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True or False: Carbohydrate loading improves aerobic exercise performance?

Posted on June 6, 2019

True.

Carbohydrate loading, also sometimes referred to as carb or carbo loading, glycogen loading and glycogen super compensation, is a strategy used by athletes to improve performance in endurance events usually lasting longer than 90 minutes.

The practice has been around since the 1960s, when scientists first noticed that low-carbohydrate diets resulted in depleted glycogen stores and quicker fatigue in research participants. These studies also showed that eating diets high in carbohydrates resulted in enhanced glycogen stores and prolonged endurance times.

Glycogen is carbohydrates (energy) stored primarily in the liver and mus- cles. When we exercise, we draw on glycogen for fuel. When we engage in long endurance events—a marathon, triathlon or 100-mile cycling race, for example—our glycogen stores become very important. Without energy to keep our bodies going during these long-distance challenges, fatigue sets in faster, and our overall performance is greatly diminished.

The first protocol used for carbohydrate loading, often referred to as the classic approach, had athletes drastically cutting back on carbs 5–6 days before an event and doing lots of intense exercise. They took in an abundance of carbs 2–3 days before the event, at the same time reducing their activity level.

 

The goal was to deplete glycogen stores, both by cutting back on carbs and doing the intense exercise, so that when they upped their carbohydrate intake, cells in the body would be much more receptive or sensitive to carbohydrates and to storing them for future use.

This classic approach worked, but it wasn’t popular with athletes. If you have ever tried to perform intense exercise on a low-carbohydrate diet, you know why. Subsequent studies have shown that you don’t need to go through the glycogen-depleting process in order to improve performance with carbohydrate loading.

Now the general protocol for carbohydrate loading is to increase carbohydrate intake 2–3 days prior to an event and to combine that with tapered or reduced activity.

Many studies on athletic performance have shown that carbohydrate loading improves performance by 2–3%. at might not sound like a lot to some people, but in a marathon, that could be the difference between win- ning and not even finishing in the top 10–20% of runners.

Sedlock (2008), in an article published in Current Sports Medicine Reports, stated that the ergogenic (performance-enhancing) value of carbohydrate loading and associated physiological mechanisms has likely been studied more than any other singular performance-enhancing strategy. She also states that the ergogenic benefit of carbohydrate loading for endurance performance is a widely accepted tenet.

So yes, carbohydrate loading does improve aerobic performance. For most of us who are considered general recreational athletes, we will probably never need to go through a carbohydrate-loading regimen. As I finish this chapter, my cute little dog Scout is looking at me with great anticipation to take him for a walk, which I am gladly going to do. Carbohydrate loading likely wouldn’t help me much during that 30-minute outing.

However, if you are planning on participating in an endurance activity that will last 90 minutes or longer, then carbohydrate loading could help delay fatigue and have a positive impact on your overall performance.

Sedlock, D.: The latest on carbohydrate loading: A practical approach. Current Sports Medicine Reports (2008), Vol 7, pp. 209-213.

True or False: Eating garlic lowers cholesterol?

Posted on April 24, 2019

False.

GARLIC (ALLIUM SATIVUM) is often used to flavor foods and is well known for its strong, distinctive odor. Because of its aromatic properties, garlic is sometimes affectionately referred to as the “stinking rose.”

Many years ago my wife and I went to San Francisco to attend a conference, and while on a long walk we came across a restaurant called The Stinking Rose. She LOVES garlic, so we decided to stop for dinner.

I’ll never forget the overwhelming smell of garlic when we walked in    the door. I’ll also never forget the first item on the menu: 50 Clove Garlic Chicken Breast—chicken breast adorned with 50 cloves of garlic. My wife was in heaven!

Garlic contains allicin, which has been shown to kill some bacteria and fungi. Garlic is touted for having many health benefits such as preventing colds and the flu as well as lowering high blood pressure and  cholesterol.

