Monday, July 27, 2009

Lactose Intolerance

Is lactose intolerance natural?

First, what is lactose intolerance? Our major source of lactose is milk (cow, goat, sheep and human) or yogurt. It is not found in hard cheese or butter. At birth, we have a digestive enzyme called lactase to break down lactose in breast milk to its constituent sugars, glucose and galactose, which are then absorbed into the blood.

By the age of 5 years, in many people on the planet their lactase enzyme is no longer produced and they can’t digest lactose. In this case large amounts of lactose can cause intestinal cramping because gut bacteria convert the lactose to gas and lactic acid. Not comfortable. They are now lactose intolerant. (Note here: lactose intolerance is not an allergy).

The human genome reveals more
Geneticists have been able to check DNA from around the world and married their findings to history, enabling to explain why many of us can drink milk later in life without problems. Around 10,000 years ago humans kept cattle as a beast of burden and a source of meat. The ability to handle lactose doesn’t seem to be in anyone around this time. A DNA mutation soon after allowed some people to be able to drink milk well past their 5th birthday and into adulthood.

Clearly, being able to drink cow milk was a benefit during times of food shortage. The mutation then became more dominant in parts of Europe through to northern India. It is thought the mutation occurred independently in parts of Arabia when the camel became domesticated and camels’ milk entered the diet.

Rapid spread of mutation
Studies of DNA from skeletal remains in central Europe show that about 80% of people in that area had the mutation for tolerating lactose about 7000 years ago. That is a rapid spread of a mutation, strongly suggesting that it offered a survival advantage, according to a new book The 10,000 Year Explosion – How Civilization Accelerated Human Evolution by Professors of Anthropology Cochran and Harpending.

In fact, being able to tolerate lactose in the diet, allowed the expansion of the Indo-Europeans, tracked by both the spread of lactose tolerance and the Indo-European languages (eg Spanish, English, Hindi, Portuguese, Russian, German, French). Put another way, if your native language was Indo-European in origin, then there was a good chance you could handle lactose over the last 7000 years or so.

Dairy produce better than meat for survival
Dairy farming generates about five times as many Calories (kJs) per area of farming when compared to raising cattle for slaughter. You can quickly see the advantage here. More Calories per hectare means a greater number of people fed, meaning more warriors to defend the land or occupy other lands. Dairy farmers were more mobile and less reliant on seasonal cereal crops, so this helpful mutation meant that both a common language and a survival advantage travelled widely.

It also explains why eastern and southern Asia, Japan, parts of Africa and the indigenous folk of Australia have both a very different language background and the inability to handle lactose after being weaned.

What does it all mean?
Some of us are designed to drink milk and others aren’t. The answer lies in evolution and genetic changes and not in ideology. Milk is a great source of calcium and riboflavin. Calcium can also be found in hard cheese, which has no lactose, and calcium fortified soy drinks. If you enjoy cow milk, I suggest that a reduced-fat milk is your better choice as most of them (in Australia) have more calcium than in regular milk. Well, I’m a dietitian, I had to say that!

Reference: The 10,00 Year Explosion by Gregory Cochran & Henry Harpending, Basic Books, New York 2009

Monday, July 13, 2009

Caffeine & Your Brain

Mark Webber has just won the German Grand Prix in a Red Bull sponsored car. Red Bull was one of the first “energy” drinks on the market, laden with caffeine at 80mg of caffeine per 250mL can, about the amount found in a strong cup of coffee. Other caffeine sources are tea and anything with guarana. There is a small amount of caffeine in cocoa and chocolate too.

That morning kick
Caffeinated drinks are the most popular way to start the day in the Western world. Around 2002 there was the first appearance of a study linking caffeine to Alzheimer’s Disease. The surprise was the link was that **too little** caffeine increased the risk of dementia. In the following years there has been much more research showing that caffeine lowered the chance of losing your marbles.

Caffeine & dementia
In Alzheimer’s there is a build-up of beta amyloid proteins in the brain that disrupt memory. In mice, caffeine halts the formation of this nasty protein. Caffeine is also anti-inflammatory, helping to protect the brain further as Alzheimer’s is an inflammatory disease of the brain. That may help explain the results of two recent studies.

A European study tracked 676 men, aged 70-90 years, for over 10 years while assessing their cognitive decline. The lowest decline in brain function was observed in the men drinking 3 cups of coffee a day. Those with the greatest decline were the non-coffee drinkers and those drinking more than 4 cups a day. In fact, if you didn’t drink coffee then your brain went downhill four times quicker than if you had three cups a day. I bet nobody would have predicted that last century.

That’s good news for blokes, but can it apply to women too? A more recent European study of 875 women and 534 men, aged 65-79 years, also found a strong correlation between coffee consumption and dementia in both the men and women. Moderate coffee drinkers reduced their risk of dementia by two-thirds compared to non-drinkers after 21 years of follow-up. What is moderate coffee drinking? Between 3-5 cups a day.

The dose makes the poison
The single most difficult concept to get across to the media and the public is the concept of hormosis, that is, health is not a linear model, it is usually a J or U-shaped curve. We have spoken about this before with alcohol – there is a healthy level of drinking (1-2 standard drinks a day max) either side of which there is less benefit, or a negative effect with heavy drinking (4+ standard drinks a day). The J-shaped curve seems to apply to caffeine too. The least risk of dementia is for 3-5 cups a day, either side of which there appears to be little benefit.

What does it all mean?
The researchers aren’t sure if it is the caffeine alone that works or if other compounds in coffee help, as coffee has anti-oxidant phenolics and any combination of these could be offering protection to the brain. Coffee drinkers have a reduced risk of Parkinson’s Disease and type 2 diabetes as well, but no-one is too sure why. Apart from being anti-inflammatory, caffeine has magnesium that makes insulin more sensitive, reducing diabetes and in turn reducing the risk of dementia. Who knows, but the future may have coffee, or even Red Bull, recommended as a health drink!

While it all looks promising for enjoying a modest amount of coffee, I can’t get too enthused because I don’t drink coffee and the dementia story doesn’t apply for us tea drinkers.

References: European Journal of Clinical Nutrition 2007; 61: 226-232 / Journal of Alzheimer’s Disease 2009; 16: 85-91

How much caffeine do you consume?

It is very difficult to know the exact amount of caffeine that anyone consumes. You can buy tea bags that come in regular, strong and extra strong, all with differing caffeine levels. Then you might be a jiggler or dangler, all influencing your caffeine intake. Be aware that green tea has the same amount of caffeine as regular tea. A strong cup of coffee will provide about 80mg caffeine, about the same as an “energy” drink. A five minute brew of tea is around 30-50mg caffeine. Two teaspoons of Milo or drinking chocolate has about 2mg caffeine. A can of regular or diet cola will have about 50mg caffeine. Dark chocolate will have around 60mg of caffeine in a 100g block.

If caffeine alone is proven to slow cognitive decline, then the above research hints that somewhere in the region of 150-300mg caffeine is a healthy “dose”.