Fish is healthy? Fishiness behind the science of fish
Fish is recommended by many health boards as a health promoting food.
- The American Heart Association (AHA) recommends eating at least two servings of fish per week.
- The US Environmental Protection Agency assert that fish is important in a healthy diet.
- The Association of Reproductive Health Professionals says fish is a great alternative to red meat and has protective properties against heart disease.
- England’s National Health Service claims a healthy diet should include at least two portions of fish per week.
- The Australian Dietary Guidelines suggest to eat fish every day.
Fish has a number of benefits over other meat sources like red meat and poultry. Fish has:
- less saturated fat;
- more beneficial omega-3 fatty acids;
- less heme iron;
- less Neu5Gc;
- and a high amount of vitamins and minerals.
There’s significant epidemiological evidence suggesting that replacing red meat with fish in one’s diet can dramatically reduce one’s chance of chronic illnesses — like cardiovascular disease and colorectal cancer.
With all the benefits fish have in comparison to other meat sources, it looks pretty good for fish. Is adding fish to diet overall beneficial for health, or is recommending fish consumption an assumption without grounds?
Is fish better than red meat?
In general, red meats (beef, pork and lamb) have more cholesterol and saturated (bad) fat than chicken [and] fish. – American Heart Association
Fish is touted as a healthy protein source, especially compared to red meat.
A study that followed over 80,000 women — evaluating risk of coronary heart disease (CHD) of different protein sources — concluded that risk of CHD can be reduced by switching from red meat to fish. It was discovered that replacing red meat with fish had a 24% reduction of risk of CHD. This is an impressive finding, only surpassed by nuts, which had a 30% reduction of risk.
A study observing over 120,000 people concluded an association between red meat consumption and increased total, cardiovascular disease (CVD) and cancer mortality. Replacing one serving of unprocessed red meat with one serving of fish reduced risk of total mortality by 5%. Fish was the lowest reduction; legumes reduced risk by 8%, low fat dairy by 9%, poultry and whole grains by 13%, and nuts by 18%.
A study following over 110,000 people gathered results suggesting that red meat consumption is associated with increased risk of type 2 diabetes (T2D). They also found that red meat consumption was associated with lower physical activity, higher body mass index (BMI) and increased smoking. This indicates that people who choose alternative sources of meat (like fish) are generally more health conscious to begin with. In increasing order, replacing unprocessed red meat with fish, low fat dairy, nuts or whole grains lowered T2D risk.
In another study following over 120,000 people, replacing red meat consumption with another meat source such as fish decreased risk for stroke.
With red meat consumption so high and the benefits of replacing red meat with fish evident, it’s easy to see why fish is purported as a health food. For improved health — including reduced risk of CHD, CVD, T2D and stroke — it can be recommended to replace red meat with fish.
Is fish healthy?
It’s well established that fish is one of the better sources of meat, especially compared to red meat, but is fish actually a healthy choice to incorporate into diet?
Opinions are divided on this topic.
What are the health benefits of fish?
Fish are high in monounsaturated (MUFA) and polyunsaturated (PUFA) fats, generally recognized as good fats.
One serving of wild Atlantic salmon provides only 155 calories with 40% being fat. Only 1% of this is saturated. It’s a significant source of long-chain omega-3 fatty acids, which are thought to support good cardiovascular health and reduce risk of heart attacks. Overall it contains a varied amount of vitamins and minerals. It’s a good source of:
- protein; Vitamin B12; Vitamin D;
- Vitamin B6; niacin; selenium;
- choline; pantothenic acid; biotin; and potassium.
Selenium and Mercury
Mercury is considered to be among the most toxic substances to the global environment.
Mercury is related to a host of health problems, including damage to the gastrointestinal tract, nervous system and kidneys, neurological damage and behavioral changes, along with higher risks for many other chronic illnesses. Mercury is considered to be among the most toxic substances to the global environment.
While mercury contamination is a major concern, it has been theorized that the high amount of selenium in seafood actually protects against mercury toxicity. The theory suggests that so long as you avoid low selenium fish, like tarpon, marlin, swordfish and some shark, mercury contamination of fish should not be concerning.
But the theory of selenium protecting against mercury damage is debated and not conclusive. Hence the risk of mercury contamination should not be completely dismissed.
Selenium doesn’t seem to provide protection against damaging behavioral effects of mercury in mice. Nor does selenium in fish seem to provide protection against mercury in pregnant women. Selenium also doesn’t provide protection of other potential toxic contaminants common in fish like dioxins, PCBs and arsenic.
