superfoods

Contents

What are superfoods

The term Superfood is used often, but not always with the same meaning because there is no official definition of a “superfood” and the European Union has banned health claims on packaging unless supported by scientific evidence 1). But that hasn’t stopped many food marketers from labelling the health benefits of their product. The food industry wants to persuade us that eating some foods can slow down the ageing process, lift depression, boost your physical ability, and even your intelligence. Superfood is really just a marketing term.

Superfoods are marketed – hard. They give us the idea that we need these special, often expensive and imported foods to be healthy. It’s adding to the myth that it costs a lot of money to eat healthy. For the majority of American, eating more vegetables and less meat would lead to a healthier diet, savings at the checkout and a smaller environmental impact. It’s a win, win, win!

The superfood trend exploits the fact that healthy lifestyle choices, including diet, can reduce our risk of chronic diseases like heart disease, stroke and cancer.

The superfoods claims are not usually backed by strong science. Many foods have been studied for their health effects and then reported in the media with flashy headlines. These studies are commonly:

  • Done in petri dishes or animals, not humans
  • Use huge, unrealistic amounts of a particular food or specific nutrient in food
  • Are done on a small number of people, or for a short amount of time

The problem is that most research on superfoods tests chemicals and extracts in concentrations not found in the food in its natural state.

Many of us want to believe that eating a single fruit or vegetable containing a certain antioxidant will zap a diseased cell.

Garlic, for example, contains a nutrient alleged to help reduce cholesterol and blood pressure. But you’d have to eat up to 28 cloves a day to match the doses used in the lab – something no researcher has yet been brave enough to try.

Foods that have been elevated to superfood status in recent years include those rich in antioxidants (such as beta-carotene, vitamins A, C, E, flavanoids and selenium) and omega-3 fatty acids.

Antioxidants are chemicals thought to protect against the harmful effects of free radicals, which are chemicals naturally produced in every living cell and known to cause cell damage.

However, evidence about this and other health benefits of antioxidants is inconclusive. In a review of the scientific evidence in 2011, the European Food Safety Authority (EFSA) found no evidence that the antioxidant action on free radicals observed in the lab was of any benefit to human health 2).

In addition, a 2012 Cochrane Review 3) suggests that certain antioxidant supplements may be harmful. In that systematic review, 78 randomized clinical trials were included with a total of 296,707 participants, who were randomized to antioxidant supplements (beta-carotene, vitamin A, vitamin C, vitamin E and selenium) versus placebo or no intervention. Twenty-six trials included 215,900 healthy participants. Fifty-two trials included 80,807 participants with various diseases in a stable phase (including gastrointestinal, cardiovascular, neurological, ocular, dermatological, rheumatoid, renal, endocrinological, or unspecified diseases). A total of 21,484 of 183,749 participants (11.7%) randomized to antioxidant supplements and 11,479 of 112,958 participants (10.2%) randomized to placebo or no intervention died. When all of the trials were combined, antioxidants may or may not have increased mortality depending on which statistical combination method was employed; the analysis that is typically used when similarity is present demonstrated that antioxidant use did slightly increase mortality (that is, the patients consuming the antioxidants were 1.03 times as likely to die as were the controls). When analyses were done to identify factors that were associated with this finding, the two factors identified were better methodology to prevent bias from being a factor in the trial (trials with ‘low risk of bias’) and the use of vitamin A. In fact, when the trials with low risks of bias were considered separately, the increased mortality was even more pronounced (1.04 times as likely to die as were the controls). The potential damage from vitamin A disappeared when only the low risks of bias trials were considered. The increased risk of mortality was associated with beta-carotene and possibly vitamin E and vitamin A, but was not associated with the use of vitamin C or selenium. Therefore the current evidence does not support the use of antioxidant supplements in the general population or in patients with various diseases. The review authors conclusion was : “We found no evidence to support antioxidant supplements for primary or secondary prevention. Beta-carotene and vitamin E seem to increase mortality and so may higher doses of vitamin A. Antioxidant supplements need to be considered as medicinal products and should undergo sufficient evaluation before marketing” 4) .

