Файл: Medical_Myths_Lies_and_Half-Truths_guidebook.pdf

8

Lecture 2: Myths about W

ater and Hydration

However, there’s a cautionary downside to this as well. Aggressively 
hydrating, even with sports drinks that contain electrolytes, can actually 
worsen the dilution of electrolytes. The only way to really maintain your 
osmolality when you’re 
drinking that much 

À

 uid  is 

to eat salty snacks. When 
you push the body to its 
limits with extremes of 
athletic endurance, you 
overwhelm the regulatory 
systems. You have to be 
careful about how much 
you drink, what you drink, 
and that you eat.

There are a few questions 
that frequently come up 
with respect to water. 
One is bottled water—
is there an advantage 
to it? Interestingly, bottled water costs about 1900 times as much 
as tap water. But bottled water, if you look at it statistically, 
is no better than tap water. It’s no more healthy, and in 
taste tests, it hasn’t been shown to taste any better. Bottled water, overall, is 
basically a scam. 

What about water puri

¿

 ers, which you install in your home to 

¿

 lter  out 

organisms, impurities, or heavy metals from your water? Most modern 
industrialized countries have agencies, like the Environmental Protection 
Agency in the United States, that closely monitor and regulate water. 
Currently, there are no major safety issues with tap water in the United 
States or other industrialized countries. If you have any concerns, you can 
look up these agencies’ reports on the quality of the water in your area. The 
legitimate use for water puri

¿

 ers is to increase the taste of water. There, 

you can just follow your own taste. If your tap water tastes 

¿

 ne to you, then 

don’t worry about it. If it doesn’t taste right, you may want to get a water 
puri

¿

 er—even though it won’t necessarily be more healthful. 

Ŷ

In a warm environment or with physical 
exertion, make sure you hydrate continuously.

© Comstock/Thinkstock.

9

Segal, “Body Fluids.” 

1. 

How does the body maintain its delicate balance of water 
and electrolytes?

2. 

Are some sources of water better for hydration than others?

    Suggested Reading

    Questions to Consider

10

Lecture 3: V

itamin and Nutrition Myths

Vitamin and Nutrition Myths 

Lecture 3

Even in ancient history, people understood that there was some 
connection between nutrition, the food that we eat, and health. For 
example, the ancient Egyptians wrote about the fact that liver could 
be used to cure night blindness. Although they didn’t understand at 
the time that it’s because liver contains vitamin A, they were treating a 
vitamin A de

¿

 ciency. 

O

ne of the most common concerns patients have is about vitamins. 
Should they take a multivitamin every day, or can they get all the 
nutrition they need from the food they eat? Vitamins are those 

nutritional substances that are essential to health in tiny amounts but that an 
organism cannot manufacture in suf

¿

 cient quantities itself. Therefore, you 

have to get vitamins from food. 

Vitamins are only part of the nutritional content of food that we need to be 
concerned with, the micronutrients. Then there are the macronutrients, those 
parts of food from which we get calories or energy and also structural 
components, the stuff that we actually build our bodies out of. The three 
main types of 
macronutrients that 
we get in our diet 
are carbohydrates, 
lipids, and protein. 
Food also contains 
minerals, including 
calcium, phosphorus, 
magnesium, iron, 
zinc, copper, sodium, 
and potassium. 

So how do we get 
optimal nutrition? 
There is general 

The best way to get good nutrition is through a well-
balanced, varied diet. 

© JupiterImages/Polka Dot/Thinkstock.

11

agreement in the scienti

¿

 c community that the best way to get good nutrition 

is through a well-balanced, varied diet. You should avoid highly restrictive 
or narrow diets that are dependent on just a few different kinds of food. The 
USDA food pyramid goes over the rough proportions of different types of 
foods that would be contained in a healthful diet. A healthful diet should 
contain and should emphasize the following: 

Ɣ

You should eat about 2 cups of fruit and 2.5 cups of vegetables 
per day. Try to pick from the different subgroups of vegetables, 
including dark green vegetables, orange vegetables, legumes, and 
starchy vegetables. 

Ɣ

You should get 3 or more ounce equivalents of whole grain products 
per day, with the rest of your carbohydrates coming from either 
enriched or whole grain products. 

Ɣ

You should have 3 cups per day of fat-free or low-fat milk or 
equivalent milk products. 

Ɣ

To round out your diet, you should get protein from lean meats as 
well as eggs, nuts, and legumes. 

Do we need to take vitamins every day? The big vitamin myth is that taking 
a daily vitamin is important for everyone’s health and well-being. In fact, 
there is no evidence for any health bene

¿

 t of routine supplementation. This 

is a very dif

¿

 cult question to study, but there have been observational studies 

that found no correlation between routinely supplementing with vitamins 
and health outcomes. Further, studies that show health advantage or a good 
outcome based on nutrition are only able to link those advantages to eating 
healthy foods—not to taking supplements. 

So far, we have been talking about supplementation for healthy people with no 
medical conditions. But what about subpopulations? Children have increased 
nutritional needs because they’re growing. Should we routinely give children 
vitamin supplements? It’s probably still the best recommendation, based 
upon the evidence, that what’s most helpful for growing kids is a healthy 
diet. But I know how dif

¿

 cult it is to get kids to eat their vegetables. If your 

12

Lecture 3: V

itamin and Nutrition Myths

children have a restrictive diet despite your best efforts, it is reasonable to 
consider supplementation as nutritional insurance.

Pregnancy is another situation in which there are increased nutritional 
demands. It is routinely recommended for pregnancy—and for women who 

are planning on possibly becoming 
pregnant—to take a prenatal 
vitamin because you need to boost 
your nutritional reserves before 
you know that you are pregnant. 
There are also a number of medical 
conditions in which our nutritional 

needs may be greater than at baseline and where supplementation may be 
bene

¿

 cial. And there are speci

¿

 c conditions or diseases in which there isn’t 

a de

¿

 ciency, but taking extra vitamins may actually improve symptoms

or outcome. 

Vitamins are, by de

¿

 nition, essential to nutrition to prevent de

¿

 ciencies and 

improve many medical outcomes. But I want to emphasize that we need to 
avoid the myth that if some vitamins are good, then more must be better. This 
has led some to recommend very high doses, sometimes called megadoses, of 
vitamins. There is no theoretical reason, nor is there any evidence, to support 
the safety or the health effectiveness of megadosing. It is not recommended. 
Aside from the possibility of overdosing toxicity, regularly supplementing 
with high doses of certain vitamins actually correlates with an increased risk 
of certain diseases. 

The best advice is to keep it simple: Don’t get overwhelmed with the 
complexity of the different types of nutritional advice that people are willing 
to give. A few simple rules are enough. Eat a variety of foods; eat plenty 
of fruits and vegetables. For most people in most situations, you will be in 
perfect health in terms of your nutrition. 

Ŷ

The best way to get good 
nutrition is through a well-
balanced, varied diet.