Why is all the nutrition news you hear and read so confusing? Mainly, it’s because writers—and nutritionists too, I’m afraid—assume that just because we all eat food (and that most of us are not dying from some form of malnutrition), we understand nutrition. They couldn’t be more wrong! The only folks who don’t seem to assume we all understand basic nutrition are the group who call themselves nutrition experts and try to sell us on the latest fad diet, super food, or nutrition scare.
So before I ever post another blog or comment on another nutrition story in the news, I want to make sure we’re all on the same playing field! To do that, I need to share with you the basic framework of nutrition knowledge that reputable nutritionists use to evaluate the evidence, and what we have in mind when we advocate things like eating a balanced diet!
What are nutrients? Nutrients are substances scientific research has demonstrated that our bodies need in certain amounts for a reasonably healthy existence. Our bodies are living factories! Although you may never have considered it, our bodies are constantly working; even just the act of getting up from the sofa to go to the fridge, involves thousands of little tasks. Even when you’re asleep, you’re breathing, digesting food, moving around, processing information, and maybe snoring! And these tasks–muscle movements, nerve function, enzymatic catalysis of biochemical reaction (i.e. performing chemical reactions like digesting protein)–all use up energy, amino acids, fatty acids, vitamins, minerals, and water, and all of these need to be replaced. That’s why we need to eat and why we need to eat a variety of foods: not just a variety of things from the snack food aisle, but a group of real foods that will deliver the nutrients our bodies need in the right proportions…to keep snoring!
Nutrients come in a few basic categories (see the table below): Proteins, carbohydrates, and fats are referred to as macronutrients because we need them in relatively large amounts. Also, the macronutrients and drinking alcohol are the only substances we consume (alcohol is not actually a nutrient) that supply energy. Energy is just another word for calories. There is nothing magical about energy, in spite of what food and “supplement” manufacturers and gym owners would like you to believe! Vitamins and minerals are referred to as micronutrients: we require them in much smaller amounts than, say protein. Micronutrients have no calories, although they are vital for enabling the body to use the calories in macronutrients.
To learn more about all the importantly different carbohydrates, see my entry in the “Terms of Interest,” Section, under “Nutrition Terms.” Eventually, I’ll post similar definitions for fats and proteins.
Vitamins come in two types: water soluble and fat-soluble. This is an important distinction! The water-soluble vitamins can’t be stored in our bodies, so if we consume more than our bodies need in a given day or two, we make really nutritious…toilet water! Water soluble vitamins include the B vitamins –B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B12 (cobalamin), pantothenic acid (sometimes called B5), folic acid (rarely called B9), and biotin–and vitamin C. Fat soluble vitamins, including vitamin A, D, E, and K are stored in our body fat (even under the skin) and in organs like the liver: As a result, they can accumulate to toxic levels if consumed in excess. Now this doesn’t mean you can’t overdose on some of the water-soluble vitamins: too much niacin, folic acid, and vitamin C taken at one time can cause some real problems. This is why the scientific organization that sets the nutrient requirements also sets “tolerable upper intake levels.”
How did we determine what nutrients are required? Basically, clever, busy nutrition researchers in the 19th and 20th centuries determined the need for the nutrients we know about by being detectives. They studied people with particular diseases (like scurvy, beri beri, pellagra, kwashiorkor, marasmus…) and deduced that those people were suffering from deficiencies in vitamin C, vitamin B1, vitamin B3, calories, and protein, respectively.
We don’t know if all the nutrients have been discovered yet. There may be some substances in foods that we need but haven’t discovered yet. That’s why it’s always better to eat real food than to rely on pills or even highly processed foods.
Who deduced how much we need of each nutrient, those numbers that the Food Facts labels are based on and how? The same folks who discovered that we needed certain nutrients also estimated how much we needed. Periodically, nutrition scientists revisit those requirements to decide if they need to be modified, based on new knowledge.