But let’s focus on whether garlic is effective at lowering cholesterol, and let’s begin by reviewing the two types of cholesterol we measure: LDL and HDL.

LDL, or low-density lipoprotein (often called bad cholesterol), is a fat/ protein complex that carries cholesterol to the arteries and contributes to cardiovascular disease.

HDL, or high-density lipoprotein (often called good cholesterol), is a fat/ protein complex that carries cholesterol from the arteries to the liver for removal and helps decrease the risk of cardiovascular  disease.

Health professionals recommend keeping total cholesterol below 200 mg/dl and LDL cholesterol below 100 mg/dl. Ideally, HDL should be 60 mg/dl or higher.

Now back to garlic. Garlic can be eaten raw or can be taken as a supplement available as a powder, tablet or capsule. Garlic is generally considered to be safe, but there can be some mild side effects from garlic such as bad breath, general body odor and gastrointestinal distress.

It is also important to note that garlic can affect the body’s ability to clot blood, so individuals taking a blood thinner should talk to their physician if they decide to start eating lots of garlic or taking a garlic supplement.

The author Khoo (2009) published a meta-analysis in the Journal of Clinical Pharmacy and Therapeutics on whether garlic lowers cholesterol levels. Khoo identified 1,228 research articles on garlic and, using strict inclusion criteria to ensure that he chose only studies of the highest quality, identified 13 research studies that tested 1,056 subjects. Khoo’s findings: “The available evidence from randomized controlled trials does not demonstrate any beneficial effects of garlic on serum cholesterol.”

Khoo also states that recommendations by proponents of complementary and alternative medicine to increase garlic consumption as a way to reduce the risk of cardiovascular disease should be viewed with caution.

I’m not a huge garlic fan, but I do think it adds a desirable flavor to many of the foods we prepare at home. If my wife and I ever take another trip to San Francisco, you can bet that we will likely make a repeat visit to The Stinking Rose restaurant.

Khoo., Y.: Garlic supplementation and serum cholesterol: a meta-analysis. Journal of Clinical Pharmacy and Therapeutics (2009), Vol 34, pp. 133-145.

True or False: Grapefruit juice can impact many medications?

Posted on April 2, 2019

True.

I WASN’T MUCH of a grapefruit fan growing up—that is, unless my mother cut the grapefruit in half, separated the pulpy and meaty portion of the fruit from the tough—and sometimes bitter—skin surrounding it, and covered the entire surface with sugar.

I find it interesting that my kids are the same way—and they weren’t even around when I was growing up! As an adult I now enjoy peeling a grapefruit and eating it slice-by-slice, the way most people eat oranges.

Grapefruit is healthy; it’s low in calories, it contains lots of vitamins and minerals, it’s a good source of fiber, and it contains antioxidants. Most of us can consider grapefruit a “safe” fruit.

However, it is true that grapefruit or its juice can have a negative impact on many medications. You should exercise caution if you take medication and you want to eat grapefruit or drink grapefruit  juice.

Grapefruit juice doesn’t interact directly with medications; it inhibits an enzyme in your small intestine that works to break down certain medica- tions. Interfering with that enzyme can result in too much medication enter- ing your blood, potentially leading to a dangerous situation.

This phenomenon was accidentally discovered in the late 1980s. Researchers investigating the interaction of alcohol and the prescription drug felodipine used grapefruit juice to cover up the taste of the alcohol. However, one result of the study was a large increase of felodipine in the blood of research participants.

Grapefruit juice can also have the opposite effect, lowering the concentra- tion of a few medications in the blood.

There are dozens of medications that can be negatively affected by grape- fruit juice, including those for pain control, hypertension, allergies, high cholesterol, depression, epilepsy, heart disease and asthma.

In an article published in Nutrition Journal, authors Kiani and Imam (2007) state, “Grapefruit juice is consumed widely in today’s health-conscious world as a protector against cardiovascular disease and cancers. It  has, however, been found to be an inhibitor of the intestinal cytochrome P-450 3A4 system, which is responsible for the first-pass metabolism of many drugs.”