While the concept of Superfoods or “miracle foods” remains a fantasy, it’s pretty well-established that obesity and alcohol are the two most common causes of major long-term illness and increased risk of premature death.

However for the sake of discussing the idea of superfoods, the simplest way to think of Superfoods is that “superfoods” offer benefits above and beyond their basic nutrient content. For example, antioxidants make berries super, while nuts and avocados have good fats. We focus on Superfoods that are naturally super, but there are also foods that are called super or functional because of ingredients that have been added to them. It is important to note however, that there is no food, including those labelled ‘superfoods’, can compensate for unhealthy eating. People shouldn’t mistakenly believe that they can ‘undo’ the damage caused by unhealthy foods by eating a superfood, because they will continue to hold false belief that they may continue making unhealthy choices that will increase their risk of long-term illness.

When it comes to keeping healthy, it’s best not to concentrate on any one food in the hope it will work miracles.

Top superfoods

Years of nutrition research has consistently shown that eating more wholefoods and plant foods is a good thing. When you think of superfoods, think of all wholefoods!

Fruit, vegetables, lean meats, dairy and wholegrain cereal products are part of well balanced diet, are affordable and readily available. Therefore, all unprocessed food from the major food groups could be considered ‘superfood’. Eat a wide variety of these, and you’ll get all the ‘super’ goodness you need.

Here is a list of top 10 superfoods

  • Beetroot
  • Blueberries
  • Broccoli
  • Chocolate
  • Garlic
  • Green tea
  • Goji berries
  • Pomegranate juice
  • Oily fish
  • Wheatgrass

Beetroot juice

Beetroot’s deep, overpoweringly red juice has earned it the reputation as the most bossy of vegetables.

Although the leaves have always been eaten, historically the beet root was generally used medicinally for a range of ailments, including fevers, constipation and skin problems.

Beetroot is a good source of iron and folate (naturally occurring folic acid). It also contains nitrates, betaine, magnesium and other antioxidants (notably betacyanin).

More recent health claims suggest beetroot can help lower blood pressure, boost exercise performance and prevent dementia.

Beetroot and beetroot juice, along with green leafy vegetables, cabbage and celery, are very useful as part of a balanced diet as their nitrate content may help to reduce blood pressure.

However, getting active, reducing the amount of salt in your diet and maintaining a healthy weight are also key strategies for getting your blood pressure under control.

Can beetroot lower blood pressure ?

Beetroot is rich in nitrates. The juice of the beetroot, has potential antioxidant and blood pressure lowering effect 5). Beetroot contains nitrate, which while in your body changes to a chemical called nitrite and then to nitric oxide in the blood. Nitric oxide is a gas that opens up blood vessels and aids blood flow. In a preliminary study, people with high blood pressure who drank a cup of beetroot juice each day had a 10 mm Hg decrease in blood pressure over the following 24 hours 6).  A well-conducted review of the current evidence from 2013 concluded that beetroot juice was associated with a modest reduction in blood pressure 7).

However further long-term trials would be needed and in people at greater risk of heart disease before we could say beetroot was clinically useful.

Does beetroot aid exercise performance ?

Another well-conducted review from 2013 8) looked at research linking beetroot juice to improved exercise performance. The review found that inactive and recreationally active individuals saw “moderate improvements” in exercise performance from drinking beetroot juice. However, the review noted there was very little effect on elite athletes.

Can beetroot help prevent dementia ?

A 2010 study 9) suggested that a diet high in beetroot juice may increase blood flow to certain areas of the brain. However, this was a small and short-term study with several limitations and as such does not provide robust evidence that a diet high in nitrates aids cognitive function. Further research is needed in larger numbers of people over a longer period.

A 2014 study 10) looked at the effects of beetroot juice on cyclists, who were cycling in a chamber designed to mimic the effects of relatively high altitude (2,500 meters above sea level).

