Coffee and Caffeine – Part 2
In the second part of this vodcast on caffeine, Dr. Astrid Nehlig and Dr. Patricia Macnair reflect on the less desirable, and often well publicised, effects associated with coffee consumption, such as sleep disruption and dependence. As well as discussing the potential benefits of caffeine on mental alertness and physical performance.
Coffee and Caffeine – Part 3
In the final part of this vodcast, some of the main preconceptions held towards caffeine are addressed including its diuretic effect and recommended intake levels for groups of society, notably pregnant women. Caffeine expert Dr Astrid Nehlig concludes the vodcast by sharing some of the latest research findings into caffeine’s relationship with cardiovascular health and osteoporosis.
Vodcast transcript
Part 1
(Dr Patrica Macnair) I am joined today by Dr. Astrid Nehlig, Research Director from the French National Medical Research Institute.
Dr Nehlig’s main research interests are in brain development and metabolism, and the effects of coffee and caffeine on human health.
We’re going to be looking at the stimulatory effect of caffeine and exploring some of the research on caffeine in the diet.
Astrid welcome, and thanks for joining us today.
(Dr Astrid Nehlig) Thank you very much, it’s my pleasure.
(Patricia) Perhaps you could start by giving us an idea about the origins of caffeine and some of the key sources in our diet.
(Astrid) Caffeine is found in many plants, in about 60 of them it is most well known in coffee beans cocoa, mate, tea leaves and guarana. As such it occurs naturally in coffee, tea and chocolate.
Caffeine is artificially added to some foods to soft drinks and also to some medicines.
(Patricia) Could you give me an idea of how much caffeine there would be say in a cup of coffee?
(Astrid) In a regular cup of coffee you should find about 60 to 135 mg of coffee but it all depends of the strength of the beverage, size of the cup and type of coffee bean
(Patricia) Caffeine is known to have stimulatory effects; perhaps you can explain these effects?
(Astrid) Caffeine is known as a mild central nervous system stimulant this has been known for years and years.
Recently the European Food Safety Authority established that 75mg of caffeine, which corresponds to the content a regular cup of coffee, increases selective attention which means focusing on specific stimulus and also prolonged or sustained attention if you will, which is maintaining your attention on the specific target.
(Patricia) Now I’m sure quite a few people have more than one cup of coffee a day, what sort of effect will this have
(Astrid) Many people when they hear that 75mg of caffeine increases attention would be tempted to have a bit more just to have even more attention, but it does not work that way, if you increase the dose it does not have this effect.
(Patricia) Research has looked at the effects of caffeine in the elderly population, could the stimulatory effects offer any benefits here?
(Astrid) It has been shown in Epidemiological studies that caffeine is able to slow down our cognitive decline which happens to all of us when we age and this effect is mostly marked in women – good for us – and especially in women over 80.
Some other studies have also looked at Alzheimer’s disease and found that lifelong consumption decreases the risk and delays the moment at which Alzheimer’s disease starts but in that case we still need a lot more studies
(Patricia) I understand caffeine has also been studied in Parkinson’s disease?
(Astrid) Yes you’re perfectly right, in fact in Parkinson’s disease caffeine has been shown to dose dependently reduce the risk and delay the onset of Parkinson’s disease.
(Patricia) How central is caffeine in the neuroprotective effects you have just described?
(Astrid) In Alzheimer’s disease and mainly in Parkinson’s disease caffeine appears to be the real player, however when caffeine is absorbed in coffee other components influence other pathways such as neural inflammation or blood brain barrier integrity that are also involved in the development of these diseases.
(Patricia) Thank you Astrid that’s very interesting. Well we’re going to take a break now so join us again later for the second part of this vodcast.
Part 2
(Patricia) Welcome back to the second part of this vodcast on caffeine, I’m joined by Dr Astrid Nehlig.
We’ve talked about the benefits of caffeine’s stimulatory effects in terms of mental performance, what about in terms of physical effects?
(Astrid) In exercise the effects of caffeine are not so clear cut – in short-term, high intensity exercise caffeine has inconclusive effects, with long-term endurance exercise the EFSA has established a causal relationship between caffeine intake and endurance capacity and performance and the rate of perceived performance
(Patricia) It’s often suggested that the stimulatory effects of caffeine may have some less desirable effects on some people, for example disrupting their sleep patterns; can you give me an idea about the effects of caffeine on sleep?
(Astrid) This is a difficult question, we all know people who can drink coffee at night and go to sleep and others that have to stop at lunch time otherwise they won’t sleep, and this variable response to caffeine is linked to a genetic viability we all have which is a genetic variation in the way we metabolise caffeine and the way our brain reacts to caffeine. In brief, some people who are particularly sensitive to caffeine may take longer to fall asleep, their duration of total sleep and deep sleep will be reduced and they will experience more frequent awakenings. These effects are usually less marked in regular consumers and caffeine abstinence can also improve these symptoms.
