I've learned a lot over the past couple years, including what I previously held as true and now have learned is very incomplete. So let's start with the big picture, and get down to a more specific answer to your question.
At the very core of understanding how the body makes use of nutrients is identifying what the nutrients are:
- Macronutrients: protein, carbohydrates, and fats
- Micronutrients: vitamins and minerals
Then we have to understand what our body can manufacture, vs. what it needs you to eat.
- Essential nutrients: those your body must consume from outside sources, and cannot manufacture at all.
- Conditionally essential nutrients: those that your body manufactures, but might not be able to keep up with demand when you exercise.
- Unessential nutrients: those that your body can manufacture from other resources, and does so without falling behind
There are 9 essential amino acids and 8 conditionally essential amino acids. As well as 21 total amino acids that your body uses on a day to day basis. You really only need to concern yourself with the breakdown if you are barely eating enough protein for survival. The USRDA only lists the minimum amount of protein for survival, which is not sufficient for people who exercise (due to the 8 conditionally essential amino acids).
There are also essential fatty acids which include your omega-3s and omega-6s. A Western diet is very heavy on omega-6s, and light on omega-3s. Additionally, it is also excessively high in fat.
There are no essential carbohydrates (carbs for short) for survival; however, they become very important for active people.
I'll avoid recommended amounts for each of these due to the fact it's not really part of the question.
Good Carb / Bad Carb
I've learned that this is really a false dichotomy. Your body does not see carbohydrates very differently whether it's from high fructose corn syrup, grains, or plants (fruits and vegetables). The difference that matters is in the amount of micronutrients, satiety, and quantity.
Typically, most people understand "bad carbs" as coming from highly processed sources such as white flour, sugar, etc. Processing does the following things:
- Removes many micronutrients through processing
- Removes fiber
- Lowers the satiety you would normally get
However, if you gain the bulk of your carbs from fruits, vegetables, legumes, and whole grains (like brown rice) you get more of everything. More micronutrients, more fiber, more satiety--i.e. keeps you full longer. NOTE: I'm avoiding the topic that some articles have discussed saying that whole grains have what are essentially anti-nutrients and remove micronutrients that your body needs. That would muddy the waters, and I personally believe that if you take multivitamins it will exceed the damage that those anti-nutrients can do.
So are refined grains good or bad?
Neither. They are amoral. If you're dietary requirements include 320g of carbohydrates a day (an example from my current diet), it really doesn't matter that 100g came from refined grains. It really only matters that you don't exceed the total goal for the day.
The following are true:
- Refined carbs can leave you hungrier than when you consumed them in the short term.
- Carbs from whole foods contain more fiber, which in turn keeps you full longer.
- Our bodies sometimes crave sweets, and as long as all your dietary goals have been met, you can indulge a little.
- It matters more that you stick to a diet plan than it does the specific details of those diet plans. (Assuming the diet plan was made by someone who knows what they are doing).
There is a lot of scaremongering by people who appear to know what they are talking about. I find that it is more useful to understand the what is meant by labeling carbs "good" or "bad" and what the end result is. The truth is that if I consume most of my carbohydrates using "good" sources (fruits, veggies, etc.) I will stay full longer and be less tempted to snack. However, if I consume nothing but "good" sources, I still get cravings for things that are typically considered "bad". At the end of the day it really matters that you find the right balance that helps you stay true to your diet.