Macronutrient Structure & Metabolism

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Stanford Introduction to Food and Health

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Stanford University

Stanford Introduction to Food and Health

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Around the world, we find ourselves facing global epidemics of obesity, Type 2 Diabetes and other predominantly diet-related diseases. To address these public health crises, we urgently need to explore innovative strategies for promoting healthful eating. There is strong evidence that global increases in the consumption of heavily processed foods, coupled with cultural shifts away from the preparation of food in the home, have contributed to high rates of preventable, chronic disease. In this course, learners will be given the information and practical skills they need to begin optimizing the way they eat. This course will shift the focus away from reductionist discussions about nutrients and move, instead, towards practical discussions about real food and the environment in which we consume it. By the end of this course, learners should have the tools they need to distinguish between foods that will support their health and those that threaten it. In addition, we will present a compelling rationale for a return to simple home cooking, an integral part of our efforts to live longer, healthier lives. View the trailer for the course here: https://www.youtube.com/watch?v=z7x1aaZ03xU

À partir de la leçon

Background on Food & Nutrients

In this section we will examine the social and cultural shifts that have contributed to our modern epidemics of overweight and obesity. We will briefly review the nutrients found in foods, their different functions in the human body and how we can support our own health by choosing wisely from the foods within each category.

Introduction2:03

A Sociocultural History of Obesity3:35

Macronutrient Structure & Metabolism4:43

Carbohydrate-rich Foods & the Glycemic Index3:45

Animal & Plant-based Proteins3:45

Dietary Fats & Their Effects on Human Health4:42

Rencontrer les enseignants

Maya Adam, MD
Lecturer
Stanford School of Medicine

[MUSIC]

In order to survive, the human organism needs to take in oxygen, water, and food.

We can survive only about three minutes without air,

three days without water, and three weeks without food.

Because food is so important to our survival, it's been studied extensively.

And since 1827 when a British physician by the name of William Prout

first proposed that humans need three macronutrients to survive,

physicians, scientists, and increasingly the general public have trying

to figure out exactly how much of each of these nutrients will optimize our health.

But to some extent, the focus on nutrients rather than food has confused many people.

>> And we tend to get lost in this conversation about nutrients, good and

bad and it's understandable because scientists

need to reduce things to a single variable to study them.

And the variable in food would appear to be the nutrient.

But we also have lots of studies that show that simply removing or

boosting nutrients or turning them into supplements doesn't seem to work.

That food is much more complicated, it's a system.

>> A basic understanding of the nutrients can give us a helpful background for

our discussions about food.

So we'll review the nutrients and how the body uses them, but

most of this course will focus on discussions about food and health.

Because ultimately, people eat food, not nutrients.

Dietary carbohydrates are combinations of sugar units that come in both simple and

complex forms.

Simple carbohydrates include the monosaccharides, or

single sugar units like glucose and fructose.

As well as the disaccharides, or two-sugar units like sucrose, or table sugar.

Complex carbohydrates, or polysaccharides,

include the dietary starches that our body can break down and digest,

and also the indigestible polysaccharides that make up dietary fiber.

During the process of digestion, carbohydrates are broken down and

converted to glucose, which can then be metabolized by the body

to produce usable energy in the form of ATP.

If energy demands are low, glucose can be stored, and

most of the time it's stored as adipose tissue.

Dietary proteins are also broken down into their component parts,

amino acids, during the process of digestion.

And these amino acids can be used to build and

repair lean tissues in the body and perform many other important functions.

But amino acids can also be broken down and used for energy.

And if they're consumed in excess,

they can contribute to fat stores in the body as well.

Dietary fats can also be broken down into smaller components and used for energy.

[MUSIC]

Or, they can be stored as adipose tissue, depending on our energy needs.

Fats are the most energy dense storage form, providing nine calories of

energy for every gram, and alcohol provides seven calories per gram.

In contrast, carbohydrates and proteins provide only four calories per gram.

This is one of the reasons we've evolved to store excess nutrients as

adipose tissue, and this brings us to the underlying

physiologic cause of overweight and obesity.

Any calories that aren't converted into usable energy

in the form of ATP are stored in the body for later use.

Most of the time they're stored as adipose tissue.

So disturbing the energy balance to favor energy expenditure

over energy storage needs to be one of the priorities for

people who are trying to lose excess weight.

This can be achieved by consuming fewer calories,

burning more calories through exercise, or a combination of both.

But in addition, when long term health is the end goal,

the quality of our food matters just as much as the number of calories we consume.

Within each category of macronutrients, we need to choose

foods that will support our health, rather than working against it.

[MUSIC]

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