Fat

Scientific studies (review articles) on the relationship between fat and disease prevention:
One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:
"Do taking dietary supplements make sense?" Yes for a positive conclusion and no for a negative conclusion.

One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of cohort studies or case-control studies will answer the following question:
"Should I change my diet?".

1. Higher tissue levels of linoleic acid reduce prostate cancer
2. Higher linoleic acid blood concentration reduces cancer mortality
3. Higher blood levels of alpha-linolenic acid reduce colorectal cancer
4. Higher plasma levels of free fatty acids increase gestational diabetes mellitus
5. Fat, cholesterol and vitamin A increase ovarian cancer
6. 0.5 g/day dietary trans fat intake increases ovarian cancer
7. Trans fatty acids intake increases cardiovascular disease
8. Dietary n-3 PUFAs reduce ulcerative colitis
9. Diet with medium-chain saturated fatty acids leads to higher HDL cholesterol
10. Monounsaturated fatty acids dietary intake reduces all-cause mortality
11. Monounsaturated fatty acids intake derived from animal sources increase risk of fracture
12. High consumption of polyunsaturated fat increases skin cancer
13. Omega-3 fatty acids consumption reduce recurrent venous thromboembolism
14. Dietary intake of n-3 PUFAs declines hip fracture risk
15. A low-fat diet reduces cholesterol level in overweight or obese people
16. Replacing saturated fat with PUFA will lower coronary heart disease events
17. A diet with 10 En% saturated fat reduces cholesterol and blood pressure in children
18. Low-fat diet reduces recurrence of breast cancer
19. High consumption of dietary trans fat increases prostate cancer and colorectal cancer
20. Saturated fat increases breast cancer mortality among women
21. Saturated fat increases Alzheimer disease
22. High saturated fat increases liver cancer
23. High intakes of saturated fat increase risk of lung cancer
24. A diet with 4.4 g/day alpha-linolenic acid during 3 months does not reduce level of HbA1c, FBG or FBI in patients with type 2
25. Alpha-lipoic acid supplementation reduces weight and BMIdiabetes
26. CLA does not reduce fasting blood glucose and waist circumference
27. Routine supplementation of full-term infant milk formula with LCPUFA cannot be recommended
28. A high total fat consumption increases non-Hodgkin's lymphoma
29. Perioperative antioxidant supplementations with NAC, PUFA and vitamin C prevent atrial fibrillation after cardiac surgery
30. Dietary low-ratio n-6/n-3 PUFA supplementation improves insulin resistance in diabetic patients
31. High-fat diets increase risk of type 2 diabetes
32. Olive oil intake reduces risk of type 2 diabetes
33. Olive oil consumption reduces stroke
34. Olive oil consumption probably reduces breast cancer and cancer of the digestive system
35. Trans fatty acids are not associated with risk of breast cancer

