The Role of Nutrient Timing in Performance and Recovery

Jesse Oswald • April 3, 2024

Key Points

  • Nutrient timing is the strategic consumption of energy, macronutrients, fluids, and micronutrients in the hours before, during, and after exercise to optimize performance, enhance the adaptations to exercise, and accelerate recovery.
  • The recommended intake of carbohydrates for most endurance athletes typically ranges from 5-12 g/kg/d, with the upper ends reserved for those engaging in ≥8 hours/week of ≥70% VO2 max exercise.
  • Most exercising individuals should consume approximately 1.2-2.0 g/kg/d of protein to optimize training-induced adaptations. The exact amount depends on the mode and intensity of exercise, protein quality, as well as the caloric intake of the individual.
  • Athletes should follow appropriate rehydration strategies during exercise to limit the total body fluid losses to <2% of body weight and thus avoid adverse outcomes in exercise performance and recovery.

 

Nutrient timing, or peri-workout nutrition, is the consumption of nutrients pre-, during, and post-exercise. The primary goal of peri-workout nutrition is to provide nutritional support to allow the athlete to stay injury-free while maximizing performance and the functional and metabolic adaptations to their exercise program. Thus, the strategic consumption of energy in the form of carbohydrates, protein and/or fats, fluids, and micronutrients in the hours before, during, and after exercise can maximize muscle repair, improve body composition, optimize performance, and enhance muscular-related adaptations, such as strength and hypertrophy.



Nutrient needs and the practical strategies for meeting them pre-, during, and post-exercise depend on various factors, including the exercise per se (mode, intensity, duration), the environment, carryover effects from previous activity, appetite, and individual preferences.


Strategies implemented in pre-, during, and post-exercise periods should address various nutrition-related factors that can cause fatigue and deterioration in performance outputs (e.g., power, strength, agility, skill, and concentration). These factors include dehydration, electrolyte imbalances, glycogen depletion, hypoglycemia, and gastrointestinal (GI) discomfort.

Overall, nutrient timing when it comes to a workout, let alone a competition or event, can influence performance, recovery, training stimuli, and adaptations to exercise.

Energy Requirements

An appropriate energy intake is the cornerstone of an athlete’s diet since it supports optimal body function, determines the intake levels of macronutrients and micronutrients, and assists in manipulating body composition when required.


Athletes must consume adequate energy in terms of both the amount and timing, especially during high-intensity and/or long-duration training, to maintain health and maximize training outcomes.


An athlete’s energy requirements depend on the periodized training and competition cycle and may significantly vary throughout the yearly training plan relative to training volume and intensity changes.


Moreover, energy requirements are influenced by biological and environmental factors. Namely, energy needs are increased during training in cold and/or hot environmental conditions, high altitude exposure, physical injuries, and by increases in fat-free mass. Conversely, energy requirements are lowered by aging, decreases in fat-free mass, and possibly during the follicular phase of the menstrual cycle.


Although there are demonstrated advantages to achieving a certain body composition and body weight, low energy intake can result in unwanted loss of muscle mass, hormonal disturbances, sub-optimal bone density, increased fatigue, injury risk, impaired training adaptation, and an extended recovery process.


This especially applies in sports such as weightlifting, combat sports, distance running, etc., where athletes may feel pressure to attain unrealistically low weight/body fat targets or to reach them in an unrealistic time frame.


Under such circumstances, extreme weight loss behaviours or continuous dieting may result in poor nutrient support and compromised health and performance.


Consequently, when loss of body weight is required, it should be programmed to occur well out from the competition phase to minimize loss of performance. It should be achieved with techniques that maximize body fat loss while preserving muscle mass and other health goals.


The first step is determining energy requirements through indirect calorimetry rather than predictive equations and/or energy intake formulas. Afterward, a slight energy deficit should be applied to achieve a slow rather than rapid weight loss rate. In this energy-restricted framework, the provision of a higher protein intake, up to 2.3 g/kg/d, will retain muscle mass while losing body fat.


For most, decreasing energy intake by ~ 250-500 kcal/d from their periodized energy needs while either maintaining or slightly increasing energy expenditure can achieve progress towards short-term (3-6 weeks) body composition goals.



Athletes who frequently restrict their energy intake for the above reasons, probably eliminating one or more food groups, may consume sub-optimal micronutrients. Therefore, they should perform frequent blood tests. In case of deficiencies, they should adequately supplement, especially with calcium, vitamin D, iron, and some antioxidants.

Carbohydrate Intake

Carbohydrates have a vital role in performance and adaptation to exercise. There is evidence that exercise performance is enhanced by strategies that maintain high carbohydrate availability, namely, matching glycogen stores and blood glucose to the fuel demands of exercise. In contrast, depletion of these stores is associated with muscle fatigue, impaired skill and concentration, and increased perception of effort.


General guidelines for the suggested intake of carbohydrates can be provided according to the athlete’s body weight and the characteristics of the workout. The timing of carbohydrate ingestion over the day and in relation to training can also be manipulated to promote optimal carbohydrate reserve.