Researchers found that cyclists given the juice had a modest but significant increase in terms of their time trial scores; on average there was a 16 second improvement.

Blueberries

The grandad of the superfood trend, blueberries are a good source of vitamin K. They also contain vitamin C, fiber, manganese and other antioxidants (notably anthocyanins).

Valued for its high levels of antioxidants, some nutritionists believe that if you make only one change to your diet, it should be to add blueberries.

Die-hards claim blueberries can help protect against heart disease and some cancers, as well as improve your memory.

While research on the health claims of blueberries is inconclusive, they are a fantastic choice as one of your five portions of fruit and vegetables a day.

Blueberries are low in calories and high in nutrients, including phenolic compounds with an antioxidant capacity significantly higher than vitamins C or E.

Try adding them to your breakfast cereal, including them in a packed lunch or mixing with low-fat yogurt for a delicious dessert.

Heart health and blueberries

A study in 2012 of 93,000 women 11) found that participants who ate three or more portions of blueberries and strawberries a week had a 32% lower risk of a heart attack compared with those who ate berries once a month or less. However, the study could not prove that these fruits definitely caused the lower risk.

Can blueberries combat high blood pressure and atherosclerosis ?

While the evidence is inconclusive, it is thought that blueberries may relax the walls of the blood vessels, which may help reduce this risk of atherosclerosis – hardening of the arteries. Atherosclerosis can increase the risk of a heart attack and stroke.

A small study in 2015 involving 48 post-menopausal women 12), found that women who were given blueberry powder supplements over the course of eight weeks experienced a small, but clinically significant, drop in blood pressure.

A study 13) from the same year involving 44 adults with metabolic syndrome (a combination of diabetes, high blood pressure and obesity), who were given blueberry smoothies, had less promising results as there was no effect on blood pressure.

A similar finding was presented in a 2013 study 14) involving 21 men. Though these men were described as healthy so the results may not be applicable for people with underlying chronic diseases.

Though it is important to note that all of these studies were relatively small which gives less “weight” to their results. They also involved different populations so the results may not be applicable to the general population.

Can blueberries prevent cancer ?

There is so far very little evidence that blueberries can help protect against cancer. In laboratory studies on cells and animals, blueberry extracts (such as anthocyanins) have been shown to decrease free radical damage that can cause cancer. However, it is not clear how well humans absorb these compounds from eating blueberries and whether or not they have a protective effect.

Does eating blueberries lead to a better memory ?

A number of small studies have found a link between blueberry consumption and improved spatial learning and memory. However, most of these studies relied on small sample groups or animals. There is currently no evidence of a link between eating blueberries and improved memory.

Broccoli

Broccoli is a good source of vitamin C and folate (naturally occurring folic acid). It also contains vitamins A, K, calcium, fibre, beta-carotene and other antioxidants (notably indole-3-carbinol and sulforaphane).

Can eating broccoli prevent cancer ?

Eating more non-starchy vegetables, such as broccoli, is associated with a reduced risk of some cancers (including mouth, throat and stomach cancers), according to a good quality 2007 review 15) of the evidence on cancer prevention by the World Cancer Research Fund. It is possible that some of the compounds in broccoli may have health benefits, but clinical trials are needed to investigate this further.

Does broccoli reduce high blood pressure ?

There is no evidence to suggest broccoli can help lower blood pressure. In a 2010 study 16), 40 patients with high blood pressure who ate 10g of dried enriched broccoli sprouts for four weeks saw no improvement to the health of their blood vessels and did not reduce their risk of atherosclerosis (narrowing of the arteries).

Can broccoli help prevent cardiovascular disease ?

In a small study from 2012 17) of 81 people with diabetes, those in a group that ate 10g a day of enriched broccoli sprouts powder for four weeks saw a reduction in their levels of cholesterol and triglycerides (a type of fat found in the blood), both of which can cause cardiovascular disease.

Does broccoli help in diabetes ?