So far all our nutrient requirements are based on curing or preventing deficiency diseases. But a huge controversy has been brewing for the past 30 years or so, maybe starting with vitamin C and Linus Pauling, as to whether certain nutrients (mostly vitamins and minerals) in larger (what we call “pharmacological” amounts because the nutrient in large amounts is now acting like a drug) have the ability to prevent or treat some illnesses, mostly the kinds of diseases that take a long time to develop, like heart disease, arthritis, and cancer, but also things like the common cold. It was a million times easier to show that depriving someone of thiamine for a few months causes beri beri and that giving the person enough thiamine will arrest the disease than it has been to try to ascertain whether giving a young woman more calcium will prevent osteoporosis in 20 years or giving a guy more omega-3 fatty acids starting in his 30s will prevent hypertension in his 60s, cancer in his 70s, or Alzheimer’s in his 80s! This conundrum is at the heart of just about all nutrition controversies these days! Some other nutrition controversies concern whether eating too MUCH of certain nutrients over a lifetime is causing heart disease, cancer, arthritis, and Alzheimer’s Why are these questions so difficult to answer? Well for starters, imagine trying to do research on the same folks for 40 or 50 years?
You’ve probably read that your body needs a certain number of calories to survive and to maintain your body weight. Consuming more than that number of calories can lead to weight gain (regardless of whether those calories came from carbs, fats, or protein!). Calories provide the energy to move around, stay warm, and perform the thousands of chemical reactions needed to keep you alive and functioning. Calorie needs are based on a few factors:
• your weight: the heavier you are, the more calories you need to carry that weight around and function,
• the proportion of your body weight that is muscle vs. fat: your muscles use more calories than your fat does,
• how much exercise you get: exercise burns calories while you’re doing it, builds a little muscle, and raises your metabolism a bit so you continue to burn more calories when you’re sitting at your computer but it does NOT negate that venti frappucino,
• your sex: men have a higher ratio of muscle to fat, and
• probably to a small extent, some other, yet unidentified genetic factors.
That’s where the controversies arise about what causes some people to be overweight and the best way to lose weight. But this is a topic for another hundred blogs.
And before I go any further, I want to get one thing clear…about the meaning of overweight.
What does overweight mean? What does it mean when the doctor tells you that you’re not obese (yet) but that you need to lose weight? Is she just expressing her opinion? Being overly critical? Would another doctor, maybe one who’s not so judgmental or who doesn’t live in L.A. and sees a different group of patients tell you you’re fine? Well, in short, no. Overweight and obese have precise definitions based on body weight and height (after all, a tall thin person is going to weigh more than a shorter thin person, just because the taller person has more bone and muscle…). The government actually defines “overweight” as having a body mass index (BMI, or one’s body weight, in kilograms, divided by the square of height, in meters) equal to 25 or greater. For example, a person 5 ft. tall (1.524 meters) who weighs 125 lbs (58.967 kilograms) would have a BMI of 58.967/1.5242=25.4. Obesity is defined as a BMI of 30 or more. So, if that same 5 ft tall person gained 30 pounds (155 lbs, or 70.3068 kilograms), her BMI would be 70.3068/1.5242=30.3. Extreme obesity is defined as a BMI greater than 35 (180 pounds for our 5 foot tall example). A BMI less than 25 is considered “normal.”
But where did these “cutoffs” come from and do they really measure something important? First, the cutoffs of 25, 30 and 35 are based on very large studies, meaning long-term studies of very large numbers of people. These studies showed that people’s chance of dying prematurely (from any cause, but usually from heat disease) is directly related to their BMI. Although your chance of living to 100 is not hugely greater at a BMI of 24.9 than at a BMI of 25.1 or even 26, the average chance of living to 100 is greater for folks with a BMI less than 25…BMI is intended to predict risk for populations, not so much for individuals like you and me, but we do know that being at a higher weight because you have more body fat increases your risk for dying prematurely, BMI is a fairly good indicator of body fat, and other ways of measuring body fat directly have not been nearly as easy, cheap, or reliable. I’ll let everyone chew on that for a while (I’m sorry…I just couldn’t resist that!) and I’ll continue with weight measurements and more on nutrients in Part 2 of Nutrition 101.