Endurance training

Manipulating nutrition and exercise in the hours and days leading up to a critical endurance workout, competition, or event, a highly prioritized feeding period, allows an athlete to maximize endogenous (muscle and liver) glycogen stores.


The delivery of carbohydrates, thus the appropriate glycogen filling, is a priority around this time since prolonged (>60-90 minutes) and moderate-to-high-intensity (65-80% VO2max) endurance activities rely extensively upon carbohydrates as a fuel source.


Therefore, carbohydrate feedings maximize endogenous glycogen stores during this time while also helping maintain blood glucose levels, improve performance, and facilitate recovery. Strategies to attain these goals should first follow a brief period of reduced training volume in conjunction with a high daily intake of 5-12 g/kg/d carbohydrates. The upper end of this range (8-12 g/kg/d) should be reserved for those athletes completing high volumes (≥8 hours/week) of moderate-to-high intensity (≥70% VO2 max) exercise and subsequently requiring rapid continuous endogenous glycogen replenishment.


Overall, if the diet contains ≥8 g/kg/d carbohydrates, maximal glycogen levels are restored within 24 hours, and only moderate levels of muscle damage are present.


Individuals who engage in low-intensity/skill-based activities or moderate-intensity exercise programs for around one hour per day should consume 3-5 g/kg/d and 5-7 g/kg/d carbohydrates, respectively.


Recommended pre-exercise carbohydrate ingestion

Pre-exercise fueling is necessary only in the hours leading up to a high-intensity (≥70% VO2max), long duration (>90 minutes) competition or workout, where glycogen levels are best maintained or increased by consuming snacks or meals high in carbohydrates (1-4 g/kg/d) for several hours before. Solid (bars, gels) or liquid (energy drinks, clear fruit juices) carbohydrates, deriving from everyday dietary choices or sports products, based on the athlete’s preference, tolerance, and experience, similarly promote glycogen resynthesis, allowing more flexibility.


Acute fueling strategies to promote high carbohydrate availability in cases of competition and/or key training sessions can also be categorized as pre-exercise nutrition. In < 90 minutes duration exercise cases, the athlete may consume their usual daily intake of 5-12 g/kg/d carbohydrates, with ≥8 g/kg/d carbohydrates, 24 hours before. In cases of >90 minutes of sustained intermittent exercise, the athlete may consume 10-12 g/kg/d carbohydrates 36-48 hours before.


Recommended during-exercise carbohydrate ingestion

As glycogen levels decline during exercise, the ability of an athlete to maintain exercise intensity and work output also decreases while rates of muscle breakdown increase. Therefore, during extended (>70 minutes) bouts of high-intensity (>70% VO2max) workouts, carbohydrates should be ingested at a rate of ~ 30-60 g/h (i.e., 230-350 ml of a 6-8% carbohydrate solution) every 10-15 minutes throughout, to spare glycogen, thus optimize performance and maintain blood glucose levels.


During ultra-endurance exercise lasting more than 2.5-3 hours, where glycogen stores are substantially depleted, carbohydrate ingestion may increase to 90 g/h.


Athletes may choose well-trialed carbohydrate-rich sources low in fat, fiber, and low-to-moderate protein to avoid GI issues and promote gastric emptying. Carbohydrate feedings during exercise are especially crucial when pre-exercise carbohydrate consumption is neglected since they may help offset the potential for performance decrement.


Mouth rinsing with carbohydrate solutions, such as sports drinks, is recommended during sustained high-intensity exercise lasting 45-75 minutes. The frequent exposure of the oral cavity to small amounts of carbohydrates can still enhance performance via stimulation of the brain and central nervous system.


Lastly, during brief exercises lasting less than 45 minutes, carbohydrates are not necessary.


Recommended post-exercise carbohydrate ingestion

Post-exercise consumption of carbohydrates is also necessary, and muscle glycogen levels can be rapidly and maximally restored using an appropriate post-exercise carbohydrate feeding regimen. Specifically, ingesting 0.6-1.0 g/kg within the first 30 minutes of completing a glycogen-depleting exercise and again every two hours for the next 4-6 hours promotes maximal glycogen replenishment.


Similar outcomes have also been demonstrated when 1.2 g/kg of carbohydrates are consumed every 30 minutes over 3.5 hours.


In situations where minimal recovery (<8h of recovery time) between two demanding sessions is available, rapid ingestion of high amounts (~ 1.0-1.2 g/kg/h) of preferably high glycemic index carbohydrates for the first 4-6 hours after exercise can rapidly stimulate replenishment of muscle glycogen (speedy refuelling).


While carbohydrate replacement is crucial as training and competition extend beyond 70 minutes of activity, the need for carbohydrates during shorter-duration exercise is less established.


