Precision Nutrition Week 3

Chapter three: Super Science-y. Rather than take us all back to physiology class, I’m going to go off on a tangent. It all started with two little side notes about the effect on vitamins on metabolism… And ended up pretty science-y anyway. Talking about chemical reactions can do that!

First, a quick recap: Metabolism is the total of all chemical reactions in your body, including both the processes that break down and those that build up. These processes are fuelled by the food we eat. For this post, any metabolic processes discussed will be catabolic or break down processes.

Vitamins (and minerals) do not themselves provide energy, but without them, metabolic processes could not be completed.  The Vitamin B complex contains eight separate vitamins; each molecule is in the same family but chemically different from one another and includes:

  • Vitamin B1 (thiamine)
  • Vitamin B2 (riboflavin)
  • Vitamin B3 (niacin)
  • Vitamin B5 (pantothenic acid)
  • Vitamin B6
  • Vitamin B7 (biotin)
  • Vitamin B9 (folic acid)
  • Vitamin B12

If they don’t provide energy, what DO they do?

If vitamins can’t supply energy, what good are they?  Well, most vitamins (B complex and others) have essential roles in our metabolism and other physical processes. The B complex gives us more than enough to look at in one post: each of the eight B complex vitamins are involved in the aerobic and anaerobic metabolic processes that refill our energy supplies.

After the food we eat is broken down into its sub-units (glucose from carbohydrates, amino acids from proteins, fatty acids from fats), it is metabolised further within our aerobic or anaerobic pathways, or both. The B vitamins are involved in these processes as coenzymes, or small molecules that help the processes take place, and as the foundations of other molecules needed in the process. Without adequate amounts of all B vitamins, all energy renewal in our bodies would grind to a complete halt!


Vitamins B2, B3, B5, and B6 are all involved in glucose metabolism in the anaerobic or aerobic pathways – respectively, glycolysis and the Krebs cycle, which is the first half of aerobic metabolism. These vitamins help move molecules from place to place and pick up by-products like the hydrogen ions that cause muscle fatigue. B5 is also a necessary component of the molecule acetyl Co-A, which is the starting point for aerobic metabolism.

I’m separating out the second half of aerobic metabolism, called the electron transport chain, because every  B vitamin is involved in this process, working as supporting coenzymes or being used to help create the other molecules necessary to complete the energy renewal process.


B3, B5, and B6 are the major players in protein metabolism. We don’t often think of proteins as a source of potential energy, but after undergoing some molecular changes, amino acids can be converted to glucose for use in anaerobic or aerobic metabolism, or to acetyl Co-A or other molecules needed for use in the Krebs cycle. Once the molecular change takes place, the B vitamins kick in and perform the same functions seen with carbohydrate metabolism.


As we all know, fat is our big time energy storage facility. When broken down, fatty acids provide far more energy replenishment than either carbohydrate or proteins. Once again, B vitamins play a major role in our cells’ ability to get the energy out: Fatty acids are broken down into acetyl Co-A to be used in aerobic metabolism. The breakdown of fatty acids requires B2, B3, B5, B7, and lastly B12. Once we get to the electron transport chain, all the other B vitamins pitch in as well.

Stocking up

B vitamins are found in a wide range of foods, including animal protein sources, whole grains, and fruit and veggies (sounds like every diet recommendation in the world). A lot of foods today are also fortified with added vitamins – check the side of the cereal box and refer to the full list of B complex vitamins above. How many do you recognise?  Though there is some argument about whether these added vitamins are as beneficial as those that occur naturally, they can’t hurt.

To get the most “B” from your diet, bear in mind that B vitamins are easily destroyed by sunlight, heat, and exposure to oxygen. You can minimize exposure by keeping your fruit and veg wrapped up tight or in an airtight container, and out of the sun. B vitamins are also water soluble, which is a double whammy: they can leach out of foods when washed or cooked in water, and they can leach out of us, too. Excess B vitamins will be filtered out by the kidneys and excreted, so it’s important to keep replenishing them, either through diet or supplementation. Just one more example of how the right diet helps you achieve your training goals – no matter what they are.