It’d be inadvisable to rely on selenium present in fish to work as a protection against harmful effects of mercury until there’s sufficient evidence supporting the theory.
Mercury and Cilantro
Cilantro, otherwise known as Chinese parsley, has some evidence supporting its ability to enhance the body’s chelation process – i.e. the process of removing heavy metals (like mercury) from the system.
It’s at least true that cilantro consumption reduces effects of lead poisoning in mice.
On top of limiting exposure to toxic heavy metals, it’s advisable to consume leafy green vegetables and herbs on a regular basis. Whether consuming cilantro along with fish effectively nullifies the risk of mercury contamination is unknown.
Given the relative safety of cilantro, if one is to eat fish then seasoning with cilantro could be a good idea.
Choose your Toxic Sources Wisely
Risk of toxic heavy metal intake can be somewhat mitigated by choosing certain types of species of seafood over others.
It’s generally better to choose fish that are lower on the food chain. Sardines can be an especially lowly contaminated choice as they have short life spans and feed only on plankton (they’re also a high source of calcium). Fish to avoid include shark, tilefish and king mackerel.
Currently, vegetables contribute more dietary PCBs than do fish. While avoiding harmful PCBs should be a priority, it would hardly be considered reasonable to suggest limiting intake of vegetables. Although there’s cancer risk associated with consuming contaminated vegetables, the cancer protective properties far outweigh any risk of cancer.
Likewise, limiting fish due to PCB contamination would be ill advised if indeed the health benefit outweigh the risks. Some analysis show that benefit of lowered CHD risk far outweigh potential cancer risk associated with consumption of fish.
Fish is a more concentrated source of PCBs than vegetables. The highest source of dioxins and PCBs is farmed fresh-water fish, which contain significantly more dioxins than wild varieties. So even though it’s advisable to not eat less vegetables, it may not be advisable to eat more fish either.
If fish consumption increases, more dietary PCBs would be contributed by fish, and overall intake of PCBs would likely increase too. If vegetable consumption increases, more dietary PCBs would be contributed by vegetables, but overall intake of PCBs would likely decrease.
Lowering Risk of Heart Disease
Higher mercury content in hair can be a risk factor for CHD. It’s also associated with higher cholesterol and higher rates of diabetes.
Higher levels of mercury in toenail clippings can predict a greater risk of heart attacks. Because fish is a primary source of mercury, this indicates that fish consumption may actually be correlated with increased risk of CHD, rather than decreased risk.
Fish consumption may actually be correlated with increased risk of heart disease, rather than decreased risk.
Adverse effects of contaminants like mercury within fish is shown to increase CHD.
When fish was in fact put to the test in a clinical trial — by telling men to eat more fish — risk of cardiac death unexpectedly increased.
Fish is thought to theoretically lower heart disease risk mainly due to healthful properties of long chain omega-3 fatty acids. In order to obtain benefit against CHD, it’s advisable to avoid or selectively source farmed fish; farmed fish generally don’t have the same concentration of omega-3 fatty acids compared to their wild counterparts.
Seeing as there may be other ways of reducing CHD — such as including dietary sources of alpha-linolenic omega-3 fatty acids (like flaxseeds, chia seeds and walnuts) — the extra cancer risk associated with fish consumption may not be worthwhile. On the other side, there’s some evidence suggesting fish plays a cancer protective role, especially against colorectal cancer.
Comparing a nonfish diet to a diet including fish, fish resulted in higher cholesterol.
Comparing a nonfish diet to a diet including lean fish, lean fish resulted in higher plasma total and LDL apolipoprotein (apo) B. This essentially means risk of CVD is increased because apo B containing lipoproteins are most likely to enter the wall of arteries.
This is seemingly contradictory to the epidemiological evidence suggesting a protective role for cardiovascular disease. So while fish may decrease risk of cardiovascular disease, it may simultaneously increase risk of CVD too.
How is this even possible? Basically because there’s no single cause of heart disease. Instead, there are several factors that help determine risk of contracting a heart attack.
Increased cholesterol is one such risk. When that cholesterol oxidizes, it becomes even more problematic. So while fish’s associated fatty acids prevent inflammation, blood clotting and heart damage, fish consumption also raises cholesterol.