(Patricia) We’ve talked about the downsides, what about the benefits of caffeine?
(Astrid) There are some true benefits of increasing alertness in some situations for example night shifts in which it has been shown that the vigilance of workers has been increased and there are less accidents, it’s also beneficial in driving at night or also with people suffering with jet lag.
(Patricia) Given these stimulatory effects of caffeine, is there any research on caffeine and addiction or dependence?
(Astrid) It is true that recently the American Psychiatry Society has included caffeine withdrawal into the symptoms that they recognise. It is known that some people may experience symptoms after the abrupt cessation of caffeine; this occurs 12-24 hours after cessation of caffeine and translates into headaches, drowsiness, and feeling of fatigue but won’t last more than 48 hours and this can avoided by the progressive decrease of intake.
Then the second item that needs to be considered is tolerance. And tolerance means that to get the same effect you need to increase the amount you get, and this is clearly not the case for caffeine if you take the example of caffeine in your coffee, you don’t every week or every month increase your intake of coffee by a cup.
And finally there is dependence per se, because in the brain we have a specific circuit for addiction and reward that is activated by substance that leads to dependence and caffeine is not activating this circuit, so caffeine does not correspond to what we call a drug of dependence.
(Patricia) Thank you Astrid
Part 3
(Patricia) Welcome back to this vodcast on caffeine, I’m joined by Dr Astrid Nehlig.
One common preconception is that caffeine increases blood pressure – is there any evidence to support this?
(Astrid) Low doses of caffeine would induce a low increase of blood pressure like having a conversation or climbing the stairs. Higher doses would increase blood pressure a bit more but in both cases its short term and not long lasting.
It has also been shown that people drinking coffee containing caffeine are not at risk of developing hypertension
(Patricia) What about other cardiovascular risk factors?
There is also evidence that caffeine doesn’t affect other cardiovascular risk factors like cholesterol levels for example and increased homocysteine levels.
(Patricia) One of the commonest beliefs around drinking caffeinated coffee is that it can lead to dehydration; can you shed some light on this?
(Astrid) Caffeine is a mild diuretic agent which increases the frequency of urination but does not increase the amount of fluid passed people get easily adapted to this situation, therefore it mostly affects non-consumers.
However the benefit that can come from the fluid intake from caffeinated beverages outweighs the potential mild diuretic effect of caffeine.
(Patricia) So we don’t need to stop drinking coffee?
(Astrid) No in fact previous advice to stop or moderate caffeinated drinks intake in order to maintain fluid balance is unfounded.
(Patricia) It has been suggested that women should lower their intake in order to reduce the risk of osteoporosis; can you shed some light on that?
(Astrid) Osteoporosis is a multifactorial condition, and it is linked to a poor diet, calcium intake, sedentary life and genetic factors.
The reason why caffeine has a bad reputation is due to old animal studies that use very high unrealistic levels of caffeine and these levels prevented ossification in rats, since then it is believed that caffeine is bad for osteoporosis.
(Patricia) What do we know in humans now?
(Astrid) In 2013 two nice reviews appeared but unfortunately they don’t totally agree. One led to inconclusive data and the other one showed a slight mineral bone loss but no further risk of fracture, so we are still on the edge of needing more research in this area
(Patricia) But are there some groups of individuals who should be careful about their caffeine intake?
(Astrid) Yes some people should be. We have seen it earlier with sleep we have all different types of genes in our brains which makes us more sensitive to caffeine effects, for example on anxiety so these people should limit their caffeine intake. If they are unsure or have further symptoms they should consult their physician.
(Patricia) Of course there is some specific advice for pregnancy?
(Astrid) Yes there are specific recommendations based on the fact that pregnant women metabolise caffeine more slowly than other women, so the advice for them is not to drink more than 200-300mg of caffeine per day from all sources combined.
(Patricia) So finally are there any recommendations around intake for general population?
(Astrid) In Europe there are no official guidelines for caffeine intake in the general population. Health Canada is the first group that set up levels and advice for the general population not to go over 400mg per day, which is roughly 4-5 cups of coffee.
(Patricia) I would have thought it is quite feasible that quite a lot of people might go over that sort of level, what can they expect?
(Astrid) For a certain category of people they won’t have any trouble because we are all different because of our genetic viability. You might sometimes experience over consumption and this will have effects on you sleep and you get nervous, you get anxious, this is like eating too much, but if you go back to your normal intake then everything is normalised quite fast.
(Patricia) So what should our advice be to people about caffeine?
(Astrid) Based on the research that has been done, I would say that most people can carry on enjoying their daily cups of coffee.
(Patricia) I’m glad to hear it! Thank you Dr Nehlig for this overview of the current research on caffeine.
For more information on coffee and caffeine visit coffeeandhealth.org
