Introduce
When people are or feel healthy, eating a variety of food to get the nutrients and calories they need is not usually a problem. Based on the nutrition guidelines, the most essential nutrients include water, proteins, carbohydrates, vegetables, fruits, grains, but it is also important to limit the amount of red meat you eat, especially processed meats or high in fat.
It is also essential to reduce the amount of fat, sugar, alcohol, and salt to stay healthy and prevent chronic diseases. But when you have cancer, or are being treated for cancer, or perhaps you have already won the battle against cancer, then these nutritional guidelines can be hard to achieve, especially if you have side effects, or if you want to prevent a recurrence.

Good nutrition for cancer patients is especially important because both the condition and its treatments can alter the way they eat. Also keep in mind that the body does not tolerate certain foods anymore. For example, if you are undergoing a cancer treatment you might need to change your diet in a way that it can also strengthen your immune system, and to help you control the side effects caused by the cancer treatment.
This may mean eating foods that are not normally recommended when you are in good health. For instance, you might need low fat, high-protein, immune-enhancing foods to keep up your immunity and weight. Still, dietary fats are needed because they give you energy, support cell function and help your body absorb nutrients from vegetables, fruits, and other foods. But keep in mind that all fats are not the same. Unhealthy sources of fat are not good for you.
Good vs. Bad Fats

Fats perform a crucial role in nutrition and cancer. Still, some fats are good for you, and some are not. Your body needs fat to survive. Fat, along with protein and carbohydrates, gives your body energy in the form of calories. It also works to store extra calories, maintain healthy skin and hair, and insulate the body. Not all fats are equal. Although you need fat in our diet, you should eat fats in moderation and choose them wisely: some fats are “good,” while others are “bad.”[1]
Below is an explanation of the different types of fats:
HEALTHY FATS: Unsaturated fats
These are “good” fats found mainly in vegetables, nuts, seeds, and fish. At room temperature, these types of fats are liquid, not solid. There are two broad categories of good fats: monounsaturated and polyunsaturated fats. Find them in most nuts, soy products, olive oil, peanut oil, canola oil, avocados, tuna, and salmon.
Essential fatty acids are a type of polyunsaturated fat, also known as omega-3 fatty acids. You need to eat a small amount of these in your diet because the body cannot produce them.[2] The intake of omega-3 fatty acids has been showed to reduce the reoccurrence of kidney, prostate, breast, and other cancers. It has also been suggested that omega-3 fatty acids in the diet may provide a protective benefit against the development of cancer.[3]
Sources of omega-3 fatty acids include:

• Oily fish, such as sardines, salmon, or mackerel
• Walnuts, flaxseeds, and linseeds
• Green, leafy vegetables
Several studies have indicated that high blood omega-6 fatty acid levels were associated with a lower risk of cancer.[4]
Sources of omega-6 fatty acids include:
• Nuts
• Seeds
• Vegetable oils or spreads, such as rapeseed, corn, or sunflower
Good fats are particularly important for breast cancer patients who have already undergone chemotherapy treatment because studies have found cognitive abnormalities in 20 to 70% of women after chemotherapy depending on the agents used, intensity and duration of treatment, predisposing factors, and type and scoring of cognitive tests.[5] DHA (an omega-3 fatty acid) is the most abundant in the brain and it is implicated in multiple functions involving cell signaling, neurogenesis, neuroprotection, and learning and memory.[6]
Saturated fats

These are the “bad” fats that are often found in meat and other animal products, such as butter, cheese, and all milk except skim. They are often solid at room temperature.[7] Some oils, such as palm and coconut oils, are also high in saturated fats, and are often used in baked goods you buy at the store.
These are the types of fats that you must stay away from! Some studies have suggested that high-fat diets or high intakes of different types of fat in the diet may be linked to various cancers, including colon, lung, and breast cancer, as well as heart disease and other chronic diseases.[8]
Trans fats

These are the unhealthiest type of dietary fat. They are mainly obtained naturally in small quantities in some animal products like red meat, cheese, and whole milk, but most trans fats are man-made using a process that turns liquid oils into solids. It is important to pay close attention to “hydrogenated” or “partially hydrogenated” oils on an ingredient list because these are trans fats.
avoid saturated and trans fats
The American Heart Association recommends cutting back on trans-fat and making saturated fat only 5% to 6% of total daily calories.[9] Still, it is best for cancer patients to avoid these unhealthy fats. Since cancer treatment can lead to changes in appetite and body weight, it is vital to pay close attention to your diet.
Instead of eating saturated and trans fats, cancer patients need to focus on eating foods high in protein, healthy fats (unsaturated), whole grains, vitamins, minerals, antioxidants, and other immune-enhancing ingredients. If possible, make these dietary adjustments before cancer treatments, during and continue after treatment so you can be healthier day-by-day.
Refrence
[1] Bojková, B., Winklewski, P.J., and Wszedybyl-Winklewska, M. (2020). Dietary Fat and Cancer—Which Is Good, Which Is Bad, and the Body of Evidence. Int J Mol Sci. 21(11): 4114.
[2] Freitas, R.D., and Campos, M.M. (2019). Protective Effects of Omega-3 Fatty Acids in Cancer-Related Complications. Nutrients. 11(5): 945.
[3] MacLean, C., Newberry, S., Mojica, W., et al. (2006). Effects of Omega-3 Fatty Acids on Cancer Risk. Journal of the American Medical Association. 295:403-415.
[4] Kim, J., and Kim, Y. (2020). N-6 Polyunsaturated Fatty Acids and Risk of Cancer: Accumulating Evidence from Prospective Studies. Nutrients. 12(9): 2523.
[5] Wefel, J.S., Saleeba, A.K., Buzdar, A.U., and Meyers, C.A. (2010). Acute and late onset cognitive dysfunction associated with chemotherapy in women with breast cancer. Cancer. 116:3348–56.
[6] Su, H-M. (2010). Mechanisms of n-3 fatty acid-mediated development and maintenance of learning memory performance neuroprotection. J Nutr Biochem. 21:364–73.
[7] Gershuni, V.M. (2018). Saturated Fat: Part of a Healthy Diet. Current Nutrition Reports. 7:85–96.
[8] Bojková, B., Winklewski, P.J., and Wszedybyl-Winklewska, M. (2020). Dietary Fat and Cancer—Which Is Good, Which Is Bad, and the Body of Evidence. Int J Mol Sci. 2020 Jun; 21(11): 4114.