Tuesday, December 21, 2010

Vitamin D

Just like there are trends in TV, fashion and music, there are trends in nutrition. If you have been around for a while then you would have seen a few – fat, fibre, calcium, vitamin C, antioxidants, organic, and the favourite of the last five years has been vitamin D. Getting insufficient vitamin D (primarily through too little sun exposure) has been linked to an increase in an ever-expanding list of medical problems such as heart disease, types 1 and 2 diabetes, multiple sclerosis, depression, colon cancer as well as the well-known problem of osteoporosis (brittle bones).

Institute of Medicine report

Three weeks ago the Institute of Medicine released a new report [http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D.aspx] on both calcium and vitamin D. The report re-affirmed that too little vitamin D, along with too little calcium, caused osteoporosis.

The report did increase the recommended daily amounts of vitamin D to Americans and Canadians (previously they were the same levels as Australia) and that increase met with support from academics. However, the report was less enthusiastic about the link with lower levels of vitamin D and common medical problems.

How much vitamin D?

Theoretically you can get all your vitamin D through sun exposure, but many are reluctant to do that for fear of skin cancer. Yet, you don’t need much sun exposure – about 5-8 minutes during the middle of the day (approx 10am – 3pm) in summer, and about 30 minutes in winter for light-skinned people living in temperate zones. In other words, not enough sun to burn, or even get red. Otherwise, you need to get from your diet:

19-50 year olds: 5 mcg (200 IU) in Australia/NZ; 15 mcg (600 IU) in US/Canada; it is assumed you will get adequate sunlight in the UK (insert own gag here).

51-70 year olds: 10 mcg (400 IU) in Australia/NZ; 15 mcg (600 IU) in US/Canada; 10 mcg (400 IU) in the UK

71+ year olds: 15 mcg (600 IU) in Australia/NZ; 20 mcg (800 IU) in US/Canada; 10 mcg (400 IU) in the UK

mcg = microgram;

IU = International Units;

1 mcg = 40 IU

Now, the problem here is that it is virtually impossible to get all your vitamin D needs through healthy eating. Our main sources of vitamin D are margarine (1 mcg in 2 teaspoons), oily fish (about 1-3 mcg per 100g), egg yolk (0.5 mcg per egg) and hard cheese (0.3 mcg in 30g). Some milks are fortified with vitamin D (eg Anlene). You can see you will need to scoff quite a bit of salmon, eggs and margarine to get your D needs. (In the US and Canada there are light-exposed mushrooms that provide 15 mcg/600 IU or more in a single serve. I am working with the mushroom industry in Australia to get high vitamin D mushrooms on the market in 2011).

Blood test

One of the most common blood tests requested is for vitamin D, because so many people appear to be low. How low is low? Mmmm. Tricky question. Last century we thought that a blood level of 25 nmol/L (10 ng/mL) was fine because that seemed to stop rickets and osteoporosis. Now experts like Professor Rebecca Mason from Sydney University say that 50 nmol/L (20 ng/mL) is a better goal for overall health. My pathology test form came back stating that a “healthy” level was 75-120 nmol/L (30-48 ng/mL). There is no universal agreement for the ideal blood levels of vitamin D.

What does it all mean?

Those who get very little sunlight, have dark skin, shield their body from sunlight, are in long term care, or are elderly are likely to have low levels of vitamin D. As diet very probably won’t make up the difference in vitamin D, then daily vitamin D supplements of 25-50 mcg (1000-2000 IU) will need to be taken. Get your blood level tested. If it is clearly at the lower level, get some judicious sunlight, eat wisely, and depending upon where you live, track down some vitamin D mushrooms.

Sunday, December 5, 2010

Cramps (mainly in sport)

We have all experienced that excruciating knot of painful involuntary muscle spasm that can stop us dead in your tracks. About two out of three fit and active people have experienced the cramp. It commonly occurs in the calf, thigh or foot. It can happen in both cool and warm environments.

What triggers a cramp?

Nobody knows for sure. Surprisingly, this topic is poorly covered in most sports medicine books and is not well researched. It has long been suspected that the most common causes in athletes are dehydration, heavy salt losses or, more recently, just plain muscle fatigue leading to a loss of muscle control.

Heavy sweating can cause significant sodium (salt) losses from the body, and this may trigger a cramp if the sodium isn’t replaced during the activity. To combat the threat of cramp, athletes add some extra salt to their meals and take a sports drink throughout training and competition. One study of a tennis player who regularly got cramps revealed that he lost more sodium through sweat than he ate in his diet. By taking a sports drink and increasing the sodium in his diet, he was able to reduce the cramps to rare occurrences.

More recently, studies have shown there are no differences in blood sodium levels or levels of hydration in crampers compared to non-crampers leading to the view that cramping is due to a tired muscle losing coordination of its contractions. If low levels of salt in the body are the cause of cramp it does not explain why only certain muscles get cramp or why rest or stretching the afflicted muscle often “cures” the cramp. The best explanation to date is that muscle cramp is due to a tiring muscle losing its ability to control its contractions and going into involuntary spasms.

The best advice we have

The truth is that we don’t fully understand muscle cramp, nor know the best advice to help avoid the cramp. You may have your own solutions that work for your body. Until we know more, the sensible advice is:

1. Drink plenty of fluids during activity to avoid dehydration. A dehydrated body seems to be more prone to cramping.

2. If you lose a lot of sweat during exercise, especially over an hour or more, try a sports drink to help replace the lost sodium.

3. Be fit. Cramps are less common in fit people.

4. Eat well. Cut the saturated fats that clogs arteries. Cramps can occur in muscles that have a reduced blood supply due toas a result of narrowed arteries.

5. Stretch before and after exercise. If you suffer night cramps, stretch before going to bed.

6. Be untrendy and wear loose, comfortable clothes. Tight -fitting clothes can reduce blood flow to muscles, making them more susceptible to cramps.

7. Acclimatise to the environment in which you perform, especially when moving from cool to warm climates.

Stretch the point

If you do get a cramp, stretching the cramped muscle is the best way to reduce the pain. If it happens in the calf, grab the toes and ball of your foot and pull them towards the kneecap, or get someone to do it for you as shown in the pic. This helps the muscle to relax. Applying ice can also stop the spasm and reduce the pain.

What does it all mean?

If you have access to millions then please start the International Research Unit for Cramp and Stitch. We need it because we know stuff-all about the nuisance pain we all experience. Because humans evolved in a warm environment, it is often said that salt depletion is unlikely to be the cause of cramp in most people, but there have been reported cases of “whole body” cramps in athletes where salt depletion is a more likely cause. Otherwise, it seems that looking after yourself may be your best bet against cramp. If you would like a bit more on the topic, here is a lengthy discussion [http://www.medicinenet.com/muscle_cramps/article.htm].

References: British Journal of Sports Medicine 2009; 43: 401-408

Night cramps

Mollie wrote: “I’m hanging out for cramps info. I am getting terrible ones, especially at night and on waking, especially with sudden movements of legs, and even hands and fingers. Can it be just because I’m getting old? Wearing different, not so comfortable shoes for a day of training seems to exacerbate them.”

Well Mollie, cramps do tend to occur more frequently with age. Lot’s of people do suffer night cramps, so you would think that there would be a whole lot more on the topic.

The Mayo Clinic can describe night cramps [http://www.mayoclinic.com/health/night-leg-cramps/MY00410] but offer no solution, and a British site [http://www.patient.co.uk/health/Cramps-in-the-Leg.htm] gives some tips to reduce night cramps. Oh yes, and stick to comfy shoes.