I know that eating fish a few times a week is really healthy/nourishing for one's diet, however, I cannot eat fish as I'm allergic to all types. A) What nourishment is contained in fish? B) What can one eat in their diet to get the same nourishment?
You're right, fish is very nutritious. It's an excellent source of protein that's low in saturated fat. It also contains nutrients that may benefit the brain such as iron, vitamin E, selenium. But most of the positive attention that's been given to fish has to do with its omega-3 fat content.
Cold water fish like salmon, trout, sardines, mackerel and herring contain two omega-3 fatty acids called DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). People with higher blood levels of these omega-3 fatty acids have a lower risk of heart disease, heart attack, coronary death and Alzheimer's disease.
With respect to heart health, omega-3 fats in oily fish make the blood less likely to form clots, lower blood triglyceride levels and protect against irregular heartbeats that can cause sudden cardiac death.
Since you are allergic to the protein in fish you can't get these two omega-3 fatty by eating fish or taking a fish oil supplement. Although fish oil supplements do not contain protein – only fish oil – most people who are allergic to fish don't take a chance by supplementing with fish oil. The same is true for foods like milk, eggs and yogurt that are fortified with DHA from fish oil.
There are other options for you to get omega-3 fats. DHA supplements made from plants – not fish – are available. These contain DHA derived from algae. These supplements are marketed to vegetarians but there are also suitable for people allergic to fish. I suggest asking for this product at a good quality natural food store or supplement store.
You'll also find an omega-3 fatty acid called alpha-linolenic acid (ALA) in certain plant foods. Good sources of ALA include flax oil, ground flaxseed, chia seeds, walnuts, canola oil and soybeans.
Research suggests that a regular intake of ALA helps protect from heart disease, but the data is much less compelling than the evidence for DHA and EPA. Still, since you don't eat fish, getting ALA from your diet could lower the odds of developing heart disease.
ALA does not have any known function in the brain however. Only a very small amount of the ALA we consume is converted to DHA in the body, an omega-3 fat that does benefit the brain. What's more, this conversion becomes even less efficient as we age.
ALA is considered an essential fat, meaning our bodies can't make it and it must be obtained from the diet. Adult women need 1.1 grams per day (1,100 milligrams) and men require 1.6 grams (1,600 milligrams). It's not hard to get your ALA. One teaspoon of flax oil provides 2.4 grams, a teaspoon of canola oil offers 0.4 grams, and ½ cup of soybeans delivers 0.5 grams of ALA.
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