Resistance training

Resistance exercise, especially resistance-based workouts of 3-6 sets of 8-20 RM, using multiple exercises targeting all major muscle groups, can also significantly decrease muscle glycogen concentration. Even though these decreases are modest compared to endurance exercise, carbohydrate ingestion during such workouts still promotes euglycemia, increases muscle glycogen stores, mitigates muscle damage, and facilitates greater acute and chronic training adaptations.


Post-workout carbohydrate supplementation offers a small contribution from a muscle development standpoint, provided adequate protein is consumed. So, benefits derived from carbohydrate administration more favorably impact aspects of muscle glycogen recovery instead of stimulating muscle mass accretion.

The Importance of Hydration

To preserve homeostasis, optimal body function, and exercise performance, athletes should consume appropriate fluids before, during, and after exercise. Fluid deficits of >2% body weight result in hypohydration and, if not corrected, eventually dehydration, severely compromising exercise performance and recovery and increasing the perception of effort and well-being. For example, skeletal muscle cramps, although typically caused by muscle fatigue, may also be associated with dehydration and electrolyte imbalances, particularly when the athlete is not acclimatized to environmental conditions, such as heat. 


It is not uncommon that athletes begin to exercise in a hypo-hydrated state and finish exercising with a fluid deficit.

Regarding pre-workout hydration guidelines, athletes may achieve euhydration by consuming a fluid volume equivalent to 5-10 ml/kg body weight 2-4 hours before exercise.


After exercise, the athlete should restore fluid balance by drinking a volume equivalent to ~ 125-150% of the remaining fluid deficit (e.g., 1.25-1.5 L of fluid for every 1 kg body weight lost through sweat). Hence, post-exercise rehydration strategies should essentially strive to replace as much sweat loss as possible.


In addition to water, sweat contains substantial amounts of sodium, with less potassium, calcium, and magnesium. Sodium should be ingested during exercise when large sweat losses occur. Scenarios include athletes with high sweat rates (>1.2 L/h), ‘’salty sweat’’, or prolonged exercise exceeding two hours. 


Sweat rates vary during exercise from 0.3-2.4 L/h, dependent on exercise intensity, duration, fitness level, heat acclimatization, altitude, and other environmental conditions (e.g., humidity, etc.). Ideally, athletes should drink sufficient fluids during exercise to limit the total body fluid deficit to <2% of body weight. Rehydration strategies should primarily involve consuming water and sodium at a modest rate that minimizes urinary losses.



The fluid rehydration plan that suits most athletes during exercise is an intake of 0.4-0.8 L/h. Otherwise, the routine measurement of pre- and post-exercise body weight can help athletes estimate sweat losses during sporting activities to customize their fluid replacement strategies. Without other factors that alter body mass during exercise, a 1kg body weight loss represents approximately 1 L sweat loss.

Protein Intake

Proteins are the building blocks of all bodily tissues, including muscles, bones, and organs. They comprise twenty amino acids, nine essential (EAAs) and eleven non-essential (NEAAs). EAAs cannot be produced in the body thus, must be consumed in the diet.

Protein sources containing higher levels of EAAs are higher quality sources of protein.


Protein quality is defined as how effectively a protein stimulates muscle protein synthesis (MPS) and promotes muscle hypertrophy. Products containing animal and dairy-based proteins contain the highest percentage of EAAs, resulting in greater hypertrophy and protein synthesis following training compared to a vegetarian protein-matched protein source, which typically lacks one or more EAAs.

For example, a standard serving of 113.4g of lean beef provides 10g of the EAAs (3.5g of leucine) and 30g of total amino acids. Among the EAAs, leucine has been shown to independently stimulate increases in MPS, with 1-3g of leucine per meal being a sufficient dose for this process. However, the most crucial factor for increasing MPS is a balanced consumption of EAAs, with an approximate dose of 10g per meal stimulating maximal MPS.


Endurance training

Very few studies have investigated the effects of prolonged periods (one week or more) of dietary protein manipulation on endurance performance. Protein does not appear to improve endurance performance and/or recovery when given for several days, weeks, or immediately before, during, and after endurance exercise.


In any case, endurance athletes should consume sufficient amounts of protein to repair and rebuild skeletal muscle following intense training bouts or athletic events.


Although the current recommended dietary intake for protein is 0.8 g/kg/d, evidence systematically indicates that this amount is insufficient for an exercising individual. Daily intakes of 1.2-2.0 g/kg/d are recommended, while greater intakes may be suitable for people attempting to restrict their energy intake while maintaining their muscle mass (refer to the energy requirements section).

 

Resistance training

It has been widely reported that protein consumption directly after resistance exercise (45 minutes to one hour maximum) is an effective way to promote a positive muscle protein balance, hence a net gain or hypertrophy of muscle. Specifically, during the post-prandial phase (1-4 hours after a meal), MPS is elevated by 30-100%, resulting in a positive muscle protein balance. In contrast, MPS rates are lower in a fasted state, and muscle protein balance is negative, meaning muscle mass accretion only occurs in the fed state.