This double sided nature of fish may at least in part explain the controversy surrounding the claims of heart protective properties of fish and fish oil, with other proponents arguing fish fats don’t reduce risk at all.
Perhaps fish isn’t so protective of CVD, but merely delays the inevitable heart failure. Even sourcing clean fish may not be enough to overtake the cholesterol increasing effects and associated health risk.
Fish is a mixed package
Food comes in packages; some elements of that package can be good, and some elements can be bad.
Fish is a mixed package. On one hand there are healthful nutrients and protective properties, but on the other hand there are potentially harmful elements like saturated fat, cholesterol, high amounts of sulfur-containing amino acids like methionine, and environmental contaminants like dioxins and mercury.
Consumer Reports has published information regarding potential benefits and risks of fish, and show classes of safe and unsafe fish to consume. Whether or not the benefit of fish consumption outweighs potential risk is a controversial matter.
Meet the Okinawans
The Okinawans have historically been one of the healthiest societies in the world.
Okinawa is known to have the highest concentration of centenarians. As a result, their diet and lifestyle have been highly studied and analyzed.
The traditional Okinawa diet has been predominantly plant-based. The primary source of meat in the Okinawa diet is fish – albeit in small amounts.
Given that seafood is relied upon as a food source in one of the world’s healthiest societies, the possible health benefits of adding seafood to diet merits investigating.
However, the amount of fish consumed by Okinawans per week averages at around one serving; this is lower than the minimum two servings per week recommended by the AHA.
Meet the Seventh-day Adventists
The Seventh-day Adventists (SDA) in California, much like the Okinawans, have a high proportion of centenarians.
The SDA are a fascinating group to study for several reasons:
- They have significantly higher life expectancies compared to the rest of the USA. As the gene pool is a close approximation to the rest of the USA, findings can be more likely applicable to the remaining population.
- Due to religious beliefs, they all follow very similar lifestyles. The main differences are only dietary. They don’t smoke, they regularly exercise and they live a relatively stress free and socially active lifestyle. Because they all follow the same principles for maintaining healthy lifestyles, differences in health status are more likely related to diet.
- The SDA live in a highly developed country (the USA) with good access to medical care and pharmaceutical drugs. This may be one reason why in some cases SDA members have lower mortality than the Okinawans.
This is where things really start to get interesting. While vegetarian diets are overall associated with lower mortality, vegetarian diets that include fish result in longer lifespan.
Is Fish the Key to Living Longer?
After analyzing 5,548 vegans (strict vegetarians who consume little to no animal products of any form) and 7,194 pesco vegetarians (vegetarians who don’t eat meat except for fish, and who don’t eat dairy or eggs), pesco vegetarians had a slightly lower mortality rate than vegans. The difference wasn’t huge, but it begs investigation (in comparison, non-vegetarians had a significantly higher mortality rate than vegetarians).
Vegans also had lower BMI compared to ovo-lacto vegetarians (vegetarians who don’t eat meat but eat dairy and eggs) and pesco vegetarians. There are a few possible explanations for this:
- Vegans may have had less calcium intake than ovo-lacto and pesco vegetarians, resulting in lower bone mineral density (BMD). Consequently this would lower overall BMI.
- Vegans may have consumed less overall fat, resulting in less stored lipids and lower body fat percentage. Plant foods in general have less fat than animal foods. Primary sources of fat for vegans likely were nuts and soy foods, which have a lower proportion of fat compared to dairy, eggs and fish.
- Vegans may have consumed less overall calories, resulting in lower body weight (both muscle and fat). Compared to animal products, plant foods generally have lower caloric density.
There are a few caveats to these SDA studies. The data is not fully inclusive and the follow up was short. Vitamin B12, Vitamin D, calcium and fatty acids intake were not recorded for any group. Lack of these nutrients (in the form of foods or supplements) may have negatively affected mortality rate of vegans compared to pesco vegetarians.
Vitamin B12 deficiency can be a serious problem and may negatively impact lifespan.
The EPIC-Oxford study, which followed 448,568 people, measured a positive health effect on fish consumption and colorectal cancer. It also showed that vegans had higher risk for bone fractures. SDA vegans may also have higher risk for bone fractures. When calcium intake was taken into account, vegans with sufficient calcium intake in the EPIC study had the same fracture rates as other diet groups.
Vitamin B12 deficiency can be a serious problem and may negatively impact lifespan. Vegans in general have greater risk of Vitamin B12 deficiency compared to other types of vegetarians. However, even the Okinawans have lower Vitamin B12 than ideal, despite their main source being fish.
