Raw Thought

by Aaron Swartz

Nutrition Basics

As part of changing my eating habits, I’ve become quite interested on the subject of nutrition. I can’t seem to find a good guide to the subject online, so in the spirit of flailing in public until someone comes to my aid, I thought I’d write up what I think I know. Feel free to correct me or point me to better sources in the comments.

Calories are the basis of eating; they’re a measure of the amount of energy a food provides. Your body gets calories from the food you eat and spends them to keep you moving. If you get more calories than you spend, your body stores the excess as fat. If you spend more than you get, your body burns some of the fat it’s stored up (for just such an occasion).

Thus the standard advice for losing weight: eat less, exercise more. Eating less brings fewer calories in, while exercising more uses up more of them. Unfortunately, both of these things are quite hard to achieve, because the body seems to regulate them through the use of “set points”: your body keeps track of how much fat you have through a chemical called leptin and makes you hungry if you’re starting to lose weight. Thus, if you skip a meal in the morning, it’ll be sure to make you extra hungry in the evening, so that your overall weight doesn’t change.

A similar setpoint seems to operate for exercise. In one experiment, doctors measured how much children moved around with pedometers. Then they tried forcing the children to exercise by giving them a PE class. They found that when kids were forced to exercise at school, they exercised less at home, and ended up doing the same amount of exercise overall. So just as your body seems to make you hungry when you’re losing weight and full when you’re gaining it, it seems to make you tired when you’ve burned too many calories and antsy when you haven’t burned enough.

Of course, we’re not total slaves to such motivations — we can force ourselves when to eat when full or not to eat when hungry, to exercise when tired or to stay still when antsy — but it’s worth keeping in mind what we’re up against.

Fats have gotten a bad rap, most likely because they share a name with body fat but also, some argue, because they seem lower-class. In truth, however, they’re largely just one way to get calories, and a calorie is a calorie no matter where it comes from.

Fats also have effects on cholesterol, a key building block for your body’s cells. There are two types of cholesterol — known informally as good and bad cholesterol. Good cholesterol consists of tightly-packed proteins of cholesterol in your blood stream, allowing cholesterol to be efficiently transported where it needs to go. Bad cholesterol is less densely packed and its cholesterol ends up sticking in the walls of arteries, clogging them and leading to heart disease. Fats have varying effects on cholesterol. Saturated fats should be avoided: they increase levels of bad cholesterol (although they also increase good cholesterol). Unsaturated fats, however, whether monounsaturated or polyunsaturated, are good: they lower bad cholesterol and raising good cholesterol. Trans fats are just the reverse: they increase bad cholesterol levels and decrease good ones; it’s recommended they be avoided as much as possible.

Often nutrition labels only break out unsaturated fats and trans fats; you have to calculate the amount of saturated fat by subtracting these from the amount of total fat. The goal, remember, is to avoid trans fats whenever possible, avoid saturated fats, and go for unsaturated fats.

Carbohydrates are another source of calories, the kind found in white wheat products, like bread and pasta. Sugars are a form of carbohydrate and, in fact, the body breaks down other carbohydrates into simple sugars. The problem with sugars is that they go directly into the bloodstream, spiking your blood sugar level. This in itself is unhealthy, but it’s even worse when the level inevitably crashes and you begin to feel hungry again and eat even more.

The exception is with fiber, which the body can’t break down. Foods made from whole wheat are high in fiber, so your body takes longer to digest them and the sugar intake is spread out over a longer period of time. Thus while carbohydrates might generally be avoided, whole wheat products (along with fruits and vegetables), include additional nutrients as well as having a safe impact on blood sugar, and are the foundation of a healthy diet.

Protein is a similar essential nutrient, allowing the body to make essential components of muscle and hair and so on. If you don’t get enough (about 9 grams of protein for every 20 pounds), the body begins breaking down its tissues. (Eating far too much protein, however, as people in low-carb diets do, can be unhealthy as it absorbs calcium from your bones.) While protein can be found in animal products, whole wheat bread is a also an excellent source — a single slice contains five grams of protein. Unfortunately, the proteins found in grains and vegetables are incomplete, so you either need to get some (complete) animal protein or eat a variety of them.

Calcium is necessary for building bones and teeth, maintaining the heart’s rhythmym, and more. Deficiency can lead to weakened bones and fractures. While dairy products contain significant amounts of calcium, they also contain a lot of saturated fat and has been linked to some cancers. Many other foods are fortified with calcium and some vegetables (kale and collard greens, dried beans, and legumes) are also a good source.

Vitamins do all sorts of good things, as well as warding off diseases like scurvy and rickets. They’re often added to juices and cereals and can be taken by themselves in a daily multivitamin as well.

For additional information, check out:

You should follow me on twitter here.