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• Fats are the most concentrated form of energy for the body (37 kJ/g or 9 kcal/g).
• A fat or oil is always a mixture of saturated and unsaturated fatty acids. Therefore, no fat or oil is 100% healthy.
• There are three major types of naturally-occurring fatty acids: saturated, cis-monounsaturated and cis-polyunsaturated. A fourth form, the trans fatty acids, are produced by partial hydrogenation of polyunsaturated oils in food processing and they also occur naturally in ruminant animal foods.
• Saturated fats contain more saturated fatty acids as unsaturated fatty acids. These fats are solid at room temperature.
  Saturated fats directly raise total and LDL (bad) cholesterol levels.
• Saturated fatty acids are found in milk, cream, butter and cheese, meats from most of the land animals, palm oil and coconut oil as well as in products such as pies, biscuits, cakes and pastries.
  Saturated fatty acids can be synthesized by the body so are not required in the diet.
• Unsaturated fats contain more unsaturated fatty acids as saturated fatty acids. These fats are liquid at room temperature.
• Trans fats are actually unsaturated fats, but they can raise total and LDL (bad) cholesterol levels while also lowering HDL (good) cholesterol levels.
• Unsaturated fatty acids are also called omega-or n-fatty acids.
• Unsaturated fatty acids can be divided into monounsaturated and polyunsaturated fatty acids (PUFAs).
• N-fatty acids are divided into n-3, 6, 7 and 9 fatty acids.
  N-7 and n-9 are monounsaturated and are synthesized by the human  body from other fatty acids​​. Therefore, n-7 and 9 are not essential.
• N-3 and n-6 are polyunsaturated and cannot be synthesized by the human body. Therefore, n-3 and n-6 are essential. The human requirements of n-3 and n-6 are depending on the content of diet.
• Essential fatty acids or PUFAs are alpha-linolenic acid (ALA), EPA, DHA and linoleic acid (LA).
  ALA primarily functions as a precursor for the synthesis of EPA which in turn forms DHA but may also have an independent role in protection against coronary heart disease via different mechanisms.
  ALA is found in legumes, canola oils and margarines, linseed oils and products, certain nuts such as walnuts, and in small amounts in leafy vegetables.
• N-3 fatty acids are fatty acids where the double bond is located at the third C-atom, counting from the methyl end.
  Alpha-linolenic acid, EPA and DHA are n-3 fatty acids.
• Linoleic acid (LA) is an n-6 fatty acid. Unlike alpha-linolenic acid linoleic acid has only two double bonds. The more double bonds, the more sensitive for fat oxidation. In other words, linoleic acid is less susceptible to fat oxidation than alpha-linolenic acid and therefore, linoleic acid is often used in the food industry.
  Fat oxidation is a major problem in the food industry. Fat oxidation makes an product more expensive.
  LA is the precursor of arachidonic acid, a substrate for eicosanoid production.
• Replacing saturated fatty acids with polyunsaturated fatty acids decreases LDL cholesterol concentration and the total/HDL cholesterol ratio.
• Replacing saturated fatty acids with carbohydrates decreases both LDL and HDL cholesterol concentration but does not change the total/HDL cholesterol ratio.
• Replacing saturated fatty acids with trans-fatty acids decreases HDL cholesterol and increases the total/HDL cholesterol ratio.
• The Western diet contains a n-3/n-6 ratio >15. In other words, the diet contains too much n-6 linoleic acid. The body can synthesize arachidonic acid from linoleic acid. Arachidonic acids can converted into pro-thrombosis and pro-inflammatory eicosanoids.
  To prevent chronic diseases, the diet should contain a n-3/n-6 ratio 5.
  However, EFSA and WHO have not set specific values for the n-3/n-6 ratio.
• Belly fat increases the risk of developing heart disease, cancer and type 2 diabetes.
  Therefore, aim for a waist circumference of 68-80 cm for women and 79-94 cm for men.
• A healthy adult male has a body fat percentage around 15%.
• A healthy adult woman has a body fat percentage around 25%.
• Body’s fat is stored in the form of triglycerides in fat cells (adipose tissues).
  In contrast to the other macronutrients there a virtually unlimited storage capacity for fat.
• EFSA (European Food Safety Agency) concludes that a daily intake of 250 mg PUFAs may reduce the risk of heart disease in adults.
  European dietary recommendations are set by EFSA.
  The RDA of vitamins and minerals on packaging is also set by EFSA.
• High fat intake (>35 En% of total daily energy intake) is an important factor in the increase of body weight.
• The body has at least 70000 calories stored as fat.
• Fats are not the important energy source during physical exercises. However, fats are the primary fuel source for muscle during low-intensity exercise.
  Low-intensity exercise corresponds to 40-50 percent of the maximum heart rate.
  Total fat oxidation is the highest at 65% VO2max.
• During low intense exercise of greater than 30 minute’s duration a gradual shift from carbohydrate to fat metabolism occurs. However, if the goal is to lose weight, it's about the total number of calories burned, not necessarily the fuel source.
• A balanced diet of adult contains 20-35 En% fat, of which:
  • 7-10 En% saturated fat;
  • 12 En% monounsaturated fat;
  • 10 En% polyunsaturated fat;
  • 2 En% essential fat and;
  • 1 En% trans fat.
• A daily diet of 20-35 En% fat means that the total amounts of fat make up for 20 to 35% of the total kcal of the diet.