Another contribution to the poorer mortality rate of vegans compared to pesco vegetarians may have been insufficient intake of omega-3. Fish is a high source of healthy fats, and the vegans studied may not have consumed enough healthy fats.
Given that data of nutrient intake is unavailable, it’s difficult to draw conclusions from the SDA studies. If vegans had adequate sun exposure and intake of calcium and Vitamin B12, plus maintained optimal proportions of healthy fatty acids, mortality may have been on par or even better than pesco vegetarians.
Are Pesco Vegetarians Really Healthier?
At first glance, it looks like the SDA fish eaters were overall more healthy than vegans. Fish eaters had the longest lifespans and lowest rates of colorectal cancer.
But what about quality of life?
Comparable mortality between SDA vegans and pesco vegetarians doesn’t necessarily imply comparable health.
In the USA there’s easy access to many drugs that delay or prevent death from chronic illnesses like cardiovascular disease and diabetes.
For example, one population can have a greater amount of cardiovascular disease, yet not have higher death of cardiovascular disease because drugs and surgery can keep people alive longer than they’d otherwise live without medical intervention.
Why did fish eaters have lower rates of colorectal cancer? Maybe it was because fish is protective against colorectal cancer. Or maybe it was because the statins they took are protective against colorectal cancer.
Vegans had the lowest use of statins and lowest rate of diabetes.
Vegans had the lowest use of statins – just 3.9%, compared to 9.1% of pesco vegetarians. Despite the pesco vegetarians only eating small amounts of fish, they had more than double the amount of hypercholesterolemia. This indicates that more often cholesterol of fish eaters got high enough to warrant medication. Subsequently, they also had slightly lower incidents of colorectal cancer.
Vegans had the lowest rate of diabetes. Pesco vegetarians on the other hand had a higher rate of diabetes than the ovo-lacto vegetarians. The link between fish and T2D remains controversial, though other population studies following Dutch and US adults have shown that higher fish intake can be associated with T2D.
This adds to the supporting evidence that a vegan diet is protective against T2D. The increase in diabetes may also be due to the increased BMI of the pesco vegetarian group.
Fish eaters had higher rates of medical intervention and higher rates of health problems.
SDA pesco vegetarians ate an average of 119g of fish per week. This is on the lower side of the AHA two servings — 115g to 170g — per week recommendation.
With seemingly little difference between two health conscious groups of people, with one group eating moderately small amounts of fish and the other group forgoing fish altogether, the fish eating group had higher rates of medical intervention and higher rates of health problems.
It’s possible that the extra medical intervention due to a greater number of health problems in pesco vegetarians lead to lower incidence of colorectal cancer and consequently delayed death.
Maybe if the vegans consumed more fiber, their risk of colorectal cancer would be significantly reduced without having to rise their cholesterol to unsafe levels in order to warrant statins.
Evidence is emerging supporting negative health risks associated with fish consumption.
Assuming the healthfulness of fish consumption is not justified with the available data. This assumption of fish eating being healthy was likely brought about due to comparisons between high fish-eaters and low fish-eaters. When non-fish eaters are brought into the picture, the benefits of fish eating are lessened. While replacing red meat with fish is advisable, replacing fish with plant foods like nuts, legumes and whole grains is even more highly advisable.
Substituting meats high in saturated fats with fish is not necessarily as optimum as eliminating meat entirely. For those who wish to continue consuming fish, good recommendations are salmon and sardines. Sardines are especially a safer choice due to their low contamination, high calcium intake and high amount of omega-3 fatty acids. Servings should be limited to no more than two per week.
Eating fish is not only unnecessary and introduces health risks, but is also not likely beneficial.
For those who do not wish to consume fish, or wish to reduce their fish consumption, good recommendations for substitution are soy products like fermented tofu and tempeh; nuts; legumes like beans, split peas and lentils; or grain based products like seitan and especially whole grains. It should be ensured that adequate calcium intake is achieved either through diet (lots of leafy greens, tofu set with gypsum, citrus fruits or other fortified products) or supplementation, alongside supplementation of Vitamin B12, either sun exposure or Vitamin D supplementation, and high ALA foods like flaxseeds and chia seeds be regularly consumed (or optionally supplement with algae sourced EPA and DHA).
Eating fish is not only unnecessary and introduces health risks, but is also not likely beneficial.