1. Berardi, J and Andrews, R. 2010. The Essentials of Sport and Exercise Nutrition. Precision Nutrition, Inc.
2. Doug Kalman MS, RD, FACN. Vitamins: Too much of a good thing? Viewed 12 June, 2011. <;
3. Christa can Tellingen, MD. 2001. Biochemistry from a phenomenologial point of view. Viewed 12 June, 2010. <;

Precision Nutrition Week 2

Chapter 2 of the Precision Nutrition test is FULL of info – lots of science. In fact, I felt like I was back in my first year university biology classes (except that I got a lot less out of those!) Since this isn’t intended as a science lesson, I’m going with the two main points that jumped out at me. All this leads toward the big picture that I’m really starting to see: nutrition is so much more than what you eat and the energy it provides.

Food versus Nutrients

This chapter begins by pointing out a few things that a lot of fitness professionals probably overlook, like the fact that people eat actual food rather than just nutrients. Indeed, most food has a combination of macronutrients (your big three nutrients, carbohydrate, fat, and protein), even if it is a “carb” or a “protein”. That big juicy steak you had last night had some fat running through it (hopefully not too much), and your bread has protein. I read this and had a “duh” moment, but after thinking about it and thinking about the current nutrition consults I do with my clients, I realized that this is a good thing to point out – to everyone!

We (fitness pros) can get so wrapped up in Calories, macronutrients, and how much of each, that it can be easy to forget that not only will people not always count their Calories or grams of anything, but that they also might overlook the actual macronutrient content of any given food. Sometimes it’s hard enough to get people to even keep a food diary!

An additional point with this? Not all carbs/fats/proteins are created equal, even though they are all eventually broken down into their subunits during the digestive process and used by the body in the same way. But equal measures of brown rice and M&Ms do not result in equal amounts of glucose in the blood stream (glucose being the carbohydrate subunit). The fibre in the rice will mean that it’s digested and absorbed much more slowly – keeping you full for a longer time – and will also bind to fat contained in the same meal, removing it from the digestive process and thereby decreasing your actual fat intake. Plus brown rice has the added bonus of a high vitamin and mineral content, giving your body greater support for enzymatic and metabolic processes. M&Ms, on the other hand, have no fibre, so they are quickly digested, which in turn results in a spike in insulin coupled with a rush of glucose into the bloodstream. We usually aren’t running marathons when eating M&Ms, so there’s usually a pretty low energy demand at the time as well. High blood glucose + high insulin + low energy demand = lots of new fat storage!

Nutrient Absorption

Regardless of what foods you eat to supply yourself with nutrients, if you can’t absorb them through the digestive process, you’re not going to get any benefit from them. In order for these nutrients to be useful, they have to pass from our digestive tract into our body so the rest of our cells can use them. This process can take minutes, or hours – depending on several factors including the nutrient composition of the meal, and the health of your digestive system.

As is true with many other aspects of our health, our sedentary Western lifestyle and highly refined diet can wreak havoc with our digestive system. Lack of exercise and an imbalance in the diet (not enough fibre for example, or excess fat or cholesterol) can negatively affect the digestive tract itself, particularly the small intestine. This is where the majority of nutrient absorption takes place, and the inner surface is covered with microscopic “villi” and “microvilli” – tiny projections from the inner membrane that result in a surface area the size of a tennis court! Deterioration of the digestive system can result in any number of digestive problems, including ulcers, irritable bowel diseases, food intolerances and the little-recognized “leaky gut syndrome”, where the intestinal lining becomes too porous to properly screen nutrients, and large nutrient molecules and even viruses and bacteria can leak into the bloodstream.  If that isn’t good incentive to eat well and exercise, I don’t know what is!