However, the extent to which protein intake, either through protein food sources alone or through the combination of food and protein supplementation in conjunction with resistance training, enhances maximal strength and hypertrophy is contingent upon many factors, including

  1. Resistance-training program variables, such as intensity, volume, and progression
  2. Duration of the resistance-training program
  3. Training status of the athlete
  4. Total energy intake
  5. Quality and quantity of protein intake
  6. Co-ingestion of additional dietary elements that may favourably impact strength, such as creatine.

Therefore, it is becoming evident that protein timing does not play such a significant role in strength and hypertrophy. This is especially true for people who already consume increased amounts of protein (e.g., ≥1.6 g/kg/d), where the alleged benefits of protein timing are attenuated anyway.


Since skeletal muscle is sensitized to the effects of dietary protein for at least up to 24 hours after resistance exercise, general recommendations for maximal MPS rates and muscle hypertrophy are 0.25-0.40 g/kg or 20-40g of protein rich in EAAs and leucine (10-12g of EAAs and 1-3g of leucine) per meal. Spreading these protein doses approximately three hours apart has been consistently reported to promote the greatest increase in MPS, muscle hypertrophy, and performance benefits.


Recommended pre-exercise protein ingestion

As stated above, total protein intake is the strongest predictor of positive adaptations to resistance training, while protein timing influences MPS and hypertrophy to a much lesser degree. Besides sufficient protein intake, the body also needs adequate energy consumption to accumulate muscle mass since amino acids are spared for protein synthesis and are not oxidized.


Although protein timing may minimally contribute to performance and recovery benefits, especially in non-athletic populations, a professional athlete for whom every single detail plays a role should consider the concept of pre-workout and post-workout protein meals.


It has been demonstrated that when enough protein (0.4-0.5 g/kg of lean body mass) is consumed less than five hours before the anticipated completion of a workout, in terms of a pre-workout meal, the need for immediate post-exercise protein ingestion is minimal. Specifically, the closer a protein pre-workout meal is consumed prior to resistance exercise, the larger the post-workout anabolic window, thus the smaller the need for a post-workout meal.

 

Recommended during-exercise protein ingestion

Potential benefits of ingesting protein during resistance training have not been identified, provided there is sufficient daily protein intake (20-40g per meal) evenly spaced throughout the day (every 3-4 hours).



Recommended post-exercise protein ingestion

Exercise and nutrition act synergistically to provide a net anabolic effect far greater than either alone. Without feeding, muscle protein balance remains negative in response to resistance exercise. Therefore, provided that the total daily protein intake is insufficient and/or pre-workout meals are not consumed, the strategic protein consumption immediately after exercise enhances muscle recovery and optimizes strength- and hypertrophy-related adaptations. Intakes of 0.25-0.4 g/kg or 20-40g of protein per meal is recommended. Higher doses do not augment MPS further after resistance exercise.


It doesn’t matter whether this protein derives from food, intact protein supplements such as egg, whey, casein, beef, soy, or free-form amino acids (i.e., EAAs) since it can evoke similar anabolic responses. Hence, protein supplements and EAAs benefit the exercising individual because, just as protein intake from diet, they increase the rates of MPS, decrease muscle protein degradation, and aid recovery from exercise.


Nevertheless, an attempt should be made to consume whole foods that contain high-quality protein sources; supplemental protein can be utilized as a practical method of achieving greater daily protein intakes when food is not convenient or readily available.


Pre-sleep protein intake and protein safety

Pre-sleep protein consumption, namely 30 minutes before sleep and two hours after the last meal, may benefit MPS rates and muscle recovery. Several studies indicate that the pre-sleep consumption of 30-40g of casein protein increases overnight MPS, improves strength and muscle hypertrophy, and may also increase metabolic rate without influencing overnight lipolysis or fat oxidation.

Chronic protein intakes of up to 2.5-3.3g/kg/d in healthy resistance-trained individuals exert no harmful effects on blood lipids or kidney and liver function markers.


Combination of protein + carbohydrate intake in the peri-workout period

The simultaneous ingestion of carbohydrates and protein close to or throughout both endurance and resistance exercise may operate as an effective strategy to enhance performance of a subsequent exercise bout or event as well as specific exercise-induced adaptations.

Furthermore, for athletes combining resistance training sessions with sport-specific training, providing carbohydrate + protein close to each session guarantees optimal recovery for subsequent bouts and adaptation.


Eventually, if rapid restoration of glycogen is required (<4h of recovery time), the combination of carbohydrate sources (0.8 g/kg/h) with protein sources (0.2-0.4 g/kg/h) increases the rate of glycogen synthesis.


However, adding protein to carbohydrates is useful in performance enhancements, muscle damage amelioration, and muscle glycogen recovery only when carbohydrate ingestion during the peri-workout period is suboptimal (<1.2 g/kg/h).


Therefore, when optimal carbohydrate intake is met, adding protein offers little to no additional benefit on endurance or resistance exercise performance and recovery.


It seems prudent for athletes who prefer combining carbohydrates and protein in their peri-workout period rather than just consuming carbohydrates since both methods similarly affect glycogen repletion rates, protein balance, performance, recovery, and muscle repair.