July 28, 2006


Get Understanding Nutrition by Ellie Whitney. Our class used the 10th edition last year. It is written mainly for undergrads but has a lot of good information and provides a good framework for further study. If you want to dig deeper into the biochemistry, get Lehninger’s Biochemistry. The 4th Edition is current and Lehninger is the gold standard among biochemistry texts. A medical student’s physiology text would also be useful. Many of the excruciating details (embryology of various recently discovered cell lines, etc) are becoming available on Wikipedia. If you really want to chew on the primary sources, PubMed is the place to go. If you get down to DC, collect your favorite PubMed citations and go to the National Library of Medicine. It’s a trip.

Niels Olson Tulane School of Medicine Class of 2009

posted by Niels Olson on July 28, 2006 #

Another reason fats have gotten a bad rap is that gram for gram they have twice as many calories as carbohydrates and proteins.

But it also stimulates the release of cholecystokinin, which helps you feel full, and slows the absorption of sugars. Both of these effects help you eat less in the long run.

So unless you’re a portion-size Nazi, eating low-fat junk food is no better, and likely worse, than eating the full-fat variety.

posted by Frank on July 28, 2006 #

If certain nutrients aren’t received by your body, over time parts of you should break down and undergo more wear and tear, I would imagine. The best way to get the right nutrients is to identify the foods which are optimally healthy, and eat a variety of them (I’m thinking raw fruits and vegetables, whole grains, and nuts/beans). Once you’ve eaten a variety of foods for a while, I think your body will learn and will start to crave the foods that it really needs most on a particular day or week. Depriving the body of enough of any type of healthy food will lead to nutritional deficiency, some as yet unknown.

As far as what foods are optimally nutritious, I don’t know of where to find an actual list. You definitely can’t get enough nutrition from a bottle of vitamins. Vitamins reflect only what the current state of nutritional science knows to be good for you, and on top of that, the chemicals in vitamins are no longer in their natural state and are probably not complete. Even just refrigerating your fruit will make it lose some of its nutrients. Imagine putting it into a dry capsule!

We’ve come a long ways since the days when a nutrition label would tell you if something was good for you. There are so many nutrients it boggles the mind. Read the Wikipedia entry on Nutrition. Besides the usual vitamins and minerals, the body also needs amino acids, fatty acids, and phytochemicals. Worse yet, there are thousands of phytochemicals. Some are antioxidants, which help your cardiovascular and immune systems.

My point is it’s impossible to quantify exactly what nutrients your body needs, and then to try to take all of them with a vitamin. We can’t and we don’t know everything about how our body functions. So the best you can do is pay special attention to eating the foods which have the most known nutrition (e.g. colored vegetables, berries, whole grains, etc.) and optimize your intake of those. If history is any guide, the best nutritional discoveries will continue to take place in those types of foods.

A further take on this is to research what humans have evolved to eat. Before farming arrived and screwed up our diet, humans probably had to eat a variety of fruits, vegetables, proteins, and carbohydrates just out of necessity of survival. I don’t know much about this, but that’s one factor in considering whether eating meat is good for you or not. Our bodies may have evolved to expect that sort of nutrition. (But maybe not… humans may not have been big meat eaters originally!) We certainly didn’t evolve to eat large amounts of processed grains from industrial farming, and I think drinking milk is also not a natural thing for adults to do, and part of its purported health benefits come from the large US Dairy Association lobby. In fact, a lot of our governmental nutritional information (e.g. nutrition labels) is shaped by the sectors of the economy which have the most power over government. There, I even fit in a Chomsky-like take on your nutrition discussion!


posted by Scott Teresi on July 28, 2006 #

More clarification than correction, but while many vitamins & minerals are essential nutrients, they yield no calories, unlike protein, carbs, & fats. The mechanisms by which various vitamins operate and the benefits they provide the body are unrelated. Fiber, too, is “part of a healthy diet,” but by definition is not nutritious. (While this may seem obvious, you’d be surprised the sorts of things people believe.) Also, protein can be used to build tissue or burned as fuel; carbs & fats can only be burned. And the text leaves the false impression that carbs are intimately associated with wheat products.

Not as clear on this point, but there was much talk of the need to complement proteins when vegetarian diets initially became popular, e.g., by pairing milk with peanut butter. I believe that’s no longer considered nearly as important as it once was, since supposedly your body can break down and repurpose the component amino acids to an extent.

It is unfortunate that the “fat” you eat uses the same word as your body “fat,” since among other problems it leaves the impression that you can’t get fat from eating carbs.

posted by Mike Sierra on July 28, 2006 #

Correction: I meant carbs & fats can be burned or stored.

posted by Mike Sierra on July 28, 2006 #

Hearking back to a previous post; You should sneak into one of Walter Willett’s lectures. He lives in the Boston Area and teaches at the Harvard Medical School. His book “Eat, Dring and Be Healthy” is one of the best written on nutrition.

posted by Michael Thomas on July 29, 2006 #

Essential aminos and essential fatty acids are ‘essential’ because the body requires them and can’t produce them. In this sense, vitamins and many minerals and phytochemicals are also essential, but in such small amounts or over relatively long time periods so that it’s hard to know exactly what’s needed. There’s also a huge individual variability in what a person needs to build cells and the enzymes critical to staying alive. (see Roger Williams or Jeffrey Bland.)