In a lab study from 2008 18), researchers applied the antioxidant sulforaphane to human blood vessels incubated with sugar. They found that sulforaphane appeared to prevent the damage to small blood vessels caused by high blood sugar (which can happen if you have diabetes). However, it is unclear from this study whether sulforaphane would protect a person with diabetes from damage.

Chocolate

Recent interest in the health benefits of chocolate was sparked by studies on the cocoa-drinking peoples of Central America.

Researchers observed that the Kuna Indians of Panama, who drank cocoa as their main beverage, had very low blood pressure, a leading cause of heart disease and stroke.

Chocolate is the processed and sweetened food produced from cocoa. Cocoa is a good source of iron, magnesium, manganese, phosphorous and zinc. It also contains the antioxidants catechins and procyanidins.

Brand experts have sought to associate chocolate – and in particular dark chocolate – with the supposed health benefits of cocoa, which include protection against cancer and stress relief.

It’s important to remember the studies on the health benefits of chocolate have focused on cocoa extracts, not chocolate.

A range of health benefits from the consumption of cocoa products have been investigated, particularly in relation to cardiovascular disease, with early results showing promise. However, the potential health benefit of some compounds in chocolate have to be weighed against the fact that to make chocolate, cocoa is combined with sugar and fat. This means chocolate is an energy-dense food that could contribute to weight gain and a higher risk of disease. As an occasional treat, chocolate can be part of a healthy diet. Eaten too frequently, it is an unhealthy choice.

Can chocolate reduce blood pressure ?

A well-conducted 2017 Cochrane review 19) of the best available evidence on the effects of chocolate on blood pressure concluded that cocoa products – including dark chocolate – may help slightly (2 mmHg) lower blood pressure.

However, most of the studies were of short duration (between two and eight weeks) and there were some weaknesses in the available research.

The authors of the review say longer-term trials are needed to further our understanding of cocoa’s effect on blood pressure, cardiovascular health and to assess potential adverse effects associated with chronic ingestion of cocoa products 20).

Can eating chocolate prevent cancer ?

Some limited animal and laboratory research suggests a cocoa-rich diet could offer protection against bowel cancer. But it’s impossible to conclude from research carried out in a laboratory that cocoa can protect people against bowel cancer.

Does chocolate stop stress ?

In a small study from 2009 21), 30 healthy people who were given 40g of dark chocolate a day for 14 days experienced a reduction in stress hormones. However, the study, which was funded by a major chocolate manufacturer, had several limitations, including its short study period, and does not provide any evidence chocolate has any benefits or effects on stress.

Do two chocolate bars a day prevent stroke ?

A recent study carried out in Norfolk in 2015 22) looked at chocolate consumption and cardiovascular disease. It reported people who ate the equivalent of two chocolate bars a day had a slightly lower risk of stroke than people who never or rarely eat chocolate.

Cumulative evidence suggests that higher chocolate intake is associated with a lower risk of future cardiovascular events, although residual confounding cannot be excluded 23). There does not appear to be any evidence to say that chocolate should be avoided in those who are concerned about cardiovascular risk.

Can venous leg ulcers be helped with chocolate ?

Venous leg ulcers are open sores that can develop on the leg or foot, and can take many weeks to heal. People who find it difficult to move around as a result of conditions such as obesity or paralysis are particularly at risk.

A 2013 Cochrane review 24) looked at whether flavonoids, a compound found in chocolate and red wine, could help accelerate wound healing. The study only found weak evidence in favor of flavanoids, but most of these trials were poorly reported, and so had an unclear risk of bias for randomisation, allocation concealment, blinding and methods for addressing incomplete outcome data. There was also a possibility of publication bias.

Garlic

Garlic contains vitamins C and B6, manganese, selenium and other antioxidants (notably allicin).

More recent evidence-based research suggests garlic may be effective against high blood pressure, cardiovascular disease, cholesterol, colds and some cancers.

Garlic is a delicious flavor used widely in Mediterranean and Asian cooking. Studies using high concentrations of garlic extracts have been associated with improved blood circulation, healthier cholesterol levels and lower blood pressure, all of which reduce the risk of cardiovascular disease. However, current evidence does not support the use of garlic supplements to improve health.