Fat Intake

Fat is a necessary component of a healthy diet, providing energy, structural elements of cell membranes, and facilitating the absorption of fat-soluble vitamins (A, D, E, and K).


The recommended fat intake for athletes is in accordance with public health guidelines, meaning 20-35% of total energy intake, with saturated fats limited to less than 10% and trans fats to less than 1%.


There are no specific guidelines regarding fat timing in relation to exercise. As stated above, athletes should avoid consuming fatty meals and/or snacks before and during exercise, especially concerning competition, to prevent any GI disturbances.


Some athletes may excessively restrict their fat intake below 20% of energy intake to lose body weight or improve body composition. The reduction in dietary variety often associated with such restrictions is likely to reduce the intake of various nutrients, such as fat-soluble vitamins and essential fatty acids, especially omega-3 fatty acids.


Therefore, athletes should be aware that not only consuming <20% of energy intake from fat does not benefit health and performance; in contrast, it is very likely to compromise them, especially if applied chronically. 


Micronutrient intake

Athletes should consume diets that provide at least the Recommended Dietary Allowance (RDA) for all micronutrients.

Therefore, vitamin and mineral supplements are unnecessary for athletes with a balanced diet, providing high-energy availability from various nutrient-dense foods.


However, athletes who restrict energy intake or use severe weight-loss practices are very likely to eliminate food groups from their diet and thus are at greater risk of micronutrient deficiencies. In such cases, a multivitamin/mineral supplement may be appropriate, always considering the specific micronutrient deficiency that ought to be treated or prevented (e.g., iron, vitamin D, etc.).

Key Takeaways

Nutrition goals and requirements are not static. Nutrition support, in terms of both the peri-workout nutrition as well as athletes’ nutrition as a whole, should be periodized, taking into account the periodization of the exercise regime (a range of ‘’easy’’ workouts to highly demanding sessions or competitions).


Nutrition must also be personalized to the individual athlete, considering the specificity of their sport, performance goals, competition, food preferences, and recovery.


Especially during competition, nutrition strategies should focus on improving substrate stores to meet the fuel demands of the exercise while striving to enhance performance, minimize psychological stress and safeguard physical health.



Supplements can be of great value when used as an addition to a well-crafted nutrition plan but are rarely effective outside these conditions, especially for young, growing athletes.

An Ounce of Prevention - Hyperion Health Blog

A woman is helping an older woman do exercises on an exercise ball in a gym.

What is a Kinesiologist?

By Jesse Oswald • January 29, 2025
What is a Kinesiologist?
A woman is wearing an oxygen mask while running on a treadmill.

Predicting Medical Costs with VO2max

By Jesse Oswald • January 20, 2025
Highlights Healthcare expenses are skyrocketing, with consumers and employers facing the significant brunt. Identifying those likely to get sick is critical as our resource-strapped healthcare system should focus on those likely to become the most significant burden to the system. VO2 max is a crucial longevity indicator that can also accurately predict healthcare expenses. The rampant chronic disease epidemic and the resulting surge in medical expenses is one of the most dire problems of modern societies, probably only second to climate change. Healthcare inflation is on a meteoric rise, and for those with limited or no healthcare coverage, a medical emergency is the equivalent of personal bankruptcy. A dire problem for employers In the US, employers and consumers who face rising health insurance premiums and astronomical out-of-pocket medical expenses feel the brunt of rising healthcare costs. Such is the problem that even large, well-capitalized corporations choose to send employees overseas for specific medical procedures since the cost of traveling and treatment in a foreign country is lower than the cost of care in the US. Another startling example is the infamous "northern caravan," a term that describes people with diabetes in the northern states who travel to Canada to secure their insulin supply. According to McKinsey , a survey conducted among over 300 employers highlighted that the average increase in the cost of health benefits over the past three years has been within the range of 6 to 7 percent. This survey also indicated that any rate increases exceeding 4 to 5 percent were deemed unsustainable. Interestingly, 95 percent of the surveyed employers expressed willingness to contemplate reducing benefits if costs surged by 4 percent or more. The primary cost-control measures that these employers indicated they might explore included elevating the portion of premium costs covered by employees and a potential transition to high-deductible health plans. Why is Breath Analysis relevant? Vis-a-vis this problem, the early and accurate estimation of who will get sick and how much they will cost is as critical as the treatment itself. The reason is that no other method of accurately identifying at-risk populations exists; it helps focus our scarce prevention resources and attention on those most in need. Breath analysis, AKA VO2max or metabolic testing, is an assessment that reveals two key biomarkers that provide significant predictive value for one's likelihood of developing costly chronic conditions. These two biomarkers are VO2max and the Respiratory Exchange Ratio. In this article, we will dive into VO2max to understand why it's a critical reflection of our overall health and, consequently, a window into our future healthcare spend. What is VO2max? Let's start with the basics. What is VO2max? VO2 max is the maximum amount of oxygen the human body can absorb. It is measured in terms of milliliters of oxygen consumed per kilogram of body weight. The below formula below indicates how VO2max is calculated: The numerator indicates the volume of oxygen your heart, lungs, and cells can absorb, expressed in milliliters per minute. The denominator indicates the weight of the individual represented in kilograms. 
There are many different types of fats in this picture.

