, Review Suggests <<Finally the science is consistently supporting something I’ve suspected for awhile: vitamin C does appear to help with colds. It seems it reduces cold incidence in stressed people, and shortens the duration in some cases. (ScienceDaily)
• Confessions of a recovering diet food junkie <<This story is very much like my own, except that I lost 15 pounds when I stopped dieting. (Washington Post)
• Why Four Workouts a Week May Be Better Than Six <<Interesting new study about  how overexercising may have unintended negative consequences. Four workouts per week seems to be the happy medium, at least for busy older adults. (New York Times)
• Dark Chocolate and Red Wine the Food of Love and Health <<No really, Valentine’s Day can be healthy. (ScienceDaily)
• How Advertising Targets Our Children <<Have kids? This will make you want to unplug the TV for good. (New York Times)
• Yet another food worry? Nanoparticles. <<Looks like the FDA is ignoring another mystery substance that is now in our foods and other products. Should be a fun ride. (Food Politics)
• Infant Gut Microbiota Influenced by Cesarean Section and Breastfeeding Practices; May Impact Long-Term Health <<Very interesting new data on the importance of gut bacteria, and how they are shaped at birth and as an infant. (ScienceDaily)
• What’s the Right Way to Season a Cast Iron Skillet? <<I learned a lot from this. Smart stuff. (Lifehacker)
• egg salad with pickled celery and coarse dijon <<Egg salad is one of my favorite foods, and now I’m dying to try it with pickled celery. (smitten kitchen)
• Calorie Detective <<Although I’m no fan of counting calories, I’m also not a fan of lying about them. Keep in mind that if you’re eating pre-made or packaged foods, you’re almost certainly eating more than you realize. (New York Times)

What inspired you this week?

Romanesco Broccoli in a Beaker

One of the most consistent themes of nutrition science is that vitamin supplements (pills, powders, liquids, etc.) are almost never able to mimic the beneficial effects of foods that contain the same vitamins. Now new evidence suggests that high doses of these antioxidant supplements–but not whole foods containing them–may actually block the beneficial effects of exercise on insulin sensitivity and metabolism.

Exercise has countless benefits for people of all levels of fitness. One of the most important of these is its ability to improve insulin sensitivity and increase metabolism. For this reason, exercise is considered among the most effective ways to protect against type 2 diabetes.

One of the byproducts of exercise, however, is the production of free radicals that results from the breakdown of oxygen in the muscles. These reactive oxygen molecules can damage cells and DNA, and are implicated in many chronic diseases. Since antioxidants can easily neutralize these reactive oxygen molecules, it has been assumed that antioxidants such as vitamins C and E could only benefit the body.

A new study published in the Proceedings of the National Academy of Sciences suggests that rather than help protect against oxidative damage from exercise, high doses of antioxidant supplements may actually hinder the body’s natural protection against oxidative damage and block exercise-induced metabolic benefits.

In the study, human subjects were given either placebo or 500 mg vitamin C twice per day and 400 IU vitamin E. They were then trained in both cardio and strength training workouts at the gym for 5 consecutive weekdays, 4 weeks in a row. This trial was performed on both previously trained and untrained individuals.

Metabolic rates were tested by blood sample both before the trial and after 1 and 4 weeks of training. Muscle biopsies were taken both before and after the trial for all participants. Several measures of metabolism and insulin sensitivity were measured including plasma glucose concentrations, plasma insulin concentrations, maximal oxygen uptake (VO₂ max), as well as several molecular markers in muscle that are linked to insulin sensitivity and are known to promote the body’s natural defense against oxidative damage.

The researchers found that exercise improved measures of insulin sensitivity in all individuals except those given antioxidant supplements. Also, molecules that protect against oxidative damage are upregulated in response to training, but not when antioxidants are administered.

Previous studies suggest that the body’s natural defenses against oxidative damage require activation by a small amount of reactive oxygen chemicals in the body. These same chemicals have been shown to mediate insulin sensitivity in muscles, and in this study both were shown to be blocked by high antioxidant administration.

The researchers suggest that small doses of reactive oxygen molecules such as the amounts produced by exercise are necessary to induce the body’s natural defense against oxidative damage, and that this process is essential for mediating exercise-induced insulin sensitivity. If this is true it could mean that some (but not all) of the metabolic benefits of exercise could be limited by taking high doses of vitamin supplements. This may be particularly important to individuals at high risk for type 2 diabetes.

Interestingly, foods that contain high levels of these antioxidants have previously been shown to be protective against type 2 diabetes. Although the reason for this is still unknown, the authors suggest the benefit is unlikely due to the antioxidant content of the foods and may depend on other factors.

Even if we do not understand the reason vegetables and fruits are the best source of nutrition, we can still enjoy all their benefits. If you choose to continue taking vitamin supplements, it is advisable to stick to a basic multivitamin that does not contain megadoses of one particular nutrient.

Do you take vitamin supplements? Why? How much do you take?
http://forms.aweber.com/form/30/split_210533730.htm

This week, the Journal of the American Medical Association (JAMA) reports that long-term supplementation with either vitamins C (500 mg) or E (400 IU) is ineffective at reducing major cardiovascular events, including heart attack and stroke.

The study was a ten year randomized, double-blind, placebo-controlled trial in low risk, healthy men over 50-years old.

Unfortunately, results do not get any more conclusive than this. Sorry boys, you are going to have to stick with diet and exercise for now.

It was thought that antioxidants such as vitamins C and E may reduce risk of cardiovascular disease by decreasing oxidative damage and reducing inflammation. But it appears that consuming these vitamins in supplement form is ineffective.

It is still a good idea to get enough of these antioxidants from dietary sources, however. Fruit is a good source of vitamin C. Almonds are good for vitamin E. A bonus is that a diet rich in fruits and nuts actually is associated with a lower risk of heart disease.

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Also in JAMA, low-dose aspirin was shown to be ineffective at reducing the risk of cardiac events in patients with type 2 diabetes. This finding is somewhat surprising because aspirin is effective at reducing cardiac events in non-diabetic individuals, and patients with diabetes are considered to be at particularly high risk for heart disease. It was thus reasoned that aspirin should be recommended for people with diabetes. However, in this group of diabetic patients in Japan, aspirin did not the reduce risk of a cardiovascular event.

One thing to note is that this study was relatively small, only 2,539 participants. So it may have lacked statistical power to find a real benefit. If you have type 2 diabetes and are currently taking daily aspirin, I wouldn’t stop just yet.

The good news for everyone is that basic dietary and lifestyle factors are by far the largest contributors to heart disease, diabetes and cancer. You can avoid most of these problems by eating a varied diet of whole foods, maintaining a healthy weight and staying moderately active. I’d choose that over aspirin any day!

Do you take many dietary supplements?

UPDATE: The problems with vitamin C and E supplements were expanded on this week by Tara Parker-Pope at the New York Times Well Blog. It is a great read if you are interested in this topic.