Garlic is particularly useful in cooking as it provides an alternative to salt in adding flavor to meals, along with lemon juice, chilli, herbs and spices. Eating less salt is important for avoiding high blood pressure.

Does garlic lower high blood pressure ?

A Cochcrane review from 2012 25) based on 2 trials in 87 hypertensive patients, it appears that garlic reduces mean supine systolic and diastolic blood pressure by approximately 10-12 mmHg and 6-9 mmHg, respectively, over and above the effect of placebo, but the confidence intervals for these effect estimates are not precise and this difference in blood pressure reduction falls within the known variability in blood pressure measurements. This makes it difficult to determine the true impact of garlic on lowering blood pressure 26). These patients were given 2 X 100 mg tablets of high potency garlic powder three times daily for 12 weeks.

Can garlic reduce cholesterol ?

A well-conducted review from 2009 27) of 29 good-quality studies involving a combined total of 1,794 participants concluded that garlic – mainly garlic powder – produced “modest reductions” in total cholesterol levels, an effect driven mostly by the modest reductions in triglyceride, without appreciable LDL “bad” lowering or HDL “good” elevation. Higher baseline line total cholesterol levels and the use of dietary modification may alter the effect of garlic on these parameters. Future studies should be conducted evaluating the impact of adjunctive garlic therapy with fibrates or statins on triglyceride concentrations.

Does garlic prevent the common cold ?

A Cochrane review from 2014 28) of the best available evidence concluded there was insufficient evidence regarding the effects of garlic supplements in treating or preventing colds. Most studies that claimed this were poor quality. The review said one reasonably good study suggested garlic may prevent colds, but more research was needed to back up the finding.

Will garlic protect against cancer ?

The evidence is mixed. A 2007 World Cancer Research Fund review 29) concluded that garlic “probably protects against” bowel and stomach cancers. A more recent review from 2009 30) of the best available research on humans concluded there was “no credible evidence” with stomach, breast, lung and womb cancers, but that there was “very limited evidence” that eating garlic may lower the risk of colon, prostate, oral, ovary or renal cell cancers 31).

Green tea

Green tea has been used in traditional Chinese medicine for centuries to treat everything from headaches to depression.

The leaves are supposedly richer in antioxidants than other types of tea because of the way they are processed.

Green tea contains B vitamins, folate (naturally occurring folic acid), manganese, potassium, magnesium, caffeine and other antioxidants, notably catechins.

All types of tea – green, black and oolong – are produced from the Camellia sinensis plant using different methods. Fresh leaves from the plant are steamed to produce green tea, while the leaves of black tea and oolong involve fermentation.

Green tea is alleged to boost weight loss, reduce cholesterol, combat cardiovascular disease, and prevent cancer and Alzheimer’s disease. However the evidence about green tea’s health benefits is inconclusive – the evidence for the majority of these conditions is weak or lacking.

However, as a social drink, green tea appears to be safe in moderate amounts ~ 3 to 5 cups per day (up to 1200 ml/day), providing a minimum of 250 mg/day catechins, so lovers of green tea can continue to enjoy it.

Does drinking green tea protect you from cancer ?

There is no evidence drinking green tea protects against different types of cancer. A Cochrane review from 2009 32) involving 51 studies, with more than 1.6 million participants, looked for an association between drinking green tea and cancers of the bowel, prostate, breast, mouth and lungs. The authors of the review concluded evidence of a link between green tea and cancer was weak and “highly contradictory”.

A more recent 2015 study 33) looked at the cancer-fighting effects of a compound found in green tea when combined with a drug called Herceptin, which is used in the treatment of stomach and breast cancer. Initial results in the laboratory were promising and human trials are now being planned.

But this shouldn’t be taken as official advice that drinking green tea while taking Herceptin will make it more effective.

Can green tea aid weight loss ?

It’s thought the antioxidants catechin and caffeine found in green tea may have a role in helping the body burn more calories – sometimes referred to as speeding up the metabolism – which can help weight loss.