Dietary Fat: An Essential Dietary Component Rather than the root of all Nutritional Health Issues

By Jesse Oswald • January 13, 2025
Key points A total fat intake between 20-35% ensures sufficient intake of essential fatty acids and fat-soluble vitamins Omega-6 PUFAs are primarily found in vegetable oils, while omega-3 PUFAs are primarily found in fatty fish and fish oils Both omega-3 PUFAs and MUFAs have established benefits for cardiovascular disease TFAs are the only dietary lipids that have a strong positive relationship with cardiovascular disease Omega-3 PUFA supplementation increases the beneficial bacteria of the human microbiome Over the last three decades, there has been a great revolution against fat due to its suspected association with several nutritional health issues, especially cardiovascular disease. There was a tremendous amount of evidence that indicated dietary cholesterol and saturated fat as the main culprits of cardiovascular disease, thus morbidity and mortality. It was when all the low-fat and no-fat dairy products started to launch, promising even complete substitution of the cholesterol-lowering heart medication if these products were exclusively consumed. Let’s start from the beginning. Dietary fat intake can vary significantly and still meet energy and nutrient needs. International guidelines suggest a total fat intake between 20% and 35% of the daily caloric consumption. This range ensures sufficient intake of essential fatty acids and fat-soluble vitamins. Not only does the quantity of the ingested fat matter, but most importantly, its quality. Some dietary fats have beneficial effects, with a significant role in maintaining good health, while others may threaten it. Which are, after all, the dietary fats? Dietary fats is a rather heterogeneous group of organic compounds, including four main types of fat, which are elaborately described in the following sections of this article. Polyunsaturated fatty acids (PUFAs) Polyunsaturated fatty acids (PUFAs) have two or more carbon-carbon double bonds. Omega-6 PUFAs and omega-3 PUFAs are the main types of PUFAs and are classified according to the location of the first unsaturated bond (sixth and third carbon atom, respectively). Alpha-Linolenic acid (ALA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and eicosapentaenoic acid (EPA) are the most important omega-3 PUFAs. ALA is an essential fatty acid that can only be obtained from diet and can be converted into EPA and then to DHA, but the rate of this conversion is finite, approximately 7.0%–21% for EPA and 0.01%–1% for DHA. In the same way, the most important omega-6 PUFAs are linoleic acid (LA) and arachidonic acid (ARA). LA is an essential fatty acid that, in order to give rise to ARA, needs to be ingested through the diet as the human body cannot synthesize it. The recommended intake for total PUFA ranges between 5% and 10% of the total energy intake, while a total omega-3 PUFA intake of 0.5%–2% and a total omega-6 PUFA intake of 2.5%-5% is suggested. A dietary ratio of omega−6/omega−3 PUFA is recommended to be 1:1–2:1 to balance their competing roles and achieve health benefits. Omega-6 and omega-3 PUFAs Omega-6 PUFAs, in the form of LA, are plentiful in most crop seeds and vegetable oils, such as canola, soybean, corn, and sunflower oils. In contrast to omega-6 PUFAs, omega-3 PUFAs are obtained from a limited range of dietary sources. Flax, chia, and perilla seeds are rich in ALA, with significant amounts also detected in green leafy vegetables. The consumption of fatty fish, such as salmon, sardines, tuna, trout, and herring, provides high amounts of EPA and DHA. Besides fish and their oils, small amounts of omega-3 PUFAs are also detected in red meat like beef, lamb, and mutton. All the above dietary sources provide EPA, DPA, DHA, LA, and ARA in different amounts, and their intake is necessary for normal physiological function. PUFAs play a critical role in many chronic diseases, affecting human cells by regulating inflammation, immune response, and angiogenesis. Omega-3 PUFAs’ role against hypertriglyceridemia has been clarified, and research indicates that systematically consuming oily fish can contribute to general heart protection. Supplementation with omega-3 PUFAs could potentially lower the risk of several cardiovascular outcomes, but the evidence is stronger for individuals with established coronary heart disease. Moreover, adequate EPA and DHA levels are necessary for brain anatomy, metabolism, and function. Although the mechanisms underlying omega-3 PUFAs' cardioprotective effects are still poorly understood, several studies have been conducted in this direction. Unfortunately, that does not hold true for their omega-6 counterparts, for which controversial emerging data tend to show anti-inflammatory behavior that needs to be further studied. Monounsaturated fatty acids (MUFAs) In contrast to PUFAs, monounsaturated fatty acids (MUFAs) are easily produced by the liver in response to the ingestion of carbohydrates. The main MUFA is oleic acid, found in plant sources, such as olive