As Mike notes, the idea of complete proteins (having a full complement of essential aminos) within a meal is no longer believed. But there is in only limited repurposing of components and you do need to get all of the essentials over time.

The general impact of all this is that it is wise to get your nutrition from a wide variety of food sources. And , for Aaron, that still applies even though he is eating relatively little.

One side issue: there are no essential carbohydrates. In other words, the body can any carbohydrate that it needs from protein. So from a nutrition standpoint, carbs are most importantly a package for essential micro-nutrients (and the fiber for effective elimination) that the body does require.

posted by Paul on July 29, 2006 #

posted by Paul on July 29, 2006 #

posted by Paul on July 29, 2006 #

posted by Paul on July 29, 2006 #

Correction: the body can make the carbohydrates that it needs from digested proteins and fats.

posted by Paul on July 29, 2006 #

To add to the carbs discussion, it’s not entirely clear from your wording that while sugars go immediately into your bloodstream, carbs are not immediately broken down into sugars, so carbs are better than raw sugar because it gives your body more time to catch up.

Your body breaks down the sugars in your bloodstream with insulin, which is released as-needed (unless you’re diabetic). But it takes a while for your body to release enough insulin to break down a sudden influx of carbs, which is why high fructose corn syrup is so unhealthy - it’s just pure, high-density sugar, which our bodies aren’t prepared to consume.

Unfortunately, high fructose corn syrup is used in more and more foods where you’d never expect it, turning otherwise healthy foods into the nutrition equivalent of candy.

posted by Scott Reynen on July 29, 2006 #

Oops…”a sudden influx of carbs” should be “a sudden influx of sugars,” the difference being my whole point.

posted by Scott Reynen on July 29, 2006 #

I should probably just RTFM, but when you say “9 grams of protein per 20 lbs” does that mean per day? And is there an equivalent rule of thumb for calcium (I worry about osteoporosis vs kidney stones)?

posted by Gordon on July 30, 2006 #

Here’s a helpful link about your diet.

posted by Ajay on July 30, 2006 #

Understanding nutrition is an endless journey.

The human body is a very complicated system, and very little is known of how nutrition affects it. You will notice this when you delve deeper into the studies and find they constantly contradict each other. Always try to get both sides of the story.

Many of the guidelines set by the government are based on old studies. It is very difficult for an authoritative institute to admit its mistakes and change course. The guidelines are also based on averages. You, as an individual, might not fit these averages, so keep a food log, even for a few days. This will teach you about your eating habits. Calculate your macronutrient intake.

The “calorie is a calorie” thing is also under debate. You might want to google “metabolic advantage”.

I wouldn’t advise avoiding saturated fats completely: http://www.westonaprice.org/knowyourfats/skinny.html#benefits

The Weston A. Price Foundation is a comprehensive source of unconventional nutrition information. Just remember that this also is just one side of the story.

Keep things very, very simple. Avoid extremities and hard rules. To eat healthy is to eat consciously, in a Zen like state where you see not only what you eat but also how you eat.

(btw, this edit box is too small)

posted by J on July 31, 2006 #

Ajay: That’s neither helpful nor convincing. Roberts has actual evidence, you’re going to need to say more than “you can’t do that! it’s a trick!” to dismiss it.

posted by Aaron Swartz on July 31, 2006 #

“A calorie is a calorie” is a misleading statement.

Sure, it’s true from a thermodynamic standpoint - once you factor in any conversion costs - but it’s not true from a “trying to lose weight” perspective. Some calories are much more damaging than others.

The key factor is the effect that calories have on blood sugar. This is measured using the glycemic index, a useful but often misused measure of how fast a food is absorbed.

It’s misused because it discounts calorie density (carrots have a high GI but low calorie density, so that don’t have a huge effect on blood sugar), and it also discounts that high GI foods are absorbed less quickly when eaten with other foods.

The common feeling that chinese food doesn’t fill you up is due to the white rice that you eat with it. High GI -> blood sugar spike -> blood sugar drop -> hunger.

The other big area that you didn’t explicitly mention is fiber. Fiber both helps slow digestion and fills you up, both of which are hugely useful.

I think Shangri La is a bizzare diet, but I’m not big on any “diet”, because that implies a short-term approach to a long-term problem - eathing healthily.

South beach is far more mainstream and healthier

posted by Eric on August 1, 2006 #

What chemicals are released when the body is hungry?

posted by Christiana on August 4, 2006 #

You can also send comments by email.

Email (only used for direct replies)
Comments may be edited for length and content.

Powered by theinfo.org.