Green tea preparations used for losing weight are extracts of green tea that contain a higher concentration of catechins and caffeine than the typical green tea beverage prepared from a tea bag and boiling water.

A well-conducted Cochrane review from 2012 34) of 18 studies involving 1,945 people found no significant effect of weight loss from drinking green tea. Green tea preparations appear to induce a small, statistically non-significant weight loss in overweight or obese adults. Because the amount of weight loss is small, it is not likely to be clinically important. Green tea had no significant effect on the maintenance of weight loss.

Does green tea cut cholesterol ?

A good-quality Cochrane review from 2013 35) of 11 studies involving 821 people found daily consumption of green and black tea (as a drink or a capsule) could help lower cholesterol and blood pressure thanks to tea and its catechins. The authors of the review caution that most of the trials were short term and more good quality long-term trials are needed to back up their findings.

Another good-quality review from 2011 36) found drinking green tea enriched with catechins led to a small reduction in total cholesterol and LDL “bad” cholesterol levels, a main cause of heart disease and stroke. However, it’s still not clear from the evidence how much green tea you would need to drink to see a positive effect on your health, or what the long-term effects of drinking green tea are on your overall health.

Can green tea help prevent or delay Alzheimer’s disease ?

Evidence of a positive link between drinking green tea and Alzheimer’s disease is weak. A 2010 laboratory study 37) using animal cells found a green tea preparation rich in antioxidants protected against the nerve cell death associated with dementia and Alzheimer’s disease.

Whether these lab results can be reproduced in human trials remains to be seen. As such, the findings do not conclusively show green tea combats Alzheimer’s disease.

Can green tea lower blood pressure ?

A 2014 survey 38) of data from previously published studies looked at the evidence of whether drinking green tea could help lower blood pressure. There was evidence of a modest reduction in people with high blood pressure who consumed green tea. But whether this reduction would lead to clinically significant results, such as preventing the onset of heart disease or stroke, is unclear.

Can green tea prevent tooth decay ?

A small study from 2014 39) looked at how effective a green tea mouthwash was in preventing tooth decay compared with the more commonly used antibacterial mouthwash chlorhexidine. The results suggested they were equally effective, though green tea mouthwash has the added practical advantage of being cheaper.

Goji berries

Goji berries contain vitamin C, vitamin B2, vitamin A, iron, selenium and other antioxidants (notably polysaccharides).

Various goji berry products are sold as health foods, but the evidence of their health benefits so far comes from scientific studies using purified extracts of the fruit at much higher concentrations than the products contain.

As these products tend to be relatively costly, it makes sense to stick to eating a range of fruits and vegetables rather than spending your money on this one item with no proven health benefits.

Can goji berries improve immunity, cardiovascular disease and life expectancy ?

There is no reliable evidence to support these alleged health benefits. Most of the research into these conditions are small-sized, of poor quality, and performed in laboratories using purified and highly concentrated extracts of the goji berry.

Do goji berries aid wellbeing, brain activity and digestion ?

One small study from 2008 40) found a daily drink of 120ml of goji berry juice for 14 days improved feelings of wellbeing, brain activity and digestion. However, the study involved only 34 people and was attempting to measure the effects of goji berry juice on a variety of conditions. The results of the study were inconclusive.

Can goji berries prevent cancer ?

One of the most talked about clinical studies on goji berries is a 1994 Chinese study 41) conducted on 79 patients with various advanced cancers. It found those treated with immunotherapy in combination with goji polysaccharides saw their cancers regress. Unfortunately, information on the design of the study and the goji berry compounds used are lacking, so it is difficult to fully assess the significance of the results.

Pomegranate juice

The Middle Eastern fruit is claimed to be effective against heart disease, high blood pressure, inflammation and some cancers, including prostate cancer.

Pomegranate is a good source of fibre. It also contains vitamins A, C and E, iron and other antioxidants (notably tannins).

