Sardines, small oily fish, have been a dietary staple in many cultures for centuries. These unassuming fish pack a powerful nutritional punch, offering a wealth of health benefits from heart health to weight management and improved cognitive function. This article delves into the nutritional composition of sardines, explores their potential role in weight loss, and examines the broader health advantages of incorporating them into your diet.
Sardines: A Nutritional Overview
Sardines are rich in essential nutrients, making them a valuable addition to a balanced diet. These nutrients include:
Omega-3 Fatty Acids: Sardines are an excellent source of omega-3 polyunsaturated fatty acids (n-3 PUFA), including EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These fatty acids are recognized as functional nutrients with multifaceted effects in preventing and managing cardiometabolic diseases with pro-inflammatory backgrounds, such as type 2 diabetes (T2D), hypertension, hypertriglyceridaemia, and fatty liver disease.
Protein: Sardines are a good source of protein, which is essential for building and repairing tissues, producing enzymes and hormones, and maintaining energy levels.
Calcium: Sardines, especially when consumed with bones, are a significant source of calcium, a fundamental nutrient in cardiovascular biochemical pathways, as evidenced by its major role as signalling ion and paramount for myocardial contractility. Calcium is indispensable for bone health, and sardines can be an alternative for individuals who cannot tolerate dairy products or milk at that volume, and also an option for those in need of complementing their total calcium intake in general. The calcium content in 100 g of sardines is equivalent to the amount found in ~ 400 ml of milk.
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Vitamin D: Sardines are rich in vitamin D, which is vital for calcium absorption and bone health.
Vitamin B12: Sardines are an excellent source of vitamin B12, which is crucial for nerve function and red blood cell formation.
Iron: Sardines contain a considerable amount of iron, higher than other commonly consumed types of fish. Sardine iron content is comparable to that of meat, the most popular source of iron worldwide. Thus, sardine consumption is an option to reach the RDA for iron, 8 mg/d for all age groups, and particularly helpful for those who do not eat meat.
Other Minerals: Sardines also contain potassium, magnesium, zinc, copper, manganese, selenium, thiamin, riboflavin, niacin, pantothenic acid, vitamin B6, folate, choline, vitamin A, retinol, vitamin E, and vitamin K.
Sardines and Weight Loss
Sardines may be a valuable addition to a weight loss plan due to their nutrient profile:
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High Protein Content: The high protein content in sardines can help you feel fuller for longer, reducing overall calorie intake and promoting weight loss.
Omega-3 Fatty Acids: Some studies suggest that omega-3 fatty acids may influence weight and fat metabolism, but their impact on weight loss appears modest and may vary among individuals.
Low Calorie Count: Sardines are relatively low in calories, making them a suitable choice for those aiming to reduce their caloric intake.
Reducing Inflammation: Sardines are a great source of omega-3 fatty acids, which can reduce inflammation and prevent overeating.
It's important to note that incorporating sardines into a well-rounded, healthy diet and physical exercise routine is more likely to contribute to overall well-being rather than serving as a standalone solution for weight loss.
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Cardiometabolic Benefits Beyond Omega-3s
Sardines contain calcium, potassium, magnesium, zinc, iron, taurine, arginine and other nutrients which together modulate mild inflammation and exacerbated oxidative stress observed in cardiovascular disease and in haemodynamic dysfunction. In a common serving of sardines, calcium, potassium, and magnesium are the minerals at higher amounts to elicit clinical benefits, whilst other nutrients are present in lower but valuable amounts. A pragmatic approach towards the consumption of such nutrients in the clinical scenario should be adopted to consider the dose-response relationship effects on physiological interactions.
Blood Pressure Regulation: Sardines, as a dietary source of n-3 PUFA, have shown benefits for blood pressure (BP) and lipid profile normalisation. Adequate potassium intake can not only normalise elevated BP by increasing natriuresis when the cause of hypertension is high sodium levels, it also favours optimal endothelial function and nitric oxide release.
Iron Intake: Given the well-established association between iron-deficiency anaemia and cardiovascular diseases, iron intake should not be neglected when managing cardiovascular patients. Iron supplementation may be necessary in specific cases, but at the same time sardine consumption could be an ideal option to be included in the diet plan.
Amino Acids: Sardines are an important source of amino acids, including arginine, taurine and others, which play fundamental roles in cardiometabolism, not only as structural biomolecules but also as modulators of antioxidant systems and vascular function.
Other Health Benefits of Sardines
Beyond weight loss and cardiometabolic benefits, sardines offer a range of other health advantages:
Heart Health: The omega-3 fatty acids in sardines can reduce the risk of heart disease by lowering triglyceride levels, reducing inflammation, and improving blood vessel function. A Harvard study found that consuming just one to two servings of sardines every week provides enough omega-3 fatty acids to reduce your chances of heart disease by more than one-third.
Brain Health: Omega-3 fatty acids are crucial for brain health and may help improve cognitive function and reduce the risk of neurological disorders.
Bone Health: Sardines are a good source of calcium and vitamin D, both essential for maintaining strong and healthy bones. You eat fish bones and skin when you eat canned sardines, and they are an excellent source of calcium, providing about a third of the amount needed by the average person in each serving. Vitamin D is vital to this process since it allows your body to absorb calcium. And sardines are even richer in vitamin D than in calcium. Sardines also contain a third bone-boosting nutrient - phosphorous, which neutralizes acids that could harm your bones.
