Medical doctors are often accused of paying little attention to dietary interventions for many diseases. On the other hand, dietary fads and commercial supplements are frequently based on little, if any, reliable clinical evidence.
It should make all parties to this conversation pleased that an article is in press in the prestigious journal Pain which reviews the scientifically supported ways you can alter your diet to improve specific pain problems.
The findings are preliminary in many cases but are scientifically robust and point the way forward to some interesting possibilities for interventions.
Omega 6/Omega 3 ratio A number of factors have led to a dramatic change in the ratio of these 2 crucial fatty acids in the average diet of affluent countries. Omega 6 fatty acids are highly important in immune function, but can contribute to inflammation. Omega 3 fatty acids by contrast have a well-established anti-inflammatory effect. An ideal ratio of these 2 in the diet is thought to be as close to 1:1 as possible. The average citizen of a developed country like Australia has a typical ratio of 10:1 or worse. This is why people who suffer from inflammatory joint pain (which includes rheumatoid arthritis and lupus arthritis) tend to benefit from boosting their Omega 3 intake. Note that joint and muscle pain which is not caused directly by inflammation does not respond to this intervention. This includes the common form of arthritis due to ‘wear and tear’ (osteoarthritis) which often has very little inflammation.
Magnesium and polyamine depletion Long-term chronic pain results from a number of irreversible changes which occur within the spinal cord and brain. One of the single most important of these microscopic events is the activation of NMDA receptors which normally are in a closed state. Activation of large numbers of NMDA receptors in the spinal cord has the effect of amplifying dramatically any incoming pain information, or transforming non-painful stimulation into a pain signal.
Drugs which selectively block NMDA receptors are very powerful and effective analgesic drugs. Their use is limited to specialised pain clinics due to their potential for significant side effects if not very carefully used, and their highly variable outcomes.
A class of molecules known as polyamines (some of which rejoice in unfortunate names such as spermine, cadaverine and putrescin) is known to have an enhancing effect on open NMDA receptors, making it harder to turn down the gain On pain signals. There is convincing evidence in rats that diets high in polyamines increase chronic pain sensitivity, and conversely that removing them from the diet results in reduced pain. Some of the most polyamine-rich foods include wheat germ, rice, mango, pumpkin, beef, pork and chicken. Soybeans, mushrooms, and green tea leaves also have high levels. There are only a couple of studies which look at how practical and tolerable these diets are for humans, but given how difficult NMDA blocking drugs are to use in practice, this deserves vigorous investigation.
The transformation of a closed NMDA receptor to an active one depends on the removal of a magnesium ion which blocks the channel in the nerve cell membrane within the receptor protein. High doses of magnesium given intravenously are effective for short-term treatment of some types of chronic pain. The authors of this article speculate that ensuring adequate levels of magnesium in the diet may be important for ensuring that as many NMDA receptors as possible remain closed. Personally I would have no problem with this recommendation, as 3 foods which are very high in magnesium include chocolate, bananas and avocado. The science however is fairly thin.
Flavonoids Given that there are over 5000 compounds in this group in plants, it is hardly surprising that some of them may have pain relieving properties. Perhaps the most robust evidence at this stage favours soy and possibly cherries as leading contenders to have useful effects in the real world. While there is not enough evidence to make firm recommendations, diabetics with painful peripheral nerve damage and people contemplating surgery with a risk of nerve damage might benefit from getting stuck into soy products if they find them palatable enough to stick with long-term.
Caffeine The news is not completely good for the coffee and chocolate brigade however. Caffeine consumption is rising worldwide, and apart from the very well-recognised caffeine withdrawal syndrome, there is also evidence that several first-line pain drugs including amitriptyline, carbamazepine and even paracetamol may be much less effective in the presence of even low doses of caffeine. Caffeine junkies should stay below an intake that causes withdrawal headaches and remember that they may not be able to depend on paracetamol as much as they can when they aren’t heavily juiced on java.
So there you go, foodies. Apart from the obvious advice to eat a varied diet and get plenty of exercise, there are possibly a few promising, low-cost and easy to understand dietary interventions to help with chronic pain. The next few years should lead to some further proof-of-concept studies and then hopefully to firmer recommendations.
Reference: Bell RF et al. Food, pain, and drugs: Does it matter what pain patients eat? PAIN (2012), http://dx.doi.org/10.1016/ j.pain.2012.05.018
(Note this is unfortunately behind a paywall)