Research suggests there may be a benefit, but the evidence around the health benefits of pomegranates are inconclusive. The studies that have found an improvement in existing health conditions were very small and more investigation into the role pomegranate plays in these improvements is needed.

Can pomegranate strengthen bones ?

A 2013 study 42) found evidence that pomegranate strengthened bones and helped prevent osteoporosis. The catch was the study involved mice, not humans.

While the biology of mice and humans are surprisingly similar, we can never be sure that these results will be applicable to us.

Does pomegranate juice slow prostate cancer progress ?

One small study from 2006 43) found that drinking a daily 227ml (8oz) glass of pomegranate juice significantly slowed the progress of prostate cancer in men with recurring prostate cancer. This was a well-conducted study, but more are needed to support these findings.

A more recent study from 2013 44) looked at whether giving men pomegranate extract tablets prior to surgery to remove cancerous tissue from the prostate would reduce the amount of tissue that needed to be removed. The results were not statistically significant, meaning they could have been down to chance.

Can pomegranate reduce carotid artery stenosis ?

A good-quality study from 2004 45) on patients with carotid artery stenosis (narrowed arteries) found that a daily 50ml (1.7oz) glass of pomegranate juice over three years reduced the damage caused by cholesterol in the artery by almost half, and also cut cholesterol build-up. However, these effects are not clearly understood and the study did not say what the results mean for conditions such as stroke.

Is heart disease prevented by pomegranates ?

A well-conducted trial from 2005 46) on 45 patients with coronary heart disease demonstrated that a daily 238ml (8.4oz) glass of pomegranate juice administered over three months resulted in improved blood flow to the heart and a lower risk of heart attack. The study did not say what the results mean for conditions such as heart attacks, and with such a small trial the positive results reported could be down to chance.

Oily fish

If there’s one food that’s good for your heart, it’s oily fish. Interest in the health benefits of oily fish started when researchers observed that Eskimos, who mainly eat oily fish, had fewer than average heart attacks and strokes.

Oily fish such as salmon, mackerel and sardines are said to help against cardiovascular disease, prostate cancer, age-related vision loss and dementia.

It’s a good source of vitamin D, protein, some B vitamins and selenium. It’s also a rich source of omega-3 fatty acids, a type of fat that is good for our health.

The benefits of eating at least two portions of fish a week, including one of oily fish, include keeping your blood pressure at a healthy level and improving blood lipids, both of which reduce your risk of cardiovascular disease: the biggest killer in the US.

Remember that you can get your omega-3 from a range of oily fish. Tinned sardines and mackerel, for example, are an easy and cheap way to stock up the store cupboard. Eaten on toast with a side salad, this makes a quick, easy and nutritious meal.

Cardiovascular disease

There is now a large body of evidence suggesting that fish consumption, particularly oily fish, reduces your risk of cardiovascular disease.

Studies have found eating oily fish can lower blood pressure and reduce fat build-up in the arteries. The evidence is strong enough to warrant the Dietary Guidelines for Americans that you eat at least two portions of fish a week, one of which should be oily 47).

However, there are maximum recommended amounts for oily fish, crab and some types of white fish. There is additional advice for women who are pregnant or breastfeeding, and children and babies.

Recommendations from the Dietary Guidelines for Americans: The 2015–2020 Dietary Guidelines for Americans  48) states that women who are pregnant or breastfeeding should consume 8–12 ounces of seafood per week, choosing from varieties that are higher in polyunsaturated omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and lower in methyl mercury, such as salmon, herring, sardines, and trout. These women should not consume certain types of fish, such as king mackerel, shark, swordfish, and tilefish that are high in methyl mercury, and they should limit the amount of white (albacore) tuna they consume to 6 ounces a week. The American Academy of Pediatrics has similar advice for breastfeeding women, recommending intakes of 200–300 mg docosahexaenoic acid (DHA) per day by consuming one to two servings of fish per week to guarantee a sufficient amount of docosahexaenoic acid (DHA) in breast milk 49).

fish consumption advice when pregnant[Source 50)]

Prostate cancer

The evidence for oily fish’s effect on prostate cancer is inconclusive. Some limited research suggests that eating fish may reduce the risk of developing prostate cancer. However, this is not backed up by other studies, so we can’t be sure of the effect.