The authors also cautioned, “In light of the wide-ranging effects of grape- fruit juice on the pharmacokinetics of various drugs, physicians need to be aware of these interactions and should make an attempt to warn and educate their patients regarding potential consequences of concomitant ingestion of these two items.”

Other citrus fruits that may interact with medications  include  Seville oranges and tangelos. Lemons, limes and regular oranges generally are thought to have a low risk of interacting with  medications.

If you take prescription or over-the-counter medications, have a conversation with your doctor or pharmacist if you wish to eat grapefruit or drink grapefruit juice.

Kiani, J., & Imam, S.: Medicinal importance of grapefruit juice and its interaction with various drugs. Nutrition Journal (2007), Vol 6, pp. 33-41.

 

True or False: Expensive vitamins are better for you than store brands?

Posted on February 15, 2019

False.

THE HUSTLE AND bustle of today’s busy world makes it difficult for many people to eat a healthful diet. It takes planning and effort to get to the grocery store, buy wholesome food and find time to prepare   it.

All of the registered dieticians I’ve spoken to over the years about vitamins—R.D.s are the gold standard for individuals giving nutritional advice— have told me it is ideal to get the nutrients your body needs directly from the food and beverages you consume.

But not everyone does that. Too often, it’s easier to opt for processed and fast-food options, a choice that can leave us far short of getting all of the nutrients we need to be healthy. Most of us realize that, which is no doubt why roughly 40% of Americans spend billions of dollars on vitamin supplements every year.

We shouldn’t be surprised that vitamin manufacturers have convinced us that taking vitamins can be fun—especially children’s vitamins that are more like candy than a supplement. I can’t tell you the number of times I’ve tried to help my kids decipher if the vitamin they were about to devour was a Tyrannosaurus Rex or a Velaciraptor. The gummy vitamins were even harder to figure out: Was that a penguin, a polar bear or an arctic fox? It didn’t matter … down they went!

Some people ask whether expensive vitamins absorb better in your body. Others are suspicious about contaminants in vitamins. (Because vitamins are considered a dietary supplement and not a food, there are no strict Food and Drug Administration guidelines for manufacturing vitamins.) Yet others wonder if the vitamins really contain the nutrients listed on the label.

In 2010, Consumer Reports surveyed over 2,000 adults and found that over half worried that vitamins contained harmful ingredients, and nearly half feared that their vitamins didn’t contain the nutrients claimed on the label.

The following from Consumer Reports Magazine (2010) details tests and results. “Our tests of 21 multivitamins at two outside labs—including leading brands, five for seniors, and six for children—will allay some of those fears. All but one of the products we tested met their label claims for key essential vitamins and minerals, and none contained worrisome levels of contaminants such as arsenic or heavy metals. Most of the pills we tested  also passed the U.S. Pharmacopeia’s dissolution test, which involves immersing them in a simulated stomach-acid solution to determine whether they’ll dissolve properly in your body. What’s more, we found that store brands did just as well in our tests as national brands, at a lower price.”

My wife and I no longer take a daily multivitamin, nor do we buy them for our kids. Instead, we try to eat lots of whole grains and a wide variety of fruits and veggies. However, when we were taking vitamins, I was aware that some of the brand-name variety could cost two or even three times more than store brands. I found that especially interesting, as many store-brand and national-brand vitamins are produced by the same manufacturer.

Here’s the bottom line: If you do take vitamins, you can feel relatively certain that, regardless of how much you pay for them, they are safe, they contain the nutrients their label claims, and they are dissolving in your body. What might remain uncertain is which of the Flintstone’s characters your child is about to eat.

Consumer Reports. Multivitamins: Most we tested were fine, so select by choice. Consumer Reports Magazine: September 2010. www.consumerreports.org/cro/magazine- archive/2010/september/health/multivitamins/overview/index.htm. Accessed 1-3-13.