Too much coffee?

Espresso machine producing strong coffee

Espresso machine producing strong coffee on demand.

We have an expensive espresso coffee machine that produces excellent coffee. As native Northern Europeans we drink large cups of coffee. The other day I took the effort of trying to calculate the amount of caffeine in one cup of coffee. The machine has three coffee choice button (apart from a number of buttons also providing different varieties of coffee with hot milk). They provide a ristretto, an espresso, and a strong coffee with increasing volumes of coffee down the buttons. We use the bottom coffee button with the coffee strength set to high and always press it twice to get a double coffee of 250 mL. Now based on data provided for caffeine content in coffee expressed from an espresso machine averaging about 2,000 mg/L,  the amount of caffeine in the cup can be calculated to be around 500 mg. That is a lot.

The European Food Safety Authority (EFSA) in a recent opinion stated that a cup of coffee with 200 mg of caffeine is fine but daily intake of caffeine should be restricted to 400 mg. We exceed this exposure with only one cup of coffee. What could be the implications?

The detrimental effects

It might not all be good.

I recently had a question about coffee and iron absorption. Looking at a recent scientific report it was clear that coffee inhibit iron absorption. A cup of coffee within an hour of an iron rich meal reduced iron absorption by at least 40%. So it is not a good idea to finish a meal with a cup of coffee in case you suffer from iron deficiency. In this case it probably doesn’t matter that much if the cup contains 200 mg or 500 mg of caffeine.

A late coffee might disturb sleep (Photo: RelaxingMusic).

A late coffee might disturb sleep (Photo: RelaxingMusic).

It is also not a good idea to have a late cup of coffee just before going to bed. Large amount of caffeine can disturb sleep patterns and cause insomnia. On the benefit side, caffeine enhances alertness and mood, and increases performance, but that is probably not what you want when going to bed. This effect is most probably influenced by the amount of caffeine consumed so a 500 mg caffeine cup should definitively be avoided before sleep.

Caffeine may also aggravate pre-existing health conditions such as migraines and heart arrhythmias and it can promote anxiety and panic attacks, especially in high doses and in those with pre-existing anxiety disorders. That doesn’t sound very encouraging except that regular coffee consumption will blunt such effects. And we have our daily dose.

So it might be fine.

The beneficial effects

And there is the other side.

The simple act of drinking caffeinated coffee seems to be able to reduce the risk of colon cancer returning after surgery and subsequent death. A clinical trial examined outcomes in patients with stage III colon cancer who were treated with surgery and various chemotherapies. All 953 patients reported their intake habits for 128 foods, including caffeinated coffee, decaffeinated coffee, and nonherbal tea, during and 6 months after chemotherapy.

The benefit was strongest in the heaviest drinkers of caffeinated coffee. Patients who consumed at least four cups of coffee a day or about 460 mg of caffeine were 52% less likely to have their cancer return or to die than noncoffee drinkers. Patients who drank fewer cups of caffeinated coffee also saw a benefit, but the degree of risk reduction tapered as the average number of cups per day dropped. In other words, there was a dose-response effect.

If you aren’t affected by colon cancer there might be more good news. Various studies in recent years have suggested that coffee protects against the development of breast cancer and skin cancer, and protects against the recurrence or progression of prostate cancer.

Among postmenopausal women, heavy coffee consumption is associated with a lower incidence of estrogen receptor (ER)-negative breast cancer. In a study involving about 6,000 females there was a small decrease of 20% in overall breast cancer risk associated with coffee consumption of more than 5 cups/day compared with 1 or fewer cups/day. However, among the heavy coffee drinkers there was a strong reduction of close to 60% in risk for ER-negative breast cancer.

Coffee might reduce cancer incidence.

Coffee might reduce the risk of some cancers.

Coffee may reduce the risk of developing basal cell carcinoma of the skin, according to new prospective data from more than 110,000 healthcare professionals who participated in two large, surveillance studies. Study participants who drank more than 3 cups of caffeinated coffee a day had a 17% reduction in their relative risk of basal cell carcinoma compared with individuals who drank less than 1 cup per month. However, no association was found between consumption of coffee and either squamous cell carcinoma or melanoma.

Drinking 4 or more cups of coffee a day was associated with a lower risk for prostate cancer recurrence and progression, according to a prospective study of a cohort of 630 prostate cancer patients. The study authors found that men who drank that much coffee daily had a 59% reduced risk for prostate cancer recurrence and/or progression, compared with those who drank 1 or fewer cups per week.

So maybe not too much coffee after all

It all sounds great but note that as prospective and observational studies the findings only reveal correlations and are not proof of causation. There are many such studies with dubious results.

However, being an optimist I think I stick to my daily large cup of coffee and hope for the best, ignoring the EFSA advice for now.

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Are omega-3 food supplements useless in old age?