Dementia

A 2012 Cochrane review 51) looked into whether consuming more omega-3, a type of healthy fat found in oily fish, could reduce the risk of dementia. The review looked at studies of healthy 60-year-olds who took omega-3 capsule supplements for six months.

The review concluded that there is no preventative effect of decline in brain function and dementia when healthy older people take omega-3. The review suggested that longer-term studies would offer researchers a better opportunity for identifying the possible benefits of omega-3 in preventing dementia.

Vision

A well-conducted review in 2010 52) found there was some evidence that eating oily fish two or more times a week could reduce the risk of age-related macular degeneration – a common cause of blindness in older people. However, the reviewers said the results should be interpreted cautiously, because of weaknesses in the research.

A more recent Cochrane review carried out in 2015 53) looked at whether fish oil supplements could reduce the progression of macular degeneration in people who already had the condition. The results were disappointing, as there was no evidence of any benefit. This review found that omega 3 long chain polyunsaturated fatty acid supplementation in people with age-related macular degeneration for periods up to five years does not reduce the risk of progression to advanced age-related macular degeneration or the development of moderate to severe visual loss. No published randomized trials were identified on dietary omega 3 fatty acids for primary prevention of age-related macular degeneration. Currently available evidence does not support increasing dietary intake of omega 3 long chain polyunsaturated fatty acid for the explicit purpose of preventing or slowing the progression of age-related macular degeneration 54).

Rheumatoid arthritis

A 2013 study 55) looked at the eating habits of around 32,000 middle-aged and older women to see if oily fish consumption had any influence on them developing rheumatoid arthritis. They did find that women who ate one or more servings of oily fish were 29% less likely to develop rheumatoid arthritis than women who never, or very rarely, ate oily fish.

However, this type of study can never prove cause and effect, as other factors could have been involved.

Schizophrenia

In 2013, the National Institute for Health & Care Excellence 56) reviewed the evidence about whether medication based on omega-3 fatty acids could improve the symptoms of schizophrenia. The results were mixed. Four out of the eight studies showed some modest benefit when compared to placebo (a dummy treatment). The other four showed no benefit.

Based on these results, it is not recommended to use omega-3 fatty acid-type drugs as an alternative to existing treatments.

Wheatgrass

Wheatgrass contains chlorophyll, vitamin A, vitamin C, vitamin E, iron, calcium and magnesium.

There is no sound evidence to support the claim that wheatgrass is better than other fruits and vegetables in terms of nutrition. It cannot be recommended above any other choices in this food group.

Nutrition claims for wheatgrass

Despite claims that a 30ml (1oz) shot of wheatgrass contains as many nutrients as 1kg (2.2lbs) of your finest veggies, tests show that, pound for pound, the nutrient content of wheatgrass juice is roughly equivalent to that of common vegetables, such as spinach and broccoli.

Can drinking wheatgrass boost red blood cell production ?

Fans of wheatgrass believe that because chlorophyll and haemoglobin (a protein that carries oxygen around your body) are similar in structure, taking wheatgrass juice enhances haemoglobin production. But as far as evidence goes, there is no scientific proof to support this claim.

Does wheatgrass salve inflammation of the colon ?

A small study from 2002 57) found patients with ulcerative colitis (inflammation of the colon) saw their symptoms improve after they were given 100ml of wheatgrass juice daily for a month. However, the study involved only 21 people and the positive results could have been simply down to chance. As such, the evidence is inconclusive.

Can wheatgrass help people with blood disorders ?

A small study from 2004 58) of 32 patients with a blood disorder called thalassaemia found half of the patients required fewer blood transfusions when 100ml (3.5oz) of wheatgrass juice was taken daily for three years. While interesting, the research has many weaknesses and further research is needed before these findings can be properly validated.

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