Saturday, March 31, 2012

Water, sports drinks & energy drinks

Derek Bannister threw me a question a while back.

“I am working outside in the hot weather lately and wonder what you recommend to help to rehydrate. I am drinking heaps of water however I feel like I need something more to assist. What are your thoughts on sports drinks? Do you have a recipe for something that can be made at home.”

When it is hot, water is a great drink, but it may need a helping hand sometimes. Recently, I was up in the north-west of Australia working with Rio Tinto employees on remote iron ore mines. They have to endure some high temperatures for six months of the year. Water is great. An electrolyte drink may be better when it heats up. Energy drink? Mmmm, no.
Energy drink ≠ Sports drink
Let’s clear up one thing first. An energy drink is not a sports drink. An energy drink (like the ones advertised on Formula 1 motor racing cars) is a soft drink with added caffeine. That’s it. Nothing more.

I’m not really that concerned with a bit of caffeine. Indeed, I love it early in the morning. It reminds my brain that there is work to be done. Each can of energy drink has 80 mg caffeine. One can; not a problem. When kids drink 6 cans a day; problem. Excess can cause anxiety and disrupted sleep in children.

Caffeine acts as a central nervous system stimulant, like, it wakes you up, makes you more alert. Caffeine can also increase endurance in athletes. That’s why some footballers, for example, take 1-2 NoDoz tablets (100-200mg caffeine) before a game.

Energy? Another word for Calories
Look at the Nutrition Information Panel on a food and it has the word “Energy”. Next to it are the kilojoules or calories. Energy = kJs/Cals. The word “Energy” doesn’t mean it gives you zip or vitality. That will come from the quality of your kJs/Cals, not from a magic drink.

Sports drinks
Swallow an energy drink, or a soft drink/soda, and it goes into your stomach. There it stops. Then small amounts get slowly released into the next section after your stomach, called the small intestine. Here it gets “analysed”. These drinks are about 12% sugar, too concentrated for the intestine to handle. So, it needs to dilute the drink with water. Where does it get the water from? Your blood. Some water from your blood passes into the small intestine, dilutes the soft drink, then the drink, and the extra water can be absorbed into the blood. Weird as it sounds, you need to slightly further dehydrate before you hydrate with a soft drink (I’m not talking about diet drinks here).

A sports drink is only 6% sugar, about half that of a soft drink or energy drink. At this concentration it will pass from the stomach into the small intestine and then into the blood quite quickly. Sports drinks (and other electrolyte drinks) also have sodium (salt). This is handy if you sweat a lot. Some people lose a lot of salt through sweat and that may trigger cramping. A sports drink may solve the problem.

You can make a sports drink at home, although they usually don't taste that good because it is basically salty, dilute cordial. This is a good article discussing making a sports drink from scratch or from fruit juice. As I say, don’t expect to immediately think “Yum”.

What does it all mean?
Water is the perfect drink for humans, except when that human being starts doing something his forebears are unlikely have done, like running 42 kms non-stop, bricklaying in 36C heat, or (and many people swear this actually happens) swim for 3 km, cycle for 180 km and then look at their watch and say: “Boy, do I feel good. I’ve got time to jog for 42 km to finish off the day.”

When the insanity gene takes hold then you are going to benefit from a sports drink. Water is for humans; sports drinks for the self-punishers (is this where I put in a smiley emoticon?). Or when your job involves working in the heat, often with all the safety clothing too. Thanks again for your question Derek.

Thursday, March 22, 2012

Nutrient Retention

Reader, food writer and nutrition student Louise Fulton Keats was kind enough to alert me to a document from the US Department of Agriculture regarding nutrient losses from food during cooking.

It is well-known that some vitamins are fragile and begin to diminish over time, when subjected to light, and when exposed to heat as we do with cooking. Folate is fragile, as is vitamin C, but some vitamins are more sturdy, such as biotin and vitamin D which can handle a stir fry.

The United States Department of Agriculture document on the nutrient retention of fresh and cooked foods is enlightening. If you read the figures be aware that they are only an average and will depend upon whether you cooked your vegies so they retained their crispness or until they cried for mercy. The fact that the figures are given to the nearest 5% shows they are just a guide. Some of the figures are quite old too and our ability to analyse nutrients has improved (although far from perfect).

Vitamin C, thiamin and folate are the most fragile of the vitamins. We can get adequate vitamin C from a salad and a couple of fresh fruit a day as we really only need 45 mg daily (half a capsicum has about 50 mg of C). Getting our daily needs of folate is trickier as the amount needed daily, about 400 mcg, means lots of green leafies, avocadoes, bananas, Vegemite and bread (because bread-making flour is fortified with folic acid). More is required during pregnancy, so women considering a family take a folic acid supplement.

May I add that freezing vegetables is a great way to retain their nutrition. Vegetables at room temperature lose about half their vitamin C in three days. As frozen vegetables are blanched before freezing they too will lose 20% of their vitamin C, with the remaining 80% not budging even after three months of freezing.

Minerals are generally unfazed by heat. Iron stays the same whether in an ice floe or in volcanic lava. The calcium, iron, magnesium and zinc content of food will remain steady independent of the quality or cooking time of the food. Nuts will provide almost the same amount of minerals whether fresh or roasted.

It is often said that the mineral content of fresh produce is on the decline. This was refuted in a report for Food Standards Australia New Zealand, although one study doesn’t necessarily prove a point. As the report says, much depends upon the season, variety, geography and level of ripeness of fresh produce so it becomes difficult to compare a vegetable now with one of yesteryear. Despite that, the report states that any minor differences “would be very unlikely to be of dietary significance.”

Bioactive compounds
There is more to food nutrition than just the essential vitamins and minerals. There are bioactive compounds, including the broad class of antioxidants, that work in our favour. The antioxidant level in stored fruit and vegetables remains fairly constant until the produce begins to spoil, after which you will plonk it in the compost bin (you do have a compost bin, don’t you?).

Many of you have already heard that the lycopene in tomatoes is more bioavailable from cooked tomatoes and that beta-carotene is more bioavailable from cooked carrots. The heat breaks down plant cell walls so they can release more of their nutrition. Cooking makes digestion more efficient for many foods, including meats and legumes. Cooking also makes food tastier, kills nasty bacteria and is an important part of defining most cultures.

What was interesting to Louise and myself were the figures on alcohol. I, and others, often parrot the view that cooking will evaporate any alcohol that you have added to the dish, such as wine or brandy. Baking a food with alcohol for 30 minutes evaporates only 60% of the alcohol. It takes over 2 hours of cooking before nearly all the alcohol has left the dish. By then, may of those fragile vitamins have probably followed suit.

What does it all mean?
Most readers are lucky in that they can buy a range of fresh, good quality food and they can cook it quickly, so the small amount of nutrient losses doesn’t adversely affect their health. It is clear that we benefit from both raw food (salad, nuts, fruit) and cooked food.

It is also clear that the person with the greatest control over the nutrient content of food is you, the consumer. Buy as fresh as possible, store to minimise nutrient loss and then eat soon after purchase as is practical. And don’t cook it to within an inch of its life.

Kevers, C., et al 2007. Journal of Agricultural & Food Chemistry 55: 8596-8603