oil, olives, avocado, nuts, and seeds, while minimal amounts are also present in meat, eggs, and dairy products. Specific guidelines around MUFAs’ dietary consumption do not exist. Therefore, MUFAs are recommended to cover the remaining fat intake requirements to reach the total daily fat intake goal. A growing body of research shows that dietary MUFAs reduce or prevent the risk of metabolic syndrome, cardiovascular disease (CVD), and hypertension by positively affecting insulin sensitivity, blood lipid levels, and blood pressure, respectively. Moreover, olive oil contains several bioactive substances, possessing anti-tumor, anti-inflammatory, and antioxidant qualities. According to a meta-analysis, consuming olive oil was linked to a lower risk of developing any sort of cancer, especially breast cancer and cancer of the digestive system. Another study found that an isocaloric replacement of 5% of the energy from saturated fatty acids (SFAs) with plant MUFAs led to an 11% drop in cancer mortality over a 16-year follow-up period. Therefore, including MUFAs in the everyday diet offers multifaceted benefits in chronic disease prevention and management, including cancer and general health promotion.  Saturated fatty acids (SFAs) Saturated fatty acids (SFAs) form a heterogeneous group of fatty acids that contain only carbon-to-carbon single bonds. Whole-fat dairy, (unprocessed) red meat, milk chocolate, coconut, and palm kernel oil are all SFA-rich foods. These fatty acids have distinct physical and chemical profiles and varying effects on serum lipids and lipoproteins. Stearic, palmitic, myristic, and lauric acids are the principal SFAs found in most natural human diets. Dietary practice and guidelines recommend limiting SFA intake to <10% of the total energy (E%), while the American Heart Association suggests an even lower intake of <7 E% because total saturated fat consumption and LDL-C levels are positively correlated. However, the role of SFAs in CVDs is quite complex, and the evidence is heterogeneous. In a recent study with a 10.6-year follow-up period, which included 195,658 participants, there was no proof that consuming SFAs was linked to developing CVD while replacing saturated fat with polyunsaturated fat was linked to an increased risk of CVD. Moreover, according to 6 systematic reviews and meta-analyses, cardiovascular outcomes and total mortality were not significantly impacted by substituting saturated fat with polyunsaturated fat. Even if these analyses were to be challenged, due to heterogenous evidence, the possible reduction in CVD risk associated with replacing SFAs with PUFAs in several studies may not necessarily be an outcome of SFAs’ negative effect but rather a potential positive benefit of PUFAs. Regarding SFAs' effect on different types of cancers, associations of their intake with an increased risk of prostate and breast cancer have been indicated. Conversely, a meta-analysis showed no link between SFA intake and a higher risk of colon cancer; similarly, consuming MUFAs, PUFAs, or total fat did not affect colon cancer risk. Hence, the role of SFA consumption in preventing, promoting, or having a neutral role in serious chronic diseases has not been fully elucidated yet. Trans fatty acids (TFAs) Trans fatty acids (TFAs) are created industrially by partially hydrogenating liquid plant oils or can be naturally derived from ruminant-based meat and dairy products. TFAs are highly found in commercial baked goods, biscuits, cakes, fried foods, etc. Guidelines regarding TFAs are stringent and limit TFA intake to <1% of energy or as low as possible. In 2015, the US Food and Drug Administration declared that industrial TFAs are no longer generally recognized as safe and should be eliminated from the food supply as their consumption is strongly linked to various CVD risk factors. Specifically, TFA intake raises triglycerides and increases inflammation, endothelial dysfunction, and hepatic fat synthesis, leading to a significantly increased risk of coronary heart disease (CHD). A meta-analysis suggested that increased TFA intake led to an increase in total and LDL-cholesterol and a decrease in HDL-cholesterol concentrations. Data also indicates that TFAs may influence carcinogenesis through inflammatory pathways, but the reported data are debatable. A recent study investigated the effects of all types of dietary fat intake on CVD risk. While PUFA, MUFA, and SFA intake were not linked to higher CVD risk, dietary TFA intake showed a strong association with CVD risk. Analysis indicated PUFA intake and CVD risk were inversely correlated, and the relative risk of CVD was reduced by 5% in studies with a 10-year follow-up. Dietary lipids and the human microbiome Dietary lipids also affect human microbiota composition. Studies have identified a close association between the human microbiome and metabolic diseases, including obesity and type 2 diabetes. Diets with a high omega-6 PUFA, SFA, and TFA intake increase the amount of many detrimental bacteria in the microbiome and reduce the amount of the beneficial ones, altering the microbiota composition