Friday, 7 October 2011

Post Workout Dairy: Yoghurt or Milk?

Recently my Paleo diet has been loosened to include dairy. This is partly due to reaching a good weight, and partly due to needing to get more calories in on workout days. I've always tried to eat all of my calories, but it's quite hard to get them all in when you are eating clean. I find it easier to not eat much food on rest days, as opposed to eating over maintenance calories on training days. A litre of milk or yoghurt is worth 800 and 1000 calories respectively, after drinking that you're well on your way to the training day's total. It's also a great mix of protein fat and carbs in a post workout drink. It's in liquid form too, so it quickly get's to the places where recovery is needed, and to where muscle synthesis takes place.

From looking at the charts it looks like milk is much better. It has a good balance of protein fat and carbs.
However post workout we need an insulin spike and lots of protein. Yoghurt contains more protein, and more carbs, I.e. more of what we want.

The sugar in milk is lactose, which is a disaccharide derived from the condensation of galactose and glucose. This requires the intestinal villi to secrete the enzyme called lactase in order to break down the lactose into the simple sugars glucose and galactose, which can in turn be absorbed. In most mammals the production of lactase gradually decreases with maturity due to a lack of constant consumption. So the older you get, the harder it is for your body to deal with milk.

Yoghurt is fermented milk. Bacteria uses the lactose in milk to produce lactic acid, which acts on milk protein to give yoghurt its texture and different taste. Most of the lactose in milk is converted to lactic acid by the bacterial culture, this process also creates lactase, meaning that the body has less lactase to make itself during the absorption process.

Glycemic Index in Milk & Yogurt

The G.I. food list below shows the Glycemic Index score for many different milks and Yoghurts. The G.I score for each food will dictate the speed at which the sugar will be absorbed. A low Glycemic index means the sugar will be absorbed slowly. The higher the G.I score the quicker the sugar is absorbed into the blood. Usually it is desirable to go for low G.I. index foods to avoid energy crashes, sugar craving and falling asleep at the desk after lunch. However, to take advantage of the 30-45min post workout window, eat high glycemic index foods to spike insulin and shuttle as many nutrients to the muscle sells as possible. After the immediate requirement for nutrients is satisfied, protein synthesis eases off, and starts to ramp up again 3-4 hours and tapers off over a 24 hour period.

The G.I. list also shows the carb content for each item as this is related somewhat to Glycemic load for the G.I. diet. However it does not necessarily mean that a food with a high carbohydrate content will automatically mean a high G.I. score.

All foods on the G.I table is based on 100g of product. The portion size doesn't change the Glycemic Index value, but it does count towards the quantity of sugar (carbs) for the item; the bigger the portion the more sugar you would be consuming.

This standard portion size simply enables you to make a sugar comparison with other products in the same group, and the different foods listed on other G.I. tables. This means you can see which foods are high or low in carbohydrate content.

Yoghurt contains 20% more protein than milk
Yoghurt is easier to digest than milk
Yoghurt & milk both spike insulin fast, but milk is good because it does the job with less carbs.
(The G.I. index of natural yoghurt is about the same as milk)
Yoghurt contains gut healing bacteria
Yoghurt is good for internal fungal infections
I'm going to go for yoghurt over milk from now on because of the protein and digestion factors.

Further Study
Milk is harder for the body to process so how can it have the same glycemic index as yoghurt?