Dubious effect of omega-3 fatty acids on cognitive decline.

Dubious effect of omega-3 supplements on cognitive decline in old age.

There goes my last hope for a food supplement that actually works in old age. The omega-3 fatty acid docosahexaenoic acid is essential for the growth and functional development of the brain in infants and is present in mother’s milk. It has also been proposed  that a diet high in omega-3 fatty acids can protect brain health and slow cognitive decline in older persons.

Omega-3 fatty acids are made by marine algae and are concentrated in fish oils. They are believed to be responsible for the health benefits associated with regularly eating fish, such as salmon, tuna, and halibut. Other omega-3 fatty acids are found in plant foods such as flaxseed, walnuts, soy products, and canola and soybean oils. And of course the food supplement industry markets omega-3 supplements.

Studies show no effect of omega-3 supplements on cognitive decline

Now researchers at the National Institutes of Health has concluded that omega-3 supplements do not slow cognitive decline in older persons. In a large double-masked randomised clinical trial they followed 4,000 patients over a five-year period. The patients were divided into four groups with one given a placebo capsule, one given an omega-3 capsule (with 350 mg docosahexaenoic acid and 650 mg eicosapentaenoic acid), one given a capsule with lutein and zeaxanthin and finally one given a capsule with omega-3, lutein and zeaxanthin. The reason for this complex design was to also establish the impact on age-related macular degeneration.

Participants were given cognitive function tests at the beginning of the study to establish a baseline, then at two and four years later. The tests, all validated and used in previous cognitive function studies, included eight parts designed to test immediate and delayed recall, attention and memory, and processing speed. The cognition scores of each subgroup decreased to a similar extent over time, indicating that no combination of nutritional supplements made a difference.

So unfortunately, contrary to popular belief, the researchers didn’t see any benefit of omega-3 supplements in delaying cognitive decline. This is similar to results from a large 2011 study that found that omega-3 supplements did not improve brain health of older patients with preexisting heart disease. However, other studies surveying people’s dietary habits and health have found that regular consumption of fish with omega-3 fatty acids in their ‘natural’ form has benefits for eye, brain and heart health. It may be that the timing of nutrients, or consuming them in a certain dietary pattern, is important.

So a big, black mark against omega-3 food supplements for old age health.

Maybe not the final word

But maybe not so clearcut. Consider that chronic inflammation plays an important role in the development of colorectal cancer, a leading cause of cancer-related death worldwide. Accumulating evidence from animal and in vitro studies indicates that omega-3 fatty acids have potent anti-inflammatory activity and inhibit colorectal carcinogenesis. However, epidemiologic findings on the association between omega-3 fatty acids and colorectal cancer are inconsistent, with even an increased incidence of cancer associated with high omega-3 fatty acid intake reported in some prospective studies.

Now researchers at Harvard have shown that omega-3 fatty acids can have a protective effect against the development of one particular subtype of colorectal cancer. This type of cancer is called microsatellite instable and comprise about 10% to 15% of all colorectal cancers. Complicating the findings, participants with higher intakes of omega-3 fatty acids were more likely to be active, to be regularly taking multivitamins and fish oil supplements, to undergo lower gastrointestinal endoscopy, and to have more frequent consumption of poultry, fruits, and vegetables and less consumption of unprocessed and processed red meat.

Robust conclusions are thus evasive but maybe some glimmer of hope.

And there is more

Fish is the best food source of omega-3 fatty acids (Photo: Johan Munk Wolfhage).

Fish is the best food source of omega-3 fatty acids (Photo: Johan Munk Wolfhage).

We have covered the microbiome before. It includes commensal gut bacteria that are generally considered to be friendly, since they can help their host in numerous ways. They can actually help to regulate the immune system, amongst many other beneficial functions that support the host’s health. Remember that inflammation can play a role in colorectal cancer.

In lab-based work on human gut cells, researchers tested whether gut cells respond differently to a commensal bacterium (Lactobacillus gasseri) and two pathogenic bacteria (Escherichia coli and Staphylococcus aureus), and also whether the responses could be altered with omega-3 fatty acids. They found that the lactobacilli increased the secretion of the immune signalling protein TGF-β1 (Transforming Growth Factor β1), but the pathogenic bacteria didn’t.  TGF-β1 has an important role in promoting tolerance towards commensal bacteria and also in dampening immune responses following inflammation. When the omega-3 fatty acid eicosapentaenoic acid was added to the cell culture model along with L. gasseri, there was a greater increase in TGF-β1 gene expression.

The results may suggest that there is an interaction between eicosapentaenoic acid and colorectal cell response to a commensal bacterial strain that could possibly be important in cancerogenesis.

Life is complicated

All I can say at this stage is that science can be complicated as is life itself. There is clearly no harm in increasing fish consumption, but you might give omega-3 fatty acid supplements a miss until more convincing results are presented.

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