The Challenges of What To Eat For Optimum Health

With current advances in nutritional science, humans are increasingly getting enlightened as to what makes optimum nutrition for optimum health. However, with widespread proliferation of nutrition and health information from various health information centres and media platforms, the challenge is getting appropriate information optimum nutrition for optimum health. The most accessible from mandated food and health related institutions within individual countries, in the form of food/nutrition guides, food plates of food pyramids.. The reality on the ground however is that not many people actually follow the  food guides/pyramids due to various reasons, including: availability of the recommended food, affordability, personal food choices, inclination to traditional foods, etc. Further more, there is no guaranty that by following the food guides, one is assured of optimum nutrients intake as some nutrition and health experts are of the view that estimate conversions of nutrient content in food portions within the food pyramids are off the realistic levels to qualify as optimum nutrient levels . This creates uncertainties as to how close we are to achieve optimum nutrient intake for optimum health. A closer look at an example of one nutrient might help us better understand optimum nutrients intake for optimum health. For this we bring into focus Vitamin A.

Vitamin A, a fat-soluble vitamin is essential for many physiological processes, including maintaining the integrity and function of all surface tissues (epithelia): for example, the skin, the lining of the respiratory tract, the gut, the bladder, the inner ear and the eye. Vitamin A supports the daily replacement of skin cells and ensures that tissues such as the conjunctiva are able to produce mucous and provide a barrier to infection. Vitamin A is also essential for vision under conditions of poor lighting, for maintaining a healthy immune system, for growth and development (essential for growth and bone development in children) and for reproduction and gene expression. Vitamin A supports many systems in the body. This makes it a challenge to definitely define the the optimum intake levels for optimum health. Within that scope of complexity, vitamin A deficiency is now referred to as vitamin A deficiency disorders. 

Vitamin A is an essential micronutrient in  that our bodies cannot manufacture it and therefore it has to be included in our diet. There are two main sources of vitamin A: animal sources and plant sources. All the sources of vitamin A need some fat in the diet to aid absorption.

In animal sources, vitamin A is found as retinol, the ‘active’ form of vitamin A. Liver, including fish liver, is a very good source. Other animal sources are egg yolk (not the white) and dairy products such as milk (including human breast milk), cheese and butter. Worthwhile to note that meat, from the animal's muscles, is not a good source.

Plant sources contain vitamin A in the form of carotenoids which have to be converted during digestion into retinol before the body can use it. Carotenoids are the pigments that give plants their green colour and some fruits and vegetables their red or orange colour. Plant sources of vitamin A include: carrots, mangos, papaya, many of the squashes, sweet potatoes and maize (not the white varieties).

The amount of vitamin A one needs depends on your age and reproductive status. Recommended intakes for vitamin A for people aged 14 years and older range between 700 and 900 mcg of retinol activity equivalent (RAE) per day. Recommended intakes for women who are nursing range between 1,200 and 1,300 RAE. Lower values are recommended for infants and children younger than 14.
However, the vitamin A content of foods and dietary supplements is given on product labels in international units (IU), not mcg RAE. Converting between IU and mcg RAE is not easy. A varied diet with 900 mcg RAE of vitamin A, for example, provides between 3,000 and 36,000 IU of vitamin A depending on the foods consumed.

For adults and children aged 4 years and older, the U.S. Food and Drug Administration (FDA) has established a vitamin A Daily Value (DV) of 5,000 IU from a varied diet of both plant and animal foods. DVs are not recommended intakes; they don’t vary by age and sex, for example. But trying to reach 100% of the DV each day, on average, is useful to help you get enough vitamin A.

The upper limits for preformed vitamin A in IU are listed below. These levels do not apply to people who are taking vitamin A for medical reasons under the care of a doctor. Upper limits for beta-carotene and other forms of provitamin A have not been established.
Life StageUpper Limit
Birth to 12 months2,000 IU
Children 1-3 years2,000 IU
Children 4-8 years3,000 IU
Children 9-13 years5,667 IU
Teens 14-18 years9,333 IU
Adults 19 years and older10,000 IU

What foods are rich in vitamin A? When it comes to plant foods with vitamin A, a good rule of thumb is that fruits and veggies that are orange, yellow or red have a high likelihood of providing vitamin A. (5) In terms of animal foods rich in vitamin A, those that naturally have a higher fat content (such as eggs, butter, liver or full-fat dairy) are more likely to provide vitamin A since it’s a fat-soluble vitamin.
Below is a vitamin A foods list that includes the best dietary sources:
1. Winter/butternut squash — 1 cup, cooked cubes: 22,869 international units (457 percent DV)
2. Sweet potato — 1 medium, cooked potato: 21,907 international units (438 percent DV)
3. Kale — 1 cup, chopped: 10,302 international units (206 percent DV)
4. Carrots — 1 medium raw carrot: 10,190 international units (204 percent DV)
5. Beef Liver — 1 ounce: 8,881 international units (178 percent DV)
6. Spinach — 1 cup raw: 2,813 international units (56 percent DV)
7. Dried apricots — 1 ounce: 1,009 international units (20 percent DV)
8. Broccoli — 1 cup raw: 567 international units (11 percent DV)
9. Butter — 1 tablespoon: 350 international units (7 percent DV)
10. Egg yolks — 1 large egg: 245 international units (5 percent DV)

Going by the DV of 5000 IU /Day Vitamin A, it might appear that we are likely to meet Vitamin A requirements from inclusion of vitamin A rich foods indicated above in our daily meals. Increasing intake of foods of plant origin from the list above would be more favorable compared to foods of animal origin, as carotenoids and other provitamin A of plant origin are not known to have potential side effects from toxicity. Issues of absorption may cause a challenge and to meet the nutrient requirements for optimum health, use of beta carotene nutritional supplements may be warranted. On the other hand some animal food sources of vitamin A might such as beef liver might contain fairly high levels of retinol, for example beef liver (approximately 10 000 IU per ounce) and regular intake of beef liver might potentially cause toxic osteoporosis, particularly in the elderly. One other interesting example of high content retinol is the polar bear liver with about 35 000 IU per gram (3.5 million IU per serving), such that consumption of polar bear liver is often associated with acute vitamin A toxicity. To avoid toxicity from retinol, take foods which provide safe levels, then fill up the gape with beta carotene nutritional supplements.


Vitamin A, Fact Sheet for Consumers NIH 

Linus Pauling Institute » Micronutrient information Centre, Vitamin A 


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