Eye Health: There's some evidence that the omega-3 fatty acids in sardines and other foods can reduce the risk for eye diseases including macular degeneration. It might also help with dry eye.
Nerve Function: Up to 40% of older adults may be deficient in vitamin B12. This deficiency can cause poor sensory nerve function and problems with the peripheral nerves. Nerve problems can cause other problems. They might reduce your mobility, which could cause you to fall and have a serious injury. One serving of sardines provides over three times the amount of B12 most people need.
Muscle Growth and Repair: The protein and heart-healthy fats in sardines can help you build muscle and strength.
Reduce Inflammation and Oxidative Stress: Sardines have many nutrients that can help with mild inflammation or oxidative stress in heart disease or other conditions. These include calcium, potassium, magnesium, zinc, iron, taurine, arginine, and more.
Increase Omega-3 Index: Two recent RCTs have investigated the effects of prolonged sardine consumption on T2D sufferers. In one study, 200 g of sardine per week for 12 months resulted in a 1.3% increment in the O3I (6.6 ± 1.2 to 7.9 ± 1.3%), whilst the other study found an increase of 2.7% (5.3 ± 0.3 to 8.0 ± 0.4%) when the participants consumed 100 g of sardines 5 days a week for 6 months.
Potential Concerns and Considerations
While sardines offer numerous health benefits, it's essential to be aware of potential concerns:
Mercury Content: Like other fish, sardines may contain mercury. However, sardines are generally considered to have low mercury levels compared to larger predatory fish. The benefits of the vitamins and minerals found in sardines outweigh the potential negative impact of trace pollutants, according to researchers.
Sodium Content: Canned sardines can be high in sodium, which may be a concern for individuals with high blood pressure. One can has about 282 milligrams of sodium, which is roughly 12% of the daily recommended value. If you need to reduce salt, you can still enjoy sardines by decreasing your serving size and making the rest of your meal low-salt.
Purine Content: Sardines are high in purines, which can increase uric acid levels and may worsen gout or kidney stones in susceptible individuals.
Allergies: Some people may be allergic to fish, including sardines. They can cause food allergy or skin reactions (atopic dermatitis). If you are allergic to sardines, you could have symptoms including swelling, redness, and anaphylaxis.
Heavy Metal Contamination: In addition to mercury, sardines may be contaminated by other heavy metals including cadmium and lead.
Choosing and Consuming Sardines
When incorporating sardines into your diet, consider the following:
Fresh vs. Canned: Both fresh and canned sardines offer health benefits. Canned sardines are often more convenient and have a longer shelf life. Fresh sardines aren't as commonly found as canned sardines, but they can be a good option if you find them. You can also prepare these little fish smoked, fried, baked, or grilled. If you're into Japanese cuisine, they serve sardines raw as sashimi, another way to enjoy this oily fish.
Preparation: Sardines can be enjoyed in various ways. You can eat them straight from the can, add them to salads or pasta dishes, or grill or bake them.
Sustainability: Look for sardines that are sustainably sourced to minimize environmental impact.
Moderation: Consume sardines in moderation as part of a balanced diet. It's best to eat them in moderation-consider eating sardines two to three days a week, for example.
Read Labels: When shopping for sardines, it’s important to pay attention to the label to ensure you’re making a healthy choice. Look for sardines packed in olive oil or water, as these options are generally lower in sodium and higher in omega-3 fatty acids. Avoid sardines packed in tomato sauce or other high-sodium liquids. Additionally, opt for wild-caught and sustainably sourced sardines to minimize environmental impact and ensure you’re getting the best quality fish.
BPA-Free Cans: Look for cans labeled “BPA-free” to minimize exposure to the chemical bisphenol A.
The "Sardine Diet" Fad and Its Risks
Recently, a sardine-only diet has gained popularity as a quick weight loss solution. This involves consuming only sardines (sometimes with MCT oil) for several days or even months. While some individuals have reported weight loss and other health improvements on this diet, experts caution against it due to the following risks:
Nutrient Deficiencies: A sardine-only diet lacks essential nutrients such as fiber, vitamin C, and various phytonutrients.
Excessive Sodium Intake: Canned sardines can be high in sodium, which may lead to high blood pressure and cardiovascular problems.
Purine Overload: High purine content can worsen gout and kidney problems.
Gut Microbiome Imbalance: A strict high-protein diet without fiber can disrupt the gut microbiome.
Unsustainability: Restrictive diets are often difficult to maintain long-term and may lead to binging on other foods.
For over three months, a woman in North Carolina ate only four cans of sardines and MCT oil each day. She says this diet helped her lose 35 pounds, resolved her pain, and decreased her inflammation. She plans to reintroduce other meats into her diet but will continue to follow a “low-carb/carnivore” lifestyle.
The sardine-only diet was popularized in 2023 as a three-day challenge by Annette “Dr. Boz” Bosworth, MD, a Florida-based internist who is an advocate of low-carb, high-protein keto diets. Some people have extended this challenge to weeks or months.
Experts caution that limiting your diet to a single food for days or longer can lead to negative health effects.