and inducing inflammation via the secretion of pro-inflammatory cytokines. These bacteria may disrupt the gut barrier function, allowing lipopolysaccharides (LPS) translocation, which are bacterial toxins. This condition is linked to metabolic perturbations such as dyslipidemia, insulin resistance, non-alcoholic fatty liver disease (NAFLD), and CVD. On the contrary, omega-3 PUFA (EPA and DHA) supplementation increases beneficial bacteria and limits harmful ones, enhancing intestinal barrier functioning and preventing LPS translocation and its implications. Omega-3 PUFA supplementation has also been studied as a means of mental health disorders management, but the evidence is still controversial. A possible protective impact of fish consumption on depression has been suggested by various studies, as well as a possible protective effect of dietary PUFAs on moderate cognitive impairment. A recent review of meta-analyses indicated that omega-3 PUFA supplementation might have potential value in mental health disorders, but data credibility is still weak. Dietary lipids and obesity Last but not least, obesity and its management is another field that dietary lipids intake seems to impact with their mechanisms. A diet high in PUFA has been shown to lower the total mass of subcutaneous white adipose tissue (the predominant fat type in human bodies), reduce blood lipid levels, and improve insulin sensitivity. In a study comparing PUFA and MUFA isocaloric intake, PUFA was more advantageous and lowered visceral adiposity in patients with central obesity. By stimulating brown adipose tissue, which aids energy expenditure through its elevated thermogenic activity, omega-3 PUFAs seem to elicit these positive effects in fat tissue, thus being useful in preventing and/or managing obesity. Another related study compared PUFA to SFA overfeeding in dietary surplus conditions that aimed to increase weight by 3%. While SFA overfeeding led to weight gain, primarily through the expansion of the visceral adipose tissue, PUFA overfeeding also led to weight gain, but because of a greater expansion of lean tissue mass. To sum up, dietary fats are an essential part of the human diet with many important physiologic functions, including cell function, hormone production, energy, and nutrient absorption. Moreover, dietary fat consumption is associated with positive outcomes in regard to cardiovascular disease, metabolic syndrome, cancer, and depression. Therefore, there is no reason to demonize this valuable dietary component, incriminating it for irrelevant adverse health outcomes, primarily weight loss failure and obesity. References 1. Astrup A, Magkos F, Bier DM, Brenna JT, de Oliveira Otto MC, Hill JO, King JC, Mente A, Ordovas JM, Volek JS, Yusuf S, Krauss RM. Saturated fats and health: A reassessment and proposal for food-based recommendations: JACC State-of-the-Art review. J Am Coll Cardiol. 2020;76(7):844-857. DOI: 10.1016/j.jacc.2020.05.077 2. Bojková B, Winklewski PJ, Wszedybyl-Winlewska M. Dietary fat and cancer-Which is good, which is bad, and the body of evidence. Int J Mol Sci. 2020;21(11):4114. DOI: 10.3390/ijms21114114 3. Custers, Emma EM, Kiliaan, Amanda J. Dietary lipids from body to brain. Prog Lipid Res. 2022;85:101144. DOI: 10.1016/j.plipres.2021.101144 4. de Souza RJ, Mente A, Maroleanu A, Cozma AI, Ha V, Kishibe T, Uleryk E, Budylowski P, Schünemann H, Beyene J, Anand SS. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies. BMJ. 2015;351:h3978. DOI: 10.1136/bmj.h3978 5. Gao X, Su X, Han X, Wen X, Cheng C, Zhang S, Li W, Cai J, Zheng L, Ma J, Liao M, Ni W, Liu T, Liu D, Ma W, Han S, Zhu S, Ye Y, Zeng F-F. Unsaturated fatty acids in mental disorders: An umbrella review of meta-analyses. Adv Nutr. 2022;13(6):2217-2236. DOI: 10.1093/advances/nmac084 6. Liu AG, Ford NA, Hu FB, Zelman KM, Mozaffarian D, Kris-Etherton PM. A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion. Nutr J. 2017;16(1):53. DOI: 10.1186/s12937-017-0271-4 7. Poli A, Agostoni C, Visioli F. Dietary fatty acids and inflammation: Focus on the n-6 series. Int J Mol Sci. 2023;24(5):4567. DOI: 10.3390/ijms24054567 8. Saini RK, Keum Y-S. Omega-3 and omega-6 polyunsaturated fatty acids: Dietary sources, metabolism, and significance-A review. Life Sci. 2018;203:255-267. DOI: 10.1016/j.lfs.2018.04.049 9. Saini RK, Prasad P, Sreedhar RV, Naidu KA, Shang X, Keum Y-S. Omega-3 polyunsaturated fatty acids (PUFAS): Emerging plant and microbial sources, oxidative stability, bioavailability, and health benefits-A review. Antioxidants (Basel). 2021;10(10):1627. DOI: 10.3390/antiox10101627 10. Zhao M, Chiriboga D, Olendzki B, Xie B, Li Y, McGonigal LJ, Maldonado-Contreras A, Ma Y. Substantial increase in compliance with saturated fatty acid intake recommendations after one year following the American Heart Association diet. Nutrients. 2018;10(10):1486. DOI: 10.3390/nu10101486 11. Zhu Y, Bo Y, Liu Y. Dietary total fat, fatty acids intake, and risk of cardiovascular disease: a dose-response meta-analysis of cohort studies. Lipids Health Dis. 2019;18:91. DOI: 10.1186/s12944-019